Efficacy of Ranolazine in Patients With Chronic Total Occlusions of Coronary Arteries

Overview

Anti-anginal drugs relieve ischemia and symptoms by reducing myocardial oxygen demand by reducing heart rate and or contractility (beta-blockers, phenylalkylamine and benzothiazepineate classes of calcium antagonists) or vasodilatation of the venous system (fall in pre-load) and coronary vessels. Late sodium channels remain open for longer in the presence of myocardial ischaemia. Ranolazine, a novel anti-anginal agent, acts by inhibiting the inward late inward sodium current (INaL), reducing intracellular sodium accumulation and consequently intracellular calcium overload via the sodium/calcium exchanger. It is currently thought that this reduction in intracellular calcium reduces diastolic myocardial stiffness and therefore compression of the small coronary vessels. There is considerable animal data to support this theory. There are good theoretical reasons to postulate that patients with chronically occluded vessels may derive less benefit from conventional anti-anginal agents, particularly vasodilators. The ischemic myocardium, subtended by the occluded vessel, will already be subject to significant concentrations of paracrine vasodilators such as adenosine. Ranolazine, therefore, may on the basis of its mechanism of action, provide greater relief of ischemia in such patients than conventional anti-anginal agents.

To test this hypothesis, a randomized study comparing addition of ranolazine to addition of a minimum of 2 conventional anti-anginal agents in patients with chronic total occlusions would be required. To be sufficiently powered, this would require a significant number of patients recruited in a multi-center trial. This study is an initial pilot study with inactive placebo, not addition of a conventional anti-anginal agent, as the control using MRI imaging data as the primary end-point.