Transient changes in left ventricular mechanics during attacks of Prinzmetal's angina: an M-mode echocardiographic study.

M-mode echocardiograms were recorded in 12 patients with Prinzmetal's angina during 29 episodes of transient myocardial ischemia at rest (18 spontaneous and 11 ergonovine-induced). At peak ST segment elevation a regional mechanical impairment was observed in the interventricular septum during 23 episodes of angina and in the posterior wall during six episodes. In the 18 spontaneous episodes the left ventricular ischemic wall, when compared to the basal state, was found to have a significant reduction in motion (-76.3 +/- 9.1%) (mean +/- SEM), in diastolic thickness (-11.7 +/- 2.5%), and in percent systolic thickening (-88.0 +/- 5.6%). Increase in left ventricular end-diastolic diameter (+13.1 +/- 2.1%) and decrease in percent fractional shortening (-38.1 +/- 3.7%) were also observed. When ST segment was back to the isoelectric line, a transient overshoot in regional left ventricular function was observed. In induced episodes statistically significant changes could be detected by M-mode echocardiography even before appearance of ST segment elevation and anginal pain. No significant difference was found in type or degree of mechanical impairment between induced and spontaneous episodes. Therefore, in patients with Prinzmetal's angina: (1) M-mode echocardiography allows detection of mechanical changes due to transient myocardial ischemia; and (2) mechanical impairment occurs earlier than clinical (pain) and electrocardiographic (ST segment elevation) signs of transmural ischemia.