First-degree Atrioventricular Block as an Early Marker of Advanced Disease of the Conduction System in a Patient with Hereditary Val142Ile Cardiac Amyloidosis

). Due to the mismatch between the degree of left ventricular hypertrophy on the transthoracic echocardiogram and the ECG findings, an investigation focused on CA was initiated. The following were ordered: cardiac magnetic resonance imaging (Figure 2), which showed a pattern suggestive of CA; 24-hour urine and blood immunofixation; and serum free light chain assay, which excluded the AL type as the cause of amyloid deposition. Myocardial scintigraphy with technetium pyrophosphate showed grade 3 uptake in the cardiac area (Figure 2), which raised high suspicion of ATTR, and, finally, genetic testing confirmed the Val142Ile mutation. Six months after diagnosis, the patient began complaining of fatigue on exertion and systemic venous