An investigation in patients with previous myocardial infarction who present with chest pain

Value of exercise electrocardiography to predict additional jeopardized myocardial regions remote from site of previous myocardial infarction

In order to evaluate the efficacy of exercise electrocardiography (ECG) to identify jeopardized myocardial regions remote from the site of previous infarction, exercise ECG, left ventriculography, and coronary arteriography were performed in 90 patients with previous transmural myocardial infarction (MI). Of the 90 patients, angiographic studies revealed jeopardized myocardial regions in 47 patients. Exercise ECG correctly identified 32 of these 47 patients for a sensitivity value of 68%. There were 43 patients without any additional jeopardized myocardial regions. Exercise ECG correctly identified only 24 of these 43 patients for a specificity value of 56%. The sensitivity and specificity values were similar in patients with prior anterior and inferior wall MI. It is concluded that relatively low sensitivity and specificity values preclude the ability of exercise ECG to accurately identify patients with jeopardized myocardial regions distant from the site of previous MI. Moreover, when such patients were correctly detected, exercise ECG was rather poor in localizing these additional jeopardized myocardial areas.

Factors affecting sensitivity and specificity of exercise electrocardiography. Multivariable analysis

Unlike the predictive value of a diagnostic test, which depends on the prevalence of disease in the population tested, its sensitivity and specificity have been assumed to be constants. This assumption was examined in patients who had both exercise electrocardiography and cardiac catheterization. The effects on sensitivity of factors from clinical history, catheterization, and exercise performance were defined by multivariable logistic regression analysis in 1,401 patients with coronary disease; effects on specificity were defined by a similar analysis in 868 patients without coronary disease. Five factors had significant, independent effects on exercise electrocardiographic sensitivity: maximal exercise heart rate, number of diseased coronary arteries, type of angina, and the patient's age and sex. Only maximal exercise heart rate had a significant, independent effect on exercise electrocardiographic specificity. Thus, the sensitivity and specificity of exercise electrocardiography vary with clinical history, extent of disease, and treadmill performance; the sensitivity and specificity of other diagnostic tests may also vary.

Peri-infarction zone at risk during the first 5 days after an acute transmural myocardial infarction: electrocardiographic evidence

An atrial pacing test was performed daily during the initial 5 days after a first myocardial infarction (MI) in 33 patients in Killip class I or II, to assess the presence of areas at risk of ischemia. Pacing caused a transient ST-segment shift of 1 mm or more in 26 patients (79%) (positive test, Group I) in the first 3.6 +/- 1.1 days after infarction, whereas no ST-segment change developed during pacing in 7 patients (negative test, Group II). Pacing-induced electrocardiographic changes were always localized in the leads involved by the MI. Right and left ventricular filling pressures were higher in Group I than in Group II (8 +/- 4 vs 5 +/- 3 mm Hg, p less than 0.05, and 16 +/- 7 vs 12 +/- 7 mm Hg, p less than 0.02, respectively). Both groups had similar increases in peak enzyme values and a similar mortality rate (2 of 26 vs 1 of 7 at an average follow-up of 16 months). The reinfarction rate was higher in Group II (3 of 7 vs 1 of 26). In 7 patients similar to the 33 patients studied, metabolic studies revealed lactate abnormalities during pacing in 4 of the 6 patients with positive test results and unchanged metabolism in the patient with a negative test result. Thus a jeopardized peri-infarction area appears to exist in most patients soon after an uncomplicated MI. Its presence is often associated with silent heart failure, but it is probably unrelated to peak enzyme increase or to prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic implications of early spontaneous angina after acute transmural myocardial infarction

We investigated the clinical, electrocardiographic and hemodynamic features and the prognostic implications of early spontaneous angina in 31 consecutive patients after acute myocardial infarction. Re-elevation of ST segments in the area of infarction occurred during angina and during reinfarction in all but one patient. Depression of ST segments, when present during pain, involved the same leads as in the acute infarction. Blood pressure and double product tended to increase during pain in 23 patients. The magnitude of this change, however, often varied from crisis to crisis and there were no increases in these parameters in one or more attacks in 15 patients. Sublingual nitroglycerin, 1.0 mg, failed to relieve one or all anginal episodes in 17 of the 28 patients in whom it was given. In-hospital mortality rate was 10% (3/31) and always followed reinfarction. In-hospital reinfarction rate was 16% (5/31) and followed a larger number of anginal crises (7.2 +/- 1.3 vs 3.0 +/- 2.1, P less than 0.001) and a higher incidence of transient hypotensive episodes than in the rest of patients (3/5 vs 3/26). Three additional patients died after discharge. Of the remaining 25 patients and during a follow-up of 26 months (16-34) only one developed reinfarction. Early resting angina after a transmural infarction is almost invariably associated with ECG evidence of ischemia in the leads overlying the infarcted zone. The inconsistent changes in blood pressure and heart rate during pain render these hemodynamic changes an unlikely cause of this form of angina. While postinfarction angina did not carry a grave short- or long-term prognosis, patients with recurrent crises demonstrated as high a risk of reinfarction and death as those with spontaneous hypotension.

Significance of exercise induced ST segment elevation in patients with previous myocardial infarction

In order to determine the significance of exercise induced ST segment elevation in patients with previous myocardial infarction, we have studied 156 patients, 26 months (mean) after myocardial infarction. Each patient underwent 16 lead precordial electrocardiographic mapping before, during, and after exercise and in addition coronary arteriography was performed. There was no significant difference in the extent of coronary disease or abnormalities of left ventricular function between patients with exercise induced ST segment elevation that was noted to occur in leads with Q waves and those with ST segment elevation plus depression or those with ST segment depression alone. Patients without exercise induced ST segment changes had fewer coronary arteries involved than those who developed ST segment changes. Nineteen patients with exercise induced ST segment elevation alone underwent coronary artery bypass surgery; in 11 this resulted in complete abolition of the exercise induced ST segment elevation and was associated with symptomatic relief and patent grafts without alteration of left ventricular function. Thus, exercise induced ST segment elevation in patients with previous myocardial infarction should be considered as important as ST segment depression in terms of underlying myocardial ischaemia, coronary anatomy, and left ventricular function.