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Continuity equation used to calculate aortic valve (AV) area in patients with aortic stenosis (AS) assumes a circular left ventricular outflow tract (LVOT) shape. However, > 50% of AS patients have non-circular LVOT shapes, potentially invalidating the standard continuity method. Predictors of which patients with AS are likely to have a non-circular LVOT shape is of importance.
In 109 adult patients with AS, AV and LVOT areas were determined by planimetry using multiplane transesophageal echocardiography (TEE). Doppler TEE of AV and LVOT was done. AV area was calculated by the standard continuity method and a modified method, whereby planimetered LVOT area was used in the continuity equation.
LVOT shape was characterized as circular (n=54), horizontally oval (n=37), vertically oval (n=8) or irregular (n=10). Patients with mild, moderate or severe AS by AV planimetry were more frequently mischaracterized using the standard (29/109) vs. modified (18/109; p<0.0001) continuity method. In patients with a horizontally oval LVOT, AS severity was more often correctly identified by the modified (32/37) vs. standard (22/37; p<0.01) method. In patients with other LVOT shapes, there was no significant difference in mischaracterization of AS severity by either method. In obese patients (n=61), increasing weight (p<0.005) and decreasing height (p<0.0001) were multivariate predictors of a horizontally oval shaped LVOT. In non-obese patients, a decreasing cardiac index (p<0.001) and congenital AV morphology predicted horizontally oval LVOT shape. In patients (n=55) with normal flow (EF > 50% and peak flow rate > 250 ml/sec), obesity was the only multivariate predictor of non-circular LVOT shape (p=0.05).
Planimetry of LVOT, when used in the continuity equation reduces mischaracterization of AS severity in patients with horizontally oval shaped LVOT. In specific subgroups, obesity, height, weight, cardiac index and congenital AV predict non-circular or horizontally oval LVOT shape. These data suggest that LVOT should be directly measured for calculation of AS severity in obese patients, or normal weight subjects with decreased cardiac index or congenital AV.
Poster Sessions, Expo North
Saturday, March 09, 2013, 10:00 a.m.-10:45 a.m.
Session Title: Imaging: Echo – Aortic Valve Diseases
Abstract Category: 18. Imaging: Echo
Presentation Number: 1144-367
- 2013 American College of Cardiology Foundation