Fragmented QRS complexes in adult patients with repaired tetralogy of fallot: a correlation study with cardiovascular magnetic resonance

Introduction: Tetralogy of Fallot (ToF) is the most frequent cyanotic congenital heart disease in adulthood and is associated with a higher risk of ventricular arrhythmias. Fragmented QRS (fQRS) reflects conduction delay caused by myocardial fibrosis and dysfunction and its analysis in ToF has recently been drawn to attention. Purpose: The aim of this study was to evaluate the association of fQRS to morphofunctional data obtained by cardiovascular magnetic resonance (CMR) in ToF patients (pts). Methods: Adult pts with surgically corrected ToF were included. All pts had contemporary ECG and CMR. fQRS was defined as the presence of >2 notches on the R/S wave, or the presence of > 1 R' (fragmentation) if QRS duration ≤120 mseg, in ≥ 2 contiguous leads. Results: 48 pts (30 women) were included, 31±9.5 years, follow-up time of 23±7 years since ToF repair; 24 pts had moderate to severe pulmonary regurgitation (PR). Late gadolinium enhancement (LGE) was present in the right ventricular (RV) wall in 44 pts. fQRS was present in 83% of pts. fQRS in the inferior leads was correlated to higher RV volumes (RV end-diastolic volume (RVEDV) (p 0.017), RV end-systolic volume (RVESV) (p 0.037], higher RVEDV/LVEDV ratio (p 0.022), and higher PR volume (p 0.022). Lateral fQRS complexes were associated to RVEDV > 150mL/m2 (X2 4.97, p 0.027) and to the presence of RVOT aneurysm (X2 6.4, p 0.012). Prolonged QRS duration correlated to higher ventricular volumes and lower ejection fraction: LVEDV (rho 0.307, p 0.036), LVESV (rho 0.442, p 0.002), LV mass (rho 0.457, p 0.001), LVEF (rho -0.457, p 0.001); RVEDV (rho 0.307, p<0.036), RVESV (rho 0.359, p<0.013), RVEF (rho -0.353, p 0.015). Pts with PR had longer QRS complexes (p 0.030) as well as did those with ascending aorta dilatation (AAD) (p 0.003). Length of cQT was positively correlated to LVESV (rho 0.378, p 0.01), LV mass (rho 0.316, p 0.031), to RVEDV (rho 0.512, p<0.001), RVESV (rho 0.559, p<0.001), ratio RVEDV/LVEDV (rho 0.513, p<0.001), PR volume (rho 0.494, p 0.002), and was negatively correlated to both LVEF (rho -0.496, p<0.001) and RVEF (rho -0.471, p<0.001). cQT was longer in pts with PR (p<0.001) and in those with AAD (p 0.045). Conclusion: In our population, fQRS complexes were present in the vast majority of patients and were associated to higher RV volumes, an established marker of prognosis, but not with fibrosis or ventricular function. QRS duration and cQT should not be forgotten in the ECG analysis, since they have strong correlations not only to ventricular morphofunctional data, but also with the presence of moderate to severe pulmonary regurgitation and ascending aorta dilatation.