Dopamine-induced aggravation of myocardial ischaemia in the paced heart: cardiosurgical perspectives.

The action of dopamine on the blood supply to acutely ischemic cardiac areas was investigated at arbitrarily selected, fixed heart rates. The A-V node of open chest dogs was crushed and the ventricles were paced between 30 and 220 beats per minute (bpm). Ischemic blood supply was assessed by computer-aided infrared thermography. It was found that the ischemic (collateral-dependent) blood flow paralleled overall myocardial blood supply (coronary sinus outflow) and was directly related to heart rate between 30 and 100-140 bpm; above this frequency it decreased moderately. Dopamine (10 micrograms/kg i.v.) elicited a marked increase of ischemic flow in the heart paced at 60 bpm, whereas the drug action was characterized by a long-lasting flow decrease (preceded by a slight dilation) at 200 bpm. It was concluded that the treatment of the tachycardic heart with dopamine, as it frequently occurs in postbypass cardiac and coronary surgery, may place the non-completely revascularized myocardium at risk.