Objectives: The purpose of this explanatory analysis was to investigate the relationship between ST-segment depression and the rate-pressure product (RPP) during exercise to determine whether ranolazine's mechanism of action was related to a reduction in myocardial oxygen demand or preservation of myocardial oxygen supply.
Background: In patients with stable ischemic heart disease, ranolazine increases exercise duration and reduces maximal ST-segment depression while exerting minimal effects on heart rate and blood pressure, although its mechanism of action during exercise has not been investigated.
Methods: Patients with stable ischemic heart disease (n = 191) were randomly allocated to a 4-period, double-blind, balanced Latin square crossover study to receive placebo, and ranolazine 500, 1,000, and 1,500 mg twice daily (bid) for 1 week each. Exercise treadmill tests were performed at baseline and at the end of each treatment period. The RPP and ST-segment depression were assessed before starting exercise, at each stage of exercise, and at maximal exercise.
Results: Compared with placebo, ranolazine produced a dose-dependent reduction in ST-segment depression that became more marked as exercise-induced ischemia became more pronounced, associated with clinically minor decreases in heart rate and blood pressure. At 12-min exercise, the amount of ST-segment depression compared with placebo and controlled for RPP was reduced by 22.3% on ranolazine 500 mg bid (p = 0.137), by 35.4% on 1,000 mg bid (p = 0.005), and by 45.8% on 1,500 mg bid (p < 0.001).
Conclusions: The progressive magnitude of ischemia reduction on ranolazine was proportionally more substantial than the minor reductions in heart rate or RPP, suggesting that ranolazine's beneficial mechanism of action is most likely primarily due to an improvement in regional coronary blood flow in areas of myocardial ischemia.
Copyright © 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.