Temporary Transvenous Pacemaker Monitoring Using Simultaneous Endocardial and Surface Electrocardiograms: Technique and Clinical Applications

A technique for simultaneous recording of surface and endocardial ECGs in patients with temporary transvenous demand pacemakers using a telemetry unit is described. Analysis of the initial endocardial ECGs recorded in 35 patients disclosed two distinct groups: group A (26 patients) characterized by a steady baseline, constant QRS amplitude of 5 mv or greater and an absence of P waves and group B (9 patients) manifesting baseline shifts and greater than 25 percent variation in QRS amplitude. Subsequent pacemaker failure invariably occurred in group B, whereas, findings in group A indicated a well-wedged catheter. The two groups could not be distinguished by fluoroscopic examination. A subsequent change in group A manifested by either a shift in baseline, or variation in QRS amplitude and morphology, or the appearance of P waves signaled impending pacemaker failure. In addition, the technique proved helpful in elucidating certain mechanisms responsible for pacemaker malfunction.