Response of coronary arteries to nitrates, the EDRF-donor SIN-1, and calcium antagonists.

Intracoronary drug administration is an important tool to study coronary effects without interaction of systemic effects. The difficult methodological aspects and the results of clinical trials in which the effects of vasodilating drugs were evaluated with respect to coronary dilatation are reviewed. Major (coronary substrate, study design) and minor (measuring devices, methods of evaluation) methodological problems make it difficult to precisely evaluate pharmacological effects such as dose-response relationship, duration of action, and selective responses, and to compare the effects of different drugs. From a clinical point of view, knowledge of the maximal effect (EDmax) in coronary stenoses and the duration of action is essential. NO-donors tend to act stronger than CA-channel blockers which may be attributable to their different modes of action. Among those NO-donors investigated, SIN-1 showed stronger effects than nitroglycerin. Only with SIN-1 were maximal effects obviously achieved. The additional administration of nitroglycerin or nisoldipine never led to a more prominent dilatation. In coronary stenoses, the underlying morphology causes a wider range of responses than is seen in normal segments: deendothelialized stenoses with high coronary tone show a larger dilatation, while fully sclerotic stenoses may not react.