OBJECTIVES.In this study, we propose a new hemodynamic (cardiomechanic) sensor based upon high frequency (HF) parameters of bipolar cardiac pacing leads. By measuring the lead HF impedance variation, or any related parameter such as HF reflection coefficient, we can quantify the lead bending due to the myocardial contraction. Therefore, the signal obtained by measuring the HF reflection coefficient on an implanted cardiac lead is named the lead bending signal (LBS). The purpose of this pilot study was to investigate the possibility of detecting the ventricular contraction in sheep utilizing LBS measurements on endovenous pacemaker and defibrillator leads. We also compared the cardiomechanic parameter - maximum rate of rise of the lead bending signal (dLBS/dtmax), i.e. the maximum lead bending acceleration (LBAmax), with the hemodynamic parameter - positive peak LV dP/dt, universally accepted as a good and highly sensitive index for contractility assessment in an individual patient. MATERIAL AND METHODS.The study was a single-centre, experimental animal feasibility study. The study was designed to evaluate the following hypotheses: (1) measuring and recording LBS in implanted bipolar or multipolar cardiac leads at the time of implantation procedure and after four months is feasible, (2) there is a correlation between LBS, LBAmax and LV dp/dtmax acquired four months after the implantation procedure. We implanted three different pacing leads and tested the measurement system in ten sheep (42 ± 6 kg) at baseline and during acute hemodynamic intervention with dobutamine infusion, esmolol infusion and tachycardia induced by fast ventricular pacing at rate up to 200 bpm. VIIRESULTS.A stable, consistent, and reproducible LBS was obtained in all sheep during the implantation procedure and four months after the implant during different experimental conditions that included hemodynamic interventions. Dobutamine infusion significantly increases heart rate (HR), left ventricular pressure (LVP), maximum rate of rise of left ventricular pressure (LV dP/dtmax) and maximum rate of rise of the lead bending signal (dLBS/dtmax) being the maximum lead bending acceleration (LBAmax). The dependence between LBAmax and LV dP/dtmax was found to be statistically significant and with high Pearson’s correlation coefficient (r = 0.855, p < 10-9). We could observe the hemodynamic deterioration caused by RV pacing. Pacing at 200 ppm decreased the LVP, LV dp/dt, LBS and LBA compared with the sinus rhythm. The return to sinus rhythm was associated with restoration of normal hemodynamics. CONCLUSION. To my knowledge, the present study is the first to evaluate and confirm the feasibility and efficacy of the hemodynamic sensor based upon HF lead parameters. Moreover, it was demonstrated that the maximum lead bending acceleration is highly correlated to the ventricular contractility and, therefore, can be efficiently used as a hemodynamic and cardiomechanic sensor. Our ongoing studies should reveal that the high-frequency system functions with every standard cardiac lead having at least two conductors. To establish fully the advantages and limits of this new method, comparison with LV pressure-volume loops in humans and multicentre study data are needed