Implantation of the Automatic Defibrillator: The Subxiphoid Approach

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1 Implantation of the Automatic Defibrillator: The Subxiphoid Approach Levi Watkins, Jr., M.D., M. Mirowski, M.D., Morton M. Mower, M.D., Philip R. Reid, M.D., Paul Freund, P.A., Andra Thomas, R.N., Myron L. Weisfeldt, M.D., and Vincent L. Gott, M.D. ABSTRACT The automatic implantable defibrillator is an electronic device capable of diagnosing and correcting malignant venticular arrhythmias. While major thoracic surgery was required in the original 24 implants, a new technique for implanting the device has been developed. The first subxiphoid implantations have been accomplished with the defibrillatory function successfully tested intraoperatively. The advantages and indications of the subxiphoid technique are reviewed. The automatic implantable defibrillator has now been successfully implanted in 30 human beings. The device is intended to protect patients at high risk of sudden cardiac death by providing them with a diagnostic and therapeutic system capable of automatically terminating malignant ventricular arrhythmias. The early clinical experience [l-41 has demonstrated that the automatic defibrillator is capable of diagnosing and correcting potentially lethal ventricular arrhythmias. Improvements in the device and in the techniques for implantation have continued. The original implants were performed through a lateral thoracotomy or a median sternotomy [4]. We report here the initial experience with the subxiphoid approach for implantation of the automatic defibrillator. Materials and Methods The automatic implantable defibrillator* is encased in titanium and hermetically sealed. It oc- cupies a volume of 145 ml and weighs 250 gm (Fig 1). The electrodes are made from titanium and coated with silicone rubber. One defibrillating electrode is located on an intravascular catheter placed in the superior vena cava at the right atrial junction. The second electrode has the configuration of a rectangular patch and is positioned over the cardiac apex. The outside surface of this electrode is insulated to optimize distribution of current. The device is powered by lithium batteries that have a projected monitoring life of three years and a discharge capability of more than 100 shocks. The sensing system detects ventricular fibrillation and sinusoidal ventricular tachycardia by continuously sampling the probability density function of the cardiac electrical activity [5]. This function reflects the time spent by the input signal between two amplitude limits located near zero potential. In essence, ventricular fibrillation is identified by the absence of isoelectric potential segments in the sampled cardiac electrogram. Recognition of a serious ventricular arrhythmia results in the delivery of Schuder s truncated exponential pulse [6] of 25 J. The device can recycle three times during a single episode if the previous discharges are not successful in terminating the arrhythmia. The strength of the third and fourth pulses increases to 30 J. Higher energy units (30 to 40 J) are available when required. Operative Technique Developed and manufactured under the name of AID by Under general endotracheal anesthesia, the Intec Systems, Pittsburgh, PA. neck, thorax, and abdomen in the operative From the Departments of Surgery and Medicine, The Johns Hopkins Medical Institutions, Baltimore, and the Depart- field are prepared. The left internal jugular vein ment of Medicine, Sinai Hospital of Baltimore, Baltimore, is localized, using an 18 gauge thin-walled needle. x I- - - IV1 LJ. A stainless steel guidewire is then introduced Accepted for publication Dec 10, through the needle into the vein. A small inci- Address reprint requests to Dr. Watkins, Department of Surgerv, The HoDkins Medical Institutions, ~ ~ sion l ~ is made ~ - to facilitate introduction of the mofe, MD sheath assembly. A No. 14F Desilets-Hoffman by The Society of Thoracic Surgeons

2 516 The Annals of Thoracic Surgery Vol34 No 5 November 1982 Fig 1. Automatic implantable defibdlator with defibrilluting electrodes for superior vena cava and cardiac apex. peel-away sheath and dilator are passed over the guidewire into the vein. This size sheath readily accepts the superior vena cava electrode. The wire and dilator are removed, and the electrode is introduced through the peelaway sheath into the vein. Figures 2 and 3 illustrate this technique. Position at the junction between the superior vena cava and atrium is confirmed by roentgenogram (Fig 4). The left subclavian vein may be used as an alternate to the left internal jugular vein. Through a subxiphoid incision, the pericardial sac is exposed. The pericardium is opened anteriorly, approximately 2.54 cm above the diaphragmatic reflection. The incision is carried down to the diaphragm and extended laterally to the left (Fig 5). The rectangular patch electrode is then introduced into the pericardial sac in such a way that its long axis parallels the diaphragm anteriorly (see Fig 5). It is pushed laterally, until the end of the patch electrode reaches the cardiac apex (Fig 6). In this posi- passes over wire Fig 2. Cannulation of the left internal jugular vein with the Desilets-Hoffman sheath assembly, After percutaneous puncture, a guidewire is introduced into the vein. The sheath and dilator are passed into the vein over the guidewire. The dilator is then withdrawn, leaving the sheath in place.

3 517 Watkins et al: Implantation of the Automatic Defibrillator,ode Fig 3. Introduction of the superior vena cava (SVC) electrode and subxipkoid incision for exposure of pericardium. Fig 4. Chest roentgenogram demonstrating position of superior vena cava (upper arrows) and apical patch (lower arrows) electrodes. tion, the insulated side of the patch is lying against the pericardium over the diaphragm, and the opposite side faces the diaphragmatic surface of the heart. The patch is then sutured to the cut edge of the pericardium. A subcutaneous pocket is developed in the left paraumbilical area to accommodate the pulse generator. Using a specially designed tunneler, the free end of each electrode is passed subcutaneously to the pocket. The completed procedure is illustrated in Figure 7. Using a previously placed right ventricular electrode, intraoperative testing is performed to document effective function of the automatic implantable defibrillator. An external defibrillator is available, of course, should the device prove ineffective in terminating the arrhythmia. Results Illustrative Case Reports PATIENT 1. A 47-year-old woman had a history of recurrent shortness of breath and ectopic ventricular beats. She was placed on quinidine, 200 mg four times a day, but episodes of syncopal ventricular tachycardia developed, which required cardioversion on two occasions. Cardiac catheterization revealed normal coronary arteries and normal ventricular function. Electrophysiological studies were negative whether the patient was on or off a regimen of antiarrhythmic drugs. She underwent implantation of the automatic defibrillator and ventricular flutter-fibrillation was induced during the operation, using alternating current. The arrhythmia was automatically converted to sinus rhythm by the implanted device in 16 seconds. During convalescence, the patient manifested a 7-beat run of ventricular tachycardia on a Holter tape recording. She was placed on a regimen of tocainide. Following discharge from the hospital, she has done very well. PATIENT 2. A 51-year-old man had a myocardial infarction associated with a cardiac arrest ten years prior to the present hospitalization. Since then, he had had several episodes of congestive failure, and two months prior to admission he sustained cardiac arrest due to ventricular fibrillation. Despite treatment with lidocaine and quinidine, recurrent ventricular

4 518 The Annals of Thoracic Surgery Vol 34 No 5 November 1982 Fig 6. Apical electrode position. (RV = right ventricle; LV = left ventricle.)

5 519 Watkins et al: Implantation of the Automatic Defibrillator Fig 7. Complete automatic implantable defibrillation implantation, subxiphoid approach. tachycardia ensued. Ventricular arrhythmias were easily induced during electrophysiological studies despite treatment with procainamide and aprindine. The automatic defibrillator was implanted and, two weeks later, while he was still taking aprindine, ventricular tachycardia with a rate of 190 beats per minute was produced with ease during the electrophysiological study. This rhythm lasted 47 seconds; because the automatic defibrillator remained quiescent, the arrhythmia had to be terminated by external countershock. The device did not discharge because the slow ventricular tachycardia rate on aprindine was below the lower limit set for the defibrillator. Aprindine was stopped, and the patient was taken to the catheterization laboratory a week later. Again, ventricular tachycardia was induced easily, but this time at a rate of 210 beats per minute, and was successfully cardioverted by the implanted defibrillator in 29 seconds. PATIENT 3. A 58-year-old man with cardiomyopathy had been resuscitated from episodes of ventricular fibrillation in 1973, 1977, and On electrophysiological testing ventricular fibrillation could not be induced, and he un- derwent implantation of the automatic defibrillator using the lateral thoracotomy approach. To test the device, ventricular fibrillation was produced postoperatively by alternating current and was automatically terminated by the implanted device in 16 seconds. The patient did well for four months, but then had a number of spurious discharges that led his physician to deactivate the implanted device with a magnet. The pulse generator was replaced two weeks later, at which time intermittent high-amplitude noise was recorded from the defibrillator leads, suggesting the possibility that lead noise led to the spurious defibrillator discharges. One month later, a new electrode was implanted intrapericardially through a subxiphoid approach, the old electrode patch being left in situ in its extrapericardial positon. A higher energy device was then implanted. Ventricular fibrillation was induced intraoperatively and automatically cardioverted by the unit in 33 seconds. Comment The subxiphoid approach obviates the need for a major thoracic operation during implantation of the automatic defibrillator. Although no surgical mortality or major complications were observed in the initial patients [4], the subxiphoid approach offers a number of important advantages. The operative and anesthesia times are considerably shortened. The incision is limited, so postoperative pain is minimal. The patients are usually awake at the end of the procedure and can be extubated immediately. The splinting, atelectasis, and pleural effusions that occasionally follow major thoracic operations are not seen. Mobilization after the operation is earlier, and hospital stay is shortened. Intraoperative electrophysiological testing of the device often eliminates the need for postoperative studies. Candidates for this approach include patients who have not had a previous cardiac operation and those in whom an open-heart procedure is not indicated. These categories represent more than 45% of the candidate population to date. Lateral thoracotomy is favored for patients who have had previous cardiac operations, and median sternotomy is used in patients requiring

6 520 The Annals of Thoracic Surgery Vol 34 No S November 1982 open-heart operation and automatic defibrillator implantation. Effective function of the automatic implantable defibrillator after subxiphoid implantation has been demonstrated. Although further validation is required, this approach is expected to become the procedure of choice in a large number of candidates for its use. References 1. Mirowski M, Reid PR, Mower MM, et al: Termination of malignant ventricular arrhythmias with an implanted automatic defibrillator in human beings. N Engl J Med 303: , Mirowski M, Mower MM, Reid PR: Automatic implantable defibrillators. Am Heart J 100: , Mirowski M, Reid PR, Watkins L, et al: Treatment of life-threatening ventricular arrhythmias with automatic implantable defibrillator. Am Heart J 102 : , Watkins L, Mirowski M, Mower MM, et al: Automatic defibrillation in man: the initial surgical experience. J Thorac Cardiovasc Surg 82: , Langer A, Heilman MS, Mower MM, Mirowski M: Considerations in development of the automatic implantable defibrillator. Med Instrum , Schuder JD, Rahmoeller GA, Stoeckle H: Transthoracic ventricular defibrillation with triangular and trapezoidal waveforms. Circ Res 19: , 1966 Notice from the American Board of Thoracic Surgery The Part I (written) examination will be held at the Amfac Hotel, DallaslFort Worth Airport, Dallas, TX, in January, The closing date for registration is August 1, To be admissible for the Part I1 (oral) examination, a candidate must have successfully completed the Part I (written) examination. A candidate applying for admission to the certifying examination must fulfill all the requirements for the Board at the time the application is received. Please address all communications to the American Board of Thoracic Surgery, E Seven Mile Rd, Detroit, MI