Abstract 1837: Measurement of the Transtricuspid Pressure Gradient by Color-Doppler M-Mode Echocardiography: A New Tool for the Noninvasive Assessment of RV Diastolic Function
The hemodynamic determinants of RV filling remain poorly characterized. Recently, the accuracy of measuring intracardiac pressure differences by color Doppler M-mode (CDMM) image-processing has been demonstrated for LV intracavitary flows. Because the driving force of RV filling is the transtricuspid pressure difference (TTPD), the aim of this study was to validate the noninvasive method to measure the TTPD, and to assess the relative contribution of preload and relaxation on the TTPD.
Material and methods: In a closed-chest porcine model (n=12), CDMM images and high fidelity pressure signals in the RV and right atrium (RA) were simultaneously acquired at baseline and after interventions on preload (nitroglycerin and volume overload n=6; arteriovenous fistula n=3), afterload (endotoxin infusion n=3), and relaxation (esmolol n=6). CDMM images were obtained during expiratory apnea and postprocessed by solving Euler’s equation using custom-built software. Pressure-gradient fields were overlaid on greyscale images and the TTPD was obtained by spatial integration of catheter-matched positions. Doppler-derived TTPDs were validated against synchronized invasive measurements. The determinants of the TTPD were assessed by multivariate analysis using a nonlinear mixed-effect model.
Results: The peak early TTPD was 1.7±1.2 mm Hg (n=601 beats), with a close agreement between invasive and Doppler measurements (Rintraclass=0.92, error: 5±16%). Determinants of TTPD (full-model R2 = 0.84) were the time-constant of RV relaxation (tau), the minimum −dP/dt, mean RA pressure (RAP) and filling time (p<0.001 for all factors). The expected modification (Δ) of the TTPD caused by a 50% relative change of RAP, tau, −dP/dt, and filling time was 6.5%, 13.5%, 7.3% and 10.2%, respectively.
Conclusions: For the first time, an accurate measurement of the RV driving filling force can be measured noninvasively. In the normal heart, the rate of RV relaxation is a more powerful determinant of the early RV filling pressure difference than RA pressure. These findings suggest that Doppler-derived TTPDs are a useful tool for the clinical assessment of RV diastolic function.