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Origin and significance of diastolic Doppler flow signals in the left ventricular outflow tract
1Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
Insights
Diastolic Doppler flow signals in the left ventricular outflow tract, termed E' and A', originate from mitral inflow. These signals are detectable in most patients and are more prominent in those with left ventricular hypertrophy.
Area of Science:
- Cardiology
- Echocardiography
- Hemodynamics
Background:
- Diastolic Doppler flow signals in the left ventricular outflow tract (LVOT) are not well-characterized.
- Their origin and clinical significance remain controversial.
Purpose of the Study:
- To characterize diastolic Doppler flow signals in the LVOT.
- To investigate the origin and significance of these signals, termed E' and A', in various cardiac conditions.
Main Methods:
- Prospective study of 59 patients with technically adequate Doppler echocardiograms.
- Classification into normal subjects, left ventricular hypertrophy, dilated cardiomyopathy, and other cardiac disease groups.
- Analysis of diastolic flow signals (E' and A') in the LVOT using pulsed wave Doppler ultrasound.
Main Results:
- Two distinct diastolic LVOT signals, E' (early) and A' (active), were detected.
- E' signals were present in 81% and A' signals in 95% of patients in sinus rhythm.
- A' velocity was higher in patients with left ventricular hypertrophy compared to normal subjects or those with dilated cardiomyopathy.
- E' and A' velocities increased from LVOT apex to base and were influenced by mitral inflow velocities and left end-diastolic dimension.
Conclusions:
- Distinct E' and A' Doppler signals in the LVOT originate from mitral inflow.
- These signals are detectable in most patients, including those with normal heart size.
- Increased prominence of E' and A' signals is observed in patients with left ventricular hypertrophy or small, normally contracting hearts.
Abstract:
Diastolic Doppler flow signals (greater than or equal to 0.2 m/s) in the left ventricular outflow tract have not been well characterized, and their origin and significance remain controversial. Fifty-nine 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 (greater than or equal to 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 less than 0.05) or dilated cardiomyopathy (0.25 +/- 0.13 m/s; p less than 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 less than 0.0001 for E'; r = 0.72, p less than 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.