[Efficacy of intravenous administration of calcium on sinus dysfunction developed under diltiazem. Apropos of 4 cases].

Four cases of sinus node dysfunction with junctional escape which developed during oral treatment with diltiazem in the usual therapeutic doses (180 to 240 mg/day) are reported. In one case the cardiac toxicity of diltiazem may have been potentiated by amiodarone taken concomitantly. In two cases a biological liver alteration may have modified the metabolism of diltiazem by slowing down its degradation. In all 4 patients, a slow intravenous injection of 1 g of calcium chloride resulted in rapid and lasting restoration of a normal sinus rhythm, making temporary ventricular pacing unnecessary. The authors underline the value of calcium administration as a therapeutic test in all disorders of cardiac rhythm or conduction occurring in patients treated with calcium channel blocking agents.