Low voltage is classically reported as an electrocardiographic (ECG) finding in cardiac amyloidosis (CA). We evaluated electrocardiograms to determine the prevalence of low voltage and its association with outcomes. Electrocardiograms in 200 patients with CA were reviewed. The presence of low voltage was assessed by all limb leads≤0.5 mV, all precordial leads≤1.0 mV, or Sokolow index≤.5 mV, and the association with time to adverse outcomes, including hospitalization, orthotopic heart transplant, and death, was assessed by the Cox proportional hazards model. Low voltage prevalence was 60% when using Sokolow index≤.5 mV, 34% by QRS amplitude≤0.5 mV in each limb lead, and 13% when ≤1.0 mV in each precordial lead with no differences in prevalence noted by the type of amyloid. Apart from atrial fibrillation and second-degree atrioventricular block being more common in wild type transthryretin cardiac amyloid (ATTRwt), the prevalence of ECG findings was similar among the 3 types of amyloid. Sokolow≤1.5 mV (HR 1.690; 95% CI of 1.069 to 2.672; p=0.0246) was independently associated with adverse outcomes. In conclusion, among the 3 main types of CA, the prevalence of low voltage is dependent on the method used for defining low voltage. Sokolow index≤1.5 mV indicated the highest prevalence and was associated with adverse outcomes in CA. Our data suggest that low voltage is a relatively late finding in CA and may not be useful for early identification.
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