Effect of combined dopamine and bunazosin on the ischemic heart after occlusion of the coronary artery.

In order to investigate whether dopamine combined with bunazosin improves cardiac function, the global and regional cardiac function and regional blood flow of 7 anesthetized dogs were analyzed before and after occlusion of the left anterior descending coronary artery (LAD), then after 10 micrograms/kg/min dopamine infusion following the LAD occlusion, and again after a bolus infusion of bunazosin 250 micrograms/kg. Dopamine with bunazosin reduced left atrial pressure from 4.9 +/- 0.9 to 3.1 +/- 0.5 mmHg (p less than 0.05) and improved cardiac output from 1.22 +/- 0.15 to 1.50 +/- 0.14 L/min (p less than 0.05), maximum positive left ventricular dp/dt from 1721 +/- 202 to 3600 +/- 663 mmHg/sec (p less than 0.05) and the time constant from 45.2 +/- 5.0 to 27.5 +/- 4.6 msec (p less than 0.01). Bunazosin added to the dopamine reduced the elevated left ventricular peak systolic pressure caused by dopamine from 130 +/- 7 to 113 +/- 8 mmHg (p less than 0.01). With regard to the regional wall motion, the impaired LAD-delta L (the segment systolic shortening) and LAD-Elmax (the slope of peak systolic pressure--endsystolic length relation) following the LAD occlusion improved from 0.5 +/- 2.5 per cent to 5.9 +/- 2.6 per cent (p less than 0.01) and from 50 +/- 9 to 82 +/- 14 mmHg/mm (p less than 0.01) after the infusion of dopamine with bunazosin. Dopamine greatly increased the Rate Pressure Product (RPP) from 12610 +/- 1120 after LAD occlusion to 16950 +/- 1420, whereas dopamine in combination with bunazosin did not increase the RPP due to a drop of LV-PSP with little change in regional myocardial blood flow. It was concluded that combining dopamine with bunazosin was useful for improving both the global and regional cardiac functions of the ischemic heart.