Low voltage on the electrocardiogram is a marker of disease severity and a risk factor for adverse outcomes in patients with heart failure due to systolic dysfunction.

Background: The prognostic implications of low QRS voltage on the electrocardiogram (ECG) in heart failure (HF) are not well characterized.
Methods: We manually measured and summed the QRS voltage in all 12 leads of the ECG (sumQRS) in two cohorts: (1) 415 patients with a low left ventricular ejection fraction followed up in a HF clinic ("clinic cohort") and (2) 100 subjects with advanced HF who had an ECG within 1 year preceding cardiac transplantation ("pretransplant cohort"). Low voltage was defined as the lowest quartile of the clinic cohort (sumQRS <12 mV) and its prevalence was compared in the two cohorts. The associations of low voltage with 1-year outcomes were assessed in the clinic cohort.
Results: In the clinic cohort, the frequency of low voltage was higher in New York Heart Association class 4 versus class 1-3 patients (34% vs 22% respectively, P = .04). The frequency of low voltage in the pretransplant cohort (47%) was twice that of the clinic cohort (24%, P < .001). After 1 year of follow-up in the clinic cohort, low ECG voltage was associated with a higher rate of death (14% vs 5%, P = .008) and the composite end point of death or HF hospitalization (35% vs 20%, P = .004). These associations persisted in multivariable analyses adjusting for important confounders.
Conclusions: Low ECG voltage is a marker of the severity of HF and is a risk factor for adverse outcomes in patients with systolic HF at 1 year.