QRS Duration During Follow-Up of Tetralogy of Fallot

Long-term results after tetralogy of Fallot (TOF) repair are determined by the extent of right ventricular remodeling to chronic pulmonary regurgitation entailing progressive RV dysfunction and a risk of developing ventricular arrhythmia. Pulmonary valve replacement (PVR) can alleviate this burden. As a predictor of ventricular arrhythmia, QRS duration remains a strong parameter in this decision. We performed a retrospective analysis of all PVR patients between 2005 and 2018, studying the time evolution of electrocardiographic parameters before and after PVR through linear mixed model analysis. 42 TOF patients underwent PVR. The median timespan between primary repair and PVR was 18 years (IQR 13-30). The indication for PVR was primarily based on the association of exercise intolerance (67%) and significant RV dilation on cMRI (median RVEDVi 161 ml/m2 IQR 133-181). Median QRS length was 155 ms (IQR 138-164), 4 (10%) patients had a QRS > 180 ms. QRS duration increased significantly before PVR, but barely showed regression after PVR. Changes of QRS duration after PVR were independent of RV dilation. In conclusion, when the decision for PVR in TOF patients is primarily based on RV volume and/or function threshold, QRS duration > 180 ms is rarely observed. In contrast with the significant increase of QRS duration before PVR, QRS length regression appears to be independent of the extent of RV dilation or QRS > 160 ms. Considering that the decision for PVR is based on mechanical RV characteristics, the utility of serial follow-up of QRS duration in contemporary operated TOF patients becomes questionable in absence of clinical arguments for ventricular arrhythmia.