Ann Thorac Surg 1995;59:764-767
© 1995 The Society of Thoracic Surgeons
How To Do It
Technique for Implantation of Cardioverter Defibrillators in the Subpectoral Position
Andrew H. Foster, MD
Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland
Accepted for publication November 1, 1994.
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Abstract
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The downsized cardioverter defibrillators in early clinical trials in the United States are smaller and lighter than approved cardioverter defibrillators, but they remain relatively bulky. Prepectoral implantation of these devices may increase the risk of erosion, particularly in those patients with cardiac cachexia. This report describes a versatile technique for submuscular pectoral cardioverter defibrillator implantation using a lateral approach to the subpectoral space that has been used in 6 patients. Alternative surgical approaches for pectoral cardioverter defibrillator implantation and potential problems with these techniques are discussed.
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Introduction
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More effective transvenous defibrillation leads, improved efficacy of biphasic energy waveforms, and greater electrogram storage capacity are among the recent developments in implantable cardioverter defibrillator (ICD) technology. Major efforts also have been expended in the fabrication of downsized ICD pulse generators that now are entering early-phase clinical trials in the United States. Although smaller (83 cm3 versus 150 cm3) and lighter (132 g versus 250 g) than market-released ICD pulse generators, these devices still remain formidable in size when compared with the smallest pacemaker generators (13 to 20 cm3, 20 to 25 g). The eagerness with which smaller ICDs have been awaited and the rush for less morbid implantation techniques have led some to equate these devices with pacemakers and to associate ICD implantation with techniques that are similar to those that are employed for pacemaker implantation.
Past experience with prepectoral or subcutaneous implantation of the large first generation pacemakers in adults projects the risk of erosion and infection for ICDs of this size in the prepectoral position to be as high as 12.6% [1]. A multiinstitutional report of ICD implantation (110 cm3, 160 g ICD) in patients less than 21 years of age (mean age, 17 ± 2 years; body weight, 61 ± 13 kg) observed erosion in 17.6% of patients [2]. These data provide the rationale for the use of abdominal implantation sites for approved ICD pulse generators [3] and for the preferential use of deep abdominal and submuscular pectoral implantation sites for pacemakers in infants and small children [4].
My concern about the prohibitively increased risk of erosion with prepectoral ICD implantation, particularly in cachetic and small patients, prompted the development of this technique for submuscular pectoral ICD implantation. This report describes the lateral submuscular pectoral implantation technique for use with smaller ICD systems (83 cm3, 132 g) that are currently in clinical trials as it has been used successfully in 6 patients.
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Technique
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The patient is positioned supine on an operating room fluoroscopy table with external defibrillator patches positioned out of the sterile field on the anterior and posterior thorax. Transvenous defibrillation coils and endocardial rate-sensing leads are positioned fluoroscopically through a left subclavicular incision using established methods through the subclavian and cephalic vein. After acceptable rate-sensing and defibrillation characteristics are obtained, each lead is secured to the pectoralis fascia at two areas using reinforced collars with an interposing 
-shaped half-loop of lead between each nonabsorbable suture to prevent lead migration. Standard acceptable system characteristics include peak-to-peak R wave amplitude during ventricular fibrillation greater than 5 mV, pacing threshold less than 1.0 V (0.5 ms pulse width), and defibrillation energy threshold less than 20 J (or three consecutive successes at 20 J) for a maximum ICD output of 34 J.
The ICD pulse generator is positioned beneath the pectoralis major muscle through a vertical incision along the anterior axillary line (Fig 1A
). The subpectoral space is entered by vertically dividing the posterior attachments of the serratus anterior muscle to the ribs lateral to the border of the pectoralis major muscle (Fig 1B). This approach is preferred because the fascial layer of the serratus can be reapproximated securely after the ICD is inserted to prevent lateral migration of the pulse generator into the axilla. After division of the serratus, the anterior surface of the intercostal muscle fascia is followed medially into the subpectoral space. The medial retraction of the pectoralis major and minor muscles by the lateral approach allows visualization and control of the perforating blood vessels to the pectoralis muscles. It is usually necessary to divide some of the lateral insertions of the pectoralis minor muscle to the ribs to obtain an adequate space under the pectoralis muscle group for the ICD pulse generator.
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Fig 1. . (A) Incisions for fluoroscopic lead and coil placement and for lateral approach to subpectoral space. (B) Division of serratus anterior muscle insertion, reflecting pectoralis muscles off the intercostal muscles and ribs. Insertions of pectoralis minor muscle may be transected to create sufficient space for the pulse generator.
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The vertical axillary incision allows placement of a subcutaneous defibrillator patch for orthogonal-three lead configurations if satisfactory defibrillation thresholds are not obtained using forward or reverse polarity with transvenous leads alone (Fig 2). The first position for the defibrillation patch electrode should be beneath the pulse generator to avoid additional dissection (see Fig 2B). If satisfactory defibrillation threshold energy is not obtained in this configuration, the defibrillation patch electrode is repositioned to an inferior and posterior position against the intercostal muscles (see Fig 2C). Additional skin incisions are unnecessary. The most posterior position (with the edge of the patch under the medial edge of the latissimus dorsi muscle) is usually the most effective in patients with high defibrillation thresholds [5]. After adequate defibrillation characteristics are obtained and the patch is secured in all quadrants with nonabsorbable suture, the high-voltage defibrillation and rate-sensing leads are tunneled through the superior–lateral aspect of the pectoralis muscle and connected to the pulse generator for final testing. Satisfactory characteristics for the final test include a less than 5 second detection time, successful defibrillation, and the absence of device interactions when a dual chamber pacemaker has been implanted previously. Redundant lengths of leads (and the bifurcated connector if the defibrillator patch electrode is implanted) are coiled lateral and posterior to the device to avoid compression of the lead insulation between ICD and ribs or clavicle (see Fig 2A). The fascia of the serratus anterior muscle insertions is reapproximated against the intercostal fascia with nonabsorbable suture. The superficial layers of each incision are closed using absorbable suture, and a compression dressing is applied to the subclavicular site. Stable lead and coil positions must be confirmed by chest roentgenogram before leaving the operating room. The patient usually is extubated and the ICD is activated before transfer to the telemetry intermediate care or intensive care unit.
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Fig 2. . (A) Final submuscular pulse generator position showing relative positions of sensing leads and defibrillation coil that have been brought through the pectoralis muscle and coiled lateral and posterior to the device. (B) Defibrillation patch electrode positioned dorsal to the pulse generator. (C) Alternative posterolateral patch electrode position placed through primary vertical axillary incision. (ICD = implantable cardioverter defibrillator.)
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Results
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Six 83-cm3 pacemaker cardioverter defibrillator generators (PCD 7219; Medtronic Inc, Minneapolis, MN) were implanted in the subpectoral muscle space using the lateral approach. Cathodal defibrillation-sense/pace leads (Transvene 6966; Medtronic Inc) and superior vena cava defibrillation coils (Transvene 6963; Medtronic Inc) were used. Patient age was 53 ± 13 years (mean ± standard deviation; range, 38 to 74 years). Four patients were male. Diseases included ischemic cardiomyopathy (1), rheumatic valvular disease (1), nonobstructive hypertrophic cardiomyopathy (1), and idiopathic dilated cardiomyopathy (3). Indications were drug-refractory sustained ventricular tachycardia (3) or syncope with dilated cardiomyopathy (3). Body weight was 66 ± 10 kg (range, 55 to 80 kg). Mean ejection fraction was 0.33 (range, 0.10 to 0.70).
Results have been satisfactory in all cases. Mean defibrillation threshold energy was 12 ± 5 J (range, 7 to 20 J). An additional large defibrillation patch lead (posterolateral position, model 6897; Medtronic Inc) was required to meet implant criteria in 1 patient (17%). The patch position dorsal to the ICD pulse generator was not effective in this patient. Median patient follow-up duration was 6.5 months (range, 2 to 10 months). Neither discomfort with arm or shoulder movement nor migration of the pulse generator has been observed.
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Comment
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Miniaturization of ICD pulse generators will continue in parallel with the development of more effective energy waveforms, optimal capacitor size, improved defibrillation leads, and advances in battery technology. The availability of smaller devices should allow ICD implantation to be performed with less morbidity than that achieved with techniques used for standard-sized ICD systems [3]. At present, however, the smallest ICD generators and leads in early clinical trials remain relatively large and would pose a significant morbidity risk if subcutaneous or prepectoral placement results in erosion and system infection [1, 2]. Electrophysiologists, who recently have demonstrated the ability to perform ICD implantation independently in the electrophysiology laboratory and the operating room, suggest that the operative skills required for ICD and pacemaker implantation are similar [6]. However, with the exception of those cardiologists who implant miniature pacemakers into infants and children into the subpectoral muscle space by the transpectoral approach [4], most cardiologists have no experience with alternate approaches to the subpectoral muscle space such as the lateral approach, which provides deep coverage for the smaller (but not miniature) ICD pulse generators. Pacemakers also have been implanted in the prepectoral area by placing them beneath the anterior pectoralis fascia. This position is problematic because the pectoral fascia interdigitates with the muscle fibers and rarely allows clean dissection away from the muscle to obtain coverage such that the ICD pulse generator does not communicate with the superficial subcutaneous space.
Certain advantages of the lateral approach to the submuscular space can be emphasized. The vertical axillary incision allows a number of options for defibrillator patch placement should the defibrillation threshold energy be excessive using transvenous coils alone, allows direct visualization of the perforating blood vessels to the pectoralis muscle, achieves adequate space for the device by transecting the insertions of the pectoralis minor in small patients, and reapproximates the serratus fascia to the intercostal fascia to prevent migration of the ICD to the axilla. The transpectoral approach to the subpectoral space, which is used effectively for pediatric pacemaker implantation [4], has been used recently in European trials of downsized ICD implantation, but ICD rotation and brachial plexus paresis has occurred in 7.1% of recipients in whom this technique was used [7]. The disadvantages of the transpectoral approach include a larger subclavicular incision, limited exposure of the perforating vessels by the use of blunt dissection for creation of the ICD space, inability to enlarge the space inferiorly to accommodate the ICD in smaller patients, and the need for a second incision for distant placement of a defibrillator patch when needed.
In initial Canadian trials, distant lateral placement of the defibrillation patch was required in 2 of 30 patients, whereas an equal number met implant criteria with the patch positioned beneath the ICD pulse generator in the pectoral region [8]. A submammary incision also may be used to obtain inferior entrance to the subpectoral space and offers a potential cosmetic advantage for female patients [9]. Disadvantages of the submammary incision include the difficulty in positioning a posterolateral defibrillator patch through the incision in those patients with high defibrillation thresholds and the need for additional transvenous lead length when the ICD is connected through the low incision. Placement of an ICD by either the lateral or submammary approach must create an adequate submuscular space for the device. This may require division of the insertions of the pectoralis minor to avoid excessive pressure of the ICD against the bony thoracic skeleton. In contrast to pulse generators positioned beneath the rectus abdominis muscle, which stretch posterior fascial layers, the pressure of the ICD against ribs and clavicle can result in postoperative discomfort and migration of the ICD into the axilla. It is necessary in all submuscular ICD insertions to coil the leads and connector just lateral to the ICD rather than directly beneath the pulse generator because the pressure of the ICD against the lead insulation has been shown in subrectus implants to result in late lead compression, insulation erosion, over-sensing from ICD-to-wire contact, and inappropriate shock delivery [10]. Careful dissection will avoid damage to leads during subsequent pulse generator exchanges.
A prepectoral ICD implantation beneath the anterior pectoral fascia that was performed at another institution resulted in early wound separation and impending erosion. Cardioverter defibrillator system infection and explantation was avoided by urgent repositioning to the subpectoral space through a separate, vertical incision using the lateral pectoral approach. This case emphasizes the potential risk of inadequate coverage when the ICD is implanted in the subcutaneous or prepectoral position. At the present time, the smallest ICD pulse generator in clinical trials in the United States remains bulky. The surgeon's choice for submuscular pectoral ICD implantation includes transpectoral, submammary, and the herein-described lateral approach. By whatever means, downsized ICDs should be implanted in the submuscular pectoral position to minimize the risk of erosion until size has been reduced further. The lateral approach to the submuscular pectoral space presented in this report offers advantages over alternative approaches and has demonstrated excellent early clinical results.
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Footnotes
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Address reprint requests to Dr Foster, Division of Thoracic and Cardiovascular Surgery, University of Maryland Hospital, Rm N4W91, 22 S Greene St, Baltimore, MD 21201.
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References
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- Choo MH, Holmes DRJ, Gersh BJ, et al. Permanent pacemaker infections. Am J Cardiol 1981;48:559–64.[Medline]
- Kron J, Silka MJ, Ohm OJ, Bardy G, Benditt D. Preliminary experience with nonthoracotomy implantable cardioverter defibrillators in young patients. PACE 1994;17:26–30.
- Shepard RB, Goldin MD, Lawrie GM, et al. Automatic implantable cardioverter defibrillator: surgical approaches for implantation. J Card Surg 1992;7:208–24.[Medline]
- Gillette PC, Edgerton J, Kratz J, Zeigler V. The subpectoral pocket: the preferred implant site for pediatric pacemakers. PACE 1991;14:1089–92.
- Swartz JF, Karasik P, Fletcher RD. Sub-scapular patch position enhances multiple pathway non-thoracotomy defibrillation in humans. Circulation 1993;86(Suppl 1):441.
- Strickberger SA, Hummel JD, Daoud E, et al. Implantation by electrophysiologists of 100 consecutive cardioverter defibrillators with nonthoracotomy lead systems. Circulation 1994;90:868–72.[Abstract/Free Full Text]
- Block M, Hammel D, Bocker D, et al. Subpectoral implantation of ICD devices [Abstract]. PACE 1994;17:800.
- Tang A, Yee R, Gillis A, et al. Initial experience with a new down-sized implantable cardioverter-defibrillator capable of pectoral implantation [Abstract]. PACE 1994;17:761.
- Camunas J, Mehta D, Ip J, Pe E, Gomes JA. Total pectoral implantation: a new technique for implantation of transvenous defibrillator lead systems and implantable cardioverter defibrillator. PACE 1993;16:1380–5.
- Peters RW, Foster AH, Shorofsky SR, Nolan DA, Gold MR. Spurious discharges due to late insulation break in endocardial sensing leads for cardioverter defibrillators. PACE 1995;18:4406–10.
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Abstract
Introduction
