[Measurement and analysis of monophasic action potentials using fractally coated electrodes--I].

The monophasic action potential (MAP) contains a wealth of information about the stat of the myocardium, which makes it very useful for numerous diagnostic and therapeutic applications in patients with heart disease. The silver-silver chloride electrodes which are currently used for the measurement of MAP have poor long-term stability in contact with biological tissue. This study was therefore undertaken with the aim of investigating the electrochemical behaviour of fractally coated leads in terms of their signal-detection performance. Experience gained with these leads in cardiac pacemakers has already demonstrated the long-term stability and biocompatibility of the fractally coated leads. Present results show that, due to their large electrochemically active surface area, fractally coated leads have a very low impedance over a wide frequency range. The negligible polarization artifact of these leads permits the measurement of cardiac potentials immediately after a stimulus. Fractally coated leads are thus highly suitable for the measurement of MAP, and have clear advantages over Ag/AgCl electrodes. The second part of this study reports on the results of MAP measurements using fractally coated leads.