Prevalence and clinical significance of low QRS voltages in healthy individuals, athletes, and patients with cardiomyopathy: implications for sports pre-participation cardiovascular screening.

Low QRS voltages (LQRSV), defined as a QRS amplitude from peak to nadir < 0.5 mV in all limb leads, are an emerging diagnostic finding on the electrocardiogram (ECG). In healthy individuals and athletes, LQRSV are rare (2.2-4% of elite athletes, 0.5% of recreational athletes, and 0.3% of sedentary individuals). LQRSV athletes commonly show ventricular arrhythmias (VAs) on exercise, and up to 40% of those with LQRSV and VAs have late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR). The prevalence of LQRSV in arrhythmogenic cardiomyopathy ranges from 17-40%, predicts left ventricular (LV) involvement, and is correlated with more extensive LGE replacement on CMR. In hypertrophic cardiomyopathy (HCM), LQRSV ranges from 0.7-11%. LQRSV-HCM patients have more segments with LGE, despite relatively smaller LV mass, suggesting a more advanced clinical stage and a worse prognosis. In dilated cardiomyopathy (DCM), LQRSV range from 6-7%, but may be higher (36%) in certain genetic forms of DCM. On a follow-up, LQRSV are independently associated with incident cardiac events, such as sudden death, sustained ventricular arrhythmia, or appropriate internal cardioverter defibrillator discharge. In cardiac amyloid, LQRSV range from 34-66% and demonstrate a negative prognostic value, with worse clinical outcomes regardless of underlying biologic, genetic, and clinical variables. In conclusion, LQRSV deserve careful consideration for exclusion of arrhythmogenic substrates in healthy individuals, athletes, and patients. While additional research is needed, it is reasonable that LQRSV should trigger clinical investigation to exclude underlying diseases at risk of life-threatening arrhythmias.