Optimal Conduit Diameter Selection in Coronary Bypass Grafting Using Saphenous Vein.

BACKGROUND: Predictors of long-term saphenous vein graft (SVG) patency following coronary artery bypass grafting (CABG) include harvesting technique, degree of proximal coronary stenosis, and target vessel diameter and runoff. The objective of this study was to evaluate the association between vein graft diameter and long-term survival. METHODS: Patients undergoing primary CABG (2000-2017) at Flinders Medical Centre, Adelaide, Australia, were categorised into three groups according to average SVG diameter (<3.5 mm [small], 3.5-4 mm [medium], >4 mm [large]). Survival data was obtained from the Australian Institute of Health and Welfare National Death Index. To determine the association of SVG diameter with long-term survival we used Kaplan-Meier survival analysis and Cox proportional hazard models adjusted for preoperative variables associated with survival. RESULTS: Vein graft diameter was collected in 3,797 patients. Median follow-up time was 7.6 years (interquartile range, 3.9-11.8) with 1,377 deaths. SVG size >4 mm was associated with lower rates of adjusted survival up to 4 years postoperatively (hazard ratio 1.48; 95% confidence interval 1.05-2.1; p=0.026). CONCLUSIONS: Vein graft diameter >4mm was found to be associated with lower rates of survival following CABG.

Quantification of the internal mammary artery size in Aboriginal and Torres Strait islanders.

BACKGROUND: Variation in size of the internal mammary artery has been demonstrated in ethnic groups, but not reported in Aboriginal patients. We hypothesised that the left internal mammary artery is smaller in Aboriginal patients compared to non-Aboriginal patients and aimed to determine the impact on survival following coronary artery bypass graft (CABG) surgery. METHODS: Left internal mammary artery size was compared between Aboriginal (n = 345) and non-Aboriginal (n = 1819) in 2343 patients undergoing CABG at Flinders Medical Centre from January 2010 to June 2021. To determine the association with-survival we used Kaplan-Meier survival analysis and Cox proportional hazard models adjusted for preoperative variables. RESULTS: There was a significant difference in left internal mammary artery (LIMA) size-Aboriginal 1.8 ± 0.4 mm; non-Aboriginal 2.1 ± 0.4 mm (P < 0.001)-and left anterior descending (LAD) artery size-Aboriginal 1.7 ± 0.3 mm; non-Aboriginal 1.9 ± 0.3 mm (P < 0.001). Aboriginal patients were more likely to have the LIMA discarded (9.3% vs. 0.4%) and to receive a LAD vein graft (17% versus 3%) (P < 0.001). There was no difference in 30-day mortality or survival <5 years. CONCLUSION: This study supports the hypothesis that the left internal mammary artery is smaller in Aboriginal patients compared to non-Aboriginal patients. Although Aboriginal patients were more likely to receive a venous conduit to the LAD, we observed no difference in survival up to 5 years. This data contrasts with reported outcomes of other ethnic groups.

Transcatheter mitral valve-in-valve: treatment of rheumatic heart disease in young patients.

BACKGROUND: Rheumatic heart disease (RHD) in young people presents a complex management problem. In Australia a significant proportion of those affected are Aboriginal and Torres Strait Islanders. Transcatheter mitral valve-in-valve (TMViV) replacement has emerged as an alternative to redo surgery in high-risk patients with degenerated mitral bioprostheses. The aim of this study is to review outcomes of TMViV replacement in young patients with RHD. METHODS: A single-centre, retrospective review of prospectively collected data on patients undergoing TMViV from December 2017 to June 2021. Primary outcome was major adverse cardiovascular events. Secondary outcome was post-operative trans-thoracic echocardiogram (TTE) results. RESULTS: There were seven patients with a mean age of 33 years and predominantly female (n = 5). Pre-operative comorbidities included diabetes (29%), chronic obstructive pulmonary disease (43%), left ventricular dysfunction (43%) and current smoking status (80%). Post-operative median length of hospital stay was 4 days with no post-operative renal failure, stroke, return to theatre, valve embolization or in hospital mortality. Post-operative TTE showed either nil or trivial central mitral regurgitation, no paravalvular leak and a median gradient of 5 mmHg (IQR 4.5, 7) across the new bioprosthesis; sustained at median follow-up of 22 months. CONCLUSION: Current literature of TMViV replacement is focused on an older population with concurrent comorbidities. This study provides a unique insight into TMViV replacement in a young cohort of patients with complex social and geographical factors which sometimes prohibits the use of a mechanical valve. The prevalence of RHD remains high for Aboriginal and Torres Strait Islanders, planning for future repeat valve operations should be considered from the outset. We consider TMViV as a part of a staged procedural journey for young patients with RHD.

Del Nido cardioplegia in adult cardiac surgery: analysis of myocardial protection and post-operative high-sensitivity Troponin T.

BACKGROUND: del Nido cardioplegia has been adopted for use in adult cardiac surgery, despite a lack of robust randomised evidence supporting equivalence or superiority to conventional hyperkalaemic blood cardioplegia. We investigated the clinical surrogates of myocardial protection, and performed an extensive analysis of post-operative high-sensitivity Troponin T (hs-TnT) values in a general adult cardiac surgery population receiving del Nido, in comparison to a historical hyperkalaemic blood cohort. METHOD: 171 consecutive patients of a single surgeon from between November 2018 and June 2020 received del Nido, and were compared to a historical cohort of 326 patients between January 2016 and November 2018 who received hyperkalaemic blood cardioplegia. Clinical markers of myocardial protection were compared, as were hs-TnT values at 6, 12, 24, and 72-h post-operatively. Equivalence between groups was determined using the two one-sided tests procedure. RESULTS: There was no difference between the groups in the incidence of post-operative low cardiac output state, inotropic support, or myocardial infarction. Del Nido patients had less defibrillation requirement, and more spontaneous resumption of normal sinus rhythm. High-sensitivity Troponin T values were similar at all time-points including in a coronary artery bypass graft subgroup, and in those patients with elevated pre-operative hs-TnT. CONCLUSION: In a broad cohort of adult cardiac surgery patients, including those undergoing coronary artery bypass surgery and those with recent myocardial infarction, del Nido provides equivalent myocardial protection and clinical outcomes when compared to hyperkalemic blood cardioplegia. Post-operative high-sensitivity Troponin T values were also equivalent between the groups.

Transcatheter Transseptal Mitral Valve-in-Valve Replacement: An Early Australian Case Series and Literature Review.

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. METHODS: Prospectively collected data was retrospectively reviewed in patients undergoing transcatheter transseptal mitral valve-in-valve implantation using the Edwards Sapien 3 balloon expandable bioprosthesis (Edwards Lifesciences, Irvine, CA, USA). 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.

Outcomes of Redo Valve Surgery in Indigenous Australians.

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. METHODS: Data from our institutional database was reviewed from 1992 to 2017. During this period, 82 redo valve surgeries were performed in 73 patients identifying as Aboriginal and Torres Strait Islander. We compared this study group to Indigenous patients undergoing primary valve surgery (n=389) and non-Indigenous patients undergoing redo valve surgery (n=154). 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.

Aortic valve prosthesis-patient mismatch and long-term outcomes: 19-year single-center experience.

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. METHODS: Patients undergoing aortic valve replacement from January 1992 to December 2010 were classified according to effective orifice area index into severe PPM (effective orifice area index<0.65 cm²/m²), moderate PPM (effective orifice area index 0.65 to 0.85 cm²/m²), and absent PPM (effective orifice area index>0.85 cm²/m²). Analyses examined major morbidity and total all-cause death. 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.