Perepeka E. Cardiac conduction system pacing in patients with life-threatening bradyarrhythmias.

Dissertation for obtaining the scientific degree of Doctor of Philosophy for specialty 222- Medicine. State University "Amosov National Institute of Cardiovascular Surgery of the National Academy of Sciences of Ukraine". The dissertation study is devoted to the optimising surgical treatment of patients with life-threatening bradyarrhythmias and with preserved left systolic function using cardiac conduction system pacing. This study included 52 patients with various variants of bradyarrhythmias, in whom pacemakers were implanted between 2012 and 2022 at the State University "Amosov National Institute of Cardiovascular Surgery of the National Academy of Sciences of Ukraine". The cardiac conduction system pacing" (CCSP) group included 18 patients with indications for permanent ventricular pacing: 16 (88%) patients with high-degree AV block (including 1 patient with Frederick syndrome), 1 (5%) patient with bradysystolic form atrial fibrillation and 1 (5%) patient with left bundle branch block (LBBB) and 1st degree AV block. The average age of the patients was 55 ± 16 years (there were 10 women and 8 men. The control group consisted of 30 patients with variants of right ventricular (RV) myocardial pacing (both septal and apical) aged 66.8 ± 10.17 years (18 men and 12 women). 30 patients with AV block of various degrees were included in the RV pacing group: 2 (7%) of these patients had Frederick syndrome, and 2 (7%) patients had AV block after radiofrequency catheter ablation of the AV node for chronic tachysystolic atrial fibrillation. Among the patients from the CCSP group there were 6 patients with true His bundle pacing (HBP), 1 patient with left bundle branch pacing (LBBp) and 11 patients with parahisian pacing (the paced QRS vector coincided with the native QRS, the LV activation time did not exceed 100 ms (interval from of the stimulus to the peak of the R wave in lead V6) and the QRS width did not exceed 125 ms. Patients with both septal myocardial and apical pacing were included in the right ventricular pacing group. 8 patients (26%) from the RV pacing group were with apical stimulation In this study author tried to study consequences of non-physiologic RV pacing. The study group of pacing-induced cardiomyopathy (PICM) included 34 patients with indications for permanent ventricular pacing (both with septal and apical RV pacing). The incidence of PICM in the studied group was 26% (cardiomyopathy developed in 9 out of 34 patients). All patients included in the study group of PICM had right ventricular myocardial pacing. Of the 34 patients, 9 (26%) had apical RV pacing. The other 25 (74%) had variants of septal myocardial right ventricular pacing. At the time of control follow-up left ventricle ejection fraction (LVEF) was significantly different in the group of PICM and in the group with preserved left ventricle (LV) contractility - 38.6 ± 5.9% vs. 53.5 ± 5.7% (p <.001). Although the LVEF was significantly smaller at the time of the follow-up than at the time of pacemaker implantation in the PICM group (55.2 ± 5.4% vs. 38.6 ± 5.9%, p <.001), in the group with preserved LVEF it was also possible to observe the decline of this parameter (57.5 ± 5.2% vs. 53.5 ± 5.7%, p =.01). The end diastolic index (EDI) of the LV significantly increased during the time from the implantation of the pacemaker to the control follow-up in the PICM group (76.68 ± 11.74 vs. 97.9 ± 20.75 ml/m2, p =.011). At the time of the follow-up observation, the LV EDI was significantly greater in the PICM group than in the group with preserved LVEF: 97.9 ± 20.75 vs. 60.9 ± 19.32 ml/m2 (p <.001). The left atrium diameter and the RV pressure were significantly greater in the PICM group than in the control group during follow-up (47 ± 2.95 vs. 42.9 ± 5.07 mm, p =.011, and 43.8 ± 8.8 vs. 35.6 ± 6.1 mmHg, p =.008). The paced QRS width in the PCIM group was significantly greater than that in the group with preserved LVEF (163 ± 22.7 vs. 150.8 ± 14.5 ms, p=.046). All patients from the PICM group were sent to a protocol echocardiographic study during controll follow-up, in which measurements of intraventricular and interventricular mechanical asynchrony were performed, the number of left ventricular segments with reduced deformation was fixed, and the global longitudinal deformation of the left ventricle (GLS) was calculated. Intraventricular mechanical asynchrony was significantly greater in the PICM group than in the group with preserved LVEF and was 261.1 ± 61 ms vs. 146.1 ± 62.8 ms (p= <.001), interventricular mechanical asynchrony exceeded in patients with cardiomyopathy and was lower in patients without cardiomyopathy (CMP) [91 ± 36.4 ms vs. 54.2 ± 22.2 ms (p =.014)]. The average number of segments with reduced deformation in PICM group was significantly higher than in the group without CMP [8.1 ± 2.6 vs. 3.91 ± 2.3 (p <.001)], and global longitudinal strain (GLS) significantly reduced [-9.7 ± 2.6 vs. -14.9 ± 3.4% (p <.001)].