Regulation of myocardial blood flow in man during strenuous exercise and severe hypoxia

Myocardial blood flow has been studied in 7 trained and 7 untrained healthy volunteers by means of the argon method. Measurements were carried out at rest, during stepwise increase in arterial hypoxia down to 8.7 vol % and during heavy exercise comparable to 65% of delta VO2 max. Measurements were carried out during hemodynamic and respiratory steady state conditions. Hemodynamic parameters were measured or even monitored. It could be shown that myocardial blood flow, myocardial oxygen consumption and myocardial oxygen consumption per heart beat are less in the trained state compared to the untrained one. The differences are particularly pronounced during heavy exercise. The reaction of the coronary conductance vessels to acute arterial hypoxia is not influenced by training effects. The surplus of oxygen and substrates supplied to the heart by the coronary circulation is well maintained during exercise and hypoxia.

Telemetry of cardiac left ventricular pressure in conscious dogs

A fully implantable telemetric system for the measurement of cardiac left ventricular pressure and derived parameters in conscious dogs is presented. It provides the following advantages: ethical acceptability, scientific relevance, economical experimentation, avoidance of stress-induced situations for the animal, experiments without anaesthesia or sedation. The system has an operation time which allows the sequential pharmacological evaluation of a great number of drugs in individual dogs as has been shown by testing the effect of the positive inotropic agent, dobutamine, and the calcium antagonists, verapamil and nifedipine.