Doppler echocardiographic transmitral peak early velocity normalized to the time-velocity
integral during diastole is equivalent to volumetric peak filling rate normalized
to stroke volume. To compare the pathophysiologic validity of normalized and nonnormalized
peak early flow velocity, pulsed Doppler echocardiography with simultaneous high fidelity
left ventricular pressure measurements was performed in 52 patients with coronary
artery disease. Left ventricular loading conditions were changed by intravenous administration
of norepinephrine in 15 patients and synthetic atrial natriuretic polypeptide in 15
others. Norepinephrine increased nonnormalized and normalized peak early flow velocities
in association with significantly elevated end-diastolic, peak systolic and mitral
valve opening pressures and decelerated the time constant of left ventricular isovolumetric
pressure decline. Atrial natriuretic polypeptide did not change either nonnormalized
or normalized peak early flow velocity, despite significant reductions in end-diastolic,
peak systolic and mitral valve opening pressure and an accelerated time constant.
Normalized peak early flow velocity showed the highest univariate correlation with
long-term change in mitral valve opening pressure (n = 52, r = 0.67, p less than 0.0001).
It provided a modest univariate correlation (n = 30, r = 0.74, p less than 0.0001)
with immediate change in mitral valve opening pressure during norepinephrine infusion,
whereas this correlation was lower (n = 30, r = 0.57, p less than 0.001) during polypeptide
infusion. However, multivariate regression analysis relating normalized peak velocity
with long- and short-term changes in end-diastolic, peak systolic and mitral valve
opening pressures, time constant and constant of left ventricular chamber stiffness
improved the correlation coefficients (r = 0.80 to 0.85, all p less than 0.0001).
In contrast, neither univariate nor multivariate correlations of nonnormalized velocity
with long- and short-term changes in these hemodynamic variables were satisfactory.
Thus, nonnormalized peak early flow velocity does not directly reflect underlying
hemodynamic changes in humans. Normalization to mitral stroke volume clarifies the
dependence of peak early flow velocity on the determinants of early diastolic filling.
When left ventricular early diastolic filling is evaluated by Doppler echocardiography,
normalized peak early flow velocity should be taken into consideration.