Clinical Factors Related to Cardiac Conduction Disturbance in Patients With Wild-Type Transthyretin Amyloid Cardiomyopathy Undergoing Tafamidis Treatment.

BACKGROUND: Cardiac conduction disturbances are frequently observed in patients with transthyretin amyloid cardiomyopathy (ATTR-CM). Because their relationships with other clinical factors have not been fully investigated, in this study we evaluated changes in atrioventricular conduction disturbances (AVCD) and intraventricular conduction disturbances (IVCD) in patients with ATTR-CM undergoing tafamidis treatment, with the aim of identifying clinical factors, including cardiac magnetic resonance (CMR) parameters, related to AVCD and IVCD. METHODS AND RESULTS: We studied 50 patients with wild-type ATTR-CM who underwent baseline CMR and subsequently commenced treatment with tafamidis. Data of cardiac biomarkers and left ventricular (LV) parameters on CMR were acquired at baseline. Changes in the PQ interval (∆PQ) and QRS duration (∆QRS) on ECG were assessed over 1 year. Despite tafamidis treatment, both the PQ interval and QRS duration significantly increased over 1 year. After adjusting for medications that might affect the cardiac conduction system, the native myocardial T1 value (T1native) was shown to determine the baseline PQ interval (β=0.31, P=0.039), baseline QRS duration (β=0.30, P=0.038), and ∆QRS (β=0.29, P=0.035), whereas Ln (serum high-sensitivity cardiac troponin T [hs-cTnT]) was a determinant of ∆QRS (β=0.32, P=0.036). CONCLUSIONS: In patients with wild-type ATTR-CM undergoing tafamidis treatment, AVCD and IVCD progress over 1 year. Baseline T1native and hs-cTnT are predictors of progression of IVCD under tafamidis treatment, and T1native is associated with AVCD and IVCD in disease-modifying therapy-naïve conditions.