Available online 17 September 2022

Long-term morbidity including hypertension often persists in coarctation patients despite current guidelines. Coarctation severity can be invasively assessed via peak-to-peak catheter pressure gradient (PPCG), which is estimated noninvasively via simplified Bernoulli equation and conventionally reported as peak instantaneous Doppler gradient (PIDG). However, underlying simplifications of the equation limit diagnostic accuracy. We studied the diagnostic performance of a new Doppler-based diastolic index called the continuous flow pressure gradient (CFPG) versus conventional indices in assessing coarctation severity.

In a rabbit model mimicking human aortic coarctation, temporal blood pressure waveforms revealed diastolic instantaneous pressure gradients and spectral Doppler features impacted by coarctation severity. We therefore hypothesized CFPG provides superior correlation with coarctation gradients measured invasively. PIDG and CFPG were quantified using color flow echocardiography in humans and rabbits with discrete coarctations. Results were compared with PPCG in rabbits (n=34) and arm-leg systolic pressure gradients (ALSG; n=25) in humans via one-way ANOVA, Pearson’s correlation, linear regression, and Bland-Altman analysis.

A threshold of CFPG ≥4.6 mmHg was identified via Youden index as representative of PPCG ≥20 mmHg (the current guideline value for coarctation intervention) in rabbits, while a CFPG ≥1.0 mmHg represented an ALSG ≥20 mmHg in humans. Accuracy measures revealed superior correlation of CFPG (R2 >0.80) and mild ROC improvement (AUC 0.94-0.95) as compared to PIDG (R2 <0.63, AUC 0.89-0.95). Inter/intra-observer variability tested by intraclass correlation coefficient revealed measurement reliability with differences ≤8.2 and 10.7%, respectively. Computational simulations of anaesthetized versus conscious hemodynamics showed parameters were minimally impacted by isoflurane inherent in data used to derive CFPG. These results confirm the potential diagnostic accuracy of CFPG in echocardiography-based coarctation severity assessment. We are optimistic that CFPG will be useful for translation of results from pre-clinical studies that revisit current guidelines in order to limit morbidity in humans with aortic coarctation.

2022 by the American Society of Echocardiography.