Specific mechanism of action of calcium antagonists in the neutralization of experimental coronary spasms
Fleckenstein-Grün, G.; Makita, Y.J.; Byon, Y.K.; Frey, M.
Zeitschrift für Kardiologie 73(Suppl 2): 71-77
1984
ISSN/ISBN: 0300-5860 PMID: 6099011 Document Number: 234784
In vascular smooth muscle cells as in myocardial fibres, a transmembrane supply of Ca ions is required for activation of the contractile system. This is especially obvious in the vasculature of the great subepicardial coronary stem arteries which rapidly lose contractility upon extracellular Ca withdrawal. Consequently, in this special section of the coronary bed, even minute concentrations of calcium antagonists, by interference with transmembrane Ca++ influx, are capable of a spectacular suppression of contractile vascular smooth muscle performance. Moreover, in the extramural coronary vasculature - in contrast with most systemic arteries - the scope of the vasodilator and spasmolytic effects of calcium antagonists is particularly broad. This means that calcium antagonists produce a nearly uniform cessation of both tonic and phasic coronary responses regardless of whether different vasoconstrictors, receptors or pathways of Ca++ delivery are involved. Thus, our animal experiments as well as successful clinical trials highlight the outstanding efficacy of calcium antagonists in neutralizing all types of extramural coronary artery spasm. This action of calcium antagonists seems to be the predominant haemodynamic factor in relieving or preventing acute ischemic episodes especially in coronary heart disease with spastic components.