The systolic left-to-right shunt in patients with uncomplicated ventri
cular septal defect is associated with a classic loud murmur, and is w
ell described. The additional diastolic left-to-right shunt, always si
lent, is less well recognized. Left-to-right diastolic shunt flow is d
irectly related to the defect size, to the diastolic pressure gradient
between. the left and right ventricle, and to the duration of diastol
e. The purpose of this study was to evaluate by Doppler echocardiograp
hy the duration, magnitude, and flow velocity characteristics of the d
iastolic left-to-right shunt. There were 30 adult patients with uncomp
licated ventricular septal defects studied by color, pulsed, and conti
nuous wave Doppler echocardiography. In each patient, the uncomplicate
d ventricular septal defect was visualized by two-dimensional echocard
iography and/or Doppler echocardiography, and the systolic and diastol
ic left-to-right shunt flow was identified by Doppler echocardiography
. Accurate Doppler flow velocity peas twice, in beginning and again. a
t end diastole. The mean diastolic flow velocity was 0.5-1.5 msec (ave
rage 0.83 +/- 22 msec). This flow velocity was markedly lower than the
mean systolic shunt flow velocity (2.4-5.3 msec, average 3.8 +/- .7 m
sec). The Doppler flow velocity integral was 0.17-0.64 m (average 0.36
+/- 0.14), markedly smaller than the systolic flow velocity integral
(0.8-1.8 m, average 1.3 +/- 0.3). The diastolic left-to-right shunt fl
ow teas 12-41% (average 21 +/- 8) of total (systolic and diastolic) sh
unt flow. In conclusion: Diastolic left-to-right shunts can be identif
ied in all patients with uncomplicated ventricular septal defects, and
analyzed in the majority of patients. A significant degree of the lef
t to right shunting in. uncomplicated ventricular septal defects occur
during diastole.