Cardiac pacing lead as hemodynamic sensor

Therapy delivery in modern cardiac electrotherapy systems is based almost exclusively on the information about cardiac electrical depolarization. This kind of detection lacks any data about the myocardial contraction. An optimal heart rhythm control should integrate the assessment of the mechanical cardiac activity and related hemodynamic parameters to the already existing electrical signal analysis. A hemodynamic sensor integrated in pacing systems would be a valuable instrument for many applications. Only few hemodynamic sensors integrated in cardiac electrotherapy systems are currently available on the market. In order to fill the gap, I have explored the possibility of building a hemodynamic sensor for myocardial contraction detection that could be easily integrated in the existing cardiac pacing and defibrillator leads. In this thesis I propose two sensors. One is based on tribolectricity and the other one requires the measurement of high frequency lead parameters. The triboelectric sensor system measures the charge generated due to the triboelectric effect between one of the lead conductors and the inserted stylet as a result of the lead bending. The measurement system consists in sterile charge amplifiers for use in sterile operation field and a non-sterile enclosure containing isolation amplifiers and power supply. Atrial and right ventricular tensiometric signals were recorded during numerous ovine and human experiments and have shown good results under different measurement conditions. The main downside is the necessity of the additional hardware in terms of chronic stylet insertion in the pacing lead lumen. The sensor based on the measurement of high frequency (HF) pacing lead parameters has its origin in previous extensive in vitro experiments on the HF characteristics of the lead. These experiments have supported the idea of considering any bipolar lead to be a HF transmission line with its characteristic impedance and attenuation. An original study revaluing lead HF parameters after being soaked for more than a decade in the saline solution is presented. A parallel study on dry new leads was also carried out. The hemodynamic HF sensor is based on the variation of the pacing lead HF impedance and reflection coefficient due to its movement during cardiac contractions. The quality of the signal was proven in a series of ovine and human experiments and during dobutamine test in sheep. Both sensors would be feasible hemodynamic sensors for various applications: capture management, rate responsiveness, heart failure monitoring, CRT optimization, tachycardia hemodynamic stability assessment, AF therapy titration and vasovagal syncope prediction. These two sensors are unique for their simplicity and universality for all existing endovenous bipolar cardiac leads.