A cardiologist, Zoll knew that external electrical stimulation of fibrillating heart could reset it to beat normally. But it was a true last-ditch procedure: at the time, such shocks were delivered directly to the heart — during open-chest heart surgery. Zoll’s research led to the external defibrillator — the now-well-known “paddles” applied to the skin of a closed chest — that is now carried in virtually all ambulances.
Zoll also developed the first practical cardiac pacemaker, which also used external activation, which led other researchers to refine the pacemaker into an internal device that would help them live for years. A long-time member of the research staff at Beth Israel Hospital in Boston, Zoll also was a clinical professor at Harvard Medical School and, all the while, he continued to see patients, too. He died January 5 at age 87, from respiratory arrest.