Fractally coated defibrillation electrodes: is an improvement in defibrillation threshold possible?

In patients with implantable cardioverter-defibrillators (ICD), the goals of lowering the defibrillation threshold (DFT) can be achieved by means of higher defibrillation safety margins, more rapid charging of capacitors, improved battery longevity, implying smaller devices. Whether an increase in the electrically active surface of ICD leads by fractal coating results in decreased DFTs is unknown.

In this prospective randomized cross-over study the defibrillation efficacy of a novel right ventricular endocardial defibrillation electrode fractally coated with iridium was compared with an uncoated but otherwise identical electrode in 30 patients undergoing ICD implantation. In each patient, DFT testing was performed twice according to a binary search protocol introducing the two different electrodes in a random order. The mean DFT was 8.4 +/- 4.1 J with the fractally coated lead and 9.6 +/- 3.6 J using the uncoated lead. The improvement of 1.2 J was statistically not significant (P = 0.11). No differences were observed between the patients with an improved DFT (n =12) and those with an unchanged or worsened DFT (n = 18) concerning age, underlying cardiac disease, NYHA class, or left ventricular ejection fraction, respectively.

Increasing the electrical surface of defibrillation leads by fractal coating does not lead to a substantial clinically relevant reduction in defibrillation thresholds. Defibrillation impedance is not influenced by the increased electrical surface of the defibrillation lead.