Sinoatrial and atrioventricular block caused by intracoronary infusion of adenosine early after heart transplantation.

Intracoronary adenosine was infused in 22 patients early (less than 2 months) after heart transplantation to study coronary flow reserve in the left anterior descending artery. Potentially serious bradycardia requiring discontinuation of the infusion occurred in three patients. This complication had not been noted when adenosine was given to 84 patients with at least 1 year after transplantation. Newly transplanted hearts may therefore have increased susceptibility to the bradycardic action of adenosine, which should be used with caution in this population.