The invention and reinvention of cardiac pacing.

Two primitive pacemakers were invented between 1925 and 1932, demonstrating that adequate knowledge existed to pace the heart for brief periods. Heart specialists ignored these interesting inventions. In contrast, Zoll's announcement of external pacing in 1952 spurred intense interest and an outpouring of research. The reasons for the different response of heart specialists in the 1950s have to do with improved medical understanding of cardiac arrhythmias, growing confidence that cardiac resuscitation was possible, and the expansion of hospital-based medicine after World War II.