RESPONSE TO CARDIAC RESYNCHRONIZATION THERAPY DEPENDING ON LOCATION OF CARDIAC DYSSYNCHRONY ZONES AND POSITION OF VENTRICULAR ELECTRODES

To reveal predictors of response to cardiac resynchronization therapy (CRT) by comparing zones of maximal intraventricular dyssynchrony (IVD) and location of ventricular electrodes (VE), the retrospective study included 40 patients, including 26 men (65%) and 14 women (35%), with the sinus rhythm and implanted CRT system according to the commonly accepted indications. The patients aged 60.91±11.43 years; ischemic cardiomyopathy was documented in 48% of cases according to the data of coronary angiography and/or the documented evidence of myocardial infarction. Patients with significant valvular disease (more than moderate valvular regurgitation or any valvular stenosis) as well as more than mild pulmonary hypertension were excluded from the study. The study subjects were distributed into two groups. Group I (n=20) included subjects with a pronounced response to CRT. The CRT response criteria were as follows: decrease in the left ventricular (LV) end-systolic volume (ESV) by at least 15%, a relative increase in the LV ejection fraction (EF) by at least 10%, improvement of the chronic heart failure (CHF) by at least 1 functional class. Group II (n=20) included patients with an inadequate response to CRT (no positive changes in size, dimensions, and EF LV). While implanting the CRT system, the right atrial (RA) electrode was positioned at the right auricle; the right ventricular (RV) electrode was positioned at basal or medial parts of the inter-ventricular septum (IVS) or the RV apex. The LV electrode was implanted into any branch of the coronary sinus. The follow-up period lasted for 12.0±1.7 months. Coincidence of the zone of maximal IVD with the site of the LV electrode implantation was assessed with the aid of the vector ECG analysis in 12 standard leads during the isolated LV pacing using 12 conventional segments, as follows: 3 posterior segments, 3 posterolateral ones, 3 lateral ones, and 3 anterolateral ones 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 IVS., medial part of IVS., and apex of RV. After 12 months of follow-up, considerable difference between the study groups in the end diameters, volume, and LV EF was shown (p<0.001). LV EF was 44.9±5.9% in Group I, 26.9±6.4% in Group II. A better functional class of CHF was found in Group I than in Group II (15 and 6 of patients with CHF II (NYHA), respectively, p=0.043). No IVD after 12 months of follow-up was observed in 19 patients of Group I and 16 patients of Group II, p=0.493. It should also be noted that in patients with IVD at baseline (13 subjects of Group I and 12 subjects of Group II), in 12 months IVD was detected in 1 patient of Group I and 4 patients of Group II. Thus, IVD recovered in 91.7% of cases in Group I and in 66.7% of cases in Group II, p=0.068. According to the ECG data, coincidence of the zone of maximal IVD with the site of the LV electrode implantation was more frequent in Group I (13 patients) than in Group II (6 patients), p=0.028. Thus, CRT is a complex process which includes the correct selection of patients, the device implantation itself, as well as subsequent long-term follow-up with the CRT parameter correction and medical therapy. IVD at baseline, coincidence of the zone of maximal IVD with the site of the LV electrode implantation and the distance between ventricular electrodes can be considered predictors of a better outcome in CRT to be taken into consideration during implantation. Coincidence of the zone of maximal IVD with the site of the LV electrode implantation in associated with a substantial long-term improvement in the hemodynamics of subjects with CRT.

chronic heart failure, intra-ventricular myocardial dyssynchrony, cardiac resynchronization therapy, electrocardiography, echocardiography, left ventricular ejection fraction

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