Ventricular tracking pacemaker and teletransmitter follow-up system

From September 1970 to March 1973, 172 patients at the University of Oregon Medical School underwent implantation of a unique unipolar dual rate ventricular tracking pacemaker. The pulse generator provides a 0.75 msec stimulating signal and 0.015 msec nonstimu-lating R wave synchronous marker signal. The latter verifies pacer sensitivity when the stimulating signal is R wave inhibited but does not deform the QRS complex and has negligible current drain. Both long and short signals are distinguished and electronically counted by a telephone transmission and receiver system. The pulse generator is rate constant and has predictable voltage response. Thus, rate analysis alone will provide satisfactory warning of impending battery depletion. Clinical evaluation of this new unit in 172 patients disclosed no operative deaths and 28 late deaths. No deaths were due to pacemaker failure. Reoperation was required in 43 patients, 8 with electronic failure due to defective transistors (7 patients) or a loose solder joint connection (1 patient). There was no instance of connector malfunction, adapter malfunction or electrode break. There was one instance of lead fracture. No patient thus far has experienced battery depletion although the longest surviving patients have been followed up for 30 months after implantation. Experience with the teletransmission has been satisfactory in detecting system malfunction and in achieving a high level of patient and physician acceptance of disciplined pacemaker follow-up.