Implantation of Transvenous Pacemakers in Infants and Small Children

Transcription

1 Implantation of Transvenous Pacemakers in Infants and Small Children J. Ernesto Molina, MD, PhD, Ann C. Dunnigan, MD, and Jane E. Crosson, MD Divisions of Cardiovascular and Thoracic Surgery and Pediatric Cardiology, University of Minnesota, Minneapolis, Minnesota A series of 14 infants and small children ranging from 7 months to 7 years in age (mean, 2.5 years) underwent implantation of transvenous pacemaker systems. Three factors are of utmost importance in children: small subclavian vein size, thin subcutaneous layer in the chest, and growth. A five-point protocol is followed strictly: (1) duplex assessment of upper veins, (2) use of active fixation leads, (3) use of short (36 to 45 cm) leads, (4) anchoring of pulse generator with nonabsorbable material to prevent migration, and (5) routine use of the "'lateral approach" in children more than 2 years old when the pulse generator is implanted in the chest. Because lead diameters measure 2 to 2.3 mm, a one-lead system needs a vein diameter of 5 mm (cross-sectional A dvances in technology and refinement of surgical techniques have allowed, with more frequency, the implantation of transvenous pacemaker systems in small children and infants. One important limitation in implanting transvenous pacemakers in children, particularly in infants, is the size of their upper chest veins. A substantial number of children still receive epicardial pacemakers via thoracotomy, because their subclavian veins are too small to accept a pacemaker lead. Whenever possible, thoracotomies should be avoided at such a young age. In addition, transvenous systems have proved to be more reliable [1, 2]. The number of complications in children's pacemaker implantations has been significantly higher than in the adult population [3-8] regardless of the approach [9-11]. Pacemaker manufacturers now make short leads and thin and small pulse generators, so they can be implanted in the chest. Careful assessment of the vein size is, therefore, a must when transvenous leads are implanted. The literature on obliteration of subclavian veins in children undergoing transvenous pacemaker implant is very scarce or nonexistent [12, 13]. In our own experience, we have seen at least 4 children who had total obliteration of the subclavian vein, the innominate vein, and in I case of the superior vena cava after transvenous pacemaker implantation. This complication occurred without any serious obvious acute manifestation, but when the children returned to have the pacemaker replaced or an attempt was made to pass new leads, we Accepted for publication Nov 23, Address reprint requests to Dr Molina, Box 182, University of Minnesota, 420 Delaware St, SE, Minneapolis, MN area of 19 mm2). A two-lead system needs a vein at least 7 mm in diameter and a cross-sectional area of 38 mm 2 to prevent vein occlusion. Therefore all children less than 3 years of age had the leads implanted via the internal jugular vein. In 50% of children between 4 and 7 years of age, the internal jugular system also was used. Children more than 7 years old have leads implanted via the subclavian veins. Duplex ultrasound assessment of the upper veins is important to decide route of implantation. Use of short leads is recommended to reduce bulk at the pulse generator site. The "lateral approach" prevents problems at the generator implantation site. (Ann Thorac Surg 1995;59:689-94) found (after performing venography) that the vein was completely occluded, and in I patient with obstruction of the superior vena cava, thoracotomy intervention was necessary to remove the lead that had caused obstruction of the superior vena cava. Placement of a patch to widen the vein and maintain continuity of that vessel was necessary. Therefore, the rate of occlusion or obliteration of veins due to this type of operation is unknown. We began looking into this problem in an attempt to come up with a sensible and objective method to decide when it was safe to implant the transvenous lead in a vein only slightly larger than the lead itself. The problem of venous thrombosis after transvenous implantation of pacemaker leads has been described in adults because this occurs suddenly and the patients usually are symptomatic. However, in children, the course is more protracted and it is not until revision or a new pacemaker implantation is attempted that the child is found to have the vein occluded. A protocol, therefore, was developed to treat these children and is herein described. As pointed out by O'Sullivan and associates [10], the advantage of using small pulse generators in small children is lost if the pacemaker lead is excessively long and the remnant needs to be wrapped with the pulse generator, increasing the bulk of the unit, making it unsuitable for implantation in the subcutaneous tissue of the chest wall of these children. We recently described a surgical technique conceived at the University of Minnesota [14] that provides for a safe method of implanting pulse generators in the chest to avoid complications at the pocket site, like overstretched scars or even dehiscence caused by a bulky 1995 by The Society of Thoracic Surgeons /95/$ (94)01050-M

2 690 MOLINA ET AL Ann Thorac Surg PEDIATRIC TRANSVENOUS PACEMAKERS 1995;59: Table 1. Age Distribution of Transvenous Pacemaker Recipients Group Age No. Percent I 7 mo to 3 y 9 64 II 4 to 7 y 5 36 Total pulse generator and lead when the incision lies over the unit. Material and Methods From 1984 through 1993, we implanted transvenous pacemaker systems in 36 children ranging from 7 months to 17 years old, but because children older than 7 years do not represent a problem, our study focuses on children under that age. There were 14 patients, therefore, divided into two groups. Group 1 comprised children from 7 months to 3 years of age, and group 2 from 4 years to 7 years. There were 9 patients in the first group and 5 in the second, bringing the total to 14 (Table 1). There were 5 patients less than 1 year of age and 4 between 1 and 3 years in group 1. The other 5 patients in group 2 were children between 4 and 7 years of age. The leads were placed either via the internal jugular vein (usually in infants and toddlers) or via subclavian veins (in older children). The pulse generator was placed in the upper chest in children more than 2 years old or in the abdomen in younger children. The indications for pacemaker implantation were complete postsurgical heart block (9 patients) or congenital heart block (5 patients) with severe bradycardia. One hundred percent follow-up of these patients has extended from 2 months to 6 years. Eight patients required pacemaker implantation after a corrective intracardiac operation as follows: correction of transposition of great vessels, 1; aortic valve replacement, mitral valve replacement, and ventricular septal defect repair, 1; atrioventricular canal, 1; Fontan, 1; Rastelli, 1; pulmonary atresia and ventricular septal defect, 1; double-outlet right ventricle, 2; and tetralogy of Fallot, 1 (1 patient had two operations). Protocol Our method fulfills five conditions: (1) Doppler ultrasound assessment of all four upper chest veins (subclavian and internal jugular veins), measuring patency, diameter, and cross-sectional area; (2) use of active fixation leads in ventricle and atrium; (3) use of short leads 36 to 45 cm long; (4) anchoring of pulse generator with nonabsorbable material to muscle fascia to prevent migration; and (5) routine use of lateral approach as previously described [14] if the pulse generator was implanted in the chest. Duplex Assessment of Veins This examination provides important information on the diameter and cross-sectional area of the subclavian and internal jugular veins, compared with the cross-sectional area of the pacemaker leads. We then are able to estimate the amount of obstruction the leads could cause in the vessel (Fig 1). Active Fixation Leads Most of our patients received an endocardial screw-tip lead. Because unipolar or bipolar leads have the same shaft diameter, we used the bipolar CPI "sweet-tip" model 4269 (Cardiac Pacemakers Inc, St. Paul, MN) in 12 patients; in 1 patient, Medtronic model 4058 screw-tip electrode (Medtronic, Inc, Minneapolis, MN) was used; in the remaining patient, a lead with a tined tip was implanted. Short leads were manufactured by CPI (CPI "sweet tip" 36 or 45 cm long). The remaining 2 children had 52-cm ventricular leads. All atrial leads in cases of dual-chamber implantations were CPI 45 cm long. In patients receiving dual-chamber systems, the atrial lead was also CPI "'sweet tip" type. Lead Fixation at Vein Entry Point Because of the small size of the subclavian veins in children less than 4 years old, our preferred site of insertion is the internal jugular vein. Even in children more than 4 years old, we preferred the internal jugular vein if they had a small subclavian vein by duplex (less than 5 mm in diameter) from whichever cause. In every case of lead implantation in the jugular system, we tunneled it under the clavicle to reach the site of the pacemaker pocket in the upper part of the chest (in children more than 2 years old) or in the left flank of the abdomen (in children less than 2 years old) (Fig 2). If the subclavian vein was chosen, a vein introducer no larger than size 8 was used and therefore the lead had to be tested by passing it through the sheath of the introducer before the actual puncture of the vein is done. A size 10 introducer is extremely large for a vein less than 5 mm in diameter (Table 2). Operative Technique Our technique for inserting the lead in the jugular system follows (Fig 3): A transverse incision is made I cm above the clavicle crossing the lateral border of the sternocleidomastoid muscle. The lateral border of this muscle is retracted medially. Some of the adipose tissue present in that fossa can be removed to facilitate visualization of the internal jugular vein. The vein now is exposed and only is dissected clean in its anterior or anterolateral aspect (the area facing the surgeon). The vein must not be dissected around. One or two pursestring sutures (single- or double-lead system) are placed, using 5-0 or 4-0 monofilament suture. This is the future site of the lead insertion. In this manner, the vein remains patent and no stricture is caused. As soon as the lead is anchored in the cardiac chamber, the pursestring suture is tied down and cut. The lead also is secured to the fascia with a transfixation stitch. Anchoring the Pulse Generator To prevent migration of the pulse generator inferiorly, with the possibility of exerting traction on the transvenous lead, the pulse generator is secured with nonab-

3 Ann Thorac Surg MOLINA ET AL ;59: PEDIATRIC TRANSVENOUS PACEMAKERS A B D Fig 1. Ultrasound images of the upper veins obtained preoperatively in children. (A) Two-year old child in whom the left internal jugular vein measured 7 9 mm in diameter. (B) Subclavian vein of the same child as in (A), which measured mm in diameter. The left internal jugular vein was chosen for implantation of the pacemaker lead in this case. (C) Transverse view comparison of the left internal jugular vein (top) versus the subclavian vein (bottom) in another child 21/2 years old. (D) Saggital view comparing the difference in caliber between the two veins in (C). The left internal jugular vein also was chosen for insertion of the pacemaker lead. (IJV = internal jugular vein; Subcl. V. Mid. = left subclavian vein midportion.) C sorbable material to the fascia of either the pectoralis major muscle or the abdominal muscles, depending on the site selected. Interrupted stitches with nonabsorbable material are placed between the subcutaneous fascia and the anterior fascia of the muscle, along the inferior and lateral borders of the pulse generator.

4 692 MOLINA ET AL Ann Thorac Surg PEDIATRIC TRANSVENOUS PACEMAKERS 1995;59: Fig 2. Posih'on of a single transvenous lead to the ventricle in a 2-year-old child. The lead was inserted via the left internal jugular vein tunneled under the left clavicle and pulse generator implanted in the left flank of the abdomen. Lateral Approach If the pulse generator is implanted in the chest, our previously described lateral approach [14] is used (see Fig 3). Basically, an incision is made along the lateral border of the pectoralis major muscle. The dissection is carried medially and superiorly, creating a pocket in the superior quadrant of the chest over the pectoralis muscle where the pulse generator is implanted. This prevents tension, dehiscence, infection, or formation of thin wide scars over the pulse generator site. Results Vein Size The routine preoperative Doppler ultrasound assessment of the veins allowed us to construct a growth curve of the subclavian and the internal jugular vein systems (Fig 4). Knowing the diameter of the veins, we calculated and compared the cross-sectional areas with those of the pacemaker lead. Based on these calculations, we could Table 2. Recommendations for Transvenous Pacemaker Lead Implants Lead Size Desired Vein Lumen Diameter Area Diameter Area System (mm) (mm 2) (mm) (mm 2) Percent One lead Two lead confidently make some practical therapeutic recommendations (see Table 2). In all infants (6 to 12 months), the diameter of the subclavian veins measured 2.5 mm versus 9 mm -+ 2 of the internal jugular veins, giving us an internal jugular to subclavian vein ratio of The dimensions of pacemaker leads vary slightly among manufacturers, but in general the diameter of the lead shaft ranges from 2 to 2.3 mm (cross-sectional area, 3.14 to 4.15 mm2). In infants, the lead diameter amounts to half the diameter of the subclavian vein. Given this situation, we thought use of the subclavian vein would be unsafe, even if implanting a single lead. The internal jugular vein in an infant with a cross-sectional area of about 78.5 mm 2 compares favorably with the cross-sectional area of the lead (4.5 mm2), equivalent to no more than 6% of the vein lumen. Therefore, it is less likely to lead to occlusion or thrombosis of the vein. Even in children 3 to 7 years old, the subclavian veins are relatively small from 2.3 to 6 mm in diameter. Not until the child is more than 10 years old are the subclavian veins larger, from 8 to 10 mm in diameter; by the same age, the internal jugular veins are up to 18 mm in diameter. This uneven ratio (with the internal jugular veins growing larger than the subclavian veins) probably is related to the growth rate of the child's head in proportion to the arms. Therefore, we did not consider it safe to implant single transvenous pacemaker leads into a vein with less than 19 mm 2 of cross-sectional area (5 mm diameter) regardless of its location. With a double-lead implantation (for dual-chamber pacemaker systems), the two leads have a combined cross-sectional area of 6.28 mm 2, so the ideal size of the vein must be at least 7 mm in diameter, equivalent to a cross-sectional area of 38 mm 2 (see Table 2). We believe that once the lead occupies close to 50% of the vein's cross-sectional area or more, the risk increases for thrombosis or vein obstruction by the lead. These recommendations are shown in Table 2. All our patients met these requirements. If in doubt about the size or integrity of the subclavian vein, we do not hesitate to insert the leads in the jugular system. Therefore, all patients less than 3 years of age underwent implantation via the jugular vein. In addition, 2 of the patients in the second group (4 to 7 years) also underwent implantation in the left internal jugular veins. Of the 14 patients followed up, lead replacement was required in 1, due to a sudden increase in the stimulation threshold. In 6 patients, we needed to replace the generator due to exhaustion of the battery, and 2 children underwent release of the lead due to obvious tension as a result of their growth. Vein Obstruction and Site Follow-up No thrombosis of the internal or subclavian veins due to partial obstruction of its lumen by the pacemaker leads has developed in any of our patients. In fact, ultrasound

5 Ann Thorac Surg MOLINA ET AL ;59: PEDIATRIC TRANSVENOUS PACEMAKERS "--- \ - / J " - _..f-. - Q,~/ / A C B Fig 3. Stages of the operative technique. (A) Neck incision over the lateral border of the sternocleidomastoid muscle and incision used for the lateral approach of implanting the pulse generator in the chesl (B) Pursestring suture has been placed in the internal jugular vein, and this is punctured directly. (C) By using a standard introducer, the lead is inserted in the vein, and (D) the pursestring suture is tightened to prevent bleeding. D examinations routinely repeated on 5 patients showed no compromise of the vein lumen or any sign of thrombosis at any level. No cases of pulse generator site dehiscence or migra- // Sub cl. Int. jug. 18 ",~, 14 o" " ~ a eo 4 2 I I i I L i I Vein Diameter (mm) Fig 4. Comparison of the internal jugular (Int. jug.) and subclavian vein (Sub cl.) size as measured by duplex ultrasound in children from 2 to 17 years of age. tion have been observed after we implemented the lateral approach as a routine technique for children. Comment Because the transvenous system has fewer problems of sensing and pacing than epicardial implantation [1, 2,13], this is our approach of choice. In children, a step-by-step surgical technique must be followed exactly when implanting a pacemaker system. The smaller the child, the more problems can occur in trying to insert a transvenous system. Children typically have small veins and a thin subcutaneous tissue layer, and are actively growing. Based on this experience, our general recommendations are shown in Table 3. Our standard approach was developed throughout the years by paying attention to the site of the insertion, the vein chosen for the implantation, and the anchoring of the lead to prevent dislodgements. In addition, our technique for implanting the pulse generator in the chest has been quite rewarding; it is highly recommended for use in children of all ages to prevent

6 694 MOLINA ET AL Ann Thorac Surg PEDIATRIC TRANSVENOUS PACEMAKERS 1995;59: Table 3. Recommendations for Implantation of Transvenous Pacemaker Leads in Children According to Age (Based on Diameter of Upper Veins) Age Approach Leads <3 y IJ Single 4 to 7 y IJ Dual system Subclavian Single >7 y Subclavian Single or dual IJ Single or dual IJ = internaljugular vein. most of the common complications seen in this type of operation. We have avoided use of the cephalic vein as has been described by other authors [13] because it imposes some limitation to the movement of the arm, which upon abduction exerts tension on the lead and traction that may induce dislodgement from the cardiac chamber. In addition, the lead in that case is very superficial and uncomfortable to the patient. We prefer, therefore, the direct puncture of the subclavian vein or the internal jugular vein. Using the lateral approach for implantation of the pulse generator, if the skin overlying the pacemaker pocket is too thin, it is very easy to bury the pulse generator under the pectoralis major muscle instead of under the skin with a highly satisfactory cosmetic appearance and no discomfort to the patient. References 1. Hayes DL, Holmes DR Jr, Maloney JD, et al. Permanent endocardial pacing in pediatric patients. J Thorac Cardiovasc Surg 1983;85: Lau YR, Gillette PC, Buckles DS, Zeigler VL. Actuarial survival of transvenous pacing leads in a pediatric population. PACE 1993;16: Benrey J, Gillette PC, Nasrallah AT, et al. Permanent pacemaker implantation in infants, children, and adolescents: long-term follow-up. Circulation 1976;53: Hofschire PJ, Nicoloff DM, Moller JH. Postoperative complete heart block in 64 children treated with and without cardiac pacing. Am J Cardiol 1977;39: Daicoff GR, Aslami A, Tobias JA, et al. Management of postoperative complete heart block in infants and children. Chest 1974;66: Williams WG, Izukawa T, Olley PM, Trusler GA, Rowe RD. Permanent pacing in infants and children. PACE 1978;1: Young D. Permanent pacemaker implantation in children: current status and future considerations. PACE 1981;4: Hill PE. Complications of permanent transvenous cardiac pacing: a 14-year review of all transvenous pacemakers inserted at one community hospital. PACE 1987;10: Simon AB, Dick M II, Stern DM, Behrendt DM, Sloan H. Ventricular pacing in children. PACE 1982;5: O'Sullivan JJ, Jameson S, Gold RG, Wren C. Endocardial pacemakers in children: lead length and allowance for growth. PACE 1993;16: Furman S, Young D. Cardiac pacing in children and adolescents. Am J Cardiol 1977;39: Ward DE, Jones S, Shinebourne EA. Long-term transvenous pacing in children weighing less than 10 kg. Circulation 1985;72(Suppl 3): Walsh C, McAlister H, Andrews C, et al. Pacemaker implantation in children: a 21-year experience. PACE 1988;11(Suppl 2): Molina JE. New technique for pacemaker implantation in the upper chest of children and women. Ann Thorac Surg 1991;51:992-5.