Evaluation of a new systolic time interval, the Q-V peak: effects of heart rate, contractile state, and loading conditions in dogs.
The authors investigated the effects of alterations in heart rate, contractility, and loading conditions on a newly defined systolic time interval, the Q-V peak, in 46 anesthetized dogs. The Q-V peak was measured as the time from the beginning of the electrocardiographic Q wave to the moment at which the blood flow rate reached its peak in the ascending aorta as determined with an electromagnetic flowmeter. The Q-V peak did not change significantly as the heart rate was varied by atrial pacing between 70 and 110 beats/minute. The Q-V peak shortened when the contractility was augmented with dobutamine (p = 0.0001) and was prolonged when it was depressed with propranolol (p = 0.0001). However, the Q-V peak did not change significantly when the left ventricular end-diastolic pressure or the mean aortic blood pressure was increased to 130% or decreased to 70% of the baseline values. These findings suggest that one may also evaluate left ventricular performance by measuring the time to systole, which the authors define as the Q-V peak.
Hashimoto
T
T
Third Department of Internal Medicine, Nagoya City University Medical School, Japan.
Ohte
N
N
Narita
H
H
Kobayashi
K
K
Fujinami
T
T
D000818:Animals; D001011:Aorta; D001783:Blood Flow Velocity; D003911:Dextrans / Q000494:pharmacology; D003971:Diastole / Q000187:drug effects; D004285:Dogs; D004562:Electrocardiography; D005069:Evaluation Studies as Topic; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D008729:Methoxamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000502:physiology; D013599:Systole; D016277:Ventricular Function, Left / Q000187:drug effects
D003911:Dextrans; D008729:Methoxamine