Premature ventricular contractions of the right ventricular outflow tract: Upward displacement of the ECG unmasks ST elevation in V1 associated with the presence of low voltage areas

Abstract

Introduction and aims: Frequent premature ventricular contractions (PVCs) originating from the right ventricular outflow tract (RVOT) are usually considered a benign entity and the ECG is typically normal. The aim of this study was to assess whether upward displacement of the ECG to the second intercostal space (ICS) would reveal any abnormal pattern.

Methods: A total of 18 consecutive patients with apparently normal hearts were studied, mean age 44±16 years, 12 women, who underwent catheter ablation of the RVOT due to frequent PVCs. A 12-lead ECG was performed in the standard position and repeated in a higher position, at the level of the second ICS. Three-dimensional bipolar electroanatomical voltage mapping (EVM) was performed in all patients and low voltage areas (LVAs) were defined as areas with amplitude <1.5 mV.

Results: The ECG in the second ICS was normal in eleven patients but in seven (39%) it revealed a pattern of ST-segment elevation in V1. EVM revealed the presence of LVAs in six patients (33%) which included the earliest activation site (EAS) in five. The ST elevation was associated with the presence of LVAs (p<0.0001) and with the LVAs at the EAS (p=0.002).

Conclusion: In this group of patients with apparently normal hearts and with frequent PVCs of the RVOT, upward displacement of the ECG revealed the presence of ST elevation in more than one third of patients, and the ST elevation was associated with the presence of LVAs in the RVOT.

Keywords: 12-lead ECG; Ablação por cateter; Arritmias ventriculares idiopáticas; Catheter ablation; Eletrocardiograma de 12 derivações; Extrasistoles ventriculares; Idiopathic ventricular arrhythmias; Mapa de voltagem; Premature ventricular contractions; ST elevation; Supradesnivelamento do segmento ST; Voltage mapping.