Diagnostic and prognostic value of low QRS voltages in cardiac AL amyloidosis.

Background: In cardiac AL amyloidosis, myocardial infiltration is typically associated with "low QRS voltages" at the 12-lead electrocardiogram (ECG). Although considered as one of the hallmarks of the disease, its reported prevalence varies from 45% to 70%, mainly because of nonhomogeneous definitions.

Methods: To identify the "low QRS voltage" parameter having the best diagnostic value in identifying cardiac amyloidosis, and to assess its possible prognostic role, ECG and echocardiographic data were collected at diagnosis in 337 consecutive never-treated AL patients (233 with, 104 without cardiac involvement). Prognosis was assessed after a median follow-up of 14.5 months.

Results: "Low QRS voltage" prevalence varied from 84.12% when using Sokolow-Lyon index ≤15 mm to 27.04% with the definition of low total voltages (QRS amplitude ≤5 mm in each peripheral and ≤10 mm in each precordial lead), the widely used definition of low peripheral voltages (≤5 mm in each peripheral lead) being able to identify 66.52% cardiac AL patients. The presence of "low peripheral voltages" was associated with a more severe cardiac involvement, and was able to differentiate Mayo stage II patients' survival (i.e., AL patients with intermediate prognosis). According to receiver operator characteristic (ROC) curve analysis, sensitivity and specificity were 58.72% and 80.00%, for a peripheral QRS amplitude ≤24.5 mm (the sum of QRS in all the 6 peripheral leads), and 76.26% and 65.00% for a Sokolow-Lyon index ≤11 mm.

Conclusions: In cardiac AL amyloidosis the prevalence of low QRS voltages is highly dependent on the method used for defining this ECG alteration.