Light-chain amyloidosis causing left ventricular outflow tract obstruction managed with a dual-chamber pacemaker: a case report

Background Amyloid light-chain (AL) cardiac amyloidosis can rarely mimic hypertrophic obstructive cardiomyopathy with systolic anterior motion (SAM) of the mitral valve and resultant left ventricular (LV) outflow tract obstruction (LVOTO). Dual-chamber pacing with a right ventricular (RV) apical lead may be another option for LVOT gradient reduction and symptomatic relief for these patients. Case summary A 67-year-old man presented with subacute bilateral lower extremity oedema and syncope. Examination revealed a systolic murmur increasing with Valsalva, bibasilar crackles, and pitting oedema. Electrocardiogram showed low QRS voltage disproportionate to the degree of LV wall thickening. Transthoracic echocardiogram demonstrated severe concentric LV hypertrophy with SAM of the mitral valve and LVOTO (65 mmHg at rest, 100 mmHg with Valsalva). Laboratory tests and renal biopsy confirmed lambda AL amyloidosis, and endomyocardial biopsy confirmed cardiac amyloid infiltration. Medical therapy included cautious beta-blockade and midodrine, but the patient experienced refractory syncope. Septal reduction therapy was not anatomically feasible. Dual-chamber pacemaker implantation with RV apical pacing resulted in an improvement in the LVOT gradient and orthostatic symptoms. At more than 1 year after initiation of dual-chamber pacing and therapy directed at his underlying plasma cell dyscrasia, the patient had no further hospitalizations and endorsed sustained symptomatic improvement. Discussion Management of LVOTO in patients with AL cardiac amyloidosis is challenging due to competing restrictive physiology and the absence of guideline-recommended practices. Dual-chamber pacing may reduce LVOT gradients and improve symptoms in cases refractory to medical management.