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.