STEROID ELUTING PACEMAKER ELECTRODES - IMPROVED STIMULATION AND SENSING PROPERTIES

The effect of local elution of dexamethasone on stimulation and sensing properties of pacemaker electrodes was studied in 20 patients with cardiac arrhythmias (11 men, 9 women; average age 73 +/- 9 years). In two randomized groups of 10 patients each a unipolar ventricular electrode (surface area 4 mm) with or without steroid was implanted. The steroid electrode contained 0.5 mg dexamethasone which elutes into the surrounding myocardium from a silicon ring at the electrode tip. Stimulation threshold was determined at 0.05 ms to 1.5 ms impulse duration in 0.8 V steps, impedance being measured by telemetry. Correct R wave sensing was tested for 1.25, 2.5 and 5.0 mV. While stimulation thresholds after implantation of an electrode without steroid rose to a maximum after two weeks, there was only a mild rise in threshold within the first week after implantation of a steroid electrode, the threshold then remaining constant. In none of the patients did the stimulation threshold rise above 0.8 V at an impulse duration of 0.5 ms. The intracardiac signal at 5.0 mV sensitivity was correctly sensed in all 10 patients with a steroid electrode, but in only 7 without steroid. A further reduction in stimulation energy over that with a standard impedance of 500 ohm was achieved at impedances greater than 600 ohm.