Abstract 10882: Validation of a Continuous Flow Pressure Gradient for Coarctation Severity Assessment

Abstract

Introduction: Coarctation of the aorta (CoA) severity is assessed via trans-CoA blood pressure gradient (BPG) estimated using simplified Bernoulli equation (SBE) with indices from noninvasive Doppler echocardiography (echo). However, simplifications of the SBE and inconsistent readings through a suboptimal insonation window limit diagnostic accuracy (DA). In a rabbit model mimicking human CoA (Fig. 1A), catheter vs. Doppler comparison of BPG revealed diastolic continuous-flow pressure gradient (CFPG) was independently associated with severity. We therefore hypothesized the unique properties of CFPG would improve DA in humans. Methods: SBE and CFPG were quantified using color flow Doppler in humans and rabbits with discrete non-recurrent CoA before repair (Fig. 1B). Quantifications used peak velocity proximal to (V p ) and at the CoA (V pk ), early diastolic velocity (V d ), doppler velocity index (DVI), and normalized diastolic pressure half-time (dPHT; see Fig. 1B and C for definitions). Results were compared with measured BPG in rabbits (peak-to-peak catheter BPG) and humans (upper-lower extremity BPG). There was a total of 18 human and 26 rabbit cases; significance was defined a priori as a BPG of ≥20 mmHg. A CFPG ≥4 mmHg threshold was identified by maximizing sensitivity plus specificity in receiver operative curves (ROC). Results: Accuracy measures (Fig. 1D) revealed the superior performance of CFPG vs. SBE. Although reports suggest <60% of measured BPG can be explained with SBE, CFPG yielded a specificity of 78% in humans. Similar improvements were observed in rabbits. Results confirm the potential DA of CFPG in echo-based CoA assessment. Fig. 1- (A) MRI confirming morphological similarities between rabbit and human CoA, (B) Spectral Doppler images show diastolic continuous flow, (C) indices derived from the generalized Bernoulli equation assuming exponential diastolic pressure loss, (D) diagnostic performance for CFPG vs. conventional SBE.