Pacesetter

Cardiac monitors and defibrillators are such fundamental components of EMS fieldwork, it’s difficult to imagine doing our jobs without them. Aesthetic differences among the dozens of models used by EMS agencies around the world obscure the fact that one man deserves much of the credit for developing these life-saving machines and bringing them to market.

Dr. Paul Zoll, a cardiologist whose legacy includes a medical equipment company that bears his name, is the subject of a just-released biography by Stafford Cohen, MD, titled Paul Zoll, MD: The Pioneer Whose Discoveries Prevent Sudden Death, in which Cohen portrays Zoll as an authoritative pioneer of electrical therapy who could be opinionated when pressed, but was best known as a tireless caregiver.

Dr. Cohen approaches his subject as a colleague; he worked with Zoll at Boston’s Beth Israel Hospital beginning in the late 1960s. It must have been tempting for the author to pepper his manuscript with technical jargon best understood by fellow physicians, but Cohen’s plain-English descriptions of cardiac anatomy, physiology and pathology pose no challenges for readers with more medical curiosity than expertise. EMS providers of all levels should find Zoll’s story easy to follow; paramedics will gain a better understanding of conditions such as R-on-T phenomenon and Stokes-Adams syndrome.

I particularly enjoyed Cohen’s discussion of early and often-problematic attempts at transcutaneous pacing (TCP). When I started working as a medic in Brooklyn in the mid-1990s, TCP was not yet an option for symptomatic bradycardia. Our protocols offered only “thump pacing” as an alternative to medication. The idea was to position yourself beside the chest of a supine patient, place the elbow of your dominant arm somewhere near the subject’s umbilicus, then strike the sternum rhythmically with your fist. I never used thump pacing in the field, but I wondered how such a primitive intervention would look to bystanders.

External stimulation of a slow or pulseless heart was precisely what Zoll had in mind when he began work on the first transcutaneous pacemaker in 1949. He had learned, as a surgeon removing munitions fragments from soldiers’ chests during World War II, that the heart tends to contract when manipulated even by light touch. He reasoned that a periodic current delivered through chest-mounted electrodes would keep an asystolic heart beating.

Zoll had to compete against two other pacemaker designs: partially implantable models with wire leads inserted through the skin and transvenous models that were threaded through major veins to the heart. A disadvantage of early transcutaneous units was pain, sometimes so severe that patients chose death rather than continued pacing. Zoll eventually reduced discomfort by lengthening the duration of electrical impulses, but Cohen’s reminder that pacing hurts highlights the importance of sedation.

Zoll believed that demand pacemakers—instruments that adjusted their firing rates to patients’ intrinsic heartbeats—were unnecessarily complicated. He argued that he’d never encountered an R-on-T phenomenon from a poorly timed pacemaker impulse and that if he did, he’d simply defibrillate the victim. Zoll continued to use fixed-rate devices even after demand pacing became the standard of care.

Unattended patient deaths in hospitals weren’t uncommon occurrences in the 1950s. Despite the popularity of tacky bromides like “it’s a blessing to die in one’s sleep,” Zoll and his associates believed they could improve the odds of survival for cardiac patients by designing a “jumpstart” machine that would monitor heart rates and alert hospital staff to prolonged asystole. The first units in 1953 relied on alarms and human intervention to stabilize patients with emergent arrhythmias. Then Zoll’s team added automated transcutaneous pacemakers that kicked in whenever a patient’s heartbeat fell below a designated value.

It’s difficult for those of us who routinely carry compact EKG equipment to imagine a world without such hardware, but monitors were still a rarity in hospitals throughout the 1950s. Some patients believed those machines–even the ones without pacing–had therapeutic value. It wasn’t unusual for monitors to disappear from one bedside and show up at another–facilitated, no doubt, by well-meaning family members.

Perhaps even more important than Dr. Zoll’s development of a pacemaker was his invention of an external defibrillator, another tool we take for granted in EMS. Before Zoll’s innovation, pulseless patients’ chests were cracked open so that electrical therapy could be applied directly to silent hearts. In 1955, Zoll became the first to resuscitate a patient transthoracically.

I was surprised to read that early defibrillators used alternating current (AC) instead of direct current (DC). Dr. Cohen even includes several anecdotes involving termination of malignant arrhythmias with hastily stripped lamp cords! Apparently, Marcus Welby was smarter than we thought.

ALS providers, in particular, will appreciate Cohen’s discussion of synchronized cardioversion as much for his review of therapeutics as for his account of history. He acknowledges that Zoll continued to favor AC shocks long after prevailing sentiment had switched to DC, and adds that the sometimes-stubborn inventor insisted on using the term countershock instead of cardioversion.

After reading Dr. Cohen’s paperback, I see Paul Zoll as a brilliant non-conformist who wasn’t always right, but who merits tribute for his precedent-setting contributions to cardiology. Zoll’s biography is a thought-provoking story of the man and his legacy.

Order Paul Zoll, MD: The Pioneer Whose Discoveries Prevent Sudden Death from Amazon or Barnes & Noble. 

Mike Rubin, BS, NREMT-P is a paramedic in Nashville, TN, and a member of EMS World’s editorial advisory board. Contact him at mgr22@prodigy.net.