Regional myocardial performance before, during and after coronary occlusion.

The effects of transient coronary occlusion upon segment length and intramyocardial pressure were studied in seven open-chest dogs. The subendocardial and subepicardial layers in the territory of the left anterior descending coronary artery were instrumented with pairs of ultrasonic crystals and miniature pressure probes. During coronary occlusion, systolic subendocardial pressure decreased from 194 +/- 11 to 141 +/- 12 mmHg (p 0.001) and systolic subepicardial pressure from 82 +/- 7 to 62 +/- 12(p 0.05). Systolic shortening was abolished in both layers. During reperfusion, systolic subendocardial pressure reached 242 +/- 22 mmHg (p 0.05) and systolic subepicardial pressure 100 +/- 10 mmHg (p 0.05). Early during reperfusion a transient overshooting was also observed in subendocardial and subepicardial systolic shortening. The observations of this study are consistent with the hypothesis that unrestricted reperfusion is associated with an overshooting in regional myocardial contractile performance.