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Doppler echocardiographic determination of the pressure gradient in hypertrophic cardiomyopathy
Z Sasson1, P G Yock, L K Hatle
1Cardiology Division, Stanford University School of Medicine, California.
Insights
Continuous wave Doppler ultrasound accurately measures pressure gradients in hypertrophic cardiomyopathy. This study validates Doppler flow velocity as a reliable tool for assessing left ventricular outflow tract obstruction.
Area of Science:
- Cardiology
- Medical Imaging
- Ultrasound Technology
Background:
- Hypertrophic cardiomyopathy (HCM) involves dynamic pressure gradients in the left ventricular outflow tract (LVOT).
- Continuous wave (CW) Doppler ultrasound shows a characteristic signal in HCM patients.
- Accurate measurement of LVOT pressure gradients is crucial for managing HCM.
Purpose of the Study:
- To assess the accuracy and reliability of peak Doppler flow velocity for measuring peak pressure gradients in HCM.
- To compare CW Doppler ultrasound measurements with simultaneous dual catheter pressure recordings.
Main Methods:
- Analysis of 340 heartbeats from five consecutive HCM patients.
- Simultaneous CW Doppler ultrasound and dual catheter pressure recordings of the LVOT.
- Measurements performed at steady state and during gradient manipulation.
- Independent observer analysis of peak velocity and calculated peak gradient.
- Digitization of 18 beats for detailed systolic gradient analysis.
Main Results:
- High correlations between Doppler-derived and catheter peak gradients (r=0.96-0.97).
- Small interobserver variability in peak flow velocity measurements (mean +/- SD 0.16 +/- 0.15 m/s).
- Identified mitral regurgitation as a cause for signal contamination in 25 beats.
Conclusions:
- CW Doppler ultrasound is an accurate and reliable method for measuring LVOT peak pressure gradients in HCM.
- Doppler-derived peak velocity is a valid surrogate for assessing LVOT obstruction severity.
- Mitral regurgitation should be considered when interpreting Doppler signals in HCM.
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 greater than 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.(ABSTRACT TRUNCATED AT 250 WORDS)