Evolution of ST Segment and Q and R Waves during Early Phase of Inferior Myocardial Infarction

. Using the aVF lead, the ST segment deviation and the amplitudes of Q and R waves were measured hourly for 48 hours after the onset of symptoms in 14 patients with inferior AMI. The average ST deviation reaches a maximum elevation at about 3 hours and then falls to a uniform level within 12 hours. The average depth of the Q waves began to increase within the first 2 hours, and the increase was linear until around the 12th hour, whereafter the depth was somewhat uneven. The average height of the R waves declined almost linearly from the 3rd to 15th hour, after which the height became fairly uniform. Within a 48-hour period after the onset of symptoms, there was a significant positive correlation not only between the average amplitudes of the Q and R waves (r = 0.951, p > 0.001), but also between the courses of the individual Q and R waves in 13 of the 14 patients. A significant positive correlation was found between ST elevation at 3 hours and the reduction in the R wave within 24 hours (r = 0.634, p > 0.05), but no correlation existed between ST elevation and the Q wave at these times. It is concluded that within 48 hours of the onset of symptoms, the magnitude of electrically inert myocardial tissue can be determined by the course of the Q or R waves, but that during the first 24 hours the R wave is superior to the Q wave for evaluating the evolution of the infarction process.