The Automatic Implantable Cardioverter/Defibrillator; Transesophageal Atrial Pacing Discloses the Potential for Erroneous Discharges

The Automatic Implantable Cardioverter/ Defibrillator; Transesophageal Atrial Pacing Discloses the Potential for Erroneous Discharges GIUSEPPE CRITELLI, VITTORIO MONDA. MARINO SCHERILLO, FERNANDO COLTORTI, CESARE GRECO and ATTILIO REALE From the Department of Cardiology, University of Rome "La Sapienza", Rome, Italy.

CRITELLI, G., ET AL.: The automatic implantable cardioverter/defibrillator; transesophageal atrial pacing discloses the potential for erroneous discharges. We report the occurrence of erroneous discharge from an implanted automatic cardioverter/de/ibriilator during transesophageai atrial pacing. Transesophageai pacing was performed as part of a study protocol on the inducibiiily 0/ ventricular tachycardia from the atrium in patients with ischemic heart disease. At an induced heart rate of 166 beats per minute (a value ;ust above the cut-o^rate of the device), the cardioverter/defibrillator was triggered. This observation suggests that transesophageaJ atrial pacing could be utilized to disclose the potential for spurious discharges in the event of fast atrial rhythms in patients with the automatic impiantable cardioverter/dejibrillator. {PACE, Vol. 11, April 1988} automatic dejibriilator, transesophageaJ pacing

Introduction A major limitation of the automatic implantable cardioverter/defibrillator^ (AICD) is the possible occurrence of erroneous discharges during supraventricular tachyarrbythmias^'^ wbicb can result in physical and psychological patient discomfort, unnecessary battery depletion, and tbe risk of inducing ventricular fibrillation.^ We bave observed inappropriate discharge from an AICD during transesopbageal atrial pacing (TAP). Tbis fortuitous event prompted us to speculate about tbe potential utility of TAP in tbe management of patients with the AICD. Case Report A 48-year-old man witb previous myocardial infarction had two episodes of ventricular tacby-

Address for reprints: Giuseppe Critelli, M.D., Via Antonio Nibby. 5/C. 00161 Rome, Italy. Received February 19, 1987; revision received June 5. 1987; accepted June 16, 1987.

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cardia wbicb resulted in syncope and required cardioversion. The 12-lead electrocardiogram sbowed rigbt bundle brancb block, in addition to Q waves in leads 2, 3, aVF, and V^ tbrougb V5 (Fig. 1). Coronary angiograms showed total occlusion of the left main and tbe proximal, mid and distal anterior descending coronary arteries. Left ventriculograms revealed anterolateral and diapbragmatic akinesia, with an ejection fraction of 0.24. An AICD was implanted in June 1986. Tbe device utilizes a combination of rate detection (the rate cut-off was 160 beats per minute in our case) and a probability-density function (a variable that monitors the QRS configuration) for tachycardia identification." Four montbs after implantation, TAP^ was performed off drugs, as part of a study protocol on ventricular tachycardia inducibility from the atrium in patients witb coronary artery disease. Eigbteen seconds after stable 1:1 atrioventricular conduction at a cycle lengtb of 360 ms (166 beats per minute) bad been reacbed witb incremental pacing, a discbarge from the AICD was observed (Fig. 2). Two months later, TAP at increasing rates was repeated during amiodarone treatment (400 mg daily), and resulted in Wenck-

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i.n.m

V4.V5.V4

AVR. A t / I , AVF

Figure 1. Twelve-lead eJectrocardiogram showing old anterior and inferior myocardial infarction and right bundJe branch block.

ebach type and 2:1 AV block at a cycle length of 440 ms, without shock delivery [Fig. 3).

Discussion Supraventricular tachyarrhythmias are not rehably distinguished from ventricular tachycardia by the AICD, so that spurious discharges can occur in some patients.^'^ This is confirmed by the present case, in whom an atrial tachycardia was simulated during TAP. The induced heart rate

CL500

above the cut-off value of the device and the preexisting bundle branch block met both criteria for ventricular tachycardia identification, thus accounting for the spurious discharge. Double counting due to the stimulus artifact was excluded, since the AICD fired only when an induced heart rate above the cut-off value was reached. This suggests that TAP could be used in patients with the AICD to disclose the potential for inappropriate discharges, should fast atrial rhythms occur after implantation. The same goal

CL 450

. . v v v v v v v v v v VVVVVVVVVVV VVVVVVVVVVVVV WWWWWWW

AICD SHOCK CL 360

Figure 2. Inappropriate discharge from the AICD during IransesophageaJ atrial pacing at increasing rates. Pacing via the esophagus at cycle length (CL) of 600, 500, 450 and 400 ms results in 1:1 AV conduction. At a cycle length of 360 ms (beart rate, 166 bpm) an AICD discharge occurred. (See text for farther explanations.) Numbers in milliseconds.

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THE AICD AND TRANSESOPHACEAL PACING

CL

1 Sec

440

W

2 :1

Figure 3. Transesophageal atrial pacing al a cycle length (CL) of 440 ms during chronic amiodarone treatment results in Wenckebach (W)-(ype and 2:1 AV block. The AICD still quiescient, since the rate cut-off of tbe device is not reacbed. See text for further explanations.

could, of course, be achieved with endocavitary pacing, but the transesophageal approach has the distinct advantages of being noninvasive and— since it utilizes bipolar sensing positioned far from the sensing electrodes of the device—of not interfering with the sensing system of the generator.^'^ In our patient the probability-density function criterion was satisfied by the preexisting intraventricular conduction aberrancy. In other cases, however, TAP could bring out a tendency to develop functional bundle branch block (easily occurring in the right bundle branch), which increases the likelihood of erroneous discharges. Likewise, induction of atrial fibrillation by TAP^ could allow prediction of the risk of improper shock delivery, should this arrhythmia occur after implantation. In such instances, once the potential for inappropriate discharges has heen detected, this technique could help establish a drug regimen capable of preventing fast ventricular rates during supraventricular tachyarrhythmias. In our patient, this goal was reached during amiodarone therapy, which resulted in the ap-

pearance of second degree AV block at a pacing cycle length of 440 ms, thus avoiding the triggering of the device. Also, TAP might be used to discriminate retrospectively between rate miscounting^ (or other system dysfunctions) and triggering of the AICD by supraventricular tachyarrhythmias in the event of spurious shock delivery. With regard to this, phonographic recordings of the device in the electrophysiological test mode has been proposed for detection for sensing dysfunction.^ Nevertheless, since sensing malfunction and triggering of the generator from sinus tachycardia, atrial fibrillation or paroxysmal supraventricular tachycardia might both occur in the same patient, TAP should be utilized in addition to phonographic recordings to define more precisely the cause of unexpected discharges. Finally, the transesophageal pacing technique might prove useful in the individual patient to adjust the rate cut-off of the device—as it pertains to the risk of spurious discharges from supraventricular tachyarrhythmias—when a programmable cardioverter/defibrillator becomes available in the future.

References 1. Mirowski M, Reid PR, Mower MM. et al. Termination cf malignant ventricular arrhythmias with an

implanted automatic defibrillator in human beings. N Engl J Med 1980; 303:322.

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CRITELLI, ET AL. Echt DS, Armstrong K, Schmidt P, et al. Clinical experience, complications, and survival in 70 patients with the automatic implantable cardioverter/defibrillator. Circulation 1985; 71:289. Manz M, Gerckens U, Luderitz B. Erroneous discharge from an implanted automatic cardioverter/ defibrillator during supraventricular tachyarrhythmia-induced ventricular fibrillation. Am 1 Cardiol. 1986; 57:343. Winkle RA, Bach SM, Echt DS. et al. The automatic implantable defibrillator: Local ventricular bipolar sensing to detect ventricular tachycardia and fibrillation, Am 1 Cardiol 1983; 52:256. Gallagher H, Smith WM, Kerr GR, et al, Esophageal pacing: A diagnostic and therapeutic tool. Circulation 1982; 65:336.

Winkle RA, Stinson ED. Echt DS, et al. Practical aspects of automatic cardioverter/defibrillator implantation. Am Heart} 1984; 108:1335. Chapman PD, Troup P. The automatic implantable cardioverter/defibrillator: Evaluating suspected inappropriate shocks. I Am Coll Cardiol 1986; 7:1075, Critelli C, Grassi G, Perticone F, et al. Transesophageal pacing for prognostic evaluation of preexitation syndrome and assessment of protective therapy. Am 1 Cardiol 1983; 51:513, 9. Mirowski M, Reid PR, Winkle RA, et al. Mortality in patients with implanted automatic defibrillators. Ann Intern Med 1983; 98:585.

Electrophysiology-PacemaKer Training Program A multidisciplinary institution is seeking qualified candidates for advanced training in PacemaKer/Electrophysiologic techniques and practices. This two-year "clinical electrophysiology-pacemaKer training program" is designed to provide competency and sKills in all aspects of cardiac arrhythmology. Clinical experiences are designed to provide sKill and competency for independent practice and include areas in invasive diagnostic electrophysiologic laboratory procedures, intraoperative electrophysiologic mapping, single and dual chamber pacemaKer system implantations, AICD implantation and management, and experience and expertise in cardiac arrhythmia pharmacology. Clinical and laboratory research activities are available and encouraged. Under special circumstances a one-year program may be considered. Positions available July 1, 1988. Prerequisites: Completion of an accredited general cardiology training program. Individuals should send resumes to: James D. Maloney, M.D. Department of Cardiology The Cleveland Clinic Foundation 9500 Euclid Avenue Cleveland, Ohio 44106

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