© 1966 American Heart Association, Inc.
Atrial Contribution to Stroke Volume in Dogs with Chronic Heart Block
1 Mayo Clinic and Mayo Graduate School of Medicine, Rochester, Minnesota
2 Mayo Clinic and Mayo Graduate School of Medicine Rochester, Minnesota
In dogs studied without thoracotomy, under morphine-pentobarbital anesthesia and with an average heart rate of 71 beats/minute, atrial systole contributes to ventricular function to a small but significant degree. Stroke volume increased by 7 to 8% when atrial systole was timed to occur 0.1 second prior to closure of the atrioventricular valves, and decreased a similar magnitude when the contribution of atrial systole to ventricular filling was rendered ineffective by the use of an A-V delay of zero so that atrial emptying into the ventricles was prevented by the closed A-V valves. Increases or decreases in right atrial pressure of several centimeters of water induced by infusion of 6% dextran and by hemorrhage, respectively, were not associated with demonstrably significant alterations in these effects.
Key Words: electrical pacing of atria and ventricles • bypass of bundle of His • effective and ineffective atrial contraction • hypovolemia • hypervolemia • stroke volume determined from pulse pressure • nonthoracotomized dogs
Accepted on January 10, 1966
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