Kentaro Honma

Significance of discordant ST alternans in ventricular fibrillation.

With the use of epicardial mapping, we investigated the electrical alternans of the ST segment during acute myocardial ischemia and studied the difference in ST alternans between dogs with resultant ventricular fibrillation and those without it. During the 7-minute occlusion of the left anterior descending coronary artery below its first diagonal branch, 60 epicardial unipolar electrograms were recorded simultaneously at 1-minute intervals by a computerized mapping system. ST alternans was found in the eight dogs we observed. The amplitude of ST alternans (difference in the ST segment elevation of two consecutive electrograms) was greater in dogs with ventricular fibrillation (n = 4) than in those without it (n = 4) (3.92 +/- 1.24 versus 0.58 +/- 0.49 mV, p less than 0.05). Three of the four dogs with ventricular fibrillation demonstrated discordant ST alternans (i.e., adjacent leads were out of phase). Results from the present study indicate that an increased amplitude and discordance of ST alternans during acute myocardial ischemia are related to ventricular fibrillation and act as indicators of time and spatial unevenness of ventricular repolarization.

Use of body surface electrocardiographic mapping to localize the asynergic site in previous myocardial infarction

Body surface electrocardiographic (ECG) maps of myocardial infarction were analyzed using the departure mapping technique, which represents the abnormal potential distribution out of normal ranges. Body surface ECG mapping using 87 leads was performed on 65 patients with previous myocardial infarction and on 40 normal volunteers. Potential departure maps at 10, 20, 30, 40, and 50 msec after the onset of QRS were constructed; each map indicated, if present, the area of abnormal decreased potential that is more than 2 standard deviations from the normal range (-2 SD area). In patients with myocardial infarction, the appearance time and the location of the -2 SD area were specific for the sites of left ventricular asynergy; the sensitivity and specificity were 86% and 100% for the asynergy of segment 2 (20 msec, on the upper left anterior chest), 87% and 97% for segment 3 (30 msec, on the middle anterior chest), 86% and 80% for segment 4 (20 or 30 msec, on the lower right anterior chest), and 88% and 90% for segment 5 (30, 40, or 50 msec, on the middle back), respectively. The sensitivity of these criteria was better than that of 12-lead ECG, while the specificity was comparable. In the analysis of body surface ECG mapping data, departure maps aid in depicting abnormalities and in making an accurate assessment. Body surface ECG mapping can be used to improve the diagnostic ability of ECG to detect myocardial infarction.

Diagnosis of right ventricular involvement in chronic inferior myocardial infarction by means of body surface QRS changes

ST segment elevation in right precordial leads is thought to be good predictor of right ventricular involvement in patients with acute inferior myocardial infarction. This view, however, is rapidly disappearing. Therefore, using QRS changes in body surface potential maps in the chronic phase, we have attempted to differentiate patients with or without right ventricular involvement. Thirty patients with chronic inferior myocardial infarction (2 or more months after onset) were studied, in whom 87 unipolar ECGs and right ventriculograms were recorded. The patients were then divided into three groups depending on the locations of their abnormal QRS potentials (-2SD area) exceeding the normal range (mean -2SD). In group A, the -2SD area was located predominantly on the right inferior chest, in group B on the left inferior chest, and in group N on both the right and left inferior chests equally. The results showed that group A had a lower right ventricular ejection fraction (RVEF) compared with group B (A, 40 +/- 7%; B, 53 +/- 10%; p less than .001), while there was no difference in left ventricular ejection fraction between the two groups (49 +/- 11% and 49 +/- 11%, respectively). Moreover, right ventricular asynergy occurred in 14 of the 18 patients (78%) of group A but in only one of the 10 patients (10%) of group B. Group N was presumed to be intermediate between groups A and B.(ABSTRACT TRUNCATED AT 250 WORDS)