Changing Indications for Pacemakers in Children

Transcription

1 Changing Indications for Pacemakers in Children William H. Fleming, M.D., Lynne B. Sarafian, M.N., John D. Kugler, M.D., Philip J. Hofschire, M.D., and Edward B. Clark, M.D. ABSTRACT Permanent pacemakers were implanted in 50 children. Indications were symptomatic sinus node dysfunction in 34 (68%), surgical block in 9 (18%), and congenital block in 7 (14%). Twenty-three (68%) of the 34 children with sinus node dysfunction had undergone prior cardiac operations. Only 4 of the 50 patients (8%) had electrode problems after a mean pacing time of 29.5 months (range, 1 to 96 months). All 35 of the mercury-cell pulse generators used in 28 patients ceased to function after an average useful life of 20.8 months (range, 1 to 51 months). The lithium-powered units in the 45 survivors all show satisfactory pacing after 5 to 44 months (mean, 28.1 months). With improved pacemaker technology, longer survival after complex repairs, and better monitoring techniques, the indications for cardiac pacing in children have broadened. Surgical block now is an indication in only a small fraction of the pediatric pacemaker population. Sinus node dysfunction accounts for an ever-increasing majority of the pacemakers we currently implant in children. The last decade has been one of marked improvement in pacemaker technology [l-51. "Demand" circuits are now reliable, the sizes of pulse generators are decreasing, and circuit failures are rare. In addition, lead durability has greatly improved [5, 61. Perhaps most importantly, the lithium-based family of energy cells has produced much greater longevity, as well as greater reliability, in pulse generators. Ten years is now a reasonable expectation for the useful life of a pulse generator. With these rapid changes in technology, it is not surprising that the indications for pacing From the University of Nebraska Medical Center, Omaha, NE. Presented at the Sixteenth Annual Meeting of The Society of Thoracic Surgeons, Jan 21-23, 1980, Atlanta, GA. Address reprint requests to Dr. Fleming, Thoracic and Cardiovascular Surgery, University of Nebraska Medical Center, 42nd and Dewey Ave, Omaha, NE are also changing [6]. Previously, pacers were used only to sustain life, but now they are also used for optimizing cardiac performance or as prophylaxis against intermittent or even merely possible events 161. Long-term (24-hour) ambulatory rhythm monitoring has greatly facilitated the decision-making process by showing that "possible" events are or are not occurring. These changes led us to review the use of pacemakers in our pediatric population. Material and Methods Records of all children who received implanted pacemakers at the University of Nebraska Medical Center between 1967 and December 1, 1979, were reviewed. There were 50 children ranging in age from 2 days to 20 years; mean age at first implant was 8.4 years. There were 31 male and 19 female patients in the group. Indications for pacing in these patients included sinus node dysfunction, congenital complete atrioventricular (AV) block, and surgical complete AV block (Tables 1, 2). Sinus node dysfunction was defined as one or more of the following [7]: (1) sinus pause or arrest (Figure, top); (2) sinus, atrial, junctional, or ventricular rhythms at slow rates alone or with (3) bradytachydysrhythmias, which included any bradycardia in association with supraventricular tachycardias, such as atrial flutterfibrillation, or sinus node or atrial muscle reentry tachycardia (Figure, bottom). Results Among the 23 patients with sinus node dysfunction following a previous operation, 10 patients had undergone a Mustard operation, 2 had had a Fontan operation, and 11 had undergone various other intracardiac procedures, none alike. Pacing was reqcired an average of 17.5 months postoperatively (range, 0 to 72 months). Of the 34 patients with sinus node dysfunction, the most common symptoms were syncope (15 patients), dizziness (6 patients), by The Society of Thoracic Surgeons

2 ~ 330 The Annals of Thoracic Surgery Vol 31 No 4 April 1981 Table I. Indications for Pacing Indication Symptomatic sinus node dysfunction After operation No operation Surgical atrioventricular block Operation prior to 1970 Complex lesions Congenital atrioventricular block Total No. of Patients Percent of Patients Table 2. Symptomatology in 34 Patients Paced for Sinus Node Dysfunction No. of Percent of Symptom Patients Patients Syncope Dizziness 6 18 Low cardiac output 8 23 Low heart rate 5 15 Total and low cardiac output (8 patients), which responded favorably to cardiac pacing maneuvers employed during cardiac catheterization. Five patients had no symptoms, but the indication for pacemaker implantation was severe sinus node dysfunction in patients who had had operation for heart disease associated with increased incidence of sudden death (e.g., Mustard repair for transposition of the great arteries). The definition of severe bradycardia we used was a heart rate below 70 beats per minute in children less than 1 year old, below 60 in children 1 to 5 years old, and below 40 in children 6 years old or older [7]. Among the 5 patients paced for low heart rate alone, 4 had a rate of 30 beats per minute or less, and 1 had a rate of 38 at 5 years of age. Leads Forty-six of the 50 patients (92%) have required only one epicardial lead system. No patients had transvenous endocardia1 leads. The five lead failures in 4 patients included two fractured wires, two infected pacing systems, and one case of exit block. Among the 45 patients now alive, 41 (91%) have sutureless electrodes. The mean duration of epicardial electrode use is 42.5 months (range, 1 to 111 months). Pulse Genera tors None of the patients presently has a mercurycell unit. The 35 mercury-cell units used in 28 patients lasted an average of 20.8 months (total months, 728). The range was 1 to 51 months. Fifty patients each had a lithium pulse generator implanted. Five patients died after an average of 14 months of pacing, and 45 now have had implanted pacemakers an average of 28.1 months (total months, 1,265) (range, 5 to 44 months). Thirty-one of the 50 patients who received lithium-powered pacemakers have programmable units. All of these have been reprogrammed for rate change at least once. All have had the pulse width adjusted six weeks or more after implantation. Presently, 28 of 31 (9Oo/o) have a pulse width of 0.3 msec or less. Two patients have AV sequential pacemakers with satisfactory function to date. Deaths There were 5 deaths among the 50 patients (10%). One infant with asplenia died of sepsis, and 2 patients had uncorrectable congenital heart disease. Two patients died suddenly after having led seemingly normal lives for 7 and 9 years of pacing. One had a history of bradytachydysrhythmias and a normally functioning lithium pacemaker at postmortem examination. The other patient, who had a lithium generator implanted for surgical AV block, died immediately after a sledding accident and was not studied after death. FOllOW-Up Pacemaker function is checked on all patients every week for six weeks, and then every 3 months, or more often, either in the clinic or by telephone monitor. Because some of our patients are as much as 500 miles away, telephone monitoring is highly desirable. Twenty-fourhour ambulatory electrocardiographic (ECG) monitoring is done at least annually.

3 331 Fleming et al: Pacemakers in Children Bradytachydysrhythmias, recorded from 24-hour ambulatory electrocardiogram of 4-year-old girl, 2 months after closure of atrial septa1 defect and repair of partial anomalous pulmonary venous connection to superior uena cava. Top recording shows sinus atrial rhythm at constant rate of slightly greater than 100 beats per minute until sinuslatrial arrest occurs. The escape rhythm originates from a different atrial focus since the P wave is different. Bottom recording shows later occurrence of supraventricular tachycardia. The ventricular rate was 265 beats per minute, and P wave morphology suggested atrial flutter. lntracardiac electrophysiological studies showed right atrial muscle reentry supraventricular tachycardia (atrial rate slightly greater than 300 beats per minute) with 2 : I ventricular response. Comment We believe that improved technology and increased survival of children born with congenital heart disease have brought about a major change in the indications for implanted pacemakers. Numerous pacemakers are now known to be highly reliable, and 10 years is a reasonable expectation for the life of a pulse generator. Improved energy sources give promise of 25- year pulse generator life in the next few years. Cardiac pacemaker leads are now reliable, with 93% (42 out of 45) of our living patients stdl pacing on their original leads. The use of programmable pulse generators in our pediatric population has provided a number of benefits. First, the rate can be decreased as the patient grows older. This is especially important in infants and small children. Second, the pacing rate can be adjusted to optimize heart rate as the patient s condition changes. Third, by adjusting both the rate and the amplitude or pulse width, it is possible to extend the longevity of the pulse generator. Finally, a much smaller stock of pulse generators is required in order to provide each patient with the optimal pacing rate. Improved technology has also contributed to our assessment of dysrhythmias and conduction abnormalities. All patients with symptoms suggestive of dysrhythmias, plus all those thought to be at risk of conduction abnormalities, e.g., patients who have had a Mustard procedure [8-101, undergo 24-hour ambulatory ECG monitoring. Presently, we find such monitoring most helpful. However, intracardiac studies are indicated in some patients to determine which type of pacing is most beneficial. By assessing AV conduction together with temporary atrial, ventricular, or AV sequential pacing while measuring cardiac output, the best choice of pacemaker can be made. As recently as 1976, complete AV block was the principal indication for pacing in children [6, 111. Now we see a decreasing incidence of surgical AV block and about the same incidence of congenital AV block. The large increase in the number of children requiring cardiac pacemakers is in those with sinus node dysfunction; we found that more than two-thirds (68%) of our total pacemaker population is now paced for that reason. The growing group of patients who have had repair of congenital cardiac defects can be expected to show increasing incidence of sinus node dysfunction. We believe that postoperative patients at risk of dysrhythmias, especially following a Mustard, Fontan, or other atrial operation, should have routine 24-hour ambulatory ECG monitoring so that symptoms can be accurately interpreted. In the child who has syncope or dizziness associated with sinus dysfunction, the decision is

4 332 The Annals of Thoracic Surgery Vol 31 No 4 April 1981 not a difficult one and virtually all authors agree that these symptomatic patients are likely to benefit from permanent pacing. However, children who have no symptoms but who have sinus node dysfunction detected on standard or ambulatory ECG recordings present a therapeutic dilemma because it is unknown which of these patients are, in fact, at risk of increased morbidity and mortality. Long-term follow-up of all such children will eventually enable us to make these decisions based on clear data. We presently believe that asymptomatic children who have severe sinus node dysfunction associated with those forms of intracardiac operation known to have an incidence of sudden, unexplained death in the postoperative period should have pacemakers implanted. This group consists primarily of those who undergo atrial operations for repair of transposition of the great arteries, or the Fontan operation. Other children with recognized sinus node dysfunction but no symptoms and no prior intracardiac operation are followed without pacing but are watched closely for the development of symptoms. The availability of ambulatory ECG monitoring and technological improvement in pacing hardware have altered our indications for pacing. Symptomatic sinus node dysfunction is now by far our most common indication for pacing. References Donahoo JS, Haller JA, Zonnebelt S, et al: Permanent cardiac pacemakers in children: technical considerations. Ann Thorac Surg 22:584, 1976 Furman S, Escher DJW, Parker B: Pacemaker longevity. Am J Cardiol 31:111, 1973 Grunkemeier GL, Dobbs JL, Starr A: Statistical analysis of pacemaker follow-up data, rate stability and reliability. Circulation 53:241, 1976 Marco JD, Codd JE, Bamer HB, et al: Implantable pacemakers in children. Arch Surg 110:880,1975 Shearin RPN, Fleming WH: Fourteen years of implanted pacemakers in children. Ann Thorac Surg 25:144, 1978 Gillette P: Pacing in the pediatric patient. Medtronic News, June, 1978 Kugler JD: Sinoatrial node disorders. In Gillette PC, Garson A Jr (eds): Pediatric Cardiac Dysrhythmias. New York, Grune & Stratton, in press Clarkson PM, Barrett-Boyes BG, Neutze JM: Late dysrhythmias and disturbances of conduction following Mustard operation for complete transposition of the great arteries. Circulation 53:519, Lewis AB, Lindesmith GG, Takahashi M, et al: Cardiac rhythm following the Mustard procedure for transposition of the great vessels. J Thorac Cardiovasc Surg 73:919, Saalouke MD, Rios J, Perry LW, et al: Electrophysiologic studies after Mustard s operation for d-transposition of the great vessels. Am J Cardiol 41:1104, Hofschire PJ, Nicoloff DM, Moller JH: Postoperative complete heart block in children: experience with 64 patients. Am J Cardiol39:559,1977 Discussion DR. PAROUK s. IDRISS (Chicago, IL): In general, I agree with Dr. Fleming and his co-workers on the expanded role of the pacemaker in infants and children. It should be noted that there was an increase of 16% in their number of patients between the writing of the abstract and the presentation of this paper. This increase occurred within a 6-month period compared with the study period of 111/2 years. I also agree with the authors on the use of the expanded pacemaker, the programmable type and the demand type, in the sick sinus syndrome, and in the intermittent atrioventricular dissociation when the heart rate drops below the optimal level for good cardiac output. Of course, the use of the 24-hour Holter monitor has been very helpful in this area. It also has been helpful in postoperative intracardiac physiological studies and sinus node recovery time. I believe that postoperative conduction defects that do not recover within two to three weeks will need a prophylactic pacemaker if the Holter monitor shows a marked decrease in the sinus rate. At Children s Memorial Hospital we recently have used a simplified technique. The median stemotomy incision is extended, and the pacemaker is placed anterior to the posterior rectus sheath, not in front of the peritoneum where it might slip. The technique provides good cosmetic results and allows easy access to the pacemaker. In Dr. Fleming s study, the number of patients with sick sinus syndrome seems to be too high among those who had undergone a Mustard or Fontan operation previously. In more than 130 patients undergoing a Mustard operation at Children s Memorial Hospital, only 2 had sick sinus syndrome that required pacing. Both of them had had a Blalock-Hanlon procedure beforehand. We have not seen the problem in any of our 10 patients who had had a Fontan procedure. We have experienced many problems with leads, especially the screw-in type. Because of this, we presently are changing to another type of lead. Dr. Fleming, would you outline the pacemaker in-

5 333 Fleming et al: Pacemakers in Children dications in transposition of the great vessels? Do you place pacemakers prophylactically in that group of patients? What are other indications in patients with congenital heart block without intracardiac defect? DR. DANIEL w. VAN HEECKEREN (Cleveland, OH): I have a couple of technical questions about the electrodes in pacemakers. My remarks are somewhat in line with what Dr. Idriss has just said. My colleagues and I reviewed our experience in pacing 36 children at Case Westem Reserve University. The early series of 13 patients, in whom the Cordis sutured Elgiloy electrode was used, had excellent results with neither fracture nor exit block. When the sutureless screw-in electrodes became available, we changed to these. With right ventricular placement, usually implanted from the subdiaphragmatic approach, we encountered three instances of exit block in 15 patients. No exit block occurred in six left ventricular insertions. Although by statistical test this is not significant, I believe it is an important problem that should be addressed. It occurred with both the 3%-tum and with the Z1/2-turn electrode. The second point about children is that sometimes they are very small when the pacemaker is implanted. With growth, the distance from the pacemaker pulse generator to the patient s heart changes. In some of our very small patients, we have used a technique described many years ago by Glenn and Sat0 in which a small envelope of Teflon is used to sequester a few coils of electrode. Ordinarily we leave the excess electrode around the pacemaker, but as the patient grows, the fibrous tissue holding the electrode fails to allow it to pay out. However, it does pay out from the Teflon baggy, as we noted on roentgenograms made several years apart. The distance from the heart to the pacer is changed dramatically, and the electrode slowly but surely uncoils. DR. FLEMING: I thank both Dr. Idriss and Dr. Van Heeckeren for their comments. I think, Dr. Idriss, that our 16% increase in patient volume in a short time was partly the result of an electrophysiologist joining our pediatric cardiology team. Things come out of the wall when someone with new talents studies them. I certainly agree with your principle of the desirability of putting the pulse generator behind muscle in children, and I do this. If it is not done, I believe there will be a high incidence of erosions. I have no quarrel with the idea of putting the generator in the rectus sheath as you do. In answer to your question about prophylactic use of pulse generators in patients with such conditions as levotransposition, our present policy is to place the wires at the time of operation in any patient whom we consider to have an unusually high risk of needing a pulse generator either immediately or in the future. We do not put in a pulse generator until we have a specific indication for pacing. Dr. Van Heeckeren, I agree that there are more problems to using the sutureless electrode on the right ventricle. I think one has to be very careful not to put the sutureless electrode so far in that the bared tip of that lead is inside the right ventricle. That certainly will give a picture of exit block if it occurs. The use of the Teflon envelope is, I think, clever and promising. We are not doing that, and, as I mentioned, I have been quite surprised that we have not encountered more problems with lead length.