Differentiation of arrhythmia originating from the right or left ventricular outflow tract based on the QRS morphology of premature ventricular beats and duration of repolarisation

Abstract

Background: Premature ventricular beats (PVBs) and monomorphic ventricular tachycardia originating from the right ventricular outflow tract (RVOT) are the most frequent forms of idiopathic ventricular arrhythmias, but arrhythmia originating from the left ventricular outflow tract (LVOT) may be found in about 10% of these patients. Aim: To compare electrocardiographic (ECG) patterns and duration of repolarisation after PVBs originating from the left and right superior part of the interventricular septum which were successfully treated with radiofrequency catheter ablation. Methods: We studied 62 patients who did not receive antiarrhythmic drug treatment before ablation, including 50 patients with RVOT arrhythmia (21 males, mean age 42 14 years, left ventricular ejection fraction [LVEF] 61 6%) and 12 patients with LVOT arrhythmia (3 males, mean age 41 17 years, LVEF 59 9%). Pre-ablation 24-h Holter ECG recordings were analysed for the total number of PVBs. In addition, we evaluated ectopic beat QRS duration, prematurity index and duration of repolarisation (QT interval, JT interval and TpeakTend values uncorrected for the heart rate) based on ten random daytime PVBs during a period of stable sinus rhythm at a rate of 60-70 bpm. Results: The study groups did not differ by age, LVEF, heart rate and the number of PVBs. RVOT arrhythmia was characterised by a lower prematurity index (0.59 0.11 vs. 0.72 0.09, p = 0.001) and a lower R/S ratio in leads V1-V3 (p < 0.01 for each lead). QRS duration of right-sided PVBs was shorter compared to that of left-sided PVBs (147 13 vs. 166 13 ms, p = 0.002), QT and JT intervals were similar (QT: 422 32 vs. 429 27 ms, p = 0.35; JT: 272 27 vs. 266 27 ms, p = 0.31), and TpeakTend was shorter in RVOT arrhythmia (100 10 vs. 110 6 ms, p = 0.01). Combination of R > S in lead V3 and TpeakTend-PVB > 110 ms identified LVOT arrhythmia with a sensitivity of 75% and specificity of 96%. Conclusions: Ventricular arrhythmias originating from the left or right superior part of the interventricular septum are not only characterised by different ECG patterns of ventricular ectopic beats but also show significant differences in the repolarisation phase© Polskie Towarzystwo Kardiologiczne.0.