Objective: The objective of the study was to evaluate right ventricular (RV) contractile function in patients with implanted devices for cardiac resynchronization therapy (CRT).
Materials and Methods: The study included 80 patients (49 men) with a diagnosis of dilated cardiomyopathy, mean age of 54 ± 10.5 years, heart failure (HF) functional class (FC) III by NYHA, left ventricular (LV) ejection fraction (EF) of 30.1 ± 3.8%, six-minute walk distance (6MWD) of 290.5 ± 64.3 m, and LV end-diastolic volume (EDV) of 220.7 ± 50.9 mL. Forty five patients had sustained sinus rhythm; 35 patients had chronic drug-resistant atrial fibrillation. All patients had complete blockade of the left bundle branch block; QRS duration ranged from 146 to 240 ms (183 ± 32 ms). CRT devices were implanted to all patients. In patients with persistent atrial fibrillation, complete artificial atrioventricular block was formed. In all patients, LV and RV myocardial contractile functions were assessed using equilibrium radionuclide tomoventriculography prior to CRT and 12 months after CRT device implantation.
Results: Follow-up examination was carried out after 1 year of CRT showing favorable clinical changes: HF FC decreased in all patients from III to II. 69 patients responded to CRT (86.25%); 11 patients (13.75%) did not respond to CRT. The criterion of patient’s response to CRT was LV EF increase by 15% or more within 12 months. Responders to CRT showed favorable clinical changes: LV EF increased from 30.1 ± 3.8% to 42.8 ± 4.8% (p = 0.001); LV EDV decreased from 220.7 ± 50.9 mL to 197.9 ± 47.8 mL (p = 0.005). In nonresponders, LV EF did not change significantly (30.1 ± 3.8% vs. 33.8 ± 3.8%, p = 0.001); LV EDV increased from 220.7 ± 50.9 to 227.8 ± 27.8 mL (p = 0.001). All patients were retrospectively divided into two groups: group 1 comprised patients who responded to CRT; group 2 included nonresponders. In patients of group 1, radionuclide tomoventriculography showed that RV peak filling rate (PFR) decreased from 1.8 ± 0.36 to 0.56 ± 0.16 (p = 0.001); mean diastolic filling rate (1/3FR-m) decreased from 0.6 ± 0.2 to 0.36 ± 0.15 (p = 0.001). In patients of group 2, these indices were significantly poorer (by 30% and 60%, respectively). Other parameters did not significantly differ between groups.
Conclusion: CRT in patients with severe HF was significantly more effective in those individuals who had preserved contractility of the right cardiac chambers. The values of RV PFR and RV 1/3FR-m may serve as prognostic criteria for favorable response of patients to CRT.