Cardiac function curves in conscious dogs

Repeated ventricular function curves were determined over a period of several weeks in seven conscious dogs. The atrial pressures were raised by infusing Tyrode's solution through a large catheter chronically implanted in the left jugular vein while recording systemic arterial pressure, right and left atrial pressures, heart rate, and ventricular output. Ventricular output was measured continually by chronically implanted electromagnetic flow probes. Right and left ventricular output curves, left ventricular minute work curves, stroke volume curves, and stroke work curves were run periodically on all animals in this study. The plateaus of the ventricular output curves were reproducible in each animal from day to day. The average deviation from each animal's mean plateau was found to be only 2.04% (± 0.39% sem). The deviations ranged from .5% to 3.5% of the mean plateau valves. However the left ventricular minute work curves and the stroke work curves were not consistant. These curves always had a descending limb associated with them.