Origin and significance of diastolic Doppler flow signals in the left ventricular outflow tract

AbstractDiastolic Doppler flow signals (≥0.2 m/s) in the left ventricular outflow tract have not been well characterized, and their origin and significance remain controversial. Fiftynine patients (55 ± 16 years of age) with technically good Doppler echocardiographic studies were studied prospectively. There were 14 normal subjects, 21 patients with left ventricular hypertrophy, 10 with dilated cardiomyopathy and 14 with other cardiac disease. The rhythm was sinus in 55 and atrial fibrillation in 4.Two distinct Doppler flow signals were detected in the left ventricular outflow tract during diastole. These were termed E′ (early) and A′ (active) because they occurred 40 to 100 ms after higher velocity mitral inflow E (passive filling) and A (atrial contraction) signals. Among 59 patients, E′ signals were present in 48 (81%) and had a mean velocity of 0.41 ± 0.23 m/s. In 55 patients with normal sinus rhythm, A′ signals were present in 52 (95%) and had a mean velocity of 0.52 ± 0.24 m/s. No A′ signals were present in the four patients with atrial fibrillation. The E′ and A′ velocities by pulsed wave Doppler ultrasound were low at the left ventricular apex and increased along the basal septum in the left ventricular outflow tract.Prominent A′ velocities (≥0.45 m/s) were seen in 62% of patients with left ventricular hypertrophy, 50% of normal subjects and 10% of patients with dilated cardiomyopathy. The A′ velocity was higher in patients with left ventricular hypertrophy (0.63 ± 0.26 m/s) than in those with a normal heart (0.45 ± 0.16 m/s; p < 0.05) or dilated cardiomyopathy (0.25 ± 0.13 m/s; p < 0.01). The major determinants of diastolic outflow tract velocity were the mitral inflow E and A velocities and left end-diastolic dimension, particularly when combined (r = 0.64, p < 0.0001 for E′; r = 0.72, p < 0.0001 for A′).Distinctive E′ and A′ Doppler outflow tract signals result from mitral inflow and may be detected in most patients with normal heart size. These E′ and A′ velocities increase from apex to base and are more prominent in patients with a small, normally contracting heart or left ventricular hypertrophy