Electrocardiographic characteristics in the patients with a persistent left superior vena cava

A persistent left superior vena cava (PLSVC) is a congenital venous abnormality and is usually asymptomatic and does not cause hemodynamic disturbances. Therefore, it is difficult to identify it by routine examinations in clinical practice. This study aimed to elucidate the electrocardiographic characteristics for the prediction of a PLSVC. Twelve patients (9 males, 56.2 ± 18.3 years) who were diagnosed with a PLSVC were enrolled. The electrocardiographic parameters, including the P-wave duration, axis, and morphology of the P waves, were automatically measured and compared to 150 controls (77 males, 57.3 ± 14.6 years). There were no significant differences in the P-wave duration. Negative or positive/negative P waves in lead III predicted a PLSVC with a sensitivity of 100% and specificity of 81%. The P-wave axis in PLSVC exhibited a significant leftward deviation as compared to the controls (14.8 ± 21.1 vs. 54.0 ± 17.4°, p < 0.001). A receiver operating characteristic curve analysis of the P-wave axis for predicting a PLSVC exhibited an area under curve of 0.93 [CI 95% (0.87–0.98), p < 0.001), and identified a P-wave axis of less than 37.5° to have a 92% sensitivity and 83% specificity in predicting a PLSVC. A negative or positive/negative P-wave morphology in lead III was a useful finding for suggesting the presence of a PLSVC.