Fragmented QRS complex in healthy adults: Prevalence, characteristics, mechanisms, and clinical implications

Background: Fragmented QRS (fQRS) complex on a 12-lead electrocardiogram (ECG) is reportedly associated with myocardial scar or fibrosis in patients with structural heart disease. In healthy persons, however, the prevalence, underlying mechanisms, and clinical implications of fQRS remain unknown. Methods: In this prospective study, the routine 12-lead resting ECGs of 1500 consecutive healthy adults (707 male, age [38 ± 12] years) were independently screened for fQRS by two ECG readers. fQRS was defined as ≥1 additional deflection or notching within the QRS complex, including the peak of the R-wave or the nadir of S-wave, in at least two continuous leads. Results: fQRS was identified in 76 participants (5.1%) in a mean of (2.3 ± 0.7) leads, most commonly inferior leads (86.8%, 66/76), followed by precordial leads (13.2%, 10/76). Longer QRS duration and left deviation of the frontal QRS axis of ≤30° were identified as independent predictors of fQRS. In addition, fQRS in the precordial leads covered the QRS transition lead (from R/S 1) in all ten participants. Sixteen healthy volunteers who were found to have fQRS underwent late gadolinium enhancement–cardiac magnetic resonance scanning, which revealed no myocardial fibrosis, scar, or other abnormalities. Conclusions: fQRS is not rare in healthy adults. The underlying mechanisms of fQRS in healthy adults seem to be mainly related to left axis deviation (especially deviations ≤30°), rather than myocardial scar or fibrosis.