Outpatient echocardiographic assessment of complex pulmonary outflow stenosis: Doppler mean gradient is superior to the maximum instantaneous gradient

Evaluation of pulmonary outflow obstruction has focused on maximum instantaneous gradient (MIG). However, experience suggests that outpatient Doppler MIG often overstates the degree of stenosis. In this study of 132 patients with complex pulmonary stenosis, the mean Doppler gradient showed superior correlation and agreement with invasive peak-to-peak gradient (PPG) (r = 0.91, bias = -6 mm Hg). Agreement between mean gradient and PPG remained excellent for patients with prosthetic conduits (bias = -4 mm Hg). When PPG was 50 mm Hg more, both mean Doppler gradient and MIG corrected for prevalve velocity provided reasonable estimates of PPG (bias = -13 and +17 mm Hg, respectively). Uncorrected MIG remained significantly greater than PPG (bias = +27 mm Hg). Outpatient MIG consistently overstated subsequent PPG. In unselected patients with conduits or with PPG of 50 mm Hg or less, mean Doppler gradient provided the best prediction of PPG. These data provide a strong argument for the routine use of mean gradients in complex pulmonary stenosis.