Pitfall of Synthesized Posterior/Right-Sided Chest Lead Electrocardiograms

Background: Posterior leads (V7–V9) and/or right-sided precordial leads (V3R–V5R) provide important information from posterior and/or right ventricular areas, but these additional ECGs are not routinely recorded because of the time-consuming procedure involved. Recently synthesize these 6 additional lead ECGs using standard 12-lead ECG system (Nihonkoden Co. Ltd.) developed. However, the accuracy of synthesized ECGs were unknown. The purpose of the present study was to evaluate the accuracy of ECG recordings using the system. Patients and Methods: 293 patients (204 men, 89 women; mean age 67 years) were enrolled. Standard 12-lead and V3R–V5R, V7–V9 lead ECGs were recorded and compared with synthesized ECGs mathematically derived from standard 12-lead signals. Results: The synthesized and actual ECG waveforms were almost identical. The coefficient of correlation was 98% in V3R, 94% in V4R, 91% in V5R, 98% in V7, 95% in V8 and 86% in V9, and gradually worse as lateral side (V7 vs V9; p<0.0001, V3R vs V5R; p<0.0001). In V9 and V5R, QRS waveform amplitude in which the coefficient of correlation was less than 70% was lower than that in more than 70% (V9; 386 µV vs 541 µV, p<0.0001, V5R; 335 µV vs 502 µV, p=0.01). Conclusions: Synthesized posterior and right-sided precordial lead ECGs appear to be highly reliable and useful. However, the interpretation of synthesized V5R and V9 waveform with low amplitude may require intensive attention.