We aimed to determine the relationship between the iCEBc in patients with structurally normal hearts and post-catheter ablation PVC burden in patients undergoing PVC catheter ablation. Here, iCEBc was significantly associated with post-ablation PVC burden independently, with significantly lower iCEBc values. To the best of our knowledge, this is the first study to investigate the relationship between iCEBc and PVC burden following PVC catheter ablation.
Although PVCs are common and generally thought to be harmless, many studies show a higher risk for all-cause and cardiovascular mortality in patients without structural heart disease (10, 12). It is now known that PVCs are potentially dangerous to susceptible patients and can occur as triggers of VF and sudden cardiac death. Alternatively, frequent ventricular extrasystoles can also cause cardiomyopathy (13). However, the mechanism by which PVCs trigger VF in a structurally normal heart remains unclear (10).
The iCEB, the ratio of QT to QRS (QT/QRS) calculated from surface ECG, is a simple ECG marker that can predict ventricular arrhythmogenesis. The iCEB is equivalent to the cardiac wavelength λ, which is measured via invasive electrophysiological study and plays an important role in ventricular arrhythmias. Previous studies have suggested that the iCEB may offer a non-invasive and easily measurable marker to detect increased arrhythmic risk in patients (14). Increased or decreased values of iCEB are associated with ventricular arrhythmic events (15). Furthermore, iCEB is associated with long QT and TdP, but also with QT shortening and associated non-TdP-like VT/VF (16). Due to its non-invasive nature and ease of measurement, it has attracted great interest in clinical practice. Recently, iCEB has been found to be a better predictor of arrhythmia risk compared to the Tp-e interval, QTc interval, and Tp-e/QTc ratio (16). In a study by Adali et al., iCEBc was found to be a marker that can predict PVCs in patients without structural heart disease (5). Our study found that iCEBc can predict PVC burden following PVC catheter ablation.
QT and QTc intervals include periods of ventricular depolarization and repolarization, and their prolongation poses a risk for malignant ventricular arrhythmias (17). Our study found no significant difference in QT and QTc intervals. There is very little information about QRS complex dispersion. One study found that QRS duration and dispersion were significantly higher in AMI-related precursors. QRS dispersion was the ECG variable more closely associated with the occurrence of VT and VF, and it also suggested that the likelihood of ventricular arrhythmias is much higher when QRS duration and dispersion are high rather than when QTc duration and dispersion are high (18). In our study, prolonged QRS duration was found to be statistically significantly higher with PVC burden following PVC catheter ablation.
It has been suggested that increased iCEB may trigger a TdP-mediated arrhythmogenic effect, whereas decreased iCEB may cause non-TdP arrhythmias. Furthermore, sotalol use and congenital long QT syndrome, TdP-related arrhythmias, increased both iCEB and iCEBc. In contrast, Brugada syndrome and flecainide use, non-TdP ventricular arrhythmias, decreased iCEB and iCEBc (19). In our study, iCEB and iCEBc values were significantly lower in the group with a higher PVC burden.