Medicine (St Vincent's) - Theses
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ItemPerioperative cardiovascular complications: incidence in patients undergoing cancer surgery and preoperative risk prediction using 18F-fluorodeoxyglucose cardiac positron emission tomography imaging( 2018)Background: Major perioperative cardiac complications affect over 10 million patients annually worldwide. Cancer is associated with multiple shared cardiovascular risk factors, but the incidence of cardiovascular complications after cancer surgery is unknown. Furthermore, cardiovascular risk prediction remains challenging. Cardiopulmonary exercise testing (CPET) objectively assesses exercise capacity and can predict overall perioperative morbidity and mortality and guide prehabilitation strategies, but cardiac imaging is required to determine the location and severity of coronary artery disease preoperatively. Currently available stress tests rely on surrogate markers for ischaemia and the evidence supporting these investigations perioperatively is weak. Cardiac positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) can image myocardial metabolism directly. Myocardial ischaemia appears as a ‘hot spot’ due to uptake of radiolabelled glucose in ischaemic myocytes undergoing anaerobic metabolism. Performing cardiac PET imaging after CPET may improve cardiac-specific perioperative risk prediction. However, accurate imaging requires preparation with a high-fat low-carbohydrate (HF-LC) diet, and the feasibility of incorporating cardiac PET imaging into existing preoperative CPET clinics is unknown. This thesis explores the incidence of cardiovascular complications in a cancer surgery population, and the feasibility of post-exercise cardiac PET imaging for preoperative risk assessment prior to major cancer surgery, within the setting of a CPET clinic. Methods: Cardiovascular complications within 30 days of cancer surgery were retrospectively investigated during a 12-month period at a single cancer institution (Peter MacCallum Cancer Centre, Melbourne, Australia). Screening identified patients via positive troponin results, ICD-10 diagnosis, and a manual search of intensive care unit discharge summaries. Standardized diagnostic criteria then identified the primary outcome—the incidence of myocardial injury after noncardiac surgery (MINS) or perioperative myocardial infarction (MI). Secondary outcomes included arrhythmias, cardiac failure, pulmonary oedema/fluid overload, pulmonary embolism, stroke, and cardiac death. A prospective pilot study investigating the feasibility of cardiac PET imaging after CPET was conducted. Feasibility endpoints included compliance with preoperative HF-LC diet and fasting; the ability to inject the FDG tracer within 15 minutes of peak exercise, the ability to complete cardiac PET imaging within 120 minutes, and the ability to suppress FDG uptake in background normal myocardium. Postoperative follow-up included cardiac complications and mortality within 30 days of surgery. Results: Over a 12-month period, 4,743 patients underwent cancer surgery. Seventy patients experienced 95 cardiovascular complications within 30 days postoperatively (overall incidence 1.5%). Amongst patients undergoing intermediate/high-risk surgery, the incidence was 8.4%. Perioperative MI/MINS occurred in 13 patients (0.27%). The 30-day all-cause mortality in those with cardiovascular complications after cancer surgery was 10% (n=7), and 42% (n=3) had a documented cardiac cause of death. Twenty-six patients undergoing intermediate to high-risk cancer surgery were enrolled in the cardiac PET pilot study over an eighteen-month period (July 2014-January 2016). Overall protocol feasibility was achieved in 81% (95% CI 62% to 91%). Of the 24 patients who completed exercise testing, FDG was injected within 15 minutes (mean 9.8 minutes) of peak exercise in all patients, and cardiac PET imaging completed within 120 minutes (mean 84.2 minutes) in 96% of patients. Twenty-one patients proceeded to surgery; three patients experienced postoperative myocardial injury or infarction, of which two had positive or equivocal cardiac PET imaging (and negative sestamibi myocardial perfusion imaging). One patient with normal CPET and cardiac PET results suffered MINS following bleeding requiring massive transfusion. Conclusions: Overall, there is a low incidence of perioperative acute myocardial infarction following cancer surgery. However, the retrospective study design and lack of routine postoperative troponin monitoring may have underestimated the true incidence. Patients undergoing intermediate/high risk cancer surgery are at greater risk, and the 30-day all-cause mortality in those with cardiovascular complications is significant.