|
Ninety-four consecutive clinically stable patients of myocardial infarction who had predischarge symptom-limited treadmill exercise test and coronary angiography were followed up for the development of cardiac events( major : death, reinfarction, minor : angina, heart failure, mean duration : 21 months ). Depending on the presence or absence of ST segment depression and chest pain, the subjects were divided into 4 groups. Thirty-six cases ( 38% ) showed neither ST segment depression nor chest pain ( group Ⅰ ). Chest pain without ST segment depression was noticed in 16 cases ( 17%, group Ⅱ ). Silent ischemia was found in 29 cases( 31% ) of these patients ( group Ⅲ ). Thirteen cases( 14% ) had both ST segment depression and chest pain ( group Ⅳ ). Incidence of diabetes mellitus( 28% vs 8%, p = 0.07 ) and absence of prior angina ( 48% vs 0%, p<0.05 ) were higher in group Ⅲ compaired to group Ⅳ. Maximum workload ( 6.9 ± 3.2 vs 4.5 ± 2.7 METs, p<0.05 ). peak systolic pressure ( 144 ± 26 vs 126 ± 25 mmHg. p<0.05 ) and douple product of heart rate and systolic pressure ( p<0.05 ) were also higher in group Ⅲ compaired to group Ⅳ, despite of similar frequency of multivessel disease and collateral circulation and similar degree of residual stenosis of infarct related artery. During the mean follow-up period of 21months, one cardiac death developed in group Ⅲ, and one reinfarction in group Ⅱ and group Ⅲ respectively, but no death or reinfarction in patients of group Ⅳ. Total and minor cardiac events developed more frequently in group Ⅲ compaired to group Ⅰ.(p<0.05) But there’s no significant difference of total and minor cardiac events between the two groups of myocardial ischemia. These findings suggest that silent ischemia is common in early postinfarction exercise testing, particularly in patients with diabetes or who had not history of angina before myocardial infarction. Despite of similar frequency of multi-vessel disease and collateral circulation, and higher maximal workload during exercise testing, the long-term prognosis of these patients is not better than symptomatic ischemic patients, particularly whose maximal tolerable workload is less than 5 METs.
|