See Also: Biography of Barouh Berkovits
Clinical Application of Demand Pacing
With early reliability, the use of demand pacing was extended to all indications for permanent pacing. Support for demand pacing for presumed permanent block is derived from the fact that three patients with such blich had return of normal sinus rhythm after pacemaker implantation. Two patients had recurrent syncope that defied etiological diagnosis. Following demand pacemaker implantation, they had no further difficulty. This successful therapeutic trial lends support to the occasional empirical use of demand pacing. Transvenous implantation has been utilized with but four exceptions. Proper electrode position is essential for proper sensing. Fluoroscopic control is used initially for positioning of the electrode in the apex of the right ventricle. Constant capture should occur with less than 1.5 volts. An endocardial tracing is then taken with a battery-powered or properly grounded electrocardiographic machine. The endocardial tracing shows a characteristic rapid depolarization signal followed by a slow repolarization wave. The unit requires a depolarization signal of 1.5-2.0 millivolts for proper sensing. A deflection of 8-10 millivolts is usually obtained. To provide an adequate safety margin, less than 6 millivolts should not be accepted. Depolarization signals of variable amplitude are indicative of a floating catheter electrode and should not be accepted. Improper electrode position is also diagnosed if the tracing resembles a peripheral electrocardiogram.
Zuckerman W, Matloff JM, Harken DE, Berkovits BV. Clinical Applications on Demand Pacing. Ann NY Acad Sci 1969; 167:1055-1059.
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Pacemaker-induced Cardiac Rhythm Disturbances
Continuous stimulation of the heart has been used successfully in the treatment of symptomatic atrioventricular conduction disturbances. Recent reports have stressed the possible occurrence of pacemaker-induced repetitive firing during coaction of natural and artificial rhythms. Repetitive firing (more than one response to a single stimulus falling in the preceding T-wave) has been observed fourteen times in our department: (a) during intermittent paired electrical stimulation, three cases, one requiring countershock; (b) at the onset of pacing during complete atrioventricular block, five cases; (c) during coaction of sinus rhythm and continuous asynchronized pacers (chronic block, three [unreported] cases, in two of which the spikes that triggered repetitive firing fell on an extrasystolic T-wave); (d) in acute myocardial infarction during coaction of supraventricular and continuous pacemakers,three cases, one requiring countershock. Stimuli fell on the T-waves of supraventricular complexes. It is for precisely this purpose that other forms of pacing have been developed.
Castellanos A, Maytin 0, Lemberg L, Berkovits BV Part VIII. Rhythm Disturbances and Pacing: Pacemaker induced cardiac rhythm disturbances. Ann NY Acad Sci 1969; 903-910
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Bifocal Demand Pacing
Transient pervenous bifocal (sequential atrioventricular) demand pacing was performed in ten patients. Six had chronic conducting system disease and four acute myocardial infarction. The control electrocardiograms showed different degrees of coexisting, alternating or intermittent sinoatrial slowing and AV block. This modality of electrical stimulation was achieved by the combination of QRS-inhibited ventricular demand pacing with QRS-inhibited atrial demand stimulation. In the presence of atrial bradycardia and normal AV conduction only the atria were stimulated. When sinus slowing was associated with AV block, both atria and ventricles were paced. A double electrode system was required for the restoration of AV synchronization. Consistent atrial capture was achieved by means of a J-shaped endocardial bipolar electrode. Permanent bifocal demand pacing has also been used in three patients with satisfactory results. Further studies are required to assess the optimal AV sequential interval as well as the long-term electrical reliability and hemodynamics benefits.
Castillo CA, Berkovits BV, Castellanos A, Lemberg L, Callard G, Jude JR. Bifocal Demand Pacing. Chest 1971; 59:360-364.
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Overdrive Pacing in the WPW syndrome
In all patients with either spontaneous or induced SVT every episode could be rapidly (<60 seconds) terminated by high right atrial, coronary sinus or right ventricular overdrive pacing. The overdrive rate was > 10% above the basal tachycardia rate. Implantable. The above results prompted the design of an implantable pacemaker for use in WPW patients with medically uncontrollable SVT. A bipolar J-shaped electrode is implanted in the right atrial appendage by the transvenous route. The unit, magnetically activated by the patient during a tachycardia, delivers stimuli at a progressively increasing frequency (150-300 beats/min) over a maximum period of 2 minutes. It can be prematurely deactivated by removing the magnet. This unit has been implanted in a 25-year-old female WPW patient with intractable SVT. The unit has functioned successfully over a 9-month period and has been used as many as 5 times/day. The presence of recurrent SVT in the WPW syndrome unresponsive to medical management has, in the recent past, been managed only by surgical approaches. The ability to rapidly terminate SVT with overdrive, utilize permanent transvenous atrial pacing and design new pacemaker circuitry has led to the development of the implantable unit described in this report. The potential benefits of this method are clear in that a limited surgical procedure with low morbidity may be realized for successful management of a previously unmanageable patient. A noncontinuous record showing the onset of supraventricular tachycardia and its termination by the implanted atrial scanning pacemaker unit. In the first strip, sinus rhythm with prominent delta waves is noted. Subsequently, supraventricular tachycardia is initiated by a premature atrial systole. The second strip shows the initiation of artificial atrial pacing at progressively increasing heart rates.The third strip shows the termination of the tachycardia followed by 1:1 anterograde conduction across the bypass tract. With termination of the atrial pacing, restoration of sinus rhythm is observed.
Mandel WJ,Yamaguchi I, Laks M, Berkovits BV. The use of overdrive pacing for termination of tachycardia episodes in the Wolff-Parkinson-White (WPW) syndrome.Cardiac Pacing:ProcV International Symposium.Tokyo,1976.YoshioWatanabe,Ed.Excerpta Medica, 1977; 162-165.
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