Effect of right ventricular myocardial contractility on the response to cardiac resynchronization therapy

AIM: To determine the effect of right ventricular myocardial contractility on the response to cardiac resynchronization therapy (CRT). MATERIALS AND METHODS: The study included 80 patients (49 men, mean age 54±10.5) diagnosed with dilated cardiomyopathy, complete left bundle branch block, and the QRS complex width 146 to 240 ms (183±32 ms). Heart failure was NYHA FC III, ejection fraction (EF) - 30.1±3.8 %, 6‑min walk test - 290.5±64.3 m, and end-diastolic volume (EDV) - 220.7±50.9 ml. 35 patients had permanent atrial fibrillation. All patients received implantable devices for CRT; complete artificial atrioventricular block was formed in patients with atrial fibrillation. LV and right ventricular (RV) contractile function was studied in all patients before and at 12 months of the implantation using equilibrium radionuclide tomoventriculography. RESULTS: At 12 months, 69 (86.25 %) patients were clinical responders to CRT and 11 (13.75 %) patients did not respond to the treatment. The responders showed positive clinical dynamics; LV EF increased from 30.1±3.8 to 42.8±4.8 % (p≤0.001), LV EDV decreased from 220.7±50.9 to 197.9±47.8 ml (p≤0.005). In non-responders, LV EF increased from 30.1±3.8 to 33.8±3.8 % (p≤0.001) and 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, CRT responders and Group 2, non-responders. A study using radionuclide methods showed that in Group 1 patients, maximum RV filling velocity increased from 1.8±0.36 to 2.17±0.67 (p≤0.001) and the mean velocity of RV filling for one third of diastole increased from 1±0.28 to 1.32±0.45 (p≤0.001). In Group 2, these parameters were significantly worse by 30 and 60 %, respectively. CONCLUSIONS: Cardiac resynchronization therapy is more effective in preserved contractility of the right heart, and higher values of maximum RV filling velocity for one third of diastole may serve a prognostic criterium for a beneficial response to CRT.