The influence of aortoseptal angulation on provocable left ventricular outflow tract obstruction in hypertrophic cardiomyopathy.
Aortoseptal angulation (AoSA) can predict provocable left ventricular outflow tract obstruction (LVOTO) in patients with symptomatic hypertrophic cardiomyopathy (HCM). Lack of a standardised measurement technique in HCM without the need for complex three-dimensional (3D) imaging limits its usefulness in routine clinical practice. This study aimed to validate a simple measurement of AoSA using 2D echocardiography and cardiac MR (CMR) imaging as a predictor of LVOTO.



We retrospectively assessed 160 patients with non-obstructive HCM, referred for exercise stress echocardiography. AoSA was measured using resting 2D echocardiography in all patients, and CMR in 29. Twenty-five controls with normal echocardiograms were used for comparison.



Patients with HCM had a reduced AoSA compared with controls (113°±12 vs 126°±6), p<0.0001. Sixty (38%) patients had provocable LVOTO, with smaller angles than non-obstructive patients (108°±12 vs 116°±12, p<0.0001). AoSA, degree of mitral valvular regurgitation and incomplete systolic anterior motion (SAM) were associated with peak left ventricular outflow tract gradient (r=0.508, p<0.0001). An angle ≤100° had 27% sensitivity, 91% specificity and 59% positive predictive value for predicting provocable LVOTO. When combined with SAM, specificity was 99% and positive predictive value 88%. Intraclass correlation coefficient of AoSA measured by two observers was 0.901 (p<0.0001). Bland-Altman analysis of echocardiographic AoSA showed good agreement with the CMR-derived angle.



Measurement of AoSA using echocardiography in HCM is easy, reproducible and comparable to CMR. Patients with provocable LVOTO have reduced angles compared with non-obstructive patients. AoSA is highly specific for provocable LVOTO and should prompt further evaluation in symptomatic patients without resting obstruction.
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
Christopher Howell
CH
Critoph
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
Antonios
A
Pantazis
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
Maria Teresa
MT
Tome Esteban
Cardiomyopathies, Advanced Heart Failure and Transplant Unit , Hospital Universitari de Bellvitge , Barcelona , Spain.
Joel
J
Salazar-Mendiguchía
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
Efstathios D
ED
Pagourelias
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
James C
JC
Moon
Department of Inherited Cardiovascular Disease , The Heart Hospital, University College London , London , UK.
Perry Mark
PM
Elliott