Unipolar pulse generators, either single or dual chamber, can be inhibited or reverted to the asynchronous mode, by skeletal muscle myopotentials. Dual chamber pacemakers may even stimulate the ventricle at the upper rate limit because of myopotential sensing via the atrial channel. A unipolar anti-tachycardia generator may be triggered by myopotentials to provoke an arrhythmia. During bipolar implanted pacing, episodic ventricular tachycardia has been induced in three patients with Chagasic cardiomyopathy and anodal stimulation has been shown to be the cause. Both unipolar and bipolar stimulation modes present problems. A stimulation mode with the cathode intracardiac and the anode remote from the generator and the patient's heart, called "tele-anode" was developed to be implanted in the presternal area or in venous system and avoid pacemaker triggering and inhibition. The subcutaneous "tele-anode" may be a spiral or a cylinder while an intravascular "tele-anode" may be positioned in the superior or inferior vena cava. Until March, 1986, 62 patients underwent "tele-anode" implantation, 57 at the sternum (51 spiral and 6 cylindrical) and 5 intramuscular. Thirty five generators were single chamber ventricular inhibited, 23 were dual chamber, 3 were atrial inhibited and 1 ventricular anti-tachycardia. In all cases the stimulation thresholds and electrogram characteristics were similar between intracardiac cathode and "tele-anode" and cathode and the puise generator site. Only electromyographic signals were consistently attenuated. One patient with an intravascular "tele-anode" died postoperatively of ventricular arrhythmias and one required ventricular lead repositioning. The 61 living patients, followed from one to twenty-one months, have shown no inhibition, triggering or noise mode reversion at nominal sensitivity setting. The authors conclude that pacemakers implanted with "tele-anode" show a clear evidence of decrease of associated complications, inherent to the conventional unipolar and bipolar cardiac stimulation system.
tele-anode; cardiac stimulation; pacemakers, cardiac