Syncope from dynamic left ventricular outflow tract obstruction simulating hypertrophic cardiomyopathy in a patient with primary AL-type amyloid heart disease.

Dynamic left ventricular outflow tract (LVOT) obstruction is seen classically in hypertrophic cardiomyopathy. Cardiac amyloidosis can present with asymmetric hypertrophy that resembles hypertrophic cardiomyopathy, and, in some cases, with dynamic LVOT obstruction. The occurrence of syncope in such patients is not uncommon. The syncope is usually thought to be related to mechanisms other than LVOT obstruction, such as arrhythmias, conduction disturbances, orthostatic hypotension, or vasovagal effects associated with neuropathy. Herein, we report the case of a patient who had immunocyte-derived (primary AL-type) cardiac amyloidosis with the echocardiographic appearance of hypertrophic cardiomyopathy and evidence of LVOT obstruction that caused syncope. We were able to provoke and identify dynamic LVOT obstruction that produced presyncopal symptoms similar to those that typically occur in such patients spontaneously. Dynamic LVOT obstruction as a cause of syncope should be considered in patients who have cardiac amyloidosis and echocardiographic evidence of hypertrophic cardiomyopathy.