Failure of normalized ventricular filling rates to predict true filling rates

Ventricular filling rates derived from radionuclide angiographic (RNA) time-activity curves are commonly expressed as normalized values. The assumption that normalized filling rates have a relationship to the actual filling rates was tested. RNA and contrast angiography were performed within 20 min of one another in 21 patients with widely disparate volumes. The RNA time-activity curve was converted from counts to milliliters by equating the contrast angiography derived end diastolic volume to the end diastolic count rate determined by RNA. Peak filling rates were normalized to end diastolic volume (EDV), stroke volume (SV), and peak ejection rate (ER). No significant correlation between the normalized filling rates and the true filling rate was found. Significant correlations were found between the EDV normalized filling rate and the EDV and the ejection fraction. Normalized filling rates are dependent upon the normalizing variable and are not a pure measure of ventricular filling rates. (author)