Doppler echocardiographic determination of the pressure gradient in hypertrophic cardiomyopathy

Abstract

The continuous wave Doppler ultrasound signal across the left ventricular outflow tract in hypertrophic cardiomyopathy has a characteristic pattern that is in keeping with the dynamic nature of the pressure gradient in this condition. To determine the accuracy and reliability of the peak Doppler flow velocity signal for measuring the peak pressure gradient in this condition, 340 beats were analyzed from five consecutive patients studied with simultaneous continuous wave Doppler ultrasound and dual catheter pressure recordings across the left ventricular outflow tract. Each patient was studied at steady state and during physiologic and pharmacologic manipulations of the pressure gradient. Peak velocity and calculated peak gradient were determined by two independent observers who did not know the catheter measurements. In addition, 18 beats with well defined flow velocity envelopes were digitized for analysis of the magnitude, timing and contour of the instantaneous Doppler ultrasound and catheter gradients throughout systole. Peak catheter gradient in the 340 beats ranged from 12 to 245 mm Hg. The correlations between the Doppler-derived and catheter peak gradients were close (r = 0.96, SEE = 4 mm Hg for Observer 1 and r = 0.97, SEE = 11 mm Hg for Observer 2). Interobserver variability for measurement of peak flow velocity was small (mean ± SD 0.16 ± 0.15 m/s). An interobserver difference >0.3 m/s occurred in 25 of the 340 beats analyzed. By retrospective analysis, this was due to contamination of the outflow tract signal by mitral regurgitation. The peak flow velocity and characteristic pattern of the continuous wave Doppler ultrasound signal accurately reflect the peak magnitude as well as the timing and contour of the dynamic pressure gradient across the left ventricular outflow tract in hypertrophic cardiomyopathy. Although the Interobserver variability of the peak flow velocity measurement is small, substantial error may occur when even a minimal signal of mitral regurgitation is superimposed on a seemingly well defined outflow tract contour. © 1988.