NEW ASPECTS IN ELECTROSTIMULATION OF THE HEART

The interaction of the autonomic nervous system (ANS) and the heart is characterized by a new interdisciplinary field known as neurocardiolo gy which presents the newest strategy for electro-cardiostimulation. I n this context, the reestablishment of chronotropy with physiological, closed-loop pacing, as well as the prevention and treatment of a mali gnant arrhythmia by ANS modulation, is of the highest priority. The ma in objective toward this goal consists of appropriate monitoring of th e autonomic balance and stimulation, respectively, so that neuromodula tion of the cardiac efferents can be established. The electrode, as a sensor and an actuator, with its interface on the cellular level becom es of essential importance. The electrode-myocardium interface is dete rmined by the structure of the Helmholtz double layer with regard to i ts physical, electrochemical, and physiological behavior. The transpor tation of electrons across the boundary, as well as the electro-chemic al reactions determining the biocompatibility of the interface, can be improved by the microstructure of the solid component by creating a f ractal surface coating with titanium-nitride or iridium. Experimental and clinical results have demonstrated that the fractal structure ensu res negligible polarization as well as improved detection performance, thus, detecting the evoked response of the myocardial cells makes it possible to monitor the neural response of the myocardium as a consequ ence of a superimposed chronotropic disturbance. The stimulation elect rode also monitors the sympathetic activity extracted from intracardia c impedance measurements, thereby providing a new principle of rate ad aptation in which the pacemaker is an integral part of the ANS, reesta blishing normal chronotropy. Further advantages of the improved electr ode interface performance open new aspects in the treatment and preven tion of tachyarrhythmia, and in the follow-up of transplanted hearts f or the prevention of the rejection processes.