Abstract
The standard ejection phase indices of ejection fraction (EF) or mean ejection rate (SER) may be normal at rest in the presence of early left ventricular dysfunction in children with hemoglobinopathies (HPt). It has been shown in animals that the y intercept of the linear force velocity relation is a function of contractile state. In man, mean BP under varying loading conditions plotted against SER normalized for end diastolic volume (EDV), represents a linear force velocity relationship. To utilize this principle to detect subclinical ventricular dysfunction in HPts we used the nuclear stethoscope to measure SER while infusing methoxamine to increase afterload in 2 HPts with Sickle Cell disease and 7 with Thalassemia major. All 9 were asymptomatic and had normal function by 2-D echo as well as normal baseline SER and EF. All were on chronic transfusion protocols. For comparison, similar data was obtained from 4 healthy volunteers. The mean value of the y intercepts for the plots of SER and mean BP for the HPt was 3.14±.7 EDV/S which was significantly lower than the mean value for the controls of 4.36±.3 EDV/S (p<.05). Furthermore, 7 of 9 HPts had values>2 SD below the control mean.
In conclusion: the use of the nuclear stethoscope to measure the response of ejection phase indices to afterload challenge is a new, noninvasive method which appears to be more sensitive in detecting subclinical abnormalities in the contractile state than standard measures of function such as EF.
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Addonizio, L., Bierman, F., Johnson, L. et al. 71 DETECTION OF EARLY VENTRICULAR DYSFUNCTION BY AFTER-LOAD CHALLENGE USING A NON-IMAGING CARDIAC PROBE (NUCLEAR STETHOSCOPE). Pediatr Res 19, 122 (1985). https://doi.org/10.1203/00006450-198504000-00101
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DOI: https://doi.org/10.1203/00006450-198504000-00101