712-5 Dynamic Left Ventricular Outflow Tract Obstruction Immediately Following Aortic Valve Replacement: Detection by Intra-operative Trans-esophageal Echocardiography

Aortic valve replacement (AVR) produces dramatic acute changes in left ventricular loading conditions that may provide a substrate for dynamic left ventricular outflow tract (LVOT) obstruction, particularly in the context of inotropic stimulation. This and related abnormalities have been described postoperatively, but their occurrence intra-operatively immediately post AVR has not been examined. To assess the prevalence and clinical impact of this phenomenon, intra-operative transesophageal echocardiography (TEE) was performed in 72 patients undergoing aortic valve replacement (AVR) for aortic stenosis (n=28) aortic regurgitation (n=15), or mixed aortic valve disease (n=29). There were 31 bioprostheses, 23 mechanical valves, and 18 homografts/autografts.ResultsNo pt had dynamic LVOT obstruction on pre-bypass TEE. TEE performed after or during weaning from bypass revealed hemodynamically significant dynamic LVOT obstruction characterized by mitral systolic anterior motion, subvalvular obstruction and variable mitral regurgitation in 5 pts (2 homografts, 2 bioprostheses, 1 mechanical). All these pts had normal left ventricular function, concentric hypertrophy, and pre-op aortic stenosis±aortic insufficiency. Although all 5 pts were hemodynamically unstable (with difficulty weaning from bypass, variable systemic hypotension, andlor left atrial hypertension) dynamic LVOT obstruction was not suspected clinically prior to TEE. All pts improved with cessation of inotropes andlor B-blockade with coincident improvement, but notelimination of the subvalvulargradient.ConclusionDynamic LVOT obstruction may occur following AVR in the immediate post-bypass period. This problem is difficult to recognize and may be inappropriately treated. Intra-operative TEE is essential to diagnose this problem and monitor therapy