S. Fujimoto et al., ASSOCIATION OF REDUCED PR-AC INTERVAL WITH VENTRICULAR EARLY POTENTIALS IN DILATED CARDIOMYOPATHY, International journal of cardiology, 50(2), 1995, pp. 167-173
We studied 31 patients with dilated cardiomyopathy, correlating mitral
valve cusp motion with the continuous wave Doppler signal of mitral r
egurgitation and the signal averaged electrocardiogram (EGG). Sixteen
patients had a B point (early partial closure) on the mitral echogram
and 15 did not. Fifteen normal cases were used as controls. The durati
on of ventricular early potentials (< 40 mu V) was measured on the sig
nal averaged ECG of the QRS complex. The PR interval was increased in
patients with a B point (190 (33) ms vs. 145 (16) ms in normal, P < 0.
01) and PR-AC interval was reduced (25 (71) ms vs. 65 (11) ms in norma
l, P < 0.05). The B point itself was effectively synchronous with the
onset of low velocity early systolic mitral regurgitation, and followe
d the Q wave of the succeeding beat by 20 ms or less. Early low veloci
ty on mitral regurgitation was not present in patients without a B poi
nt. The duration of early potentials was greatly increased in patients
with a B point (43 (26) ms) compared both to those without (17 (20) m
s, P < 0.01) and to normals (12 (7) ms, P < 0.01) and their duration c
orrelated with B-C interval (r = 0.6, P < 0.02). We conclude that a B
point on the mitral echogram in patients with left ventricular disease
is due to early systolic low velocity mitral regurgitation which itse
lf results from an abnormal pattern of left ventricular activation, pr
obably bilateral bundle branch block. Once established, this low veloc
ity jet delays complete mitral valve closure.