Evaluation of the Relative Frequency of Late Potential Based on Signal Average Electrocardiogram in Patients With Premature Ventricular Contraction Originating From Right Ventricular Outflow Tract

Background: The role of signal average electrocardiogram (SAECG) has not been studied in patients with frequent right ventric- ular outflow tract (RVOT) Premature Ventricular Contraction (PVC), therefore we decided to perform noninvasive tests including SAECG in these patients, and compare various parameters in two groups with normal and abnormal SAECG; and therefore deter- mine whether it can provide a noninvasive method to recognize high risk patients with respect to Arrhythmogenic right ventricular cardiomyopathy (ARVC). Methods: Eighty-eight consecutive patients with right ventricular outflow tract PVC without structural heart disease were prospec- tively enrolled in this study. History report, SAECG, maximum QRS duration in right precordial leads; nadir S to isoelectric line in V1, maximum QRS ratio (ratio of QRS duration in leads V1 + V2 + V3/V4 + V5 + V6), LVEF and RV abnormalities by echocardiography, presence of VT during 24-hour holter monitoring, and response of PVC during EST were done in all of the study groups. Results: Signal Average Electrocardiogram was abnormal in 11.4% of patients. The following measurements were recorded for pa- tients with abnormal SAECG versus normal SAECG: QRS duration in right precordial leads (mean SD: 107.6 6.9 versus 90.8 9.2, P < 0.001): Nadir S to isoelectric line (mean SD:50.2 5.8 versus 44.2 5.2, P = 0.001): mild RV dilation (40% versus 9%, P = 0.005), mild RV systolic dysfunction (60% versus 9%, P < 0.001), NSVT in holter (50% versus 10.5%, P = 0.001), and filtered QRS duration (118.5 15.9 versus 99.9 13.1, P < 0.001). Conclusions: Patients with idiopathic RVOT-PVC may have abnormal SAECG. Progression of the patients with abnormal SAECG to apparent ARVC is unknown. In order to assess the natural history of the disease, the patients should be kept under close observation until further information is available.