Left ventricular outflow tract obstruction following aortic valve replacement: A review of risk factors, mechanism, and management

Abstract

The presence of dynamic left ventricular outflow tract obstruction (LVOTO) can complicate the postoperative course of patients undergoing surgical aortic valve replacement (AVR). The phenomenon of LVOTO is a consequence of an interplay of various pathoanatomic mechanisms. The prevailing cardiovascular milieu dictates the hemodynamic significance of the resultant LVOTO in addition to the anatomical risk factors. A thorough understanding of the predisposing factors, mechanism, and hemodynamic sequel of the obstruction is pivotal in managing these cases. A comprehensive echocardiographic examination aids in risk prediction, diagnosis, severity characterization, and follow-up of management efficacy in the setting of postoperative LVOTO. The armamentarium of management modalities includes conservative (medical) and surgical options. A stepwise approach should be formulated based on the physiological and anatomical substrates predisposing to LVOTO. The index phenomenon occurs more frequently than appreciated and should be considered when the post-AVR patients exhibit hemodynamic instability unresponsive to conventional supportive measures. The present article provides an overview of various peculiarities of this under-recognized phenomenon in the context of the perioperative management of patients undergoing AVR.

Keywords: Aortic valve replacement; asymmetrical septal hypertrophy; left ventricular outflow tract obstruction; mitral systolic anterior motion.

Figure 1

Echocardiographic findings which anatomically, physiologically, or geometrically predispose a post aortic valve replacement patient to the development of LVOTO. LVOTO: Left ventricular outflow tract obstruction, ASH: Asymmetric septal hypertrophy, LVOT: Left ventricular outflow tract, LV: Left ventricle, AML: Anterior mitral leaflet, PML: Posterior mitral leaflet

Figure 2

A midesophageal aortic valve long-axis TEE view at 120° showing the hypertrophied interventricular septum predisposing a patient of severe AS to midcavity obstruction. TEE: Transesophageal echocardiography, AS: Aortic stenosis, MV: Mitral valve, Ao: Aorta

Figure 3

A midesophageal long-axis transesophageal echocardiography view at 120° depicting a normal C-sept distance (a) and a markedly reduced C-sept distance (b) in a patient with septal hypertrophy. C: Coaptation of mitral valve leaflets, Sept: Interventricular septum

Figure 4

A midesophageal aortic valve long-axis TEE view at 120° demonstrating turbulent flow in the LVOT resulting from the combination of SAM and midventricular hypertrophy, with the resultant mitral regurgitation, in a case of post-AVR patient for predominant AS. TEE: Transesophageal echocardiography, LVOT: Left ventricular outflow tract, SAM: Systolic anterior motion, AVR: Aortic valve replacement, AS: Aortic stenosis, LVOTO: Left ventricular outflow tract obstruction

Figure 5

A deep transgastric TEE view at 106° demonstrating a “dagger”-shaped continuous-wave Doppler profile across the LVOT with a characteristic late systolic peaking, in a case of post-AVR patient for predominant AS. TEE: Transesophageal echocardiography, LVOT: Left ventricular outflow tract, AVR: Aortic valve replacement, AS: Aortic stenosis

Figure 6

The figure showing the distinguishing features of a valvular gradient (a) and a subvalvular LVOT gradient (b) on continuous-wave Doppler profile, wherein a symmetrical envelope (a) characterizes a valvular obstruction and a “dagger”-shaped envelope (b) signifies a LVOTO, with the gradients peaking in late systole. LVOTO: Left ventricular outflow tract obstruction