Clinical and echocardiographic correlates of mitral E-wave transmission inside the left ventricle: potential insights...

The mitral inflow wave is initially directed to the left ventricular apex and then turns around facing the left ventricular outflow tract. The E and A waves are transmitted to the left ventricular outflow tract where they are registered as Er and Ar waves, respectively. We hypothesized that the E-wave transit time to the left ventricular outflow tract recorded as the E-Er interval may depend on left ventricular early diastolic performance such as relaxation. This hypothesis was tested in clinical settings known to have abnormal left ventricular relaxation. Mitral E and left ventricular outflow tract Er waves were recorded with pulsed wave Doppler technique in 63 subjects: 25 healthy subjects, 18 patients with secondary left ventricular hypertrophy, and 20 patients with hypertrophic cardiomyopathy. The E-Er interval was measured from the onset of E wave to the onset of Er wave timed to the R wave of the electrocardiogram. The E-Er interval ranged from 45 to 300 msec: 96 +/- 28 msec in the controls, 127 +/- 46 msec in patients with left ventricular hypertrophy (p = 0.0091 versus controls), and 179 +/- 57 msec in patients with hypertrophic cardiomyopathy (p < 0.0001 versus controls). It correlated with left ventricular free wall thickness (r = 0.42, p = 0.0006), thickness of the ventricular septum (r = 0.43, p = 0.0004), left ventricular end-diastolic diameter (r = -0.38, p = 0.0022), left ventricular end-systolic diameter (r = -0.55, p < 0.0001), left ventricular isovolumic relaxation time (r = 0.39, p = 0.0063), RR interval (r = 0.28, p = 0.045), mitral E/A velocity ratio (r = -0.33, p = 0.010), and E-wave deceleration time (r = 0.38, p < 0.0044) but not with age. Multivariate analysis with all the previously mentioned variables and the group the patient belonged to as the dichotomous variable showed that the grouping variable was the sole independent determinant of the E-Er interval (multiple r = 0.74). The E-Er interval is an easily measurable Doppler parameter which is increased in left ventricular hypertrophy and hypertrophic cardiomyopathy. It is related to left ventricular wall thickness, left ventricular isovolumic relaxation time, mitral E/A velocity ratio, and E-wave deceleration time and may provide useful insight into left ventricular early diastolic performance-possibly the relaxation process.