Ambulatory Blood Pressure and Left Ventricular Changes Evaluated in Relation to Acute Myocardial Infarction

In 16 patients of acute myocardial infarction (AMI), studies were made to elucidate the possible relationship between ambulatory blood prepssure and structural changes incurred in the left ventricle. Among the patients selected, 7 had anterior AMI and 9 inferior, and the infarction was not accompanied by any serious complication. M-mode Doppler echocardiography were performed and the ambulatory blood pressure was monitored 1 week, and 4 weeks after the onset of AMI. The dimensions of the left ventricle in end-diastole (Dd) and in end-systole (Dd), the interventricular septal thickness (IVST), and the posterior wall thickness of the left ventricle in end-diastole were determined by echocardiography, and the left ventricular inflow waves were determined from Doppler indexes. During the monitoring of ambulatory blood pressure, readings were obtained every 30 minutes for a 25-hour period to determine the systolic blood pressure (Ps), diastolic blood pressure (Pd), and heart rate (HR), then 24-hour averages (24 Ps, 24 Pd, 24 HR), daytime averages (DPs, DPd, DHR), and nocturnal avarages (NPs, NPd, NHR) were calculated. Over the 4-week examination period, no important changes were observed in the M-mode and Doppler echocardiographic parameters, and the echocardiographic indices associated with anterior AMI were not significantly different from those of inferior AMI (p=0.014). One week after AMI onset, the nocturnal systolic blood pressure was lower (p<0.01) in anterior AMI than in inferior AMI. However, a rise in the nocturnal systolic blood pressure was noted in anterior AMI from week 1 to week 4 (p=0.01), a phenomenon seen only in the patients of anterior AMI. In inferior AMI the nocturnal heart rate decreased from week 1 to week 4 (p<0.01), and an abnormal diurnal pattern showing a negligible decline in the nocturnal systolic blood pressre was observed 1 week after onset of infarction. Between weeks 1 and 4, the thickness of the interventricular septum changed in an inverse correlation with the average 24-hour systolic blood pressure (r=-0.601, p=0.014) and the average 24-hour diastolic blood pressure (r=-0.53, p=0.036), with the average daytime systolic blood pressure (r=-0.604, p=0.017), and with the average daytime diastolic blood pressure (r=-0.571, p=0.021). These results indicate that soon after the onset of AMI the site of infarction plays an important role on the regulation of blood pressure and heart rate and that changes incurred in the interventricular septal thickness have a marked influence on the blood pressure soon after an AMI.