EFFECTS OF DILTIAZEM ON TOTAL CARDIAC-OUTPUT DISTRIBUTION IN CONSCIOUS RATS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 222  (2) , 359-366
Abstract
The effect of a Ca channel blocker, diltiazem (DZ), on cardiovascular dynamics and the distribution of total cardiac output in the conscious rat were studied. Animals were instrumented for right atrial, left ventricular, arterial and venous pressure recordings and the radioactive microsphere technique was used to measure regional blood flow and cardiac output before (control) and during the i.v. infusion of either DZ at 3 dosage levels (0.4, 2.0 and 10.0 mg/kg per h) or saline placebo at rates matching those of the DZ protocol (0.015, 0.1 and 0.5 ml/min). Maximum volume infusion rate equaled approximately a 2% increase in blood volume/min. Systemic vascular resistance, stroke volume, regional vascular resistances and the regional percent distribution of total cardiac output were calculated. In the experimental group (n = 9, body wt = 404 .+-. 7 g), DZ at the highest dose caused a nonsignificant increase in cardiac output of 61% (cardiac output decreased in 1 animal) and a significant drop in systemic vascular resistance (45%) while no changes occurred in the control group (n = 5, body wt = 440 .+-. 9 g). The major effect of DZ was to increase blood flow and reduce vascular resistance in the coronary circulation (percent distribution of total cardiac output to the coronary circulation, control vs. maximum infusion: saline placebo, 3.9 .+-. 0.5 to 4.5 .+-. 0.4%; DZ, 3.5 .+-. 0.5 to 6.9 .+-. 0.5%, P < .01). Evidently, DZ does not suppress cardiac function and may actually increase cardiac output secondary to afterload reduction. DZ results in a balanced increase in regional blood flow and no major change in total cardiac output distribution in the conscious rat.