Dynamic redistribution of coronary blood flow in the dog as measured by a thermistor technique

The effect of heart rate upon the coronary blood supply to the right and left ventricles was studied in anaesthetized, open-chest dogs. Indirect recording of coronary supply was obtained using thermistors placed locally on the surface or in the wall of the ventricles. The validity of the thermistor technique was examined in vivo as well as by using an in vitro laboratory model. Myocardial perfusion was also measured using electromagnetic flowmeters placed around the anterior descending and circumflex arteries, as well as the coronary sinus and Thebesian drainage. It was found that at heart rates lower than about 150/min, coronary perfusion to all areas increased equally as rate was elevated. At higher heart rates, coronary flow to the right ventricle continued to increase linearly with rate, whereas perfusion to the left ventricle either increased much less or declined. It is concluded that tachycardia causes coronary flow to be dynamically redistributed in favour of the right ventricle.