Background: Vast majority of ventricular arrhythmias in patients (pts) without structural heart disease (NHVA) originate from the right ventricular outflow tract (RVOT). Premature ventricular contractions (PVC) and ventricular tachycardia (VT) ECG morphology are proposed to localize the site of radiofrequency ablation (RFA). An ECG algorithm to localize the arrhythmogenic focus in RVOT was designed and verified in a prospective study.
Methods: Analysis of ECG morphology of spontaneous PVC and VT was performed in 30 pts (25 women), mean age 42 ± 10, after successful RFA of arrhythmogenic focus (AFo) in RVOT (PVC in 11 pts, VT in 5 pts, PVC + VT in 14 pts). In the first step ECG data and fluoroscopic RVOT sites of successful RFA were combined to gain the characteristic QRS morphology patterns for exact sites of successful ablation (first 16 pts). This own algorithm was used to recognize AFo in the following 14 pts.
Results: First step: RVOT in RAO 30° view was divided into 9 zones: 3 vertical (1, 2, 3) and 3 horizontal (superior, intermediate and inferior). Q, R and S waves < 0.5 mV in 12-lead ECG were coded as q, r, s and waves ≥ 0.5 mV as Q, R, S. Vertical zones: zone 1 (RVOT postero-lateral part): r in lead I; zone 3 (RVOT anterior wall): QS/qs in lead I. Other QRS morphologies in lead I: zone 2. Horizontal zones: superior - transition from QS wave or r < S in V1 into R > s in lead V4, intermediate - R = S or r = s in V4, inferior - transition from qs/QS or r < S in V1–V4 into r, R in V6. Second step. Concordant ECG locations were predicted by two independent cardiologists in 14 pts. Concordant AFo locations (ECG and fluoroscopic) were achieved: in all 14 pts in horizontal zones and in 13 pts in vertical zones. Overall (30 pts) no AFo discordances were noted in horizontal zones. In vertical zones AFo location was concordant in 28 pts (93.3%).
Conclusions: Our data show that simple ECG algorithm based on spontaneous arrhythmia morphology precisely localizes the arrhythmogenic focus in RVOT. This analysis applied before RFA may shorten and simplify ablation procedure in patients with RVOT arrhythmia.