Publications:
Jones DR, Chew DP, Horsfall MJ, Chuang AM, Sinhal AR, Joseph MX, Baker RA, Bennetts JS,
Selvanayagam JB, Lehman SJ.
Heart Lung Circ. 2020 May;29(5):719-728. doi: 10.1016/j.hlc.2019.06.717. Epub 2019 Jun 25. PMID: 31285152.
Background
Outcomes following an initial strategy of balloon aortic valvuloplasty (BAV) prior to medical therapy or intervention with surgical or transcatheter aortic valve replacement (SAVR or TAVR) are unclear in the modern transcatheter intervention era.
Methods
A retrospective, observational cohort study of the echocardiography, cardiothoracic surgery and TAVR databases between 1 January 2006 and 31 December 2016 was performed to compare outcomes between all patients with severe aortic stenosis (AS) treated with or without BAV prior to medical or invasive therapy.
Results
3,142 patients were available for analysis. 223 BAV treated patients had lower mortality relative to medically treated patients, particularly early (20.1% v. 7.6% at 6 months, 58.1% v. 52.5% at 5 years). Over 5 years, the adjusted hazard ratio (HR) was 0.62 (95% CI 0.48–0.80, p < 0.001).
Compared with 630 patients proceeding directly to intervention, 75 patients receiving BAV experienced a higher mortality (HR = 2.76, 95% CI 2.07–3.66, p < 0.001). No subsequent excess perioperative mortality was observed with BAV compared with those receiving surgery directly (HR = 1.45, 95% CI 0.91–2.31, p = 0.117).
Conclusions
The risk associated with BAV is low, and improves mortality compared with medical therapy. Balloon aortic valvuloplasty treated patients have poorer outcomes, but treatment with BAV does not increase perioperative mortality and may lessen it.
Koerber JP, Bennetts JS, Psaltis PJ.
J Clin Med. 2020 Aug 20;9(9):2694. doi: 10.3390/jcm9092694. PMID: 32825345; PMCID: PMC7563468.
Abstract:
Timing of aortic valve intervention for chronic aortic regurgitation (AR) and/or aortic stenosis (AS) potentially affects long-term survival. The 2014 American Heart Association/American College of Cardiology (AHA/ACC) guidelines provide recommendations for the timing of intervention. Subsequent to the guidelines’ release, several studies have been published that suggest a survival benefit from earlier timing of surgery for severe AR and/or AS. The aim of this review was to determine whether patients who have chronic aortic regurgitation (AR) and/or aortic stenosis (AS) have a survival benefit from earlier timing of aortic valve surgery. Medical databases were systematically searched from January 2015 to April 2020 for randomized controlled trials (RCTs) and observational studies that examined the timing of aortic valve replacement surgery for chronic AR and/or AS. For chronic AR, four observational studies and no RCTs were identified. For chronic AS, five observational studies, one RCT and one meta-analysis were identified. One observational study examining mixed aortic valve disease (MAVD) was identified. All of these studies, for AR, AS, and MAVD, found long-term survival benefit from timing of aortic valve surgery earlier than the current guidelines. Larger prospective RCTs are required to evaluate the benefit of earlier surgical intervention.
Brown M, Jersmann H, Crowhurst T, Van Vliet C, Crouch G, Badiei A.
Respirol Case Rep. 2020 Sep 19;8(8):e00664. doi: 10.1002/rcr2.664. PMID: 32995012; PMCID: PMC7507382.
Abstract
Malignant pleural mesothelioma (MPM) is an insidious primary neoplasm of the pleura that can be challenging to diagnose and is commonly considered to be only locally invasive. We present the case of a 74-year-old male who presented with clinical features of MPM but from whom pleural fluid and biopsies initially suggested benign pathology. He later developed diffuse bony metastases and re-examination of pleural biopsies using modern immunohistochemistry and molecular testing revealed a diagnosis of sarcomatoid and desmoplastic MPM with heterologous osteosarcomatous differentiation. This case not only demonstrates the rare potential of skeletal metastasis of MPM, but also highlights the importance of recognizing the utility of modern diagnostic tests and their potential to prevent the need for unnecessary invasive procedures. To our knowledge this is the first description of this rare histological sub-type presenting with skeletal metastases.
Crouch G, Sinha S, Lo S, Saw RPM, Lee KK, Stretch J, Shannon K, Guitera P, Scolyer RA, Thompson JF, Ch'ng S.
Eur J Surg Oncol. 2020 Sep 23:S0748-7983(20)30800-3. doi: 10.1016/j.ejso.2020.09.028. Epub ahead of print. PMID: 33023795.
Abstract
Introduction: Lentigo maligna (LM), a subtype of melanoma in-situ commonly occurring in the head and neck region, often presents a treatment challenge due to anatomical constraints, particularly on the face of mostly elderly patients. This study sought to assess the clinical outcomes of wide local excision of head and neck LM, identify predictors of recurrence and define optimal excision margins.
Materials and methods: Patients with LM treated between January 1997 and December 2012 were identified from the large institutional database of a tertiary center and their data were analyzed.
Results: In 379 patients, 382 lesions were eligible for analysis. Median maximal lesion diameter was 10.5 mm. The mean surgical excision and histopathological clearance margins were 6.2 mm and 4.0 mm, respectively. Median follow-up was 32 months. The LM recurrence rate was 9.9%, and subsequent invasive melanoma developed in 2.3% of cases (mean Breslow thickness 0.7 mm). The recurrence rate was 27.2% if the histological margin was <3.0 mm (median time to recurrence 46.5 months) compared with 2.6% if the margin was ≥3.0 mm. The mean surgical margin required to achieve a histological clearance of ≥3.0 mm was 6.5 mm.
Conclusions: Our data suggest that to minimize recurrence, a histological margin of ≥3.0 mm is required. To achieve this, a surgical margin of ≥6.5 mm was required. This is greater than the 5 mm margin recommended in some national guidelines. Careful long-term follow-up is required for all patients because of the risk of recurrence.
Hayes N, White J, Lillie P, Bennetts JS, Tu CG, Bain GI.
Arch Orthop Trauma Surg. 2020 Apr;140(4):443-447. doi: 10.1007/s00402-019-03242-3. Epub 2019 Aug 5. PMID: 31385020.
Abstract:
An intrathoracic shoulder dislocation is a rare injury, usually the result of high-energy trauma [Hawkes et al. in Am J Orthop 43(4):E74-E78, 2014; Tsai et al. in Ann Thorac Cardiovasc Surg 20:592-594, 2014, in Rupprecht et al. Bull Emerg Trauma 5(3):212-214, 2017; Abellan et al. J Orthop Surg (Hong Kong)18(2):254-257, 2010]. It often occurs in conjunction with thoracic, pelvic, and long bone injuries. In addition, there is often significant injuries to the shoulder girdle and chest wall associated with neurovascular compromise [Abellan et al. J Orthop Surg (Hong Kong)18(2):254-257, 2010; Lin et al. JBJS Case Connect 6(1):e61, 2016]. Following a literature review, it appears that no cases have been reported of an intrathoracic shoulder dislocation associated with a rupture of the ipsilateral main bronchus. We present a case of a rupture of the right main bronchus that occurred due to high-energy impact and an associated intrathoracic right-shoulder fracture dislocation. Computed tomography identified diastasis of the ipsilateral first intercostal space, humeral head indentation in the hilum of the lung, and a pneumoarthrogram of the right glenohumeral joint.
Govender M, Bihari S, Bersten AD, De Pasquale CG, Lawrence MD, Baker RA, Bennetts J, Dixon DL.
Heart Lung. 2019 Jan;48(1):55-60. doi: 10.1016/j.hrtlng.2018.08.004. Epub 2018 Sep 14. PMID: 30220431.
Introduction: Cardio-pulmonary bypass (CPB) is associated with prolonged mechanical ventilation (PMV) in the intensive care unit (ICU), and an increase in morbidity and mortality. Surfactant dysfunction could result in atelectasis and contribute to PMV. However, it is unclear whether cessation of mechanical ventilation, with resultant atelectasis, and the use of a foreign bypass circuit during CPB, would affect the concentration of surfactant constituents and whether this, in turn, is associated with PMV. Pulmonary surfactant, which increases lung compliance and opposes atelectasis by reducing alveolar surface tension, is produced in the lung by alveolar type II cells. It is comprised of 10% protein, predominantly the surfactant proteins A, B, C & D, and 90% phospholipid, which can be separated into large surfactant aggregates (LA) and small surfactant aggregates (SA). LA, the metabolic precursors to SA, are the greatest contributors to reduction of surface tension.
Results: Of the total 22 patients included in this retrospective analysis, 15 patients received CPB and 7 received off-pump surgery. The median EuroSCORE II and proportion of patients with NYHA III was not significantly different between groups. Clinically diagnosed heart failure was identified at admission in 9 patients in the CPB group (60%) and only 2 patients in the off-pump group (29%). This resulted in greater left atrial area, left ventricular end diastolic diameter and mitral valve inflow E-wave velocity: mitral valve inflow A-wave velocity in the CPB group. There was no difference in BAL small aggregate concentration between the two groups. A significant difference in BAL large aggregate concentration per mL ELF between the off-pump and CPB groups may have contributed to a trend toward an increase in the small to large aggregate ratio in the CPB group ( p = 0.051). The duration of CPB was 73.7 ± 20.53 min (mean ± SD). Intra-operative fluid balance was higher and length of mechanical ventilation longer in the CPB group. However, this was not associated with an increase in ICU or hospital total length of stay. No other clinical parameters were significantly different between the groups, including duration of surgery (median of 235 (192–285) min for the CPB group and 220 (210–315) min for the off-pump group; p = 0.91).
Conclusions: In this retrospective exploratory study, there was a difference in pulmonary surfactant LA concentration following cardiac surgery in patients who underwent CPB compared to those treated without the use of CPB (off-pump). This is a novel finding in adult patients undergoing CPB. This difference in the more surface-active component of surfactant in the CPB group may be associated with the longer length of mechanical ventilation in the ICU in CPB patients found in this study. This observation warrants confirmation with larger cohorts. Future studies should include examining the effect of PEEP and lung recruitment versus lung deflation on surfactant concentrations for patients receiving CPB, and whether this reduces the length of mechanical ventilation.
Keenan, N. M., Bennetts, J. S., McGavigan, A. D., Rice, G. D., Joseph, M. X., Baker, R. A., & Sinhal, A
Heart, lung & circulation, 29(6), 921–930. https://doi.org/10.1016/j.hlc.2019.07.010
Background: Transcatheter mitral valve implantation for degenerated bioprostheses has recently emerged as an alternative to redo mitral valve surgery, particularly in patients at high risk for reoperative cardiac surgery. We sought to examine our early experience of transcatheter transseptal mitral valve-in-valve procedures.
Results: Seven (7) patients underwent the procedure between December 2017 and November 2018. Three (3) patients were young Indigenous Australians (age range 33-41years) who were not suitable for mechanical prostheses; four patients were elderly (age range 82-92 years) and considered high risk for reoperative surgery. The median (maximum, minimum) EuroSCORE II of the group was 7.32 (4.81, 19.89). Procedural success was obtained in six of the seven patients; these six patients had no significant complications and had a median hospital stay of 3 days. In one patient, the device displaced towards the left ventricle on inflation, resulting in left ventricular outflow tract obstruction and haemodynamic instability. Urgent redo mitral valve surgery and explantation of the transcatheter prosthesis was undertaken, however, this patient died postoperatively of multi-organ failure. Of the successfully deployed valves, the median (maximum, minimum) gradient across the new mitral prosthesis was 5.5 mmHg (4, 7) and only one patient had mild mitral regurgitation, all others had no or trivial regurgitation. At 30 days, these six patients are well and all are in New York Heart Association (NYHA) Class I.
Conclusions: Our early experience with transcatheter transseptal mitral valve-in-valve implantation demonstrates this procedure to be feasible in our institution with acceptable early results. Further follow-up is necessary to determine the longevity of valves implanted in this manner, especially in the younger population.
Jones DR, Chew DP, Horsfall MJ, Chuang AM, Sinhal AR, Joseph MX, Baker RA, Bennetts JS, Selvanayagam JB, Lehman SJ.
Open Heart. 2019 Jul 29;6(2):e000983. doi: 10.1136/openhrt-2018-000983. eCollection 2019.
PMID: 31413842
Objectives: To analyse the effect of the implementation of a transcatheter aortic valve replacement (TAVR) and multidisciplinary heart team programme on mortality in severe aortic stenosis (AS).
Results: Of 3399 patients, there were 210 deaths (6.2%) at 30 days and 1614 deaths (47.5%) at 5 years.Overall, patients diagnosed in the post-TAVR programme era were older, with a lower ejection fraction and more severe AS, but were less comorbid.Among 705 patients undergoing intervention, those in the post-TAVR programme era were older, with a lower ejection fraction and more severe AS but no significant differences in comorbidities.Using an inverse probability weighted cohort and a Cox proportional hazards model, a significant mortality benefit was noted between eras alone (HR=0.86, 95% CI 0.77 to 0.97, p=0.015). When matching for age, comorbidities and valve severity, this benefit was more evident (HR=0.82, 95% CI 0.73 to 0.92, p=0.001).After adjusting for the presence of aortic valve intervention, a significant benefit persisted (HR=0.84, 95% CI 0.75 to 0.95, p=0.005).
Conclusion: The implementation of a TAVR programme is associated with a mortality benefit in the population with severe AS, independent of the expansion of access to intervention.
Grant KMK, Reid F, Crouch G, Lawrence M.
No abstract available for this article.
Farnsworth JH, Krieg BM, Bennetts JS, Baker RA.
Heart Lung Circ. 2019;28(11):1720-1727. doi:10.1016/j.hlc.2018.08.028
Background: The cost of performing cardiac surgery in the public health system in Australia is unclear. This paper analyses the cost of cardiac surgery performed at Flinders Medical Centre (FMC), South Australia, comparing cost by procedure, rheumatic valvular heart disease status, Aboriginality and location.
Results: Across all procedures, Northern Territory (NT) Aboriginal patients had a mean total cost of $78,506 which was $24,113 more than NT non-Aboriginal, $28,443 more than South Australian (SA) Aboriginal and $22,955 more than SA non-Aboriginal patients. The total cost of a patient undergoing a repeat sternotomy (re-operative procedure) was found to be significantly higher than a primary procedure ($85,797 versus $59,097). In patients undergoing valve surgery procedures, those identified with rheumatic heart disease had a higher mean total cost than those without (a difference of $25,094). Significantly, the rheumatic patient group showed a higher proportion of re-operative procedures (19% versus 5%).
Conclusions: The cost of treating NT Aboriginal cardiac surgical patients remotely has a significant financial impact upon the health care delivery system, as does the impact of rheumatic heart disease. This study found that the cost for the NT Aboriginal patient group was substantially higher than the NT non-Aboriginal, SA Aboriginal and SA non-Aboriginal patient groups. The additional cost to family and dislocation of social structures is not able to be calculated, but would also clearly weigh heavily on both patient groups. These findings suggest that future health funding models should recognise Aboriginality, remoteness and rheumatic heart disease.
ANZ J Surg. 2020;90(5):905-907. doi:10.1111/ans.15375
Outcomes of Redo Valve Surgery in Indigenous Australians.
Keenan NM, Newland RF, Baker RA, Rice GD, Bennetts JS.
Heart Lung Circ. 2018 Jul 30.
pii: S1443-9506(18)30728-5.
Background: Rheumatic heart disease often leads to valve surgery at a young age in our Indigenous population. Anticoagulation can be problematic and therefore repeat surgery to replace degenerated bioprosthetic valves is common. We sought to examine outcomes following redo valve surgery in this population.
Results: Redo patients had a median age of 29.5 years (IQR 24, 44), 59% were female, and they had significant comorbidities. The 30-day mortality in this cohort was 6% (EuroSCORE II 3.57), and they had significant morbidity. The median time to repeat surgery in those who had previous mitral valve surgery was 6.3 years, with no difference between mitral valve repair or replacement at the index procedure. Compared to non-Indigenous patients undergoing redo valve surgery, the Indigenous patients were significantly younger with higher left ventricular function but a greater proportion of pulmonary hypertension. There were no significant differences in short-term outcomes. Compared to Indigenous patients undergoing primary valve surgery, the Indigenous redo patients were significantly younger with more co-morbidities. There was no difference in 30-day mortality, but the redo patients did have significantly greater resource utilisation (increased hospital and intensive care unit (ICU) lengths of stay, ventilation and blood transfusion), and poorer long-term survival.
Conclusions: Indigenous patients presenting for redo valve surgery represent a complex and comorbid group of patients, with outcomes worse than expected in a young population, albeit comparable within study groups. Time from original surgery was short at 6 years, and thus a strategy must be in place in terms of planning future surgeries in this cohort of predominantly young rheumatic heart disease patients.
Nucifora G, Tantiongco JP, Crouch G, Bennetts J, Sinhal A, Tully PJ, Bradbrook C, Baker RA, Selvanayagam JB.
Int J Cardiol. 2017 Feb 1;228:184-190. doi: 10.1016/j.ijcard.2016.11.200. Epub 2016 Nov 9.
Background: Left ventricular (LV) mechanics are impaired in patients with severe aortic stenosis (AS). The aim of the present study was to assess their changes early and late after trans-catheter aortic valve implantation (TAVI) and surgical aortic valve replacement (AVR) using cardiac magnetic resonance (CMR) tissue-tracking imaging.
Results: The TAVI and surgical AVR groups were similar with respect to baseline (p=0.14) and early post-procedure (p=0.16) LV ejection fraction. However, baseline LV GLS was significantly impaired in TAVI patients compared to surgical AVR patients (p=0.025). Early post-procedure, TAVI resulted in a significant improvement of LV GLS (p=0.003), while a significant worsening of LV GLS was observed early after surgical AVR (p=0.012). At longer term follow-up, both TAVI and surgical AVR groups experienced a significant reduction of LV mass and a significant improvement of LV myocardial mechanics in all the three directions.
Conclusions: Treatment-specific differences in the changes of LV myocardial mechanics early after afterload release by TAVI and surgical AVR are present. Later, both interventions are associated with an improvement of LV myocardial deformation, alongside a regression of LV hypertrophy.
Markman PL, Tantiongco JP, Bennetts JS, Baker RA.
Heart Lung Circ. 2017;26(8):833-839. doi:10.1016/j.hlc.2016.09.017
Background: Postoperative serum troponin levels and perioperative myocardial infarction (MI) rates correlate with mortality and morbidity following cardiac surgery. The objective of this study was to document the release profile of high sensitivity troponin T (hsTnT) following different cardiac operations.
Results: There were 10 patients in the on-pump coronary artery bypass group and 5 each in the remaining groups (off-pump coronary artery bypass, open aortic valve replacement, transcutaneous aortic valve implantation and mitral valve replacement). Five additional patients were excluded due to perioperative MI or renal failure. Median [range] of peak hsTnT was 241[99-566], 64[50-136], 353[307-902], 115[112-275], and 918[604-1166] ng/L, respectively. Operations with the lowest peak hsTnT values peaked earliest (four hours) while those with highest values peaked latest (eight hours).
Conclusion: After cardiac surgery, the hsTnT profile peaks four to eight hours after the initial surgical insult. The magnitude and timing of the peak correlates to the expected degree of surgically-induced myocardial injury.
Russell EA, Walsh WF, Tran L, Tam R, Reid CM, Brown A, Bennetts JS, Baker RA, Maguire GP.
Int J Cardiol. 2017;227:100-105. doi:10.1016/j.ijcard.2016.11.070
Background: Atrial fibrillation (AF) is the most common preoperative arrhythmia in heart valve surgery patients and its prevalence is rising. This study aims to investigate the impact of AF on valve surgery early complications and survival and on valve disease of different aetiologies and populations with particular reference to Indigenous Australians with rheumatic heart disease (RHD).
Results: Outcome of 1594 RHD and 19,029 non-RHD-related surgical procedures was analysed. Patients with preoperative AF were more likely to be older, female, Indigenous, to have RHD and to bear a greater burden of comorbidities. Patients with RHD and preoperative AF had a longer hospital stay and were more likely to require reoperation. Adjusted short (OR 1.4, 95% CI 1.2-1.7) and long term (HR 1.5, 95% CI 1.3-1.7) survival was inferior for patients with non-RHD preoperative AF but was no different for Indigenous and non-Indigenous Australians with RHD.
Conclusions: In this prospective Australian study, patients with valve disease and preoperative AF had inferior short and long term survival. This was particularly the case for patients with non-RHD valve disease. Earlier intervention or more aggressive AF management should be investigated as mechanisms for enhancing postoperative outcomes. This may influence treatment choice and the need for ongoing anticoagulation.
Russell EA, Baker RA, Bennetts JS, Brown A, Reid CM, Tam R, Tran L, Walsh WF, Maguire GP.
Int J Cardiol. 2016;221:144-151. doi:10.1016/j.ijcard.2016.06.179
Background: In Australia, it has been suggested that heart valve surgery, particularly for rheumatic heart disease (RHD), should be consolidated in higher volume centres. International studies of cardiac surgery suggest large volume centres have superior outcomes. However, the effect of site and surgeon caseload on longer-term outcomes for valve surgery has not been investigated.
Results: Outcomes associated with 20,116 valve procedures at 25 surgical sites and by 93 surgeons were analysed. Overall adjusted analysis showed increasing site and surgeon caseload was associated with longer ventilation, less reoperation, and more anticoagulant complications. Increasing surgeon caseload was also associated with less acute kidney injury. Adjusted 30-day mortality was not associated with the site or surgeon caseload. There was no consistent relationship between increasing site caseload and long term survival. The association between surgeon caseload and outcome demonstrated poorer adjusted survival in the highest volume surgeon group.
Conclusions: In this Australian study, the adjusted association between surgeon and site caseload was not simple or consistent. Overall larger volume sites or surgeons did not have superior outcomes. Mandating a particular site caseload level for valve surgery or a minimum number of procedures for individual surgeons, in an Australian context, cannot be supported by these findings.
Tully PJ, Baumeister H, Bennetts JS, Rice GD, Baker RA.
Int J Cardiol. 2016;206:44-50. doi:10.1016/j.ijcard.2016.01.015
Objectives: To report the 6-month longitudinal outcomes of routine depression screening in cardiac patients.
Results: By six-month follow-up, the depression screen-positive group was at a higher risk of MACE (adjusted odds ratio [OR] 2.16; 95% confidence interval [CI] .98-4.74). The depression screen-positive group was also at a higher risk of depressed mood (PHQ scores ≥10: adjusted OR 6.54; 95% CI 3.16-13.53). The depression screen-positive group also reported significantly poorer QOL in five domains (all p<.001 with Bonferroni correction). The depression screen-positive group was more likely to be initiated on antidepressant and anxiolytic (ORs 5.89 and 4.74 respectively) at follow-up. The number needed to screen to achieve one additional depression remission case was 9 in the screen-positive group (versus the depression-control group).
Conclusion: Depression screening was associated with an increase in psychotropic medication use however depression, morbidity, and quality of life remained poor at six months.
Abstract:
The effects of acute and chronic heart failure on pulmonary function are complex. In acute cardiogenic pulmonary oedema, lung elastance is increased, parallel to acute alveolar flooding and associated surfactant dysfunction. However, in compensated CHF lung elastance has been variably reported as normal, or increased, likely reflecting a complex interplay between pulmonary remodelling and surfactant function. Surface tension normally comprises 60–70% of elastic recoil and is largely determined by surfactant function which is influenced by both phospholipid and surfactant protein (e.g. SP-B) content and function. Surfactant phospholipid can be separated into large surface-active aggregates (LA) and less surface-active, small aggregates (SA).
Crouch G, Selvanayagam JB.
Quant Imaging Med Surg. 2016 Jun; 6(3): 259–273.
Abstract:
Degenerative aortic stenosis (AS) is the most common valvular disease in the western world with a prevalence expected to double within the next 50 years. International guidelines advocate the use of cardiovascular magnetic resonance (CMR) as an investigative tool, both to guide diagnosis and to direct optimal treatment. CMR is the reference standard for quantifying both left and right ventricular volumes and mass, which is essential to assess the impact of AS upon global cardiac function. Given the ability to image any structure in any plane, CMR offers many other diagnostic strengths including full visualisation of valvular morphology, direct planimetry of orifice area, the quantification of stenotic jets and in particular, accurate quantification of valvular regurgitation. In addition, CMR permits reliable and accurate measurements of the aortic root and arch which can be fundamental to appropriate patient management. There is a growing evidence base to indicate tissue characterisation using CMR provides prognostic information, both in asymptomatic AS patients and those undergoing intervention. Furthermore, a number of current clinical trials will likely raise the importance of CMR in routine patient management. This article will focus on the incremental value of CMR in the assessment of severe AS and the insights it offers following valve replacement.
Int J Cardiol. 2016;207:213-214. doi:10.1016/j.ijcard.2016.01.134
Dixon DL, Bersten AD, Lawrence MD, Bihari S, Crouch G, De Pasquale CG.
BMC Cardiovasc Disord. 2015;15:103. Published 2015 Sep 23. doi:10.1186/s12872-015-0094-1
Background: Globally, rheumatic heart disease (RHD) remains an important cause of heart disease. In Australia it particularly affects younger Indigenous and older non-Indigenous Australians. Despite its impact there is limited understanding of the factors influencing outcome following surgery for RHD.
Results: Outcome of 1384 RHD and 15843 non-RHD valve procedures was analysed. RHD patients had longer ventilation, experienced fewer strokes, and had more readmissions to hospital and anticoagulant complications. Mortality following RHD surgery at 30 days was 3.1 % (95 % CI 2.2 – 4.3), 5 years 15.3 % (11.7 – 19.5) and 10 years 25.0 % (10.7 – 44.9). Mortality following non-RHD surgery at 30 days was 4.3 % (95 % CI 3.9 - 4.6), 5 years 17.6 % (16.4 - 18.9) and 10 years 39.4 % (33.0 - 46.1). Factors independently associated with poorer longer-term survival following RHD surgery included older age (OR1.03/additional year, 95 % CI 1.01 – 1.05), concomitant diabetes (OR 1.7, 95 % CI 1.1 – 2.5) and chronic kidney disease (1.9, 1.2 – 2.9), longer invasive ventilation time (OR 1.7 if greater than median value, 1.1– 2.9) and prolonged stay in hospital (1.02/additional day, 1.01 – 1.03). Survival in Indigenous Australians was comparable to that seen in non-Indigenous Australians.
Conclusion: In a large prospective cohort study, we have demonstrated survival following RHD valve surgery in Australia is comparable to earlier studies. Patients with diabetes and chronic kidney disease were at a particular risk of poorer long-term survival. Unlike earlier studies we did not find pre-existing atrial fibrillation, being an Indigenous Australian or the nature of the underlying valve lesion were independent predictors of survival.
Russell, E. A., Tran, L., Baker, R. A., Bennetts, J. S., Brown, A., Reid, C. M., Tam, R., Walsh, W. F.,
& Maguire, G. P.
Crouch G, Tully PJ, Bennetts J, Sinhal A, Bradbrook C, Penhall AL, De Pasquale CG, Baker RA, Selvanayagam JB.
J Cardiovasc Magn Reson. 2015;17(1):32. Published 2015
May 8. doi:10.1186/s12968-015-0134-0
Background: Paravalvular aortic regurgitation (PAR) following transcatheter aortic valve implantation (TAVI) is well acknowledged. Despite improvements, echocardiographic measurement of PAR largely remains qualitative. Cardiovascular magnetic resonance (CMR) directly quantifies AR with accuracy and reproducibility. We compared CMR and transthoracic echocardiography (TTE) analysis of pre-operative and post-operative aortic regurgitation in patients undergoing both TAVI and surgical aortic valve replacement (AVR).
Results: Pre- and post-operative left ventricular ejection fraction (LVEF) was similar. Post-procedure aortic regurgitant fraction using CMR was higher in the TAVI group (TAVI 16 ± 13% vs. AVR 4 ± 4%, p < 0.01). Comparing CMR to TTE, 27 of 56 (48%) TAVI patients had PAR which was at least one grade more severe on CMR than TTE (Z = -4.56, p <0.001). Sensitivity analysis confirmed the difference in PAR grade between TTE and CMR in the TAVI group (Z = -4.49, p < 0.001).
Conclusion: When compared to CMR based quantitative analysis, TTE underestimated the degree of paravalvular aortic regurgitation. This underestimation may in part explain the findings of increased mortality associated with mild or greater AR by TTE in the PARTNER trial. Paravalvular aortic regurgitation post TAVI assessed as mild by TTE may in fact be more severe.
Crouch G, Bennetts J, Sinhal A, Tully PJ, Leong DP, Bradbrook C, Penhall AL, De Pasquale CG, Chakrabarty A, Baker RA, Selvanayagam JB.
J Thorac Cardiovasc Surg. 2015;149(2):462-470. doi:10.1016/j.jtcvs.2014.10.064
Objectives: There remains a paucity of mechanistic data on the effect of transcatheter aortic valve implantation (TAVI) on early left and right ventricular function and quantitative aortic valve regurgitation. We sought to assess and compare the early effects on myocardial function and aortic valve hemodynamics of TAVI and aortic valve replacement (AVR) using serial cardiovascular magnetic resonance (CMR) imaging and echocardiography.
Results: Groups were similar with respect to Society of Thoracic Surgeons score (TAVI, 7.7 vs AVR, 5.9; P = .11). Preoperative left ventricular (TAVI, 69% ± 13% vs AVR, 73% ± 10%; P = .10) and right ventricular (TAVI, 61% ± 11% vs AVR, 59% ± 8%; P = .5) ejection fractions were similar. Postoperative left ventricular ejection fraction was preserved in both groups. In contrast, decline in right ventricular ejection fraction was more significant in the TAVI group (61%-54% vs 59%-58%; P = .01). Postprocedure aortic regurgitant fraction was significantly greater in the TAVI group (16% vs 4%; P = .001), as was left atrial size (110 vs 84 mL; P = .02). Further analysis revealed a significant relationship between the increased aortic regurgitant fraction and greater left atrial size (P = .006), and a trend toward association between the decline in right ventricle dysfunction and increased postprocedure aortic regurgitation (P = .08).
Conclusions: There was no significant difference in early left ventricular systolic function between techniques. Whereas right ventricle systolic function was preserved in the AVR group, it was significantly impaired early after TAVI, possibly reflecting a clinically important pathophysiologic consequence of paravalvular aortic regurgitation.
Tully PJ, Roshan P, Rice GD, Sinhal A, Bennetts JS, Baker RA.
J Geriatr Cardiol. 2015;12(1):30-36. doi:10.11909/j.issn.1671-5411.2015.01.004
Objective: To determine the extent to which differences in generic quality of life (QOL) between transcatheter aortic valve implantation (TAVI) and surgical aortic valve replacement (AVR) patients explained by EuroSCORE and heart-team operability assessment.
Results: The AVR group required longer ventilation (> 24 h) (TAVI 5.0% vs. AVR 20.6%, P = 0.004) and more units of red blood cells [TAVI 0 (0-1) vs. AVR 2 (0-3), P = 0.01]. New renal failure was higher in TAVI (TAVI 5.0% vs. AVR 0%, P = 0.06). TAVI patients reported significantly lower vitality (P = 0.01) by comparison to AVR patients, however these findings were no longer significant after adjustment for operability. In both procedures, clinically significant QOL improvement was common [range 25.0% (general health) - 62.9% (physical role)] whereas deterioration in QOL occurred less frequently [range 9.3% (physical role) - 33.3% (mental health)].
Conclusions: Clinically significant improvement and deterioration in QOL were evident at six months in high risk elderly aortic valve replacement patients. Overall QOL did not differ between TAVI and AVR once operability was taken into consideration.
Prakash R, Crouch G, Joseph MX, Bennetts J, Selvanayagam JB, Sinhal A.
JACC Cardiovasc Interv. 2014;7(2):e13-e15. doi:10.1016/j.jcin.2013.06.019
Case Study
A 74-year-old man presented to our center with acute pulmonary edema. This was in the context of a transfemoral transcatheter aortic valve replacement (TAVR) with a 26-mm Sapien XT valve (Edwards Lifesciences, Irvine, California), 63 days before. Mild paravalvular regurgitation (PVR) had been noted both immediately after the procedure and before discharge on day 3, which remained unchanged on transthoracic echocardiography (TTE) on day 20.
Transcatheter aortic valve dislocation, albeit a rare phenomenon, has been documented both early (<7 days) and late (>30 days), but no incidences as delayed as this case have been reported. The mechanism of the late transcatheter aortic valve displacement resulting in severe PVR, in this case, was likely a combination of under-sizing of the valve, the relative nonuniformity, and the paucity of annular calcification. A single imaging modality to assess the annulus was used then with 2-dimensional TEE, which may have underestimated the annular dimensions. The current practice of using complementary imaging modalities such as 2-dimensional TEE and multislice computed tomography will provide a more accurate assessment of annular dimensions and degree of calcification, aiding in better valve size selection.
Russell EA, Tran L, Baker RA, Bennetts JS, Brown A, Reid CM, Tam R, Walsh WF, Maguire GP.
BMC Cardiovasc Disord. 2014;14:134. Published 2014 Oct 2. doi:10.1186/1471-2261-14-134
Background: Globally, rheumatic heart disease (RHD) remains an important cause of heart disease. In Australia, it particularly affects older non-Indigenous Australians and Aboriginal Australians and/or Torres Strait Islander peoples. Factors associated with the choice of treatment for advanced RHD remain variable and poorly understood.
Results: Surgical management of 1384 RHD and 15843 non-RHD valve procedures was analysed. RHD patients were younger, more likely to be female and Indigenous Australian, to have atrial fibrillation (AF) and previous percutaneous balloon valvuloplasty (PBV). Surgery was performed on one valve in 64.5%, two valves in 30.0%, and three valves in 5.5%. Factors associated with receipt of mechanical valves in RHD were AF (OR 2.69) and previous PBV (OR 1.98) and valve surgery (OR 3.12). Predictors of valve repair included being Indigenous (OR 3.84) and having fewer valves requiring surgery (OR 0.10). Overall there was a significant increase in the use of mitral bioprosthetic valves over time.
Conclusions: RHD valve surgery is more common in young, female, and Indigenous patients. The use of bioprosthetic valves in RHD is increasing. Given many patients are female and younger, the choice of valve surgery and the need for anticoagulation has implications for future management of RHD and related morbidity, pregnancy, and lifestyle plans.
Varzaly J, Chaudry J, Crouch G, Edwards J.
Heart Lung Circ. 2014;23(3):e77-e79. doi:10.1016/j.hlc.2013.08.004
Introduction: The management of complex aortic aneurysms and dissections involving both the aortic arch and descending aorta include operations associated with significant risks of mortality and morbidity. The advent of hybrid systems such as the E-VITA Jotec open hybrid stent graft system (E-VITA) provides the advantage of single stage repair with follow up repair of any remaining downstream aneurysm and dissection being easier to manage.
Results: The average patient age was 66.9 years of age (range: 55-78 years). The average cardiopulmonary bypass and circulatory arrest times were 237.14 min and 47.83 min. There was one operative mortality. Follow up as far as three years revealed good results with few complications.
Conclusion: The E-VITA is a feasible management option in the treatment of complex aortic aneurismal disease and dissections. It allows treatment of patients that may have previously not been considered suitable for two-stage surgical procedure.
Tully PJ, Aty W, Rice GD, Bennetts JS, Knight JL, Baker RA.
Ann Thorac Surg. 2013;96(3):844-850. doi:10.1016/j.athoracsur.2013.04.075
Background: The clinical effects of prosthesis-patient mismatch (PPM) after aortic valve replacement, with respect to morbidity and survival, remain controversial, particularly in high-risk patient subgroups.
Results: Prosthesis-patient mismatch was classified as severe (92 of 1,060; 8.7%), moderate (440 of 1,060; 41.5%), or absent (528 of 1,060; 49.8%). Moderate and severe PPM were unrelated to in-hospital morbidity or mortality. There were 440 deaths (41.5%) at 5.6 years median follow-up (interquartile range, 2.9 to 9.1). Trend toward poorer survival according to PPM group (χ2=5.46; p=0.07) was attenuated further with covariate adjustment. Sensitivity analyses demonstrated discrete mortality effects for moderate PPM in association with concomitant coronary artery bypass grafting, impaired left ventricular function, and older age (significant hazard ratios range, 1.05 to 1.57). Severe PPM also increased mortality risk in association with older age, concomitant coronary artery bypass grafting, and New York Heart Association Class III or IV (significant hazard ratios range, 1.06 to 2.65).
Conclusions: Prosthesis-patient mismatch was not associated with mortality in covariate-adjusted models. However, a discrete mortality risk was attributable to moderate and severe PPM in patients of older age, or those with left ventricular dysfunction, New York Heart Association class III or IV, and concomitant coronary artery bypass grafting.
Penhall, A. Perry, R. Crouch, G. Judd, Selvanayagam J.
Background: Two-dimensional speckle tracking echocardiography (2D STE) has been widely used as a clinical and research tool in assessing myocardial strain. Recent advances in probe technology and software now allow us to assess this deformation from a 3D dataset. This allows the measurement of myocardial strain of the whole left ventricle instead of selected 2D slices. We sought to compare global longitudinal strain (GLS) using the novel 3D STE to the widely validated 2D STE as well as the time required for analysis in a population of patients with pathological left ventricular hypertrophy.
Results: There was no significant difference between 3D GLS and 2D GLS values (p = 0.51). Time taken for 3D analysis was significantly longer than 2D analysis (209.8 ± 37.4 s vs. 104.9 ± 17.8 s, p < 0.0001). 3D GLS inter and intraobserver variability were both 2%. 2D GLS inter and intraobserver variability was 4% and 5% respectively. Out of a possible 18 datasets, all were able to be analysed using 3D analysis compared to 14 using AFI method.
Conclusion: Three-dimensional GLS is a feasible and reproducible technique, more so than standard 2D STE. Although analysis time is slightly longer it is able to analyse more segments than 2D GLS and gives additional information such as LV volumes, ejection fraction, as well as circumferential, radial and area strain in the one analysis.
Prabhu A, Tully PJ, Bennetts JS, Tuble SC, Baker RA.
Heart Lung Circ. 2013;22(8):599-605. doi:10.1016/j.hlc.2013.01.003
Background: Though Indigenous Australian peoples reportedly have poorer survival outcome after cardiac surgery, few studies have jointly documented the experience of major morbidity, and considered the influence of patient geographic remoteness.
Results: The 297 Indigenous Australian patients (10.8% of total) had greater odds for total morbidity (adjusted odds ratio = 1.55; 95% confidence interval [CI] 1.04-2.30) and prolonged ventilation (adjusted odds ratio = 2.08; 95% confidence interval [CI] 1.25-3.44) in analyses adjusted for propensity deciles and geographic remoteness. With a median follow-up of 7.5 years (interquartile range 5.2-10.2), Indigenous Australian patients were found to experience 30% greater mortality risk (unadjusted hazard ratio = 1.30; 95% CI: 1.03-1.64, p = 0.03). The effect size strengthened after adjustment for propensity score (adjusted hazard ratio = 1.49; 95% CI: 1.13-1.96, p = .004). Adjustment for ARIA categorisation strengthened the effect size (adjusted HR = 1.54 (95% CI: 1.11-2.13, p = .009).
Conclusion: Indigenous Australian peoples were at greater risk for prolonged ventilation and combined morbidity outcome, and experienced poorer survival in the longer term. Higher mortality risk among Indigenous Australians was evident even after controlling for remoteness and accessibility to services.
Xu RB, Crouch G, Jurisevic C, Stuklis RG.
J Thorac Cardiovasc Surg 2013 Jun;145(6):e64-5. doi: 10.1016/j.jtcvs.2013.02.029.
A 71-year-old man presented with ongoing expectoration of milky, foul-tasting sputum, while denying any systemic symptoms. He first presented in 2007 with a type B dissection with an aneurysmal complex. He underwent distal aortic arch repair via a left anterolateral thoracotomy approach with femoral-femoral bypass via percutaneous cannulas. The distal aortic arch was transected and a 26-mm Dacron graft was sutured, with a distal anastomosis formed below the pulmonary hilum to the distal descending thoracic aorta.
Conclusions
Iatrogenic injury to the thoracic duct is not an uncommon consequence of thoracic cavity surgery. We present a case of such an injury after a distal aortic arch repair, with persistent chylothorax and chyloptysis as a consequence. Although the preference of the original treating surgeon was to attempt surgical correction via redo thoracotomy, in this case, right-assisted video-assisted thoracoscopy duct ligation was used as a successful conclusive treatment modality. Because video-assisted thoracic surgery has relatively low morbidity and cost, earlier use of this approach is supported by the literature.
Tully PJ, Cardinal T, Bennetts JS, Baker RA.
Heart Lung Circ. 2012;21(4):206-214. doi:10.1016/j.hlc.2011.12.002
Background: No Australian study has reported the association between selective-serotonin reuptake inhibitor (SSRI) and serotonin noradrenaline reuptake inhibitor (SNRI) with coronary artery bypass graft (CABG) surgery morbidity and mortality.
Results: Median follow-up was 4.7 years (interquartile range, 2.3-7.9 years) and there were 727 deaths (17.6% of total). Use of SSRI/SNRI was associated with new requirement for renal dialysis (adjusted OR = 2.18; 95% CI, 1.06-4.45, p = .03) and ventilation >24h (adjusted OR = 1.69; 95% CI, 1.03-2.78, p = .04). Neither SSRI/SNRI use nor SSRI/SNRI and concomitant anti-platelet medication increased the odds for any bleeding events (all p>.20). No association was evident with all-cause mortality (adjusted hazard ratio = 1.60; 95% CI .59-4.35, p = .36), or cardiac mortality (adjusted hazard ratio = .31; 95% CI, .04-2.26, p = .25).
Conclusions: SSRI/SNRI users experienced an increased risk of renal dysfunction and prolonged ventilation, but not bleeding events or long-term mortality after CABG surgery.
Ritwick B, Chaudhuri K, Crouch G, Edwards JR, Worthington M, Stuklis RG.
Minim Invasive Surg. 2013;2013:679276. doi:10.1155/2013/679276
Abstract
Since its early days, cardiac surgery has typically involved large incisions with complete access to the heart and the great vessels. After the popularization of the minimally invasive techniques in general surgery, cardiac surgeons began to experiment with minimal access techniques in the early 1990s.
Although the goals of minimally invasive cardiac surgery (MICS) are fairly well established as decreased pain, shorter hospital stay, accelerated recuperation, improved cosmesis, and cost-effectiveness, a strict definition of minimally invasive cardiac surgery has been more elusive.
Minimally invasive cardiac surgery started with mitral valve procedures and then gradually expanded towards other valve procedures, coronary artery bypass grafting, and various types of simple congenital heart procedures. In this paper, the authors attempt to focus on the evolution, techniques, results, and the future perspective of minimally invasive mitral valve surgery (MIMVS).
Edwards J, Mazzone A, Crouch G.
J Extra Corpor Technol. 2012;44(1):P51-P54.
Abstract
The introduction of any new surgical technique is fraught with dangers and difficulties, and in cardiac surgery, these potential negative outcomes are magnified by inherent small margins for error. Buxton's law states that it is always too early for rigorous evaluation (of a new technique) until, unfortunately, it is suddenly too late
(1). This insightful statement was used to describe the phenomenon to often seen in the introduction of new technologies or procedures in medicine. There is a natural reluctance to subject new techniques to standardized assessment too early in the introductory phase in an attempt to avoid negatively biased results while operator learning is still occurring
(2). Over the last two or three decades, this phenomenon has been described as the learning curve and has most often been applied to minimally invasive surgery of all specialties, including general surgery, gynecology, and cardiothoracic surgery. Buxton's concern was justified, because by the time the procedure has become well-practiced, there is a reluctance to subject it to rigorous trials on the argument that this will deny the latest, and perhaps greatest, treatment to patients. Whereas each argument, pre-emptive assessment, or delaying access is valid in isolation, the combination is a dangerous system to follow because it prevents rigorous evaluation and denies best practice.
Tully PJ, Bennetts JS, Baker RA, McGavigan AD, Turnbull DA, Winefield HR.
Heart Lung. 2011;40(1):4-11. doi:10.1016/j.hrtlng.2009.12.010
Objective: We sought to determine whether preoperative and postoperative anxiety, depression, and stress symptoms were associated with atrial fibrillation (AF) after cardiac surgery.
Results: Fifty-six (24.8%) patients manifested incident AF, and they spent more days in hospital (mean [M], 7.3; standard deviation [SD], 4.6) than patients without AF (M, 5.5; SD, 1.4; P < .001). No baseline psychological predictors were associated with AF. When postoperative distress measures were considered, anxiety was associated with increased odds of AF (odds ratio, 1.09; 95% confidence interval, 1.00 to 1.18; P = .05). This analysis also showed that age was significantly associated with AF (odds ratio, 1.07; 95% confidence interval, 1.03 to 1.12; P < .001). Analyses specific to the symptomatic expression of anxiety indicated that somatic (ie, autonomic arousal) and cognitive-affective (ie, subjective experiences of anxious affect) symptoms were associated with incident AF.
Conclusion: Anxiety symptoms in the postoperative period were associated with AF. Hospital staff in acute cardiac care and cardiac rehabilitation settings should observe anxiety as related to AF after cardiac surgery. It is not clear how anxious cognitions influence the experience of AF symptoms, and whether symptoms of anxiety commonly precede AF.
G. Crouch, P. G. Devitt, S. K. Thompson
Diseases of the Esophagus, Volume 24, Issue 3, 1 April 2011, Pages 145–146
Summary
Progressive dysphagia of unknown etiology may still provide a diagnostic challenge despite an increase in the number and quality of investigations available. We describe a 64-year-old man who presented with progressive dysphagia and weight loss. Following a number of investigations, a diagnosis of diffuse esophageal leiomyomatosis was made and the patient was treated appropriately.
Andrew MJ, Baker RA, Bennetts J, Kneebone AC, Knight JL.
ANZ J Surg. 2002;72(2):105-109. doi:10.1046/j.1445-2197.2002.02317.x
Objective: To compare the incidence of neuropsychologic deficits 1 week and 6 months after coronary artery bypass graft (CABG) surgery (extracardiac) and valve surgery with or without CABG surgery (intracardiac) using reliable change indices to define the incidence of neuropsychologic deficits.
Design: Prospective study.
Setting: Cardiac surgical unit in a university teaching hospital.
Participants: Patients scheduled for elective multiple-graft (> or =3 grafts) CABG surgery (n = 59), or elective valve surgery (with or without concomitant CABG surgery) (n = 50) and a matched sample of nonsurgical controls (n = 53).
Interventions: Neuropsychologic assessments were performed 1 day before surgery, 7 days and 6 months after surgery.
Measurements and main results: The 7-day assessment showed no significant differences between valve surgery patients and CABG surgery patients in the incidence of neuropsychologic deficits. When reassessed 6 months postoperatively, the valve group displayed a significantly higher incidence of deficits on the digit symbol test compared with the CABG group (valve 26.7% v CABG 6.8%). In the CABG group, there was a significant change in the incidence of deficits per patient from 7 days to 6 months (p = 0.03) that was not evident in the valve group.
Conclusion: There are some differences in the neuropsychologic outcome of extracardiac and intracardiac surgery. Patients undergoing isolated CABG surgery showed a greater reduction in the incidence of persisting deficits at 6 months than patients undergoing valve surgery with or without CABG surgery. This finding warrants further investigation, with particular attention to patients undergoing combined valve and coronary artery procedures.
Bennetts JS, Baker RA, Ross IK, Knight JL.
ANZ J Surg. 2002;72(2):105-109. doi:10.1046/j.1445-2197.2002.02317.x
Purpose: The present study was undertaken to assess the degree of myocardial injury, using troponin T (TnT), in off-pump coronary artery surgery (OPCAB) and in a comparable patient group undergoing conventional coronary artery graft surgery (CABG).
Results: The OPCAB group had significantly greater Canadian Heart Classification 3 patients (P = 0.003); however, other demographic data were similar between the two groups. All patients had normal TnT at initial sampling. The mean number of grafts in each group was 1.8 +/- 0.6 for OPCAB and 1.9 +/- 0.3 for CABG (P = NS). There were two new Q wave myocardial infarctions in the CABG group and none in the OPCAB group. These cases were excluded from biochemical analyses. Troponin T release was significantly less in the OPCAB group at 12 and 24 h (P < 0.001 and P = 0.03, respectively). Peak TnT release occurred at 6-8 h in both groups. Troponin T release was significantly lower in the OPCAB group at 2, 4, 6, 8, 10 and 12 h (P = 0.01, P = 0.03, P = 0.02, P = 0.02, P = 0.03 and P = 0.04, respectively). Postoperatively, the OPCAB group required less blood transfusion (P = 0.02).
Conclusions: The OPCAB group demonstrated a significantly reduced TnT release profile compared with the CABG group.
Bennetts JS, Arnolda LF, Cullen HC, Knight JL, Baker RA, McKitrick DJ.
Clin Exp Pharmacol Physiol. 2001;28(9):768-772. doi:10.1046/j.1440-1681.2001.03522.x
Abstract:
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Evidence suggesting the presence of coronary artery baroreceptors on coronary arteries has existed for over 30 years.
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Evidence that activation of ventricular mechanoreceptors can elicit cardiovascular changes has been challenged, with those changes now thought to be due to coronary artery mechanoreceptors.
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Studies have suggested that coronary artery mechanoreceptors act as coronary baroreceptors with a role in cardiovascular regulation. However, all evidence to date has been obtained in anaesthetized animal models in physiologically compromised intra-operative states.
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The purpose of the present study was to design an ovine model that would allow the discrete stretch of coronary arteries without causing ischaemia or changing flow or intra-arterial pressure and that would confirm results seen in previous studies. In addition, the possibility that the technique could be used for studies of coronary artery baroreflexes in conscious sheep was investigated.
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Controlled stretch of the proximal left anterior descending coronary artery elicited decreases in arterial pressure without changes in heart rate or electrocardiographic activity in halothane-anaesthetized sheep. Similar results were demonstrated in conscious sheep after surgical recovery of up to 2 weeks.
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The present study supports the possibility that coronary artery baroreceptors exist and likely have a role in cardiovascular regulation. The results of the present study in anaesthetized sheep are in agreement with previous results in anaesthetized animals, but also provide the first demonstration of coronary baroreceptor activity in a conscious animal model, underscoring the potential use of the model in the study of coronary artery baroreceptors in the intact animal.