A Challenging Case of Wild-Type Transthyretin Amyloidosis (ATTR) Amyloidosis Treated With Cardiac Resynchronization Therapy.

Wild-type transthyretin amyloidosis (ATTRwt) is an age-associated systemic disorder characterized by extracellular deposition of misfolded transthyretin amyloid fibrils, leading to progressive organ dysfunction. Cardiac involvement is common and may result in restrictive cardiomyopathy, arrhythmias, and conduction disturbances, including left bundle branch block (LBBB). Although pharmacological therapy with transthyretin stabilizers, such as tafamidis, has been shown to reduce mortality in patients with ATTRwt cardiac amyloidosis (ATTRwt-CA), the role of device-based therapies, such as cardiac resynchronization therapy (CRT), remains controversial, particularly in patients with coexisting conduction abnormalities. We report the case of an 81-year-old woman diagnosed with ATTRwt-CA who presented with symptomatic heart failure and LBBB. Tafamidis therapy was initiated to improve her exercise tolerance and to reduce her risk of mortality. Owing to the presence of LBBB and evidence of mechanical dyssynchrony, CRT was also introduced in an effort to prevent the deterioration of her heart failure with reduced ejection fraction. Device optimization was guided by gated myocardial perfusion imaging, performed using single photon emission computed tomography (SPECT), which enabled a detailed assessment of her left ventricular synchrony and informed CRT programming. Following CRT implantation and optimization, the patient exhibited marked symptomatic improvement, including resolution of her exertional dyspnea and fatigue. Objective assessments demonstrated improved left ventricular contractility and reverse remodeling, suggesting a favorable response to CRT. This case underscores the potential value of CRT in selected patients with ATTRwt-CA and conduction system disease, particularly when mechanical dyssynchrony is evident. Furthermore, it highlights the utility of nuclear imaging modalities such as SPECT in guiding CRT optimization in this unique patient population. Prospective studies are warranted to better define the indications, predictors of response, and long-term outcomes of CRT in patients with ATTRwt-CA.