Heart position by ECG: baseline and post-TAVR LBBB

Abstract

Left bundle branch block (LBBB) is a frequent complication after transcatheter aortic valve replacement (TAVR), altering ventricular activation and challenging ECG interpretation. This study sought to establish novel electrocardiographic criteria to define the electrical position of the heart (EPH) before and after LBBB post-TAVR. In this single-center, retrospective study, 439 TAVR patients (2018–2023) were screened; 74 developed new LBBB. Patients with pre- and post-TAVR ECGs, without pacemaker, infiltrative disease, or baseline conduction disorders, were included. ECGs were analyzed for QRS duration, electrical axes (AQRS, AT), and patterns of concordance/discordance in leads II/III and aVL/aVF. EPH was categorized as intermediate (IEP), horizontal (HEP), or vertical (VEP) by AQRS. Morphology in leads I, aVL, V5, and V6 was also assessed. Among 74 patients with LBBB, 36 (48.6%) had IEP, 32 (43.2%) HEP, and 6 (8.1%) VEP. In patients without LBBB, AQRS averaged 50°±15° in IEP and –10°±20° in HEP (p<0.0001). With LBBB, AQRS shifted to –20°±25° in IEP and –60°±30° in HEP (p<0.0001). Positive concordance in II/III and aVL/aVF identified IEP, whereas positive discordance indicated HEP. In LBBB, negative concordance in II/III with positive discordance in aVL/aVF defined HEP, while positive discordance in II/III with positive concordance in aVL/aVF characterized IEP. Novel ECG criteria enable reliable classification of cardiac electrical position in both baseline and post-TAVR LBBB. Leftward axis deviation with LBBB often reflects intrinsic EPH rather than new pathology, enhancing interpretation and clinical decision-making.Figure 1Figure 2