The assessment of cardiac risk in elective aortic surgery

Matley, Philip John

The assessment of cardiac risk in elective aortic surgery

Thesis / Dissertation

1990

Publisher

University of Cape Town

Department

Department of Surgery

Faculty

Faculty of Health Sciences

Abstract

The high prevalence of coronary artery disease in patients undergoing elective abdominal aortic reconstruction accounts for the fact that the commonest cause of postoperative death or major morbidity is myocardial infarction or left ventricular failure . Accurate assessment of cardiac risk is essential in patient selection for surgery and in the allocation of limited medical resources and invasive monitoring techniques. The factors which are clinically valid in predicting cardiac risk have yet to be defined in a large prospective study of patients undergoing aortic reconstruction. Scoring systems such as the Goldman cardiac risk index (CRI) developed in patients undergoing largely non vascular operations and the Cooperman formula developed in patients undergoing a wide range of vascular procedures require prospective evaluation in patients undergoing aortic surgery before their validity in this high risk group can be established. Several non invasive or minimally invasive procedures are now available to assess ventricular performance or myocardial perfusion. To date the few studies that have investigated the predictive ability of radionuclide ventriculography or dipyridamole/thallium-201 scintigraphy in patients undergoing vascular surgery have been limited by small patient numbers and conflicting results. In a prospective study representing a complete capture of all 220 patients undergoing elective abdominal aortic reconstruction in a single institution over a 3 year period, this study has demonstrated seven clinical factors lo be valid in cardiac risk prediction using both univariate and multivariate analysis of a large number of possible risk factors. These factors arc age greater than 70 years, angina, previous myocardial infarction, past or present evidence of congestive heart failure, an abnormal electrocardiogram, arrhythmia or previous stroke. No patient developed a major cardiac event postoperatively in the absence of at least one of these factors. The non-invasive studies evaluated were not found to be clinically useful in the absence of these factors as the results were almost invariably normal in such patients. Despite having a significant correlation with the risk of major cardiac events, the usefulness of the Goldman CRI was limited by the large number of patients in the lowest risk category that developed cardiac events. The Cooperman formula was found to be a remarkably accurate predictor of statistical cardiac risk. The computation of left ventricular ejection fraction by equilibrium radionucliude angiocardiography significantly added to cardiac risk prediction and defined a subgroup of patients with poor left ventricular function in whom the operative risk was prohibitively high. The performance of dipyridamole-thallium scintigraphy as a predictive test was disappointing. Patients who are at increased cardiac risk can be reliably identified using simple clinical criteria. Cardiac risk estimation can be further refined in those with clinical risk factors by simple non-invasive tests, particularly radionuclide ventriculography. The widely promoted policy of routine coronary angiography to detect coronary lesions prior to aortic surgery cannot be supported on the basis of this data and the clinical relevance of asymptomatic coronary lesions that may be detected by routine coronary angiography is questioned by this study. The potential for sudden death or acute myocardial infarction in patients with non-flow-limiting coronary stenoses will continue to be a source of error in any system of clinical risk prediction. None of the currently available non-invasive tests are able to detect such lesions or predict their natural history.

Keywords

Surgery

Reference:

Collections

Masters

Full item page