Defibrillation: the Spark of Life

Defibrillation: The Spark of Life In the 50 years since doctors first used electricity to restart the human heart, we have learned much about defibrillators and little about fibrillation by Mickey S. Eisenberg he operation had gone well. The goal of a defibrillatory shock is to There was a brief period of fast jolt the heart into a momentary stand- T heart rate, when the ether was still. With the chaotic pattern of contrac- given, but that was easily controlled tions interrupted, the cardiac muscle cells with digitalis. The two-hour surgery had have the chance to resume work in an been technically demanding. The 14- orderly sequence again. The first shock year-old boy’s congenitally deformed did not work, and Beck began open- chest allowed respiration only 30 per- heart massage again while calling for ad- cent of normal. The task of the attend- ditional medications. Twenty-five min- ing surgeon, Claude S. Beck, was to sep- utes passed, and Beck ordered a second arate the ribs along the breastbone and shock. This time the shock blasted away repair nature’s botched work. Beck re- the fibrillatory waves, and a normal laxed as the easy part began. But as the rhythm ensued. Three hours later the boy 15-inch wound was being closed, tri- responded appropriately to questions umph abruptly turned to crisis: the boy’s and went on to make a full recovery. heart stopped. Beck grabbed a scalpel, Beck realized the significance of this sliced through his sutures, enveloped first successful human defibrillation. In the heart in his hand and rhythmically the 1940s the nation was in the midst of squeezed. He could feel the heart’s inef- an epidemic of coronary artery disease— fective quivering and knew at once that an epidemic that continues today and it had gone into the fatal rhythm called one that remains the leading cause of ventricular fibrillation. In 1947 no one death in adults. Beck knew most coro- survived this rhythm disturbance, but nary deaths, especially from sudden car- that did not deter Beck. diac arrest, were triggered by ventricu- He called for epinephrine and digital- lar fibrillation. Ventricular fibrillation is is to be administered and calmly asked the fatal rhythm in some 65 percent of for an electrocardiograph and a defib- cardiac arrests. About 3 percent of ar- rillator, all the while continuing to mas- rests are caused by ventricular tachy- sage the boy’s heart. It took 35 minutes cardia (a very fast heart rate), which to obtain an electrocardiogram, which— usually deteriorates into fibrillation, and wavering and totally disorganized—con- the remainder is the consequence of an At the instant of fibrillation, the heart firmed the distinctive appearance of ven- asystolic (flat line) rhythm or a rhythm pumps no blood, so the pulse ceases and tricular fibrillation. Ten minutes later called pulseless activity (a flaccid heart the blood pressure falls to zero. This is assistants wheeled in an experimental unable to contract). called clinical death, and it will turn defibrillator from Beck’s research lab The exact cause of ventricular fibrilla- into irreversible biological death if cir- adjoining the University Hospitals of tion is poorly understood. In many in- culation is not restored within minutes. Cleveland. Beck positioned the machine stances, it is triggered by a partially or Ventricular fibrillation, though it oc- and placed its two metal paddles direct- completely occluded coronary artery casionally happens during surgery, most ly on the boy’s heart. The surgical team causing an ischemic—and irritable—area often occurs outside a hospital setting, watched the heart spasm as 1,500 volts of muscle in the heart. But sometimes during routine activities. Of the 350,000 of electricity crossed its muscle fibers. the heart goes directly into ventricular sudden cardiac deaths a year in the U.S., Beck held his breath and hoped. fibrillation without an obvious cause. 75 percent happen at home, striking 86 Scientific American June 1998 Defibrillation: The Spark of Life Copyright 1998 Scientific American, Inc. DEFIBRILLATION REMAINS the first, last and best hope for victims of ventricular fibrillation. Paddles coated with a con- duction gel send a shock through the heart muscle, which, for reasons still not clearly understood, allows its internal timing mechanism to reset and return to normal. that would remain undamaged if the defibrillation could occur quickly enough. His expression is apt because a heart that is successfully defibrillated usually has many years of mileage left; a heart that fibrillates is like a million-dollar piece of equipment failing because of a 20-cent fuse. Fifty years later is a good time to ask whether Beck’s vision has been achieved. Did the world embrace his invention? Has its huge potential been realized? What does the future hold? Beck’s defibrillator was a large, pon- derous machine. It used alternating current directly from a wall socket and required a bulky and heavy step-up trans- former. The voltage, usually 1,000 volts, was applied for a quarter or half of a second. The machine was barely portable, although wheels gave it some mo- bility. Its biggest drawback was the sup- posed need to place its metal paddles directly on the ventricles, because not enough was known about how much electricity to use to shock through the chest. But it was a start. From such humble beginnings, defibrillators have grown smaller, smarter and far more sophisticated. As the technology developed, so did the clinical applications. Shortly after Beck’s 1947 report, defibrillators were placed in operating national er rooms throughout the Western world. nt But they would remain in operating iaison I L rooms and have very limited use so HY AP long as the chest had to be opened and OGR T the paddles placed directly on the heart. HO This problem was solved in 1956 by Paul UER P A M. Zoll of Harvard Medical School, who demonstrated that defibrillation LIEN/NIB could successfully occur across an in- tact chest. Now the device could move people who are in the prime of their lives. but he needed to demonstrate its life- to the rest of the hospital. Defibrillators In 1947 Beck’s only option was to re- saving potential on a human. One case began appearing in emergency depart- open the chest and manually compress was all he needed. He published a report ments as well as coronary care units. the heart. Cardiopulmonary resuscitation in the Journal of the American Medical Because defibrillators were large and (CPR), as we know it today, would not Association and immediately prosely- inherently stationary and required al- be invented until 1960. Beck knew that tized physicians to recognize fibrillation ternating current to operate, they were manually compressing the heart only and learn how to use defibrillators. confined to hospitals. To leave the hos- bought time—electricity was (and re- Beck envisioned being “at the thresh- pital, defibrillators had to become por- mains) the only means for treating ven- old of an enormous potential to save table, and there had to be a way of bring- tricular fibrillation. For a decade, Beck life.” He saw the defibrillator as the ing them to patients where they lived. had developed and perfected his ma- tool for dealing with, to use his expres- The obstacles were overcome in 1960 chine, defibrillating hundreds of dogs, sion, “hearts too good to die”—hearts by Bernard Lown of the Harvard School Defibrillation: The Spark of Life Scientific American June 1998 87 Copyright 1998 Scientific American, Inc. MANN T ORBIS-BET I/C UP FIRST HUMAN TO RECEIVE DEFIBRILLATION (shown at left 20 years later) went into ventricular fibrillation while undergoing surgery in 1947 to expand his congenitally deformed chest. At that time, ventricular fibrillation was invariably fatal. But the surgeon, ONA MEDICINE Claude S. Beck (above), was able to revive his patient using a defib- ARIZ rillator similar to the one shown at the top on the opposite page. of Public Health and K. William Ed- homes. Resurrecting an old ambulance, emergency care are now found in virtu- mark of the University of Washington. they established the world’s first mobile ally every urban and suburban area of They demonstrated not only that defib- intensive care unit in 1966. The unit was the U.S. and in many Western countries. rillators could be powered by direct cur- staffed with a doctor and nurse and But paramedics and ambulances are rent but also that these DC machines equipped with a jerry-rigged defibrillator not enough. When a person goes into were, in fact, safer because there were powered by two 12-volt car batteries. defibrillation, every minute counts, and fewer postshock complications such as Success came slowly, but within 18 waiting for an ambulance to arrive eats heart blocks or other difficult-to-treat months they had accumulated enough away at precious time. Clearly, it would rhythm disturbances. Also, direct cur- experience to publish their findings in be beneficial to have defibrillators in the rent allowed relatively portable batter- the international medical journal Lancet. hands of a still wider group of laypeo- ies to power the device and used capac- Of groundbreaking importance: infor- ple or emergency service personnel. itors for collecting and concentrating mation on 10 patients with cardiac ar- Up into the 1970s defibrillators were the charge. Although these first-genera- rest. All had ventricular fibrillation, and manually operated. The operator—doc- tion battery-powered devices weighed all were resuscitated and admitted to the tor, nurse or paramedic—had to inter- 35 pounds, portable defibrillators could hospital.

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