Introduction and aim: The non-responder rate for cardiac resynchronization therapy (CRT) among heart failure (HF) patients appears to be about 25-30%. Suboptimal atrioventricular (AV) and ventricle-to-ventricle (VV) timing are 2 of the proposed contributing factors. With no standardized method for CRT optimization, echocardiogram is an acceptable and well recognized technique for this practice. The Non-Invasive Cardiac System (NICaS: NI Medical, Israel), calculates the cardiac output (CO) and stroke volume (SV) by measuring impedance cardiography in a tetra-polar mode, derived from electrodes placed on patient’s body. This simple to operate, non-invasive technique was validated in previous studies to be reliable in estimation of CO and SV compared to traditional, invasive techniques in different settings including HF patients. In the present study we assessed the ability of NICaS system to help in the optimization of CRT devices compared with echocardiography.
Methods and results: eighteen CRT implanted patients, who were scheduled for CRT optimization according to their cardiologist's decision, underwent CRT optimization by a professional echocardiogram technician and an echocardiogram specialist, and also by NICaS operator. The two teams were blinded to their counterparts' findings. SV and CO were measured in different CRT settings. In 33% of the patients no specific programming parameters of the CRT device contributed to optimization. Analysis of the results demonstrated poor correlation between NICaS system and echocardiogram findings. Parameters for CRT optimization were programmed according to echocardiogram results.
Conclusion: as in previous studies, a significant portion of CRT implanted patients do not benefit from optimization. A poor
correlation was found between echocardiogram and NICaS system results. Further trials attempting to dictate CRT optimization according to NICaS system results might be of value.
