The paper by Dr. Mclvor and colleagues broadly entitled "Clinical Effects and Utility of Intracoronary Diltiazem" raises significant issues about adjunctive therapy during angioplasty. There is limited published data on parenteral diltiazem use during PTCA; this study describes a small number of patients receiving a fixed dose via intracoronary administration.Intracoronary diltiazem has at least five potential applications during coronary angioplasty. First, it could provide epicardial vasodilation prior to instrumentation: a 10 to 20% increase in luminal diameter in both normal [ I ] and diseased [2] segments has been demonstrated by others and confirmed in this paper, albeit in diseased segments only. Second, it could attenuate ischemia during balloon inflation, allowing for better-tolerated and longer inflations, and potentially limit myocardial necrosis [3]. Careful studies of a number of agents, including nitroglycerin [4], propranolol [ 5 ] , verapamil (61, nifedipine [7], as well as intravenous diltiazem [8,9] have demonstrated reduction of ischemia during balloon occlusion. Third, intracoronary diltiazem could provide treatment for severe coronary vasospasm or no-ref low phenomenon, the latter seen after embolization of clot, debris from degenerated vein grafts, or during routine rotational atherectomy. Fourth, diltiazem could have adjunctive benefit, based on data from intravenous studies, on heart rate control during angioplasty by preventing supraventricular tachycardia and preventing catecholamine mediated sinus tachycardia [lo]. Finally, it may have potential hemodynamic benefits through its vasodilator activity and early improvement in segmental systolic function [ 1 I ] in selected patients.McIvor and colleagues report the effects of intracoronary diltiazem on heart rate, blood pressure, electrical conduction, and coronary artery diameters. In an earlier study, we looked at myocardial ischemia as measured by ST segment changes and chest pain score \ 121, using a much higher dose of intracoronary diltiazem (100 pg/kg) in a randomized comparison with placebo. We found marked reduction of ST segment elevation and chest pain. This was achieved at the penalty of a >40% incidence of significant but transient conduction distrubances, although the dosage was substantially higher than that described in this issue of the Journal. We speculated initially that avoiding infusion into a right coronary artery supplying both the sinus and a-v nodal arteries might eliminate conduction problems, but experienced similar bradyarrhythmias with injection into the LAD and nondominant left circumflex arteries as well.Thus we would like to sound a note of caution regarding the encouraging findings reported by Dr. McIvor and colleagues that intracoronary diltiazem given slowly at low dose appeared to be safe in their 12 patients. The use of intracoronary diltiazem is likely to be considered for severe vasospasm and for no-reflow type ischemia, currently most common with use of the Rotablator. In most laboratories, this pa...
