Incidental Diagnosis of TTR Amyloidosis During Left Bundle Branch Pacing Implantation

Background Transthyretin cardiac amyloidosis (ATTR-CM) is increasingly recognized in elderly patients with conduction disturbances and left ventricular hypertrophy, although it often remains underdiagnosed. Conduction system involvement frequently leads to permanent pacing during the disease course. Case Summary An 82-year-old patient was referred for syncopal episode in the setting of atrial fibrillation with slow ventricular response. Transthoracic echocardiography showed mildly reduced left ventricular systolic function, moderate concentric hypertrophy, and a small pericardial effusion. Given an anticipated high ventricular pacing burden, a dual-chamber pacemaker with left bundle branch area pacing was implanted. During lead repositioning, an unplanned myocardial fragment adherent to the pacing lead helix was retrieved and sent for histological analysis. Congo red staining demonstrated amyloid deposition, and immunohistochemistry was positive for transthyretin. Subsequent bone scintigraphy showed concordant findings, corroborating the diagnosis of ATTR-CM. Disease-specific therapy with tafamidis was initiated. Discussion This case illustrates an unusual diagnostic pathway in which an incidental procedural finding, interpreted within the appropriate clinical context and supported by noninvasive imaging, led to the recognition of ATTR-CM. It highlights the importance of disease awareness, particularly among electrophysiologists, who often encounter conduction disturbances as early manifestations of cardiomyopathies in an era of expanding disease-modifying therapies.