Adaptation to myocardial ischemia during repeated ventricular pacing in patients with coronary artery disease

Objective: The purpose of our study was to evaluate whether repeated ventri cular pacing is able to induce adaptation against ischemia in coronary arte ry disease patients. Design: Fifteen patients with documented coronary arte ry disease were subjected to two successive periods of rapid ventricular pa cing (150 bpm) of equal length (195 +/- 33 s), the first bring limited by i ntolerable anginal pain. The second pacing period, of the same length us th e first. was initiated Lifter the disappearance of angina and ST depression , the mean resting lime being 433 +/- 30 s. Blood samples Tur the determina tion of transcardiac differences in glucose, lactate, free fatty acids, K+, pCO(2), FH, oxygen saturation and noradenaline were taken from the femoral artery and coronary sinus before and at the rad of each pacing period. The mechanical performance of the hearts was followed by continuous monitoring of intra-arterial blood pressure and pulmonary capillary wedge pressure, a nd the observed adaptation in the measured variables during the successive pacing tests was correlated with the duration of angina, severity of corona ry artery disease and degree of collateralization. Results: Changes in the transcardiac pH and K+ differences, ST segment and pulmonary capillary wedg e pressure were less pronounced during the second pacing period. The subgro up with net lactate production before or after the first pacing period demo nstrated metabolic adaptation manifested as improved lactate extraction dur ing the second pacing period. Rate-pressure product and oxygen extraction, and thus presumably also overall oxygen consumption and oxygen delivery, we re similar during both tests. The magnitude of adaptation did not correlate with the duration of angina, severity of coronary artery disease or overal l collateral score. Conclusion: Rapid ventricular pacing is able to induce adaptation to myocardial ischemia. but the exact mechanisms in this process remain to be elucidated.