Early right atrial pacing after myocardial infarction. I. Comparison with early treadmill testing.

Right atrial (RA) pacing and modified treadmill testing (TT) were performed in 111 patients recovering from acute myocardial infarction (MI) before hospital discharge to determine whether ischemic responses are more common with RA pacing than with TT and whether the prognosis could be better determined by the results of 1 test compared with the other. Patients with predischarge congestive heart failure, chest pain, physical disability or age older than 70 years were excluded. Ischemic responses were significantly more frequent during RA pacing than during TT (41% vs 34%, p = 0.02). The results of the 2 tests were concordant in 102 patients (92%): Both were positive in 37 and both negative in 65. In 8 patients, results of RA pacing were positive and results of TT were negative; only 1 patient had positive TT and negative RA pacing responses. The higher percentage of positive responses during RA pacing than during TT can be attributed to the significantly higher pressure-rate product achieved during pacing (18,773 vs 16,831 mm Hg/min, p less than 0.001). The ischemic threshold, defined as the pressure-rate product at which an ischemic change was first noted in a particular patient, was almost identical in both tests. During a mean follow-up period of 16 months, 10 patients had recurrent MI; 8 had positive predischarge RA pacing but only 5 had positive TT responses (p = 0.008). Six patients died; in 3 RA pacing responses were positive and in 2 TT responses were positive.(ABSTRACT TRUNCATED AT 250 WORDS)