Incidence of unwarranted implantation of permanent cardiac pacemakers in a large medical population.

Because of allegations that the implantation of many permanent cardiac pacemakers has been unjustified, we reviewed the indications for all new pacemakers implanted at 30 hospitals in Philadelphia County between January 1 and June 30, 1983, and paid for by Medicare. Complete chart data were evaluated for 382 implants. We determined whether the indications for implantation were appropriate and adequately documented on the basis of standard clinical practice. Implants were classified as possibly indicated primarily because of inadequate diagnostic evaluation (63 percent) or inadequate documentation of an accepted indication (36 percent). Implants were classified as not indicated primarily because a rhythm abnormality was incorrectly identified as a justifiable indication (84 percent). We found that 168 implants (44 percent) were definitely indicated, 137 (36 percent) possibly indicated, and 77 (20 percent) not indicated. Unwarranted implantation was both prevalent (73 percent of hospitals had an incidence of 10 percent or more) and independent of the type of hospital (university teaching, university-affiliated, and community hospitals). The additional tests most often required to clarify the need for a pacemaker in inadequately evaluated cases included electrophysiologic studies (37 percent) and ambulatory monitoring (31 percent). We conclude that in a large medical population in 1983, the indications for a considerable number of permanent pacemakers were inadequate or incompletely documented.

Measurement of intracellular 42K diffusion in frog ventricular strips.

The longitudinal distribution of 42K was measured in strips of frog ventricular muscle placed in a partitioned perfusion chamber. A radiation detector placed directly under the chamber was moved from point to point to scan the longitudinal distribution of 42K. The detector was focussed on a 0.6 mm segment of the strip by means of two slits and two Geiger tubes. A beta-particle from the strip was counted only if it passed through both Geiger tubes. This arrangement improved the spatial resolution and decreased the background and the sensitivity to Compton electrons. The intracellular diffusion constant measured with this system is 3.7 X 10(-6) cm2/s.