Tharumenthiran Ramanathan

Diagnosis of MI after CABG with high-sensitivity troponin T and new ECG or echocardiogram changes: relationship with mortality and validation of the universal definition of MI.

Aims: Criteria for diagnosing myocardial infarction (MI) after coronary artery bypass grafting (CABG) are controversial. Uncertainties remain around the optimal threshold for biomarker elevation and the need for associated criteria. There are no studies of high-sensitivity troponin (hs-TnT) after CABG. We assessed whether using hs-TnT to define MI after CABG was associated with 30-day and medium-term mortality and evaluated the utility of adding to the troponin criteria new Q-waves or imaging evidence of new wall motion abnormality as suggested in the Universal Definition of MI. Methods: Isolated CABG was performed in 818 patients from July 2010 to June 2012 and hs-TnT was measured 12–24 hours after CABG. Patients with rising baseline or missing troponins (n=258) were excluded. Thresholds of 140 ng/l (10-times 99th percentile upper reference limit) and 500 ng/l (10-times coefficient of variation of 10% for fourth-generation troponin T applied to hs-TnT) were prespecified. Results: Mean follow up was 1.8±0.6 years. On multivariate analyses, isolated hs-TnT rise >140 ng/l (n=360) or >500 ng/l (n=162) were not associated with mortality. Additional ECG and/or echocardiographic criteria plus hs-TnT >140 ng/l was associated with 30-day mortality (hazard ratio, HR, 4.92, 95% CI 1.34–18.1; p=0.017) and medium-term mortality (HR 3.44, 95% CI 1.13–10.5; p=0.030), whereas ECG and/or echocardiographic abnormalities with hs-TnT >500 ng/l was not (p=0.281 and p=0.123 for 30-day and medium-term mortality, respectively). Conclusions: A definition for MI following CABG using hs-TnT with a cut point of 10-times 99th percentile upper reference limit and ECG and/or echocardiographic criteria predicts 30-day and medium-term mortality. These findings validate the Third Universal Definition of type 5 MI.

Glucose-insulin-potassium solution improves left ventricular mechanics in diabetes

BACKGROUND The mechanism by which glucose-insulin-potassium solutions enhance recovery of left ventricular function after myocardial ischemia in diabetic patients is not well understood. We evaluated the effect of glucose-insulin-potassium on ventriculoarterial coupling and left ventricular mechanics in a chronic ovine model of diabetes. METHODS Diabetes was induced in 6 sheep with streptozotocin. After 6 months of diabetes, the response of the left ventricular pressure-volume relationship to 60 minutes of intravenous glucose-insulin-potassium solution (1,000 mL of 5% dextrose in water, 100 IU of regular insulin, 90 mmol of KCl at 1.5 mL x kg(-1) x h(-1)) was determined. RESULTS Glucose-insulin-potassium solution increased end-systolic elastance 68% (p = 0.01) and improved ventriculoarterial coupling (1.7+/-0.3 to 1.0+/-0.1; p < 0.01). Potential energy decreased 35% (p = 0.01), and pressure-volume area decreased 20% (p = 0.01). However, stroke work did not change; therefore stroke work efficiency increased from 50.1%+/-3.5% to 60.2%+/-5.1% (p = 0.01). CONCLUSIONS Glucose-insulin-potassium solution improves left ventricular contractility and ventriculoarterial coupling in diabetes. Left ventricular mechanics is improved by decreasing total mechanical work without significantly affecting stroke work, resulting in improved stroke work efficiency. Improved efficiency facilitates understanding of the enhanced tolerance to myocardial ischemia afforded by glucose-insulin-potassium solution.

Left ventricular oxygen utilization efficiency is impaired in chronic streptozotocin-diabetic sheep

OBJECTIVE Energy metabolism is altered in the diabetic heart. However, direct in vivo evidence that diabetes impairs energetics at the chamber level is lacking. Therefore, we investigated the effect of diabetes on left ventricular (LV) energetics in a chronic ovine model. METHODS Diabetes was induced in Merino-cross sheep with streptozotocin. Experiments were performed in five animals following 12 months untreated diabetes and six animals served as controls. Open-chest anesthetized sheep were instrumented to determine the LV pressure-volume relationship, oxygen consumption and free fatty acid uptake. RESULTS Diabetes impaired LV contractility (1.5+/-0.5 vs. 2.3+/-0.5 mmHg/ml, P<0.01). Stroke work was preserved but stroke work efficiency (stroke work/pressure-volume area) deteriorated (52+/-4 vs. 58+/-3%, P<0.01). Plasma free fatty acid levels increased (1885+/-1078 vs. 354+/-203 mmol/l, P<0.01) as did LV free fatty acid uptake (312+/-278 vs. 90+/-47 micromol/beat per 100 g LV, P=0.04). Contractile efficiency decreased (31.9+/-1.4 vs. 50.0+/-8.7%, P<0.01) while unloaded oxygen consumption did not change significantly. Therefore, LV oxygen utilization efficiency (stroke work/LV oxygen consumption) was compromised in the diabetic heart (14.9+/-2.8 vs. 24.3+/-4.0%, P<0.001). CONCLUSION This is the first study to demonstrate that diabetes alters ventricular energetics in vivo. LV oxygen utilization efficiency is impaired as a consequence of decreased contractile efficiency and stroke work efficiency. Impaired efficiency of oxygen utilization may explain in part the increased sensitivity of the diabetic heart to ischemia and the accelerated deterioration of ventricular function in diabetic patients.

Preoperative atrial fibrillation predicts mortality and morbidity after aortic valve replacement

OBJECTIVES Atrial fibrillation (AF) is the commonest cardiac arrhythmia, becoming increasingly prevalent as the population ages. There is conflicting information around whether AF is associated with adverse outcomes after aortic valve replacement (AVR) from the few studies that have investigated this. We compared the characteristics and outcomes of patients undergoing AVR with their history of AF. METHODS Isolated AVR patients at Auckland City Hospital 2005-2012 were divided into those with and without preoperative AF for comparative analyses. RESULTS Of 620 consecutive patients, 19.2% (119) had permanent or paroxysmal AF preoperatively. Patients with AF were significantly older (70.5 vs 63.4 years, P < 0.001) and were more likely to be New Zealand European (82.4 vs 68.1%, P = 0.004). They also had higher prevalence of NYHA class III-IV (55.4 vs 37.4%, P = 0.004), inpatient operation (62.1 vs 48.3%, P = 0.008), history of stroke (10.9 vs 5.0%, P = 0.031), lower creatinine clearance (73 vs 82, P = 0.001) and higher EuroSCORE II (5.2 vs 3.4%, P < 0.001). Operative mortality (6.7 vs 2.0%, P = 0.012) and composite morbidity (27.7 vs 16.5%, P = 0.006) were also higher in patients with AF. After adjusting for significant variables, preoperative AF remained an independent predictor of operative mortality with an odds ratio of 3.44 (95% confidence interval 1.29-9.13), composite morbidity of 1.79 (1.05-3.04) and a mortality during follow-up hazards ratio of 2.36 (1.44-3.87). CONCLUSIONS AF was associated with several cardiovascular and cardiac surgery risk factors, but remained independently associated with short- and long-term mortality. AF should be incorporated into cardiac surgery risk models and surgical AF ablation may be considered with AVR.

Transcatheter Aortic Valve Implantation In Patients With a Large Aortic Annulus

BACKGROUND As the indications for transcatheter aortic valve implantation (TAVI) have expanded, so to have the demands on interventionists to allow as many patients to access this technology as possible. METHODS We retrospectively reviewed our TAVI database for patients who had received a 29mm SAPIEN 3 valve despite having an annular area greater than the manufacturer-recommended upper limit of 683mm2, as determined by multi-detector computed tomography (MDCT). Procedural and inpatient outcome data were collected. RESULTS The study population was 5 of 121 patients receiving a SAPIEN 3 valve since it became available in March 2015. Their annular area ranged from 691 to 800mm2. Valve deployment was successful in all patients. The deployment balloon volume was nominal, except for an additional 1ml in one patient. No patient had a new indication for permanent pacing, and no significant valvular or paravalvular regurgitation (PVR) was identified on post-procedure transthoracic echocardiography. All patients survived to hospital discharge. CONCLUSIONS In this select group of patients we have demonstrated that it is safe and feasible to use the 29mm SAPIEN 3 in patients with annular dimensions greater than those recommended, with minimal balloon overfilling.

Thoracoscopic Lobectomy for Synchronous Intralobar Pulmonary Sequestration and Lung Cancer

Bronchopulmonary sequestration is a rare congenital pulmonary malformation for which surgical resection is recommended, and several reports have described successful resection by video-assisted thoracoscopic surgery. Coexistence of sequestration with lung malignancy is extremely rare. We report the first case of thoracoscopic resection of synchronous intralobar pulmonary sequestration and non-small cell lung cancer.

Relationship Between Diabetic Variables and Outcomes After Coronary Artery Bypass Grafting in Diabetic Patients

BACKGROUND Nearly half of the patients undergoing coronary artery bypass grafting (CABG) have diabetes. There is mixed data as to whether preoperative (haemoglobin A1c{HbA1c}) and/or perioperative diabetes control is associated with mortality and morbidity after CABG. We reviewed the characteristics and outcomes of diabetic patients undergoing CABG with a focus on HbA1c, perioperative glucose levels and diabetic treatment regimens. METHODS Diabetic patients undergoing CABG during July 2010 to June 2012 were studied (n=306). The last preoperative HbA1c levels, and perioperative glucose levels (mean and coefficient of variation {CV}) were retrospectively recorded, as well as the pre-existing and perioperative diabetes treatment regimens for analyses. RESULTS Mean HbA1c was 7.7+/-1.6%, and 11.1% (34), 56.2% (172), and 32.7% (100) of patients were managed preoperatively with diet only, oral diabetic medications and insulin respectively. For operative mortality which occurred in 2.0%, C-statistics (95% confidence interval) was only significant for HbA1c, 0.855 (0.757-0.975), and glucose CV on the day of surgery, 0.722 (0.567-0.877). HbA1c also detected postoperative renal failure, C-statistic 0.617 (0.504-0.730), but not other complications or mortality during follow-up. In multivariate analysis, HbA1c was the only diabetes-related independent predictor of operative mortality, hazards ratio 4.13 (1.04-16.4), and none of the diabetes-related variables predicted mortality during follow-up or other postoperative complications. CONCLUSION Preoperative HbA1c was the only diabetic variable to independently predict operative mortality after CABG, suggesting medium-term preoperative diabetes control is more important and prognostic of operative outcomes than perioperative diabetes control.

Isolated Aortic Valve Replacement in Octogenarians Before and After the Introduction of Trans-catheter Aortic Valve Implantation

BACKGROUND Trans-catheter aortic valve implantation (TAVI) became available at Auckland City Hospital in 2011 for patients with severe aortic stenosis in whom surgical aortic valve replacement (AVR) was deemed at high risk. We assessed whether introduction of TAVI affected the characteristics and outcomes of octogenarians undergoing AVR. METHODS Isolated AVR performed in patients ≥80 years of age during 2008-2012 were divided into two groups, pre- and post-TAVI introduction, for analyses. RESULTS Isolated AVR was undertaken in 35 and 33 octogenarians pre- and post-TAVI introduction. The post-TAVI group were older (84.2 vs 82.3 years, P=0.003), had lower ejection fraction (P=0.026), more had inpatient surgery (76% vs 29%, P<0.001), with higher EuroSCORE II (5.4 vs 3.9%, P=0.033). Operative mortality was 0.0% in both groups. One-year survival was similar (97.6% vs 94.3%, P=0.613), but composite morbidity was lower in the post-TAVI group (9.1% vs 31.4%, P=0.035). Chronic respiratory disease (P=0.043) independently predicted mortality during follow-up, while number of coronary vessel>50% stenosis (P=0.050), creatinine clearance (P=0.016) and being in the pre-TAVI era group (P=0.022) predicted composite morbidity. CONCLUSIONS Since TAVI was introduced, mean age and risk scores significantly increased in octogenarians undergoing AVR, while mortality rates remained similar and composite morbidity decreased.

Performance of contemporary surgical risk scores for mitral valve surgery: Risk scores and mitral surgery

Risk stratification for mitral valve repair or replacement (MVR) is important in the decision‐making for treating several mitral valve disease but is rarely studied. We compared the prognostic utility of EuroSCORE, EuroSCORE II, and Society of Thoracic Surgeons (STS) Score for MVR.

Aortic Valve Replacement With or Without Concurrent Coronary Artery Bypass Grafting in Octogenarians: Eight-Year Cohort Study

BACKGROUND With the introduction of transcatheter aortic valve implantation (TAVI), there is increasing interest in evaluating outcomes of aortic valve replacement (AVR) with or without (+/-) concurrent coronary artery bypass grafting (CABG) particularly in high-risk patients. We reviewed the characteristics and outcomes of octogenarians undergoing isolated AVR and AVR+CABG. METHODS All patients 80 years of age or older undergoing AVR+/-CABG at Auckland City Hospital during 2005-2012 were included, and their characteristics and outcomes analysed. RESULTS There were 93 and 104 octogenarians respectively undergoing isolated AVR and AVR+CABG with mean follow-up of 4.4+/-2.2 years and 4.1+/-2.3 years. Significant differences in baseline and operative characteristics contributed to higher EuroSCORE II (5.9 vs 6.4%, P=0.016) and STS Score (4.9 vs 6.9%, P<0.001) for AVR+CABG patients. They also had a significantly higher rate of 30-day mortality (0.0% vs 6.7%, P=0.015) and prolonged ventilation>24hours (10.7% vs 23.1%, P<0.001), but not composite morbidity (P=0.248) or stroke (P=0.709). Long-term survival was similar at one, three and five years; 94.6%, 82.6% and 73.0% for AVR and 91.3%, 86.1% and 67.6% for AVR+CABG. Independent predictors of 30-day mortality included reduced creatinine clearance and history of myocardial infarction. CONCLUSION AVR+CABG had significantly higher but acceptable 30-day mortality in octogenarians than AVR. We have identified prognostic factors important in the decision-making of treatment modality, where age alone should not preclude surgery.