Abstract 3262: Dynamic Left Ventricular Outflow Tract Obstruction In Patients Without Hypertrophic Cardiomyopathy

Abstract

Background: Although dynamic left ventricular outflow tract (LVOT) obstruction is a hallmark for hypertrophic obstructive cardiomyopathy (HOCM), it can occur in other conditions. The aim of this study was to determine underlying conditions and clinical importance of LVOT obstruction in patients without HOCM. Methods: We reviewed the echocardiographic and clinical data of patients who underwent transthoracic echocardiography in Mayo Clinic Rochester from October 2001 to August 2006, and had LVOT peak pressure gradient (PG) > 25mmHg at rest. Results: Of 719 patients identified, 159 (22 %) patients had dynamic LVOT obstruction without HOCM (77 men; mean age, 66.6 ± 12.9 years). Main presenting symptoms were chest pains in 95 (59.7 %), and dyspnea in 46 (28.9 %). LVOT PG was 51 ± 24 mmHg at rest and 68 ± 27 mmHg after provocation. In 114 (71.7 %) patients, early diastolic transmitral inflow velocity (E) and early diastolic mitral annular tissue velocity (Ea) were obtained. Mean E, Ea, and E/Ea were 105 ± 47 cm/s, 6.4 ± 5.7 cm/s, and 18.3 ± 11.0, respectively. Systolic anterior motion of mitral apparatus was observed in 100 (62.9 %) patients. Concentric increase in LV wall thickness or LVH was most common condition present in 57 patients (36%). The cause of LVH was hypertension in 40 (70.1%), aortic stenosis in 8 (14.0%), and chronic renal failure in 4 (7.0%). In these patients, major precipitating factors were hyperdynamic LV systolic function in 54 (94.7%), use of vasodilator in 34 (59.6%) and small LV cavity in 30 (52.6%). Other prominent associated conditions were basal septal hypertrophy, mitral valve repair, cardiac amyloid, and apical ballooning. There were 28 (17.6%) all-cause mortalities during follow up (25 ± 17 months) including malignancy in 6 (21.4 %), sudden cardiac deaths in 4 (14.3 %), congestive heart failure in 3 (10.7 %). Conclusions: Dynamic LVOT obstruction can be found in patients without HOCM. The most common condition to develop dynamic LVOT obstruction without HOCM, is concentric increase in LV wall thickness in the setting of hyperdynamic motion, small LV cavity, and use of vasodilator. Other conditions which predispose patients for dynamic LVOT obstruction are hypovolemia, cardiac amyloidosis, apical ballooning syndrome, and mitral valve repair.