We investigated the presence of low QRS voltage (LQRSV) in a large sample population presenting for cardiovascular diseases. Further studies on LQRSV prevalence and clinical implications are warranted.

We conducted a cross-sectional study using ECG data from the National Center for Cardiovascular Diseases of China, collected from January 2015 to December 2023. LQRSV was defined as QRS amplitude <0.5 mV in limb leads (L-LQRSV), <1.0 mV in precordial leads (P-LQRSV), or both (C-LQRSV). The primary endpoint was a composite of in-hospital death or discharge against medical advice.

We analyzed ECG data from 712,362 patients, with echocardiographic data from 454,717, cardiac magnetic resonance (CMR) results from 17,712, and hospitalization data from 187,125 patients. LQRSV prevalence was 2.0%, with 81.4% L-LQRSV, 12.3% P-LQRSV, and 6.4% C-LQRSV. The most common cardiomyopathies associated with LQRSV were cardiac amyloidosis (49.4%), arrhythmogenic cardiomyopathy (31.2%), and Takotsubo syndrome (25.7%). C-LQRSV patients exhibited worse echocardiographic parameters and higher prevalence of myocardial fibrosis on CMR compared to those with L-LQRSV or P-LQRSV or normal QRS voltage (NQRSV). LQRSV was an independent predictor of in-hospital death or discharge against medical advice (OR 3.27, 95% CI 2.94-3.64, P < .001), and C-LQRSV conferred the highest risk of primary endpoint (12.41%, OR 8.63, 95% CI 6.72-11.07, P < .001).

LQRSV is an uncommon ECG pattern associated with severe cardiac dysfunction and the majority presents in limb leads, few in precordial leads, a tiny minority in both. C-LQRSV might be an ominous marker indicating the highest risk of adverse clinical outcomes.