Effect of Pressure Recovery on Pressure Gradients in Congenital Stenotic Outflow Lesions in Pediatric Patients—Clinical Implications of Lesion Severity and Geometry: A Simultaneous Doppler Echocardiography and Cardiac Catheter Correlative Study

Background: Doppler pressure gradients (PGs) are routinely used as a surrogate for catheter peak-to-peak gradient (PPG) for referring pediatric patients with aortic stenosis (AS), pulmonary stenosis (PS), and coarctation of the aorta (CoA) for intervention but do not always predict the catheter PPG accurately, which results in misclassification of lesion severity. We hypothesized that recovered pressure (RP) accounts for the discrepancy between Doppler PG and catheter PPG. We aimed to study the occurrence of clinically significant RP in AS, PS, and CoA. Methods: Simultaneous Doppler and catheter PGs were prospectively measured in 82 patients (median age, 12.2 months; weight, 7.5 kg) with isolated AS (n = 30), PS (n = 24), and CoA (n = 28), and agreement before and after correcting for RP were analyzed. RP was calculated from a fluid dynamic–based equation. Effects of lesion geometry on the magnitude of RP were analyzed. Results: Recovered pressure–corrected Doppler peak instantaneous gradient (PIG) had significantly closer agreement and correlation with the catheter PPG (P < .001) than the uncorrected PIG and mean Doppler gradients. Recovered pressure–corrected Doppler PIG predicted PPG with high specificity and accuracy in all lesions (95% CI, 36%-97% and 85%-100%, respectively, P < .05 for both). RP magnitude was weakly related (r = 0.33 to 0.47) to valve area and inversely related (r = −0.22 to −0.34) to downstream vessel area. Conclusions: Significant RP occurs in congenital AS, PS, and CoA, accounting for misclassification of lesion severity by Doppler PIG. The RP magnitude is at a maximum in mild to moderate stenotic outflow lesions, with small-size downstream vessels causing the most misclassification of lesion severity by Doppler PIG.