VECTOR ECG ANALYSIS IN PATIENTS RECEIVING CARDIAC RESYNCHRONIZATION THERAPY

To describe electrocardiographic (ECG) features of isolated right ventricular (RV) and left ventricular (LV) pacing in case of different electrode location in standard radiographic projections, 40 patients receiving cardiac resynchronization therapy were assessed. ECG in the area of LV electrode was assessed during the isolated LV pacing using 12 conventional segments of myocardium, as follows: 3 posterior, 3 postero-lateral, 3 lateral, and 3 antero-lateral segments on the basal, medial, and apical levels. The RV electrode location was assessed during the isolated RV pacing using 3 following conventional segments: basal part of interventricular septum (IVS), medial part of IVS., and RV apex. The following positions of ventricular electrode were revealed in the study group: LV lateral wall (in most patients; 47.5%), including its basal part (30%); the electrode was positioned in the postero-lateral wall (35%) as well as in the posterior wall of LV (17.5%). The RV electrode was placed in in the RV apex (62.5%) or in the IVS basal part (30%). The difference in the ECG pattern of pacing of apical area of postero-lateral and posterior walls of LV consisted in the axis in leads I and aVL; more positive it was more posterior location of the pacing area took place; right chest ECG leads remained positive. In the study group, the LV electrode apical location was found in 17 cases (42.5%) and was confirmed by standard radiological projections, including lateral wall in 3 cases, postero-lateral wall in 8 cases, and posterior LV wall in 6 cases. Thus, ECG appears to be a useful tool for follow-up of patients with CRT without additional time expenditure. The ECG pattern of isolated RV and LV pacing correctly reflects the radiological position of the corresponding electrodes. The vector ECG analysis can be used as a safe indirect method of evaluation of the LV electrode location during follow-up of patients with CRT.

chronic heart failure, cardiac resynchronization therapy, electrodes, electrocardiography, radiography

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