Characterization of the warm-up phenomenon in patients with coronary artery disease

The warm-up phenomenon, that is, attenuation of myocardial ischemia during repeated physical exercise, has been demonstrated in numerous studies. However, its duration and underlying factors have not been properly studied in patients with coronary artery disease.

Fifty-two patients with stable angina pectoris and previous positive stress testing underwent cardiac catheterization and 2 successive exercise tests randomly separated by resting periods of 15, 30, 60, or 120 minutes (groups 1-4).

The percentage of patients demonstrating the warm-up phenomenon was 85%, 31%, 31%, and 46% in groups 1 through 4, respectively (P =.018). The differences in the parameters (test 2 to test 1) registered during exercise tests were 28.1 +/- 7.1, 3.5 +/- 5.8, -4.9 +/- 4.8, and 4.9 +/- 5.1 (P =.003) for the double product (beats/min x mm Hg. 100) at 0.1 mV ST depression; 1.1 +/- 0.2, 0.2 +/- 0.2, 0.2 +/- 0.2, and 0.2 +/- 0.2 (P =.004) for the time (min) to 0.1 mV ST depression; -3.4 +/- 1.2, 0.5 +/- 0.7, -0.3 +/- 0.8, and -0.3 +/- 0.3 (P =.032) for the ST/HR-slope (microV/beats/min); and -0.3 +/- 0.2, 0.1 +/- 0.1, -0.1 +/- 0.1, and -0.7 +/- 0.4 (P =.047) for the ischemic burden (mV x min) in groups 1 through 4, respectively. The patients having angiographically less severe disease showed significantly better ischemia adaptation (P =.012), but there was no correlation between the extent of adaptation and other clinical or angiographic findings.

The warm-up phenomenon is commonly encountered in patients with coronary artery disease, although the protection appears to wane relatively quickly. The adaptation appears to be markedly better in patients with less severe disease.