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A 45 year old man with a history of hypertrophic obstructive cardiomyopathy (HOCM) was admitted to our hospital because of a syncope. The diagnosis of HOCM had initially been made at cardiac catheterisation in 1975. He had been given 120 mg propranolol daily and his subsequent clinical history was uneventful. Since 1981 he had been undergoing echocardiography every two years. Echocardiography revealed notably hypertrophied ventricles and severe obstruction to the left ventricular outflow (in 1985 continuous wave Doppler was performed disclosing a peak gradient of 80 mm Hg). The gradient to the left ventricular outflow decreased over the years and in 1998 no gradient to both left and right ventricular outflow was detected. In March 2000 he had paroxysmal atrial flutter with syncope; sinus rhythm was restored after intravenous flecainide. Cross sectional echocardiography showed pronounced asymmetric left ventricular hypertrophy and thickened right ventricular muscular components (prominently the crista supraventricularis). Impediment to right ventricular outflow was caused by simultaneous systolic contraction of the hypertrophied ventricular septum and crista supraventricularis (top right: LV, left ventricle; RVOT, right ventricular outflow tract). Colour Doppler demonstrated turbulent flow across the right ventricular outflow tract and laminar flow across the left ventricular outflow (bottom right: LA, left atrium; LVOT, left ventricular outflow tract). Right ventricular outflow peak gradient was 45 mm Hg. Valsalva manoeuvre did not induce any variation in both right and left ventricular outflow tract Doppler velocities. Cardiac catheterisation confirmed the echo findings and showed an intramural left anterior descending coronary artery.
Right ventricular outflow tract pressure gradients may occur infrequently in HOCM and are usually associated with subaortic gradients. To our knowledge this is the first case in which the obstruction switched from the left to the right ventricular outflow in a long term follow up.