Prognostic Values of Exercise Testing after Acute Myocardial Infarction

Doo, Young Cheoul; Suh, Joong San; Kim, Hyun Soo; Park, Tae Rim; Lee, Rok Yun; Oh, Heung Kook; Han, Yoon Chang; Koh, Soon Hee; Rim, Chong Yun; Koh, Young Bahk; Lee, Young

Abstract

BACKGROUND
Uncomplicated myocardial infarction is often the harbinger of future cardiac events such as unstable angina pectoris,recurrent myocardial infarction or death. The feasibility and safety of exercise testing performed soon after myocardial infarction have been established but the prognostic value of exercise test after myocardial infarction remain inconclusive. The object of this study is to determine whether exercise test results can be utilized to predict of future cardiac events after uncomplicated myocardial infarction.
METHODS
The study group comprised 149 patients with an uncomplicated myocradial infarction. A low level exercise test was performed before discharge from the hospital 8 to 10 days after myocardial infarction. The exercise thst results was considered positive if there was new > or =1mm horizontal or downsloping ST segment depression at 0.08 sec after the J point compared with baseline. The patients were followed for the development of new cardiac events.
RESULTS
1) The exercise test after acute myocardial infarction was performed in 149 patients without complication. The mean duration of exercise test was 14 min(range 1-20 min) and the mean work-load(Metabolic equivalents) was 3.7+/-1.1 METs. 2) 37 patients had ST-segment depression, 13 had ST-segment elevation and 27 had an inadequate blood pressure response to exercise. During the exercise, there were angina in 5 patients, dyspnea in 17 and no symptom in 127 patients. 3) During the follow-up period(1 to 75 month, mean 27.4 month), 29 patients experienced post-myocardial infarction angina, 1 had recurrent myocardial infarction, 4 had revascularization therapy(PTCA 2, CABG 2),5 had ischemic cardiomyopathy and 5 died a cardiac death. 4) The patients with cardiac events such as cardiac death, myocardial infarction and post MI angina had a significantly shorter exercise duration(13.1+/-4.0 and 14.6+/-2.7min, p<0.05), lower exercise tolerance(3.5+/-1.0 and 3.9+/-1.0 METs, p<0.05) and lower peak heart rate(117 +/- and 126+/-5, p<0.05). 5) The ST-segment depression, lower exercise tolerance(<3.0 METs) and history of hypertension were associated significantly with cardiac events(p<0.05) but ST-segment elevation, inadequate blood pressure response to exercise, the use of thrombolytic agents and non-Q wave infarction did not predict future cardiac events. Conclusions: The exercise test after acute myocardial infarction is safe and of limited value for predicting patients at risk of cardiac events in the follow-up period. The ST-segment depression and lower exercise tolerance(<3.0 METs) can predict cardiac events and the prognosis of the patients of this group can be improved with aggressive management and careful follow-up.