QRS fragmentation on the 12-lead electrocardiogram and its association to physiological cardiac adaptation in elite cyclists

Background The relationship between electrocardiographic based QRS fragmentation (fQRS) and physiological cardiac adaptation is not fully understood. We aimed to determine the prevalence of fQRS in elite male and female cyclists, and relationship between fQRS and cardiac structure and function. Methods 181 Elite international cyclists underwent their national cycling team's pre-participation cardiac screening. This included a resting 12‑lead electrocardiogram and transthoracic echocardiogram. Fragmented QRS was defined as an additional notch >1 mm deep from the peak of the wave within the QRS complex in any lead. We excluded RSR' or RSR'S′ patterns in V1–2 to differentiate from bundle branch block. Results Fragmented QRS was observed in 73 (41 %) of the cyclists. The most common lead was V1, followed by lead III, aVL and aVF. Of those cyclists with fQRS it was observed in just one lead in 38 cyclists (52 %), two leads in 22 cyclists (30 %) and ≥ three leads in 13 cyclists (18 %). Cyclists with fQRS demonstrated greater left ventricular (LV) diastolic diameter index ( p = 0.008), mean wall thickness ( p < 0.001), LV mass index ( p = 0.001), proximal right ventricular (RV) outflow diameter (RVOT PLAX ) index ( p = 0.040), distal RVOT 2 index (p < 0.001), RV systolic area index ( p = 0.005), and RV:LV ratio ( p = 0.008). In addition, cyclists with fQRS had significantly lower RV fractional area change ( p = 0.002). Conclusion Fragmented QRS in athletes is associated with indices of physiological LV and RV adaptation. In isolation, fQRS may not raise concern or initiate any further onward investigations.