- Email: [email protected]
Canadian Society of Cardiac Surgeons (CSCS) CSCS410 Oral: Let's Have Some Fun! Tuesday, October 26, 2010
Abstracts
608
NEONATAL HYPOXIA IS ASSOCIATED WITH LASTING CHANGES IN LEFT VENTRICULAR SURVIVAL SIGNALLING AND CARDIOMYOCYTE CALCIUM HANDLING IN THE ADULT RAT D Del Duca, A Tadevosyan, F Karbassi, D Rodaros, BG Allen, S Nattel, CI Tchervenkov, TE Hébert, CV Rohlicek Montréal, Québec BACKGROUND: The growing population of adults with repaired cyanotic congenital heart disease remains at significant risk of impaired cardiac health, the need for cardiac reoperation, and premature death. We have previously demonstrated that hypoxia in early life causes lasting changes in left ventricular structure and function, as well as decreased cardiomyocyte survival following ischemic stress, in the adult rat. The objective of this study was to characterize the mechanisms underlying this myocardial vulnerability. We hypothesized that neonatal hypoxia is associated with lasting changes in cardioprotective regulatory and signalling events which may influence cardiomyocyte resistance to physiological stress in later life. CONCLUSION: Neonatal hypoxia is associated with significant alterations in ERK1/2 and AKT signalling pathways known to have important cardioprotective functions in the context of physiological stress. Decreased expression of HK II, a key metabolic enzyme that also mediates antiapoptotic AKT activity, was also observed. Finally, hypoxic stress in early life results in lasting changes in calcium handling which may negatively influence diastolic function and predispose the cardiomyocyte to stressinduced calcium toxicity. These observations may have pathophysiological implications for the growing population of adults with repaired or palliated cyanotic congenital heart disease.
Featured Research 609
PRODUCTION OF DONOR SPECIFIC ISOHEMAGGLUTININS FOLLOWING ABO-INCOMPATIBLE PEDIATRIC HEART TRANSPLANTATION J Conway, C Manlhiot, T Allain-Rooney, BW McCrindle, AI Dipchand Toronto, Ontario Pediatric ABO-Incompatible (ABO-I) heart transplant (HTx) recipients are capable of long-term acceptance of their grafts with excellent short and intermediate outcomes. Graft acceptance has been thought to be the result of donor specific B-cell elimination with a lack of detectable donor-specific blood group isohemagglutinins. Recent reports have now described patients who do produce donor-specific isohemagglutinins following an ABO-I HTx. The aims of this study were to determine the pattern, risk factors for, and clinical consequences of donor-specific isohemagglutinin development following ABO-I HTx. Almost one-third of infants undergoing ABO-I heart transplantation develop donor-specific isohemagglutinins. The only impact on clinical outcomes observed was a tendency towards a higher maximum grade of cellular rejection in those patients that produced donor-specific isohemagglutinins. However, there was no increased risk of antibody mediated rejection, graft loss or death. This pilot data clearly points to mechanisms other than B cell elimination as the explanation for continual graft acceptance in this patient population and emphasizes the need for further research into the possible mechanisms of graft accommodation in this patient population. Finally, the novel observation of differential responses and risk factors for development of antibodies to A versus B blood group antigens warrants further study.
118D
Canadian Society of Cardiac Surgeons (CSCS) CSCS410 Oral LET’S HAVE SOME FUN! Tuesday, October 26, 2010 612
TWENTY-FOUR HOUR CONSULTANT HYBRID ICU: ADDRESSING THE NEEDS OF PATIENTS POST-CARDIAC SURGERY KK Kumar, B Hiebert, R Zarychanski, H Grocott, RK Singal, RA Manji, AH Menkis, RC Arora Winnipeg, Manitoba The majority of patients following cardiac surgery are admitted to a Level I intensive care unit (ICU). Despite recommendations for 24-hour intensivist staffing models for Level I institutions, few Canadian centers have adopted this practice as an association between patient outcomes and ICU staffing model is unclear. Furthermore, a dichotomous surgical population exists, each with distinct requirements. Firstly, low-risk, “fast-track” patients, and secondly, higher-risk, multi-system issue patients who may benefit from focused 24-hour intensivist coverage. We sought to assess the impact of a hybrid (intensivist and cardiac anesthesiologist) ICU, with 24-hour consultant coverage, on outcomes in these two patient cohorts. As the “typical” patient undergoing cardiac surgery continues to evolve, our approach to their post-operative management also needs to adapt. A hybrid 24-hour consultant staffed ICU represents a novel approach to the management of complex post-cardiac surgical patients and is in keeping with the latest recommendation for Level I ICUs. With the presence of a dedicated cardiac anesthesiologist in addition to 24-hour intensivist coverage, our CICU model of care was associated with a reduction in blood products transfused, mechanical ventilation, and hospital length-of-stay in both the low and high-risk cohorts. Mortality within the ICU setting remains difficult to study, and will require larger multi-center collaborations.
613
LATE AORTIC ROOT BIOMECHANICS FOLLOWING DIFFERENT AORTIC ROOT REPLACEMENT OPERATIONS I El-Hamamsy, R Torii, S Babu-Narayan, P Kilner, MH Yacoub London, United Kingdom BACKGROUND: Aortic root biomechanics play an important role in long-term valvular and ventricular function. The objectives of this study were to evaluate late aortic root biomechanics following autograft, homograft and xenograft aortic root replacement, and compare them to healthy subjects. CONCLUSION: Autograft aortic root replacement (the Ross procedure) preserves late aortic root biomechanics better than xenograft or homograft root replacement. This is likely due to the long-term viability of the aortic root following the Ross procedure. These findings could have important clinical implications and help explain the better durability and survival advantage following the Ross procedure. Canadian Institutes of Health Research (CIHR)
614
SUCCESSFUL WEANING AND EXPLANTATION OF IMPLANTABLE VENTRICULAR ASSIST DEVICES AFTER RECOVERY OF MYOCARDIAL FUNCTION Y Lamarche, MJ Kearns, H Shayan, A Kaan, A Cheung Vancouver, British Columbia BACKGROUND: Ventricular assist devices (VADs) are used in cases of heart failure refractory to medical therapy. Most VADs are used as a bridge to heart transplantation, however, in certain cases, the myocardial function recovers and VADs can be weaned and explanted. The objectives of this study were to describe patients that required VAD insertion, followed by myocardial recovery and explantation in a quaternary heart center. The type of support used and post-explant outcomes are also reported.
Can J Cardiol Vol 26 Suppl D October 2010
Abstracts CONCLUSION: Patients requiring VAD support for myocardial failure can undergo significant reverse remodeling in a broad spectrum of cardiomyopathies. When it occurs, VAD explantation can lead to optimal outcome with minimal morbidity. Methods for assessment of reverse remodeling, weaning protocol and optimal timing of explantation remain controversial. Better understanding of the mechanism of reverse remodeling and aggressive screening may identify patients who are candidates for bridge to recovery.
615
USING DISCRETE EVENT SIMULATION TO UNDERSTAND AND TO IMPROVE THE FLOW OF PATIENTS THROUGH A CARDIAC SURGERY UNIT MZ Tong, V Padiyar, RJ Novick London, Ontario Between 2006 and 2009, our cardiac surgery unit has experienced an increased number of cancelled cases due to unavailability of an adequate number of beds. Strategies have been proposed to minimize cancellations, but there are no quick methods to evaluate these strategies. Discrete event simulation (DES) is used to forecast and optimize processes in many industries but its usage in health-care is limited. We built a DES model of the flow of patients through our unit to identify the bottlenecks to patient flows and to test different strategies to alleviate them. We found that, the main bottleneck to patient flow is the availability of ward beds, however this can change between the CSRU and ward daily depending on the day’s case volume, the number of CSRU patients, the number of ward patients, patient’s expected LOS and the off-service patient load. Strategy 1 decreased case cancellation by 34% when the bottleneck to flow was the ward. Strategy 2 decreased case cancellations by 25% when the bottleneck was the CSRU. Strategy 3 identified that we would need 36 dedicated ward beds to minimize cancellations. Discrete event simulation allowed us to gain insights on the causes of case cancellations and allowed us to test strategies rapidly and prior to clinical implementation to alleviate the bottlenecks to patient flows.
616
CLINICAL AND ECHOCARDIOGRAPHIC OUTCOMES FOLLOWING TRICUSPID VALVE REPLACEMENT: AN EXPERIENCE OF 134 PATIENTS G Marquis Gravel, D Bouchard, LP Perrault, P Pagé, P Demers, NC Poirier, Y Hébert, M Carrier, R Cartier, H Jeanmart, M Pellerin Montréal, Québec BACKGROUND: Tricuspid valve disease often presents as functional regurgitation, and occurs as a consequence of left-sided valve disease, pulmonary hypertension, and right ventricular dilatation. Repair of the tricuspid valve is usually sufficient for correcting regurgitation. Organic involvement of the tricuspid valve does not occur frequently, but usually mandates tricuspid valve replacement (TVR) when present. This procedure is seldom performed in the clinical practice, therefore outcomes following TVR are not well defined. The objectives of this study were to describe a cohort of patients undergoing TVR, and to assess echocardiographic and clinical outcomes following such procedure. CONCLUSION: Even though operative mortality associated with TVR improved through the years, this procedure is still associated with a substantial operative mortality rate, particularly in patients with important tricuspid stenosis, high pulmonary pressure, and those with a concomitant valve procedure. However, TVR should still be performed because it is associated with significant improvement of the NYHA functional class and of tricuspid regurgitation severity. When TVR is considered, it should be performed as early as possible in the course of the disease, before markers of late mortality develop or worsen, such as cardio-thoracic index, systolic PAP, and peripheral oedema.
Can J Cardiol Vol 26 Suppl D October 2010
617
DECREASING VOLUME AND INCREASING RISK PROFILE FOR PATIENTS UNDERGOING ISOLATED CORONARY ARTERY BYPASS GRAFTING KD Algarni, M Maganti, A Elhenawy, TM Yau Toronto, Ontario Patients undergoing isolated CABG surgery now are older and have more comorbidities than those operated on previously. At the same time, many cardiac centers around the world are experiencing a reduction in the volume of isolated CABG. It is unclear whether reduced volumes and sicker patients may negatively impact outcomes. We therefore analyzed our institutional experience to evaluate changes in the volume of isolated CABG procedures, trends in patient risk profiles and postoperative outcomes, and changes over time in the independent predictors of in-hospital mortality. There is a common perception that the prevalence of most preoperative risk factors in our patients has been increasing with time. While this was true of many risk factors, the prevalence of the 3 most significant predictors, including emergency CABG, severe LV dysfunction and reoperative CABG actually declined with time. However, these 3 risk factors remain the most important determinants of mortality. because their associated odds ratios actually increased over time. Overall mortality has decreased despite an overall increase in patient risk profile. However, severe LV dysfunction, the need for emergent surgery, and reoperative surgery remain challenges for cardiac surgeons, and highlight the need for further innovation in these areas.
Canadian Society for Atherosclerosis, Thrombosis and Vascular Biology (CSATVB) CSATVB200 Oral MACRO- AND MICRO-VASCULAR ASPECTS OF ATHEROSCLEROSIS Tuesday, October 26, 2010 620
INVESTIGATING THE PRO-ATHEROGENIC POTENTIAL OF CHRONIC HYPERGLYCAEMIA: IS DIABETIC ATHEROSCLEROSIS A MICROVASCULAR COMPLICATION? KJ Veerman, MI Khan, Y Shi, HC Gerstein, GH Werstuck Hamilton, Ontario BACKGROUND: Diabetes is associated with a significantly increased risk of microvascular complications, including retinopathy, nephropathy, neuropathy, and peripheral vascular disorders, as well as macrovascular complications, such as cardiovascular- and cerebrovascular disease. Traditionally, micro- and macrovascular complications have been considered independent disorders; however, accumulating evidence suggests the two may be linked. We hypothesize that diabetes-associated accelerated atherosclerosis results from the direct effects of hyperglycaemia on the vasa vasorum, the microvascular network which supplies the walls of large muscular arteries. In this study, we investigated the possible correlation between hyperglycaemia-associated alterations to the vasa vasorum and the progression and development of atherosclerosis. CONCLUSION: These findings provide the first indication that, in addition to retinal and glomerular capillary beds, hyperglycaemia alters the microvessel structure of the vasa vasorum. Such microvascular changes directly correlate to the development and progression of atherosclerosis in hyperglycaemic ApoE-deficient mice, suggesting that accelerated atherosclerosis can occur in the absence of vasa vasorum neovascularisation. It remains to be determined whether dynamic changes in the vasa vasorum play a causative or merely reactive role in atherogenesis.
119D
608
NEONATAL HYPOXIA IS ASSOCIATED WITH LASTING CHANGES IN LEFT VENTRICULAR SURVIVAL SIGNALLING AND CARDIOMYOCYTE CALCIUM HANDLING IN THE ADULT RAT D Del Duca, A Tadevosyan, F Karbassi, D Rodaros, BG Allen, S Nattel, CI Tchervenkov, TE Hébert, CV Rohlicek Montréal, Québec BACKGROUND: The growing population of adults with repaired cyanotic congenital heart disease remains at significant risk of impaired cardiac health, the need for cardiac reoperation, and premature death. We have previously demonstrated that hypoxia in early life causes lasting changes in left ventricular structure and function, as well as decreased cardiomyocyte survival following ischemic stress, in the adult rat. The objective of this study was to characterize the mechanisms underlying this myocardial vulnerability. We hypothesized that neonatal hypoxia is associated with lasting changes in cardioprotective regulatory and signalling events which may influence cardiomyocyte resistance to physiological stress in later life. CONCLUSION: Neonatal hypoxia is associated with significant alterations in ERK1/2 and AKT signalling pathways known to have important cardioprotective functions in the context of physiological stress. Decreased expression of HK II, a key metabolic enzyme that also mediates antiapoptotic AKT activity, was also observed. Finally, hypoxic stress in early life results in lasting changes in calcium handling which may negatively influence diastolic function and predispose the cardiomyocyte to stressinduced calcium toxicity. These observations may have pathophysiological implications for the growing population of adults with repaired or palliated cyanotic congenital heart disease.
Featured Research 609
PRODUCTION OF DONOR SPECIFIC ISOHEMAGGLUTININS FOLLOWING ABO-INCOMPATIBLE PEDIATRIC HEART TRANSPLANTATION J Conway, C Manlhiot, T Allain-Rooney, BW McCrindle, AI Dipchand Toronto, Ontario Pediatric ABO-Incompatible (ABO-I) heart transplant (HTx) recipients are capable of long-term acceptance of their grafts with excellent short and intermediate outcomes. Graft acceptance has been thought to be the result of donor specific B-cell elimination with a lack of detectable donor-specific blood group isohemagglutinins. Recent reports have now described patients who do produce donor-specific isohemagglutinins following an ABO-I HTx. The aims of this study were to determine the pattern, risk factors for, and clinical consequences of donor-specific isohemagglutinin development following ABO-I HTx. Almost one-third of infants undergoing ABO-I heart transplantation develop donor-specific isohemagglutinins. The only impact on clinical outcomes observed was a tendency towards a higher maximum grade of cellular rejection in those patients that produced donor-specific isohemagglutinins. However, there was no increased risk of antibody mediated rejection, graft loss or death. This pilot data clearly points to mechanisms other than B cell elimination as the explanation for continual graft acceptance in this patient population and emphasizes the need for further research into the possible mechanisms of graft accommodation in this patient population. Finally, the novel observation of differential responses and risk factors for development of antibodies to A versus B blood group antigens warrants further study.
118D
Canadian Society of Cardiac Surgeons (CSCS) CSCS410 Oral LET’S HAVE SOME FUN! Tuesday, October 26, 2010 612
TWENTY-FOUR HOUR CONSULTANT HYBRID ICU: ADDRESSING THE NEEDS OF PATIENTS POST-CARDIAC SURGERY KK Kumar, B Hiebert, R Zarychanski, H Grocott, RK Singal, RA Manji, AH Menkis, RC Arora Winnipeg, Manitoba The majority of patients following cardiac surgery are admitted to a Level I intensive care unit (ICU). Despite recommendations for 24-hour intensivist staffing models for Level I institutions, few Canadian centers have adopted this practice as an association between patient outcomes and ICU staffing model is unclear. Furthermore, a dichotomous surgical population exists, each with distinct requirements. Firstly, low-risk, “fast-track” patients, and secondly, higher-risk, multi-system issue patients who may benefit from focused 24-hour intensivist coverage. We sought to assess the impact of a hybrid (intensivist and cardiac anesthesiologist) ICU, with 24-hour consultant coverage, on outcomes in these two patient cohorts. As the “typical” patient undergoing cardiac surgery continues to evolve, our approach to their post-operative management also needs to adapt. A hybrid 24-hour consultant staffed ICU represents a novel approach to the management of complex post-cardiac surgical patients and is in keeping with the latest recommendation for Level I ICUs. With the presence of a dedicated cardiac anesthesiologist in addition to 24-hour intensivist coverage, our CICU model of care was associated with a reduction in blood products transfused, mechanical ventilation, and hospital length-of-stay in both the low and high-risk cohorts. Mortality within the ICU setting remains difficult to study, and will require larger multi-center collaborations.
613
LATE AORTIC ROOT BIOMECHANICS FOLLOWING DIFFERENT AORTIC ROOT REPLACEMENT OPERATIONS I El-Hamamsy, R Torii, S Babu-Narayan, P Kilner, MH Yacoub London, United Kingdom BACKGROUND: Aortic root biomechanics play an important role in long-term valvular and ventricular function. The objectives of this study were to evaluate late aortic root biomechanics following autograft, homograft and xenograft aortic root replacement, and compare them to healthy subjects. CONCLUSION: Autograft aortic root replacement (the Ross procedure) preserves late aortic root biomechanics better than xenograft or homograft root replacement. This is likely due to the long-term viability of the aortic root following the Ross procedure. These findings could have important clinical implications and help explain the better durability and survival advantage following the Ross procedure. Canadian Institutes of Health Research (CIHR)
614
SUCCESSFUL WEANING AND EXPLANTATION OF IMPLANTABLE VENTRICULAR ASSIST DEVICES AFTER RECOVERY OF MYOCARDIAL FUNCTION Y Lamarche, MJ Kearns, H Shayan, A Kaan, A Cheung Vancouver, British Columbia BACKGROUND: Ventricular assist devices (VADs) are used in cases of heart failure refractory to medical therapy. Most VADs are used as a bridge to heart transplantation, however, in certain cases, the myocardial function recovers and VADs can be weaned and explanted. The objectives of this study were to describe patients that required VAD insertion, followed by myocardial recovery and explantation in a quaternary heart center. The type of support used and post-explant outcomes are also reported.
Can J Cardiol Vol 26 Suppl D October 2010
Abstracts CONCLUSION: Patients requiring VAD support for myocardial failure can undergo significant reverse remodeling in a broad spectrum of cardiomyopathies. When it occurs, VAD explantation can lead to optimal outcome with minimal morbidity. Methods for assessment of reverse remodeling, weaning protocol and optimal timing of explantation remain controversial. Better understanding of the mechanism of reverse remodeling and aggressive screening may identify patients who are candidates for bridge to recovery.
615
USING DISCRETE EVENT SIMULATION TO UNDERSTAND AND TO IMPROVE THE FLOW OF PATIENTS THROUGH A CARDIAC SURGERY UNIT MZ Tong, V Padiyar, RJ Novick London, Ontario Between 2006 and 2009, our cardiac surgery unit has experienced an increased number of cancelled cases due to unavailability of an adequate number of beds. Strategies have been proposed to minimize cancellations, but there are no quick methods to evaluate these strategies. Discrete event simulation (DES) is used to forecast and optimize processes in many industries but its usage in health-care is limited. We built a DES model of the flow of patients through our unit to identify the bottlenecks to patient flows and to test different strategies to alleviate them. We found that, the main bottleneck to patient flow is the availability of ward beds, however this can change between the CSRU and ward daily depending on the day’s case volume, the number of CSRU patients, the number of ward patients, patient’s expected LOS and the off-service patient load. Strategy 1 decreased case cancellation by 34% when the bottleneck to flow was the ward. Strategy 2 decreased case cancellations by 25% when the bottleneck was the CSRU. Strategy 3 identified that we would need 36 dedicated ward beds to minimize cancellations. Discrete event simulation allowed us to gain insights on the causes of case cancellations and allowed us to test strategies rapidly and prior to clinical implementation to alleviate the bottlenecks to patient flows.
616
CLINICAL AND ECHOCARDIOGRAPHIC OUTCOMES FOLLOWING TRICUSPID VALVE REPLACEMENT: AN EXPERIENCE OF 134 PATIENTS G Marquis Gravel, D Bouchard, LP Perrault, P Pagé, P Demers, NC Poirier, Y Hébert, M Carrier, R Cartier, H Jeanmart, M Pellerin Montréal, Québec BACKGROUND: Tricuspid valve disease often presents as functional regurgitation, and occurs as a consequence of left-sided valve disease, pulmonary hypertension, and right ventricular dilatation. Repair of the tricuspid valve is usually sufficient for correcting regurgitation. Organic involvement of the tricuspid valve does not occur frequently, but usually mandates tricuspid valve replacement (TVR) when present. This procedure is seldom performed in the clinical practice, therefore outcomes following TVR are not well defined. The objectives of this study were to describe a cohort of patients undergoing TVR, and to assess echocardiographic and clinical outcomes following such procedure. CONCLUSION: Even though operative mortality associated with TVR improved through the years, this procedure is still associated with a substantial operative mortality rate, particularly in patients with important tricuspid stenosis, high pulmonary pressure, and those with a concomitant valve procedure. However, TVR should still be performed because it is associated with significant improvement of the NYHA functional class and of tricuspid regurgitation severity. When TVR is considered, it should be performed as early as possible in the course of the disease, before markers of late mortality develop or worsen, such as cardio-thoracic index, systolic PAP, and peripheral oedema.
Can J Cardiol Vol 26 Suppl D October 2010
617
DECREASING VOLUME AND INCREASING RISK PROFILE FOR PATIENTS UNDERGOING ISOLATED CORONARY ARTERY BYPASS GRAFTING KD Algarni, M Maganti, A Elhenawy, TM Yau Toronto, Ontario Patients undergoing isolated CABG surgery now are older and have more comorbidities than those operated on previously. At the same time, many cardiac centers around the world are experiencing a reduction in the volume of isolated CABG. It is unclear whether reduced volumes and sicker patients may negatively impact outcomes. We therefore analyzed our institutional experience to evaluate changes in the volume of isolated CABG procedures, trends in patient risk profiles and postoperative outcomes, and changes over time in the independent predictors of in-hospital mortality. There is a common perception that the prevalence of most preoperative risk factors in our patients has been increasing with time. While this was true of many risk factors, the prevalence of the 3 most significant predictors, including emergency CABG, severe LV dysfunction and reoperative CABG actually declined with time. However, these 3 risk factors remain the most important determinants of mortality. because their associated odds ratios actually increased over time. Overall mortality has decreased despite an overall increase in patient risk profile. However, severe LV dysfunction, the need for emergent surgery, and reoperative surgery remain challenges for cardiac surgeons, and highlight the need for further innovation in these areas.
Canadian Society for Atherosclerosis, Thrombosis and Vascular Biology (CSATVB) CSATVB200 Oral MACRO- AND MICRO-VASCULAR ASPECTS OF ATHEROSCLEROSIS Tuesday, October 26, 2010 620
INVESTIGATING THE PRO-ATHEROGENIC POTENTIAL OF CHRONIC HYPERGLYCAEMIA: IS DIABETIC ATHEROSCLEROSIS A MICROVASCULAR COMPLICATION? KJ Veerman, MI Khan, Y Shi, HC Gerstein, GH Werstuck Hamilton, Ontario BACKGROUND: Diabetes is associated with a significantly increased risk of microvascular complications, including retinopathy, nephropathy, neuropathy, and peripheral vascular disorders, as well as macrovascular complications, such as cardiovascular- and cerebrovascular disease. Traditionally, micro- and macrovascular complications have been considered independent disorders; however, accumulating evidence suggests the two may be linked. We hypothesize that diabetes-associated accelerated atherosclerosis results from the direct effects of hyperglycaemia on the vasa vasorum, the microvascular network which supplies the walls of large muscular arteries. In this study, we investigated the possible correlation between hyperglycaemia-associated alterations to the vasa vasorum and the progression and development of atherosclerosis. CONCLUSION: These findings provide the first indication that, in addition to retinal and glomerular capillary beds, hyperglycaemia alters the microvessel structure of the vasa vasorum. Such microvascular changes directly correlate to the development and progression of atherosclerosis in hyperglycaemic ApoE-deficient mice, suggesting that accelerated atherosclerosis can occur in the absence of vasa vasorum neovascularisation. It remains to be determined whether dynamic changes in the vasa vasorum play a causative or merely reactive role in atherogenesis.
119D