Iterative Cardiac Output Measurement for Optimizing Cardiac Resynchronization Therapy: A Randomized,Blinded, Crossover Study

Background: Many invasive and noninvasive methods have been proposed for guiding optimal programming of cardiac resynchronization therapy (CRT) devices. However, results are not satisfying. Preliminary results suggest that cardiac output (CO) measurements using inert gas rebreathing (IGR) might be an eligible method to tailor atrioventricular (AV) and ventriculo‐ventricular (VV) programming. The aims of the present study were: (1) to evaluate whether an optimization of CRT can be obtained by noninvasive CO measurements and (2) to evaluate whether acute hemodynamic improvements obtained by this approach relate into increase in cardiac exercise capacity. Methods: In 24 patients on CRT, iterative VV‐ and AV‐delay optimization was done using the IGR method. This blinded, randomized, crossover study compared the responses to optimization during two periods: a 4‐week optimized and a 4‐week standard programming. Exercise capacity after optimization was assessed after each period by New York Heart Association (NYHA) classification, a 6‐minute walking test, and quality of life (QoL) questionnaire. Results: CO could be determined by IGR in all patients. The NYHA class decreased by 17.8% (2.8 ± 0.3 vs 2.3 ± 0.4, P < 0.001), the mean (± standard deviation) distance walked in 6 minutes was 9.3% greater after optimization (456 ± 140 m vs 417 ± 134 m, P < 0.001), and the QoL improved by 14.5% (41.8 ± 10.4 vs 36.5 ± 9.5, P < 0.001). The portion of responders to CRT increased from 66.5% to 87.5%. Conclusion: CRT optimization by iterative CO measurements leads to an increase in CO and an improvement of exercise capacity. Our results suggest that this method might become an important additive tool to adjust CRT programming. (PACE 2010; 33:1188–1194)