Right atrial pacing soon after myocardial infarction

To assess the presence of residual myocardial ischemia and its prognostic significance soon after an acute myocardial infarction (MI), right atrial pacing (RAP) was performed in 85 consecutive patients 1 day before hospital discharge. No patient was excluded from the study because of his clinical condition. The mean age of the patients was 61.2 years (range 29-85 years). The study was performed at the bedside 10-28 days (mean 14.2 days) after the MI. No complications occurred during or after the test. RAP was considered positive if 1 mm or more of horizontal St depression developed. The mean maximal pacing rate achieved was 147 beats/min (range 100-160 beats/min). There were 46 patients (54%) with negative and 39 patients (46%) with positive RAP. Of the 30 patients with anterior MI, 17% had positive RAP, compared with 61% of the 23 with inferior MI and 63% of the 32 patients with subendocardial MI. The average follow-up period was 5.8 months. Among the 46 patients with a negative RAP, there was one sudden death; no reinfarction occurred, but eight patients required cardiac hospitalization and five patients suffered chest pain. Among the 39 patients with a positive RAP, three died (one suddenly and two after reinfarction); four additional patients had reinfarction. There were 20 cardiac hospitalizations in this group. Eighteen patients suffered from chest pain. A treadmill test was performed 6 months after MI in 37 patients. Seventeen of the 21 patients with negative RAP had a negative test, whereas 13 of the 16 with positive RAP had a positive treadmill test 6 months later. We conclude that RAP can be performed safely in patients after MI. Forty-six percent of all post-MI patients had residual areas of stress-induced myocardial ischemia. RAP was sensitive in predicting subsequent reinfarction, cardiac death, cardiac rehospitalization, angina pectoris and the response to a treadmill test 6 months after MI.