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Contrast echocardiography in segmental analysis and intraventricular gradient quantification in hypertrophic
António Cândido1, José Coucelo, João Galvão
1Laboratório de Ecocardiografia-Hospital de São Francisco Xavier, Lisboa.
Introduction:
Hypertrophic cardiomyopathy (HCM) is a hereditary disorder characterized by ventricular hypertrophy, diastolic dysfunction and hyperdynamic left ventricular systolic function. This excessive contraction is sometimes associated with significant intraventricular pressure gradients. These gradients are dynamic and therefore vary at different times. Echocardiography can identify and quantify the functional and morphologic changes characteristic of the disease. Ultrasound contrast agents (UCAs) are indicated in patients with poor transthoracic image quality, enabling better visualization of the endocardial border. These agents also strengthen the Doppler signal, which enables better quantification of the transvalvular and intraventricular gradients. In HCM, definition of the endocardial/blood interface and visualization of the myocardial structure, as well as quantification of intraventricular gradients, are fundamental to the study of the pathology.
Objectives:
The objective of this study was to evaluate the clinical utility of new UCAs in morphologic study (segmental analysis) and quantification of maximum intraventricular gradients (IVG Max) in HCM, as well as the feasibility and interest of determining mean gradients (IVG Med) in HCM.
Methods:
Thirty-four patients with clinical and echocardiographic diagnosis of HCM were studied. Baseline IVG was considered significant when over 30 mmHg. Left ventricular morphology and IVG quantification were assessed before (study A) and after (study B) UCA injection. Maximum (Max) and mean (Med) values of delta IVG were calculated. Endocardial border definition of ventricular segments was analyzed in studies A and B and the percentage of ventricular segments that were completely visualized throughout the cardiac cycle was established.
Results:
The mean values of delta IVG Max for studies A and B were 51 +/- 31 mmHg and 61 +/- 32 mmHg, p = NS. The mean values of delta IVG Med were 26 +/- 16 mmHg in study A and 31 +/- 17 mmHg in study B, p = NS. The correlation between delta IVG Max and Med in study A was r2 = 0.74, p < 0.01, while in study B it rose to a value of r2 = 0.82, p < 0.01. Segmental analysis: In all segments studied the visualization percentage was higher after UCA injection, with a statistically significant difference in all lateral and anterior wall segments.
Discussion And Conclusions:
HCM is usually evaluated in a non-invasive way by echocardiography. There are no references to systematic use of UCAs in HCM patients. The value of determining the maximum gradient in HCM is generally accepted, but the importance of the mean gradient is not known. In this work, UCAs improved the Doppler signal without distorting values. In HCM, values measured using UCAs have a better correlation, with a smaller discrepancy between Max and Med gradients. This study suggests that mean gradient determination enables better characterization of the dynamic variability of the gradients because there is a correlation between Max and Med gradients. The real importance of mean gradients is not yet established, so further studies are necessary. In conclusion. UCAs are very useful in morphological assessment. The interest of UCAs in determining intraventricular gradients and the value of mean gradients in HCM are not clearly demonstrated in this study.