New cardiomechanic pacing lead sensor based on high frequency parameters: experimental studies in sheep.

UNLABELLED: Pacing Lead as a High Frequency Cardiomechanic Sensor. INTRODUCTION: The purpose of this study was to investigate the possibility of detecting and quantifying ventricular contraction in sheep utilizing the cardiomechanic sensor based upon the high frequency (HF) parameters measurements on bipolar cardiac pacing leads. Measurement of the HF reflection coefficient yields the lead-bending signal (LBS) caused by myocardial contraction. The correlation between the lead-bending acceleration (LBA) expressed as the rate of rise of LBS and LV dP/dt should reveal that LBS may be utilized as a cardiomechanic sensor in implantable cardiac electrotherapy devices. METHODS AND RESULTS: We implanted 3 different pacing leads and tested the measurement system in 9 sheep (42 ± 6 kg) at baseline and during acute hemodynamic intervention with dobutamine infusion and tachycardia induced by VVI pacing at 200 bpm. A stable, consistent, and reproducible LBS was obtained in all sheep during the implantation procedure and 4 months after the implantation during different experimental conditions that included hemodynamic interventions. 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 <0.001). We could also observe the hemodynamic deterioration caused by fast ventricular pacing with the decrease of LV dp/dt and LBA compared with sinus rhythm. CONCLUSION: This study confirms the feasibility and efficacy of the hemodynamic sensor based upon HF lead parameters. Moreover, it was demonstrated that LBAmax is highly correlated to the ventricular contractility and, therefore, can be efficiently used as a hemodynamic and cardiomechanic sensor. (J Cardiovasc Electrophysiol, Vol. 24, pp. 338-346, March 2013).

Acute and chronic high-frequency properties of cardiac pacing and defibrillation leads.

The purpose of our study was to investigate variety of cardiac lead conductor designs as high-frequency (HF) transmission lines. Special attention was given on evaluation of chronic HF applications in cardiac electrotherapy. We measured the characteristic impedance and the attenuation coefficient of six pacing leads between 1 and 21 MHz. They were subsequently immersed into the saline solution simulating the body fluid and the measurements were repeated 10 years later. Identical measurements were performed on 15 new pacing and defibrillation leads. The results revealed that lead geometry is the main factor affecting the HF parameters. Attenuation coefficients of old and contemporary leads do not differ significantly. Penetration of saline within the leads during a decade did not influence much their HF characteristics. Thus, a chronic cardiac contraction sensor based on lead's HF impedance variation is feasible. The signal losses of ultrasonic transducers mounted on the lead might be stable for years at acceptable levels without significant variation. Due to mutually similar values of HF parameters in different leads, design of tensiometric or ultrasonic applications could be universal for majority of commercially available leads. Automatic system calibration could be developed for each and every lead after determination of its HF parameters.

Acute animal and human study of tensiometric pacing lead sensor based on triboelectricity.

Cardiac contractions bend the implanted cardiac lead body, extend and compress the lead conductors, their insulation and the inserted stylet. Magnitude of lead deflection depends on cardiac muscle contraction forces. The purpose of study was to measure the charge generated due to triboelectric effect between one of the lead conductors and the inserted stylet. The charge was measured by differential charge amplifier being connected to isolation amplifier and power supply. Sensor signal, ECG and intracardiac electrograms were acquired. Three models of custom designed leads were implanted in 8 sheep. Measurements were done in 18 patients undergoing pacemaker implantation and replacement procedures. Atrial and ventricular tensiometric signals were recorded in dual chamber and in single-lead VDD patients. Recordings in sinus rhythm at various AV intervals and in supraventricular tachycardia were done. In average, charge variation between 1 and 600 pC was measured. Tensiometric stylet could be feasible hemodynamic sensor for myocardial contraction detection. Its main advantage is that it is easily exchangeable and universal for all leads.