THE INCIDENCE OF ATRIAL ARRHYTHMIAS DURING INFERIOR WALL MYOCARDIAL-INFARCTION WITH AND WITHOUT RIGHT VENTRICULAR INVOLVEMENT

The atrial arrhythmia profile during inferior wall acute myocardial infarction (AMI) has not been systematically examined with respect to right ventricular (RV) involvement. To this end, 62 consecutive patients with first inferior wall AMI and no other conditions known to increase susceptibility for rhythm disturbances were studied by 24-hour Holter monitoring during the first and tenth day of infarction. Based on radionuclear ventriculography performed on day 2 of infarction, patients were allocated to two groups: group A-36 patients (58%) with right ventricular ejection fraction (RVEF) <40% (mean +/- SD, 31 +/- 6%) and group B-26 patients (42%) with normal (>40%) RVEF (mean +/- SD, 47 +/- 5%). There were no significant differences between the two groups with respect to age, sex, or left ventricular (LV) function. In the group as a whole, ectopic activity in the different categories of atrial arrhythmias was significantly higher during the first day than on the tenth day of infarction. Comparing the two groups, 33 patients (92%) in group A had a mean hourly frequency of one or more atrial premature contractions (APCs) during the first day of infarction compared with 18 patients (69%) in group B (p < 0.001). Atrial and supraventricular tachycardia were recorded more frequently in group A patients (16 of 36 [44%] versus 8 of 26 [31%]) as well as atrial fibrillation (AF) (7 of 36 [19%] versus 1 of 26 [4%]). Quantitative analysis showed a similar trend for a higher rate of ectopic events in group A patients. Ectopic activity was neither influenced by LVEF nor by age or sex. Using stepwise regression analysis, RVEF was independently related to the prevalence of AF and APCs. The data presented indicate that patients with inferior wall MI accompanied by RV dysfunction are more prone to develop atrial rhythm disturbances than patients with preserved RV function. Atrial infarction or ischemia, atrial distension, and a raised right atrial pressure may account for this trend.