BACKGROUND: A sigmoid ventricular septum (SVS) may be related to normal aging, but some people with an SVS develop a left ventricular outflow tract (LVOT) obstruction (defined as a gradient of >30 mmHg). Therefore, we investigated the association of LVOT obstructions with an SVS by dobutamine stress echocardiography (DSE) and assessed the possible mechanism of the latent LVOT obstruction. METHODS AND RESULTS: DSE was performed in 64 subjects with SVS (mean age: 73.3±7.7 years; 36 women) without an LVOT obstruction. In 40 of the 64 subjects, an LVOT obstruction occurred during the DSE (defined as latent obstruction). At rest, the subjects with a latent obstruction had a shorter end-systolic mitral leaflet tethering distance ("α" distance, i.e. the distance between the tip of the posterior papillary muscle and the contralateral anterior mitral annulus) than those without one (29.9±4.2 mm versus 35.2±4.6 mm), as well as a smaller end-systolic LVOT diameter (13.4±2.7 mm versus 16.1±3.4 mm) and larger ejection fraction (72.0±5.0% versus 67.8±5.9%) (all p<0.05). They also had a higher LV outflow velocity at rest (1.23±0.24 m/s versus 1.03±0.24 m/s) and during the Valsalva maneuver (1.31±0.27 m/s versus 1.03±0.27 m/s) (both p<0.05). After adjusting for these parameters, the resting end-systolic "α" distance and LV outflow velocity at rest remained independent predictors of a latent obstruction. CONCLUSION: A short leaflet tethering distance ("α") was the major determinant of a latent obstruction, suggesting that a mitral leaflet displacement/redundancy caused by a short "α" distance contributes to the LVOT obstruction.
BACKGROUND: A sigmoid ventricular septum (SVS) may be related to normal aging, but some people with an SVS develop a left ventricular outflow tract (LVOT) obstruction (defined as a gradient of >30 mmHg). Therefore, we investigated the association of LVOT obstructions with an SVS by dobutamine stress echocardiography (DSE) and assessed the possible mechanism of the latent LVOT obstruction. METHODS AND RESULTS: DSE was performed in 64 subjects with SVS (mean age: 73.3±7.7 years; 36 women) without an LVOT obstruction. In 40 of the 64 subjects, an LVOT obstruction occurred during the DSE (defined as latent obstruction). At rest, the subjects with a latent obstruction had a shorter end-systolic mitral leaflet tethering distance ("α" distance, i.e. the distance between the tip of the posterior papillary muscle and the contralateral anterior mitral annulus) than those without one (29.9±4.2 mm versus 35.2±4.6 mm), as well as a smaller end-systolic LVOT diameter (13.4±2.7 mm versus 16.1±3.4 mm) and larger ejection fraction (72.0±5.0% versus 67.8±5.9%) (all p<0.05). They also had a higher LV outflow velocity at rest (1.23±0.24 m/s versus 1.03±0.24 m/s) and during the Valsalva maneuver (1.31±0.27 m/s versus 1.03±0.27 m/s) (both p<0.05). After adjusting for these parameters, the resting end-systolic "α" distance and LV outflow velocity at rest remained independent predictors of a latent obstruction. CONCLUSION: A short leaflet tethering distance ("α") was the major determinant of a latent obstruction, suggesting that a mitral leaflet displacement/redundancy caused by a short "α" distance contributes to the LVOT obstruction.