Effect of Infarct Site on Diastolic Time During Exercise: Methods

Effect of Infarct Site on Diastolic Time During Exercise: MethodsDiastolic time (DT), an important determinant of myocardial oxygen supply, has been shown to have a nonlinear relation to heart rate (HR) in various conditions. DT is especially important to the residual functioning myocardium of the noninfarcted segment after acute myocardial infarction (MI) because subendocardial blood flow decreases with increased intra-myocardial pressure. A higher mortality rate has been reported after anterior wall than after inferior wall MI, independent of infarct size.” However, the difference in cardiac function during exercise between patients with anterior and those with inferior MI have not been fully evaluated. In this study, we sought to clarify the difference in left ventricular systolic and diastolic function during exercise in relation to the infarct site. Accordingly, patients whose first anterior and inferior MI of equivalent infarct size performed supine bicycle exercise.
Among 114 consecutive patients with their first Q wave acute MI admitted to our hospital, we evaluated 21 male patients (anterior MI, 11 patients; inferior MI, 10 patients) who not only underwent both exercise test and coronary arteriography but also had a singlevessel disease with negative exercise test. All patients included in this study had had their first MI 6 to 8 weeks before the study, and none of the patients had renal dysfunction, mitral regurgitation, atrial fibrillation, intraventricular conduction defects, or critical arrhythmias. The diagnosis of MI was made when the patients had an S-T elevation with a new Q wave (anterior MI, two or more in VM; inferior MI, 2, 3, and aVF in the serial ECG and at least twice the normal elevation in serum creatine Idnase-MB equal to or greater than 5 percent. Sixteen patients (anterior MI, eight patients, and inferior MI, eight patients) had reperfusion therapy (intracoronary thrombolysis or percutaneous transluminal coronary angioplasty) at the time of admission. Patients with 1 mm or more of S-T segment elevation and Q-S or Q-R in the right precordial lead (V4R) at the time of admission were considered diagnostic of right ventricular MI and were not included in this study. The patients were followed up with serial serum enzyme determinations at 12-h intervals for a total of 72 h after admission. Before entry into the study, each patient underwent a complete physical examination, and the patients were excluded from the study if they had physical signs of obstructive lung disease, angina pectoris, or intermittent claudication that limited their exercise capacity. All medications were discontinued for at least 24 h before the study. None of the patients was receiving P blockers. The exercise protocol was approved by our institutional committee on human research, and informed consent was obtained from all patients before the study.

This entry was posted in Cardiology and tagged anterior inferior, coronary arteries, ejection fraction, norepinephrine, pulmonary artery.