Coffee, catecholamines and cardiac arrhythmia.

It is generally agreed that a high release of noradrenaline in the heart may elicit cardiac arrhythmia. Furthermore, administration of aminophylline to patients with ischaemic heart disease frequently elicits ventricular premature beats and ventricular tachycardia. Recent data from animal experiments demonstrate that methylxanthines (aminophylline, caffeine, theophylline) can facilitate noradrenaline release from sympathetic nerve endings. Such facilitation of transmitter release is amplified when myocardial oxygenation is impaired, stressing its clinical significance in relation to ischaemic heart disease. If a similar amplification is also operative in man, a dose of methylxanthine causing a very modest increase in myocardial sympathetic transmitter release in the heart of a healthy subject may be sufficient to cause a three- to six-fold elevation in the local myocardial concentration of noradrenaline in a patient with ischaemic heart disease. We hypothesize that such hypoxia-induced facilitation of sympathetic transmitter release lies behind the reported connection between cardiac events and methylxanthines, for instance sudden cardiac death following coffee consumption.