Ventricular premature beat (VPB) with a left bundle branch block morphology and an inferior axis usually originates from the right ventricular outflow tract (RVOT) and is a frequent clinical problem. Although some investigators have suggested that RVOT VPBs are associated with RVOT ventricular tachycardia, few data are available on patients with RVOT VPBs. The purpose of this study was to determine the clinical characteristics and prognosis of RVOT VPB.

The study subjects were 161 consecutive patients with frequent RVOT VPBs on standard electrocardiography. All patients underwent clinical examinations, echocardiography and 24-hour ambulatory electrocardiography. Among these patients, 50 were followed up for a period averaging 28.5±18.1 months.

No structural cardiac abnormalities were found in 149 (92.5%) of the 161 patients with frequent RVOT VPBs. The prevalence of complex VPBs was relatively high (101 of 161 patients: 62.7%) on initial 24-hour electrocardiography. In the case of the 50 follow-up patients, there was no significant difference in mean frequency of RVOT VPBs between baseline and follow-up study (636±482/hour vs. 569±502/hour, p=NS). Furthermore, VPBs tended to persist over the follow-up period in the majority (92%) of patients with frequent RVOT VPBs. Five patients (10%) developed nonsustained ventricular tachycardia, 2 (4%) sustained ventricular tachycardia and 1 (2%) died suddenly. Antiarrhythmic drugs are effective in decreasing the frequency of VPBs, and beta-blockers especially seem to be effective in decreasing the severity of VPBs.

In the patients with frequent RVOT VPBs, sustained ventricular tachycardia or sudden death could develop. Therefore, careful observation is required in patients with frequent RVOT VPBs.