Pathophysiology and Natural History Coronary Artery Disease

The functional and prognostic significance of exercise-induced ST elevation (by computer averaging) in ambulatory patients with coronary heart disease was recently reported for 181 patients in the Seattle Heart Watch (SHW). To further evaluate this, 3050 approximately similar patients enrolled in CASS were analyzed with respect to initial findings, survival, and incidence of secondary coronary events over the next 6 years. The ST elevation responses in CASS patients were classified by visual interpretation of 1 mm or more, whereas the SHW patients were identified by voltage greater than 0 mV. Accordingly, prevalence of exercise-induced ST elevation was lower in CASS patients, but they had greater frequencies of prior myocardial infarction and left ventricular enlargement and dysfunction. The poor survival was similar in the subgroup with ST elevation during exercise and recovery in CASS and SHW. Although not an independent predictorwhen invasive variables are known, ST elevation emerges as a useful predictorwhen exercise testing is performed before diagnostic invasive studies. Circulation 77, No. 4, 897-905, 1988. A RECENT ANALYSIS of 5303 nonrandomized patients from CASS revealed the independent beneficial effect of surgical treatment on survival as compared with contemporary medical treatment (p < .0001).' This benefit was maximized in 789 patients who were unable to exercise beyond stage I of the Bruce protocol and who manifested at least 1 mm of ST depression. These findings were consistent with the earlier nonrandomized Seattle community experience2 and the randomized European Coronary Surgery Study.3 Unfortunately none ofthese studies considered another, albeit infrequent potential marker of poor survival, namely the role of exercise-induced ST elevation in ambulatory patients with coronary heart disease. The unusual prognostic significance of this response in From the Department of Medicine, Division of Cardiology, and Department of Biostatistics, University of Washington/the CASS Coordinating Center, Seattle, Boston University Medical Center, St. Louis University Medical Center, and Associated Investigators. The Seattle Heart Watch Study was funded by the M. J. Murdock Charitable Trust and the.National Heart, Lung, and Blood Institute and Health Resources Administration of the Department of Health and Human Services. The CASS is funded by the National Heart, Lung, and Blood Institute. Address for correspondence: Lloyd D. Fisher, Ph.D., CASS Coordinating Center, U District Building, 1107 NE 45th, Room 530, Seattle, WA 98105. Received Dec. 14, 1987; accepted Jan. 14, 1988. Vol. 77, No. 4, April 1988 patients has been reported for a subset of Seattle Heart Watch patients who happened to have computer-averaged and quantitatively measured ST responses to provide a more consistent and objective appraisal of electrocardiographic manifestations of exertional myocardial ischemia and/or dyskinesis.4 With concern that this observation might be limited by small sample size and multiple comparisons within the data, the larger data base of CASS was surveyed to provide an independent comparison of exercise-induced ST responses and survival. In the latter group the ST responses were based on clinical interpretation rather than a uniform computer analysis program. In contrast to ST depression commonly induced by exercise in patients with coronary heart disease, ST elevation is an infrequent and often disregarded electrocardiographic response. However, its association with ventricular aneurysm was described in 1963.5 In 1978 Froelicher6 considered it "an ominous finding that is more frequent than previously thought" which "usually occurs over a dyskinetic area in relation to critical obstruction [of the coronary artery]." Manvi and Ellestad7 associated it with ventricular aneurysm, while others associated it with severe stenosis of the proximal left anterior descending artery,8 especially 897 by gest on A ril 7, 2017 http://ciajournals.org/ D ow nladed from