Learned control of coronary blood flow.

Mongrel dogs with chronically implanted electromagnetic flow probes on the left coronary artery were curarized and trained to decrease coronary blood flow in order to avoid and escape from stress. Each of four animals learned to consistently decrease coronary flow with increasing independence from changes in other cardiovascular dynamics. One animal achieved dramatic decreases suggestive of profound coronary vasoconstriction. The results may have important implications for the understanding of ischemic heart disease.

Electrocardiogram during experimental coronary thrombolysis.

The electrocardiogram (ECG) was analyzed before and after enzymatic lysis of an intracoronary thrombus in six closed-chest dogs, and in a control group of five dogs without a thrombus. Thrombolysin (18,000 to 50,000 Merck units in 250 ml of 5% dextrose in water) was infused directly into the anterior descending coronary artery in both groups under the same conditions. Complete recanalization of the obstructed artery was achieved in all cases after development of an occluding thrombus and signs of myocardial infarction. In the experimental group, statistically significant differences were found in the mean HR and the R-R,QRS, Q-T and Q-Tc intervals. Changer in the mean values for these parameters were also observed in the control groups without coronary thrombosis but were not significant. Sinus rhythm was maintained in both groups. Histologic findings of the affected myocardium following Thrombolysin infusion was compatible with those seen in acute myocardial infarction. No evidence of necrosis, hemorrhage or inflammation was observed in the control hearts. Infusing Thrombolysin directly into the anterior descending artery had no adverse effect on the myocardium.