Prognostic value of serial exercise test results in physically active coronary artery disease patients
The purpose of this study was to determine whether graded exercise test (GXT) variables known to have prognostic importance in the setting of severe-moderate coronary artery disease (CAD) and early post-myocardial infarction (MI) patients can also differentiate which physically active male patients with lesser disease and/or old MIs (undergoing serial GXT evaluation and an exercise maintenance program) will have a serious cardiac event, i.e., MI, coronary artery bypass surgery (CABG), or death. Data were obtained at two cardiac rehabilitation sites from three GXT results in 14 paired cardiac event (CE) and nonevent (NE) group subjects based on peak estimated oxygen consumption (VO2estpk). Comparisons were also made with seven of these 14 paired group subjects for whom peak measured oxygen consumption (VO2pk) were available. Statistical analyses were done on certain continuously-scaled, ordinally-scaled, and dichotomized dependent variables from selected GXTs. The continuously scaled dependent measures included VO2estpk peak heart rate (HRpk), resting heart rate (HRrest), peak rise in exercise heart rate (HRdiff), peak systolic blood pressure (SBPpk), rise in exercise systolic blood pressure (SBPdiff) and peak rate pressure product (RPBpk), whereas, the ordinally-scaled dependent measures included functional aerobic impairment (FAI) and cardiac rehabilitation potential (CRP). For the dichotomized variables, ischemic ST-segment deviation at peak exercise (ischemic STdev} I exercise-induced ventricular dysrhythmias (VENTdys) and exercise-induced chest pain were selected. Hotelling's T² test was utilized for analysis of the continuously- and ordinally-scaled dependent measures, whereas chi-square test was used for the dichotomized variables. There was a significant difference (F = 3.53; df = 3,11; p = .05) found between the paired CE-NE groups at and within each GXT time period for HRdiff in the 14 paired groups. Statistical analyses revealed no significant differences for any other variables in either the 14 paired and 7 paired groups. The small sample size limited the potential for statistical testing of the results in this study. However, the findings do appear to support that a poor chronotropic response indicated by HRdiff may have prognostic importance for those active CAD participants in supervised exercise maintenance programs who are at risk of a future cardiac event, i.e. MI, CABG, or death.