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Internal consistency of echocardiographic estimates of the severity of left ventricular outflow obstruction
H P Gutgesell1, D Smith, N L McDaniel
1Department of Pediatrics, University of Virginia Medical School, Charlottesville 22908.
Insights
M-mode and Doppler echocardiography show good agreement for estimating left ventricular outflow tract gradients in congenital aortic stenosis. Combined use of these noninvasive methods minimizes, but does not eliminate, estimation errors.
Area of Science:
- Cardiology
- Pediatric Cardiology
- Medical Imaging
Background:
- Congenital aortic stenosis presents a significant challenge in pediatric cardiology.
- Accurate noninvasive estimation of the left ventricular outflow tract (LVOT) gradient is crucial for patient management.
- Existing noninvasive methods require validation for internal consistency and correlation with invasive measures.
Purpose of the Study:
- To assess the internal consistency of M-mode and Doppler echocardiography in estimating LVOT gradients.
- To compare the accuracy of these noninvasive techniques against each other and cardiac catheterization.
- To evaluate the combined utility of M-mode and Doppler echocardiography in assessing congenital aortic stenosis severity.
Main Methods:
- M-mode and Doppler echocardiography were employed in 74 evaluations of 50 pediatric patients with congenital aortic stenosis.
- M-mode gradient estimation utilized the wall-stress formula.
- Doppler methods applied the Bernoulli formula for gradient calculation.
Main Results:
- Good agreement was observed between M-mode and Doppler gradient estimates (r = 0.69).
- In 62% of comparisons, the difference between methods was < 20 mm Hg, placing patients in the same clinical severity class.
- Correlation with cardiac catheterization gradients was fair for both M-mode (r = 0.50) and Doppler (r = 0.58), with instances of significant over/underestimation.
Conclusions:
- M-mode and Doppler echocardiography are complementary tools for assessing congenital aortic stenosis.
- Combined use of these noninvasive techniques helps minimize, but does not eliminate, errors in outflow gradient estimation.
- Further refinement or combined interpretation strategies may be needed for optimal accuracy.
Abstract:
To determine their internal consistency, M-mode and Doppler echocardiography were used to estimate the gradient across the left ventricular outflow tract during 74 evaluations of 50 infants, children, and young adults with congenital valvular (n = 43), subvalvular (n = 6), and supravalvular (n = 1) aortic stenosis. By M-mode the gradient was estimated from the wall-stress formula (left ventricular pressure = 225 x wall thickness/end-systolic diameter) minus systolic blood pressure determined by sphygmomanometry. Doppler (pulsed or continuous wave) methods utilized the Bernoulli formula (gradient = 4 x V2). There was good agreement between the M-mode and Doppler estimates of outflow gradient in most patients (r = 0.69, standard error of the estimate = 26.9). In 46 of 74 comparisons (62%) the two estimates differed by less than 20 mm Hg, and the estimates placed the patient in the same clinical class (mild, moderate, or severe). In 22 patients undergoing cardiac catheterization, there was only a fair correlation between the M-mode (r = 0.50) and Doppler (r = 0.58) gradients and those obtained at catheterization. Each noninvasive technique yielded major overestimates or underestimates of the gradient in several instances. The M-mode and Doppler techniques for estimating the severity of congenital aortic stenosis are complementary. Their combined use minimizes but does not totally eliminate errors of overestimation or underestimation of outflow gradient.