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We investigated the influence of quantitative changes in myocardial contractile state, reflected by changes in the end-systolic pressure-volume relationship (its slope and volume intercept) and by changes in the slope of the relationship between change in pressure per unit time and end-diastolic volume induced by beta-adrenergic stimulation or inhibition, on the Doppler derived blood flow velocity wave form of the carotid artery, using a newborn lamb model. Acceleration time of the velocity wave form was investigated during control state I, during 4 and 8 micrograms/kg/min dobutamine infusion, during control state II, and during 0.5 mg/kg propranolol infusion, respectively. Using multiple linear regression analysis with dummy variables, confounding effects such as interanimal variability were removed. Acceleration time showed a strong relationship to both the slope and the volume intercept of the end-systolic pressure-volume relationship and to the change in pressure per unit time-end-diastolic volume relationship. The relations appeared to be independent of aortic pressure and relative resistance in the vascular bed of the carotid artery. These results indicate that acceleration of cerebral blood velocity may prove to be useful in assessing changes in myocardial contractile state of the newborn.

Acceleration of Blood Flow Velocity in the Carotid Artery and Myocardial Contractility in the Newborn Lamb