See Also:Biography of Paul Zoll
External Stimulation for Stokes-Adams Disease
Two years following the initial report of successful transthoracic cardiac pacing, Zoll and coworkers reported their results in 14 additional cases. Most patients had Stokes-Adams attacks. Nine patients required prolonged periods of stimulation which was defined as 25 minutes to 108 hours. Case #1 required long periods of pacing for asystole for complete heart block on two occasions. The first period was for 96 consecutive hours and the second for 108 consecutive hours. Overall, mortality was high. Yet, some patients survived for many months.
This paper contains several important observations. #1) "external cardiac pacing appears to be the method of choice for the immediate treatment of patients with unexpected circulatory arrest from cardiac standstill." #2) Chest pain and muscle twitch intensity varied from patient to patient. In two patients it was intolerable. Discomfort was reduced with meperidine hydrochloride or paraldehyde. Curare-like drugs and local anesthetics were not helpful. There is a recognition that a better method should be developed to diminish discomfort. (Zoll achieved this goal 29 years later.) #3) An algorithm is presented for response to cardiac arrest based upon success or failure of transthoracic pacing. Zoll predicts that closed chest defibrillation will be possible (he achieved this goal two years later). #4) There was the implied need for a method to continuously pace patients (permanently) following acute resuscitation. Zoll and his team accomplished this goal six years later with his implantable pacemaker. Zoll PM, Linenthal AJ, Norman LR, Belgard AH. Treatment of Stokes-Adams Disease by External Electric Stimulation of the Heart. Circulation 1954; 9:482-493
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Transthoracic Defibrillation 
The figure is from a landmark paper demonstrating that ventricular fibrillation can be interrupted by transthoracic countershock. Four cases with ventricular fibrillation are described. The etiologies were acute myocardial infarction, idiopathic, digitalis intoxication and Stokes-Adams attacks. Only the last patient survived. The alternating current defibrillator was built by Dr. Zoll's team. One episode of ventricular tachycardia was corrected by countershock. Dr. Zoll comments that the procedure should be effective for supraventricular arrhythmias including atrial fibrillation, based upon his laboratory experiments with animals. In his first description of successful clinical transthoracic defibrillation, Dr. Zoll points out that "successful defibrillation depends on immediate recognition of the emergency and prompt application of the external defibrillator". Today, 44 years later, smart compact defibrillators have been positioned into public places. Dr. Zoll preferred the term "countershock" in deference to Carl Wiggers' historic description of electrically shocking the heart of animals into ventricular fibrillation during the vulnerable phase and then countershocking the heart back to normal sinus rhythm with a second discharge.
Zoll PM, Linenthal AJ, Gibson W, Paul M, Norman LR. Termination of Ventricular Fibrillation in Man by Externally Applied Electrical Countershock. New Eng J Med 1956; 254: 727-732.
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Treatment of Unexpected Cardiac Arrest by External Electric Stimulation of the Heart
Cardiac arrest may occur unexpectedly during various diagnostic and therapeutic procedures, particularly under anesthesia. Though infrequent (1 in every 500 to 5000 operations), each accident is a catastrophe, current therapy is too often unsuccessful. The commonly recognized mechanisms of cardiac arrest are ventricular standstill and ventricular fibrillation; standstill is the usual cause. In a compilation of 1200 cases of cardiac arrest, the occurrence of standstill was 88 percent. Eight successful cases of cardiac resuscitation from unexpected arrest by electric stimulation of the heart are reported here. The cases occurred during various procedures - 7 during surgery, and 1 during pericardiocentesis. The cardiac arrest was terminated in each case by the electric pacemaker so that thoracotomy and cardiac massage were not necessary. Five patients recovered completely, 2 died of unsuccessful cardiac surgery, and 1 died eight hours after operation. A practical monitoring device to signal immediately the cessation of the heart beat would obviate crucial delay in recognizing the onset of arrest. Ideally, such an alarm system should register the electric activity of the ventricles by an audible signal of each heart beat and sound an alarm upon the onset of cardiac arrest. In 1 well documented case with such a monitor, thoracotomy was performed and cardiac massage begun eighteen seconds after the onset of arrest. The routine application of a cardiac monitor to all patients under anesthesia would give greatest assurance of immediate recognition of cardiac arrest. Ventricular standstill may persist despite effective massage, may recur after massage or may follow defibrillation. Electric stimulation may then be applied directly to the heart, preferably by needle electrodes a few millimeters apart. Epinephrine hydrochloride (0.2 ml. If 1:1000 aqueous solution) or calcium gluconate (4 ml. Of a 10 per cent aqueous solution) may be injected into a cardiac chamber.
Zoll PM, Linenthal AJ, Norman LR, Paul MH, Gibson W. Treatment of Unexpected Cardiac Arrest by External Electric Stimulation of the Heart. New Eng J Med 1956; 254: 541-546.
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Ventricular Fibrillation: Treatment and Prevention by External Electric Currents
Ventricular fibrillation, usually a rapidly fatal arrhythmia, occurs most commonly in coronary-artery disease, in patients with atrioventricular block and in toxic reactions to digitalis, quinidine and procaine amide. Occasionally, it succeeds ventricular tachycardia. This paper presents additional experiences confirming the clinical value of external countershock in terminating ventricular tachycardia and fibrillation and of external electric stimulation in preventing these arrhythmias. Alternating current (60 cycle, 0.15 second, 150 to 450 volts) was applied to the unopened chest with large electrodes. A cardiac pacemaker providing monophasic rounded impulses of 2 milliseconds duration over wide ranges of rate and amplitude was used to stimulate the heart externally. Ventricular tachycardia and fibrillation were terminated by externally applied electric countershock more than five hundred and thirty-two times in 8 patients; 5 have survived for one month to two and a half years. The technique is immediately effective, clinically feasible and safe. Prevention of recurrent ventricular tachycardia and fibrillation in patients with complete heart block remains an unsolved problem. Drugs are largely ineffective; external electric cardiac stimulation at rates above the basic idioventricular rate has been effective in preventing these recurrent ventricular arrhythmias, but long-term stimulation is difficult.
Zoll PM, Linenthal AJ, Normal Zarsky LR. Ventricular Fibrillation: Treatment and Prevention by External Electric Currents. New Eng J Med 1960; 262:105-112.
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Supernormal Periods in Man
| Zoll and his team member, Arthur Linenthal, performed electrophysiological studies in both animals and mad. The methodological tools were the electrocardiogram and both endocardial and epicardial pacemakers. They studied timing in P wave and electrical stimuli on ventricular excitation. Figure 2 defines the phases of ventricular excitability. Figure 3 defines the absolute and relative refractory periods of the ventricle with greater relative refractoriness determined by the interval between the stimulus and conduction. Figure 5 demonstrates the supernormal period of ventricular excitability. The phases of cardiac excitability were also studied to understand the mechanism of A-V block. The other electrophysiological observations were made regarding features of retrograde atrio-ventricular conduction and fusion beats. | Fig. 2 |
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| Fig. 5 | Fig. 3 |
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Linenthal AJ, Zoll PM. Quantitative studies of ventricular refractory and supernormal periods in man. Tr A A Physicians, 1962; 75: 285-292.
Linenthal AJ, Zoll PM. Ventricular fusion beats during electrical stimulation in man. Application to conduction. Circulation 1965; 36: 651-660.
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