Evaluation of exercise performance after cardiac resynchronization therapy in heart failure patients

INTRODUCTION More than one third of the patients with congestive heart failure presents ventricular conduction delay which results in a decrease in heart’s contractility and reduced oxygen consumption (VO2). Those patients have more symptoms, worse clinical prognosis and the risk of death is higher. Biventricular pacing of the left and right ventricle simultaneously improves ventricular coordination, hemodynamics and peak VO2 increases significantly during cardiopulmonary exercise testing. Based on Fick’s law, peak VO2 depends on cardiac output and the arteriovenous content difference [C(a-v)O2]. METHODS We have enrolled in our clinical trial 104 patients who were meeting the criteria of the European Society of Cardiology from 2016 for the implantation of the biventricular cardiac resynchronization therapy. A total 14 patients refused to participate in the study and the remaining 90 patients were analyzed based on clinical, electrocardiographic and echocardiographic evaluation, non-invasive inert gas rebreathing method before implantation of CRT and 9±5 months after the implantation. RESULTS AND CONCLUSIONS Functional NYHA class has improved significantly from 2.5±0.5 to 1.97±0.44; as well as all echocardiographic parameters: LV ejection fraction has improved from 29.1±7 % to 35.6±9 %; LV end-diastolic volume has decreased from 212.8±69 mL to 188±70 mL; LV end-systolic volume has decreased from 152.5±59 mL to 125.2±60 mL. At peak exercise we have achieved a significant improvement of peak VO2 from 1065±338 mL/min to 1171.1±369 mL/min which relates to an improvement of cardiac output from 6.09±1.9 L/min to 6.93±2.2 L/min; while the arteriovenous O2 content difference has remained unchanged. The results from the study suggest that CRT is a useful therapeutic modality to preserve or improve cardiac function and submaximal and maximal exercise capacity in patients with heart failure and intraventricular conduction delay. OBJECTIVE: to evaluate exercise performance after cardiac resynchronization therapy (CRT) in heart failure patients and to analyze the effects of biventricular PM therapy in the pathophysiology of heart failure.