Clinical Correlates and Prognostic Value of Low QRS Voltages in Non-Ischemic Dilated Cardiomyopathy: A Retrospective Cohort Study

Background: Data on the prognostic significance of low QRS voltage (LQRSV) in non-ischemic dilated cardiomyopathy (NIDCM) are limited. Therefore, this study aimed to determine whether LQRSV is associated with a composite endpoint of all-cause mortality or heart failure (HF) re-hospitalization in patients with NIDCM. Methods: Patients with NIDCM who met predefined criteria were retrospectively enrolled and divided into LQRSV and non-LQRSV groups based on electrocardiographic findings. The primary outcome was a composite of all-cause mortality or HF re-hospitalization. Secondary outcomes included all-cause mortality, cardiovascular (CV) death, and HF re-hospitalization. The prognostic significance of LQRSV was evaluated using Kaplan–Meier analysis and Cox proportional hazards models. Restricted cubic spline (RCS) functions were applied to examine potential nonlinear relationships between continuous QRS voltage and the primary outcome. Receiver operating characteristic (ROC) curves were used to assess predictive performance. Propensity score matching (PSM) was performed to balance baseline characteristics, and sensitivity and subgroup analyses were conducted to test the robustness of the findings. Results: The overall cohort included 784 consecutive patients with NIDCM (median age 56 years; 30% female). During a median follow-up of 1079 days, 335 primary outcome events occurred. After PSM, 463 patients were matched, with 186 in the LQRSV group and 277 in the non-LQRSV group. In the matched cohort, Kaplan–Meier analysis with the log-rank test showed that the LQRSV group had a significantly worse long-term prognosis than the non-LQRSV group (p < 0.001). Multivariable Cox analyses demonstrated that LQRSV was significantly associated with the composite of all-cause mortality or HF re-hospitalization (hazard ratio, (HR) 2.048, 95% confidence interval (CI) 1.519–2.760; p < 0.001), all-cause mortality (HR 2.526, 95% CI 1.660–3.844; p < 0.001), and CV death (HR 2.820, 95% CI 1.776–4.476; p < 0.001). RCS analyses showed a linear association (p for nonlinearity > 0.05), with the highest risk observed at the lowest QRS voltage amplitudes. ROC analysis revealed that incorporating LQRSV into the clinical model significantly increased the area under the curve (0.808 vs. 0.723; p < 0.001). Conclusions: LQRSV is associated with poor prognosis in NIDCM. Routine electrocardiographic assessment of QRS voltage may provide valuable information for risk stratification.