Cardiac Resynchronisation and Haemodynamic Monitoring: the Living-CHF Study

Abstract

Since multisite stimulation was first performed in heart failure (HF) [1], a few specific devices have been designed with capabilities for providing separated output control of pacing parameters for the right and left ventricular leads, as well as inter ventricular (VV) sequence programming. So far, there are no haemodynamic sensors to improve understanding of and follow up the effects of biventricular (BiV) stimulation and help in the programming of the resyn-chronisation parameters. In the meantime, Sorin Biomedica has developed the Living-BEST system, which is based on a sensor that is able to measure the amplitude of mechanical vibrations generated by the myocardium during the isovolumetric contraction of ventricles. The peak of endocardial acceleration (PEA) reflects events that produce vibrations that originate mainly in the left ventricle and are transmitted through the cardiac mass [2, 3]. It has been shown that PEA is correlated with contractility indexes, such as dP/dt_max, and is influenced by catecholamine levels. PEA variations are related to the capability of the myocardium to respond to adrenergic stresses. Human experiments [4,5] have shown that PEA variation is greater during exercise with biventricular pacing than compared with to other modes, and it has been suggested that PEA might be used as a marker for selecting the position of ventricular pacing leads that provides the best haemodynamic effect. The version of the Living-BEST system designed specifically for biventricular pacing (Living CHF) has the capability of recording amplitudes and timings of PEA and providing realtime telemetry of the whole endocardial acceleration signal. Secondly, the device has the VV Interval programming feature, which can influence the efficacy of resynchronisation provided by biventricular stimulation. Recent studies [6–13] have been focused on improving understanding of the effects of cardiac resynchronisation therapy. Biventricular stimulation provides a more homogeneous contraction of ventricles, which becomes faster and allows prolongation of the diastolic filling phase. Filling pressures are reduced with the frequent reduction in the mitral valve regurgitation. The most relevant parameter is the aortic pre-ejection interval [14], which has to become shorter to predict the beneficial effect of biventricular stimulation, and also the shortening in the contraction timing of the uncoordinated ventricular segments. In this context the use of a haemodynamic sensor is an interesting possibility as an analytic tool for the evaluation and optimisation of ventricular resynchronisation therapy.