Doppler-Derived Arterial Load Indices Better Reflect Left Ventricular Afterload Than Systolic Blood Pressure in Coarctation of Aorta.

Abstract

Patients with vascular stiffening may display increased arterial afterload that is out of proportion to systolic blood pressure (SBP). Since vascular and endothelial dysfunction develop in patients with coarctation of aorta (COA), we hypothesized that for any SBP, patients with mild COA (COA peak velocity <2 m/s) will have a higher arterial afterload and increased left ventricular mass index (LVMI) compared with controls, and that Doppler-derived arterial load indices would be a better predictor of LVMI compared with SBP alone. We studied 204 COA patients (age 35±12 y) and 204 matched controls. Doppler-derived arterial afterload was assessed using effective arterial elastance index and total arterial compliance index. Despite similar SBP, the mild COA group displayed higher arterial afterload as evidenced by a higher elastance index (3.3±0.9 versus 2.9±0.7 mm Hg/mL·m2; P<0.001) and lower total arterial compliance index (0.8±0.3 versus 1.2±0.5 mL/mm Hg·m2; P<0.001). This was associated with higher LVMI in COA (109±35 versus 93±32, g/m2; P<0.001). Compared with SBP (β=0.24 [95% CI, 0.02-0.45]), elastance index (β=20.2 [95% CI, 15.8-44.1]) and total arterial compliance index (β=-32.5 [95% CI, -43.8 to -123.6]) were better predictors of LVMI. Elastance index (but not SBP) was predictive of longitudinal increases in LVMI (r=0.43, P<0.001). COA patients had higher arterial afterload compared with controls with similar SBP. In comparison to SBP, Doppler-derived arterial load indices correlate more strongly with LV hypertrophy. These data suggest that SBP may underestimate LV afterload in this population. This has important clinical implications since titration of antihypertensive therapy is currently based on SBP.