Transthyretin cardiac amyloidosis (ATTR-CA) is an increasingly recognized infiltrative cardiomyopathy in which conduction system disease is common. The aim of our study was to define the incidence and prevalence of high-grade atrioventricular (AV) block requiring pacemaker implantation in our quaternary referral center. This was a single-center retrospective cohort study of 369 consecutive patients with ATTR-CA who underwent 12-lead electrocardiogram at the time of ATTR-CA diagnosis. During a mean follow-up of 28 months, serial ECGs and the electronic medical record were examined for the development of high-grade AV block and pacemaker implantation. Wild-type ATTR-CA (wtATTR-CA) was diagnosed in 261 patients and 108 had hereditary ATTR-CA (hATTR-CA). A total of 35 (9.5%) had high-grade AV block requiring pacemaker implantation at the time of diagnosis of ATTR-CA. The most common conduction abnormalities evident on the baseline ECG were a wide QRS complex, present in 51% with wtATTR-CA and 48% with hATTR-CA (p = 0.62), followed by first-degree AV block, which was present in 49% with wtATTR-CA and 43% with hATTR-CA (p = 0.31). During follow-up, high-grade AV block developed in 10% of those with hATTR-CA and 12% of patients with wtATTR-CA (p = 0.64). On multivariable models, high-grade AV block was not significantly associated with increased mortality. More advanced ATTR-CA stage and a history of obstructive coronary artery disease were associated with increased mortality on multivariable models. In conclusion, the incidence and prevalence of high-grade AV block is high in patients with ATTR-CA. Patients with ATTR-CA require close monitoring during follow-up for the development of conduction system disease.
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