Objectives. This study sought to determine the spectrum of electrophysiologic abnormalities found in patients with cardiac involvement due to AL (primary) amyloidosis and to evaluate the prognostic implications, particularly in relation to subsequent sudden death.
Background. Only case reports, but no series of invasive electrophysiologic studies, exist in patients with cardiac AL.
Methods. Twenty-five patients with biopsy-proven AL and cardiac involvement underwent standard invasive electrophysiologic studies.
Results. The function of the sinus and the atrioventricular node was preserved in most patients, but the infra-His (HV) conduction times were usually abnormal. The mean (±SD) HV interval for the 25 patients was 79 ± 18 ms (range 50 to 110), and 23 patients (92%) had an abnormally prolonged interval (>55 ms). Marked HV prolongation (≥80 ms) occurred in 12 patients, 6 of whom had an interval ≥100 ms. Among the 23 patients who died during follow-up, HV prolongation was the sole independent predictor of sudden death by multivariate analysis (p = 0.05).
Conclusions. Patients with cardiac AL are prone to disease in the His-Purkinje system. Prolongation of the HV interval is common and may not be suspected from the surface electrocardiogram in the presence of a narrow QRS complex. These patients have a high prevalence of sudden death, of which the HV interval is an independent predictor. The association of HV prolongation and sudden death is probably multifactorial, representing either a marker of severe myocardial infiltration with an increased propensity to lethal ventricular arrhythmias or electromechanical dissociation, or indicating severe conduction system disease eventually leading to complete atrioventricular block and bradycardic death.
