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Ann Thorac Surg 2007;83:1420-1423
© 2007 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Long-Term Follow-Up After Pacemaker Implantation in Neonates and Infants

^a Division of Pediatric Cardiology, University Children’s Hospital, Zurich, Switzerland
^b Division of Congenital Cardiovascular Surgery, University Children’s Hospital, Zurich, Switzerland

Accepted for publication November 13, 2006.

^_* Address correspondence to Dr Balmer, Division of Pediatric Cardiology, University Children’s Hospital, Steinwiesstrasse 75, Zurich 8032, Switzerland (Email: christian.balmer{at}kispi.unizh.ch).

Pediatric cardiac surgery: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

	Abstract

Top Abstract Introduction Patients and Methods Results Comment References

 
Background: Pacemaker (PM) system implantation in neonates and infants is often complicated by hemodynamic instability, small vessel size, and abnormal cardiovascular anatomy. Thus, an open surgical approach for epicardial lead insertion is often required. We assessed the long-term outcomes after epicardial PM implantation in this age group.

Methods: Between 1992 and 2004, 22 consecutive patients underwent PM implantation within the first year of life. Bipolar steroid-eluting epicardial leads (Medtronic CapSure Epi 10366 and 4968) were inserted through median sternotomy, the sybxyphoid approach, or thoracotomy, and connected to various pulse generators.

Results: Pacemakers were implanted at a median age of 35 days (range, 1 to 300). Intracardiac anatomy was abnormal in 17 patients. Indications for PM therapy were heart block in 18 patients and sinus node dysfunction in 4 patients. During a median follow-up of 4.6 years (range, 4 days to 12.8 years), 7 devices were replaced owing to end of battery life (n = 6) or elective device repositioning (n = 1), at a median of 4.1 years (range, 1 to 7.8). One dislodged ventricular lead and 2 atrial lead sensing failures were observed. Sensing, pacing thresholds, and lead impedances showed good implant and stable follow-up values.

Conclusions: Pacemaker-associated morbidity is low. Pacemaker system complications with epicardial leads are rare. Battery life is relatively shorter compared with children and adults because of the fast heart rate and complete PM dependency in most of these children. Even for neonates and infants, modern pacemaker therapy is feasible, safe, and effective.

The most important indication for permanent pacemaker (PM) therapy in neonates and infants is symptomatic bradycardia due to complete atrioventricular block or sinus node dysfunction, either from a congenital etiology or acquired after open heart surgery [1, 2]. Importantly, some age-specific characteristics and challenges must be taken into consideration: first, the PM leads may not be inserted by the transvenous approach because of small vessel size, with the inherent risk of stenosis or thrombosis [3]. In addition, cardiovascular malformations with intracardiac shunting or limited access to the heart may preclude transvenous leads [4, 5]. Second, the implantation often occurs in an emergency setting because of rapidly deteriorating hemodynamics with advanced heart failure. Third, fast heart rates and frequently observed complete PM dependency result in high energy consumption, with accelerated battery depletion at follow-up. Fourth, in the past, high failure rates and complications such as lead fractures, sensing failures, or high stimulation thresholds continued to occur [6–9]. Therefore, an individual surgical approach is required, including sternotomy, subxyphoid, or left thoracotomy for epicardial positioning of the PM leads, with an abdominal or subscapular positioning for the generator.

Fortunately, advances in lead and pacemaker technology, such as the introduction of steroid-eluting epicardial leads, or pacemakers with automatic threshold measurements and output adaptation, have resulted in a significant improvement of lead performance and device longevity [10–12].

Little has been published about modern pacemaker therapy in neonates and infants. The purpose of this retrospective study was to assess outcome after permanent pacemaker implantation in this age group.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment References

 
Patients
The study population consisted of 22 consecutive patients undergoing permanent PM implantation within their first year of life, between February 1992 and January 2004, at a single tertiary referral center. Patient charts and electronic database were retrospectively reviewed. Epicardial pacing systems were inserted in all patients. Patient data and indications for pacing are shown in Table 1. All 17 patients with structurally abnormal hearts underwent concomitant cardiac surgery. The hospital Ethical Committee approved data collection, and individual patient consents were obtained.

Data Collection
Atrial and ventricular lead impedances, as well as sensing and pacing thresholds, were obtained at implantation and at 6-month intervals thereafter. Echocardiographic measurements for left ventricular size and function were obtained at each follow-up. For comparison between patients, the stimulation threshold values were calculated for a standard value of 0.5 ms pulse width using the formula: Energy (µjoules) = Force (volts)² x Pulse width (ms) x 1000000/Impedance (ohms) x 1000 (ms/s) [11].

Statistics
Descriptive statistics were applied where appropriate. Paired Student t tests were used to analyze the difference of paired variables. The pacemaker survival curve was calculated by the Kaplan-Meier method. A p value less than 0.05 was considered statistically significant.

	Results

Top Abstract Introduction Patients and Methods Results Comment References

 
Perioperative Complications
There were no perioperative complications related to PM implantation. No PM system infection was observed.

Lead Positioning and Failures
From 13 implanted atrial leads, 9 were positioned on the right atrium and 4 on the left atrium. Fifteen of the ventricular leads were positioned on the right ventricle and 7 on the left ventricle. Ventricular function was not judged to be significantly impaired in any patient to justify multisite pacing. There was sensing failure of the atrial leads in 2 patients. As a consequence, the pacing mode was switched to VVI on postoperative days 1 and 5, after postoperative atrioventricular block showed signs of recovery in one patient, and VVI pacing was hemodynamically tolerated in the other patient, respectively. Early in the learning period, one ventricular lead dislodgement occurred on day 7 after the implantation and required repositioning. As a result of the atrial lead failures in 2 patients, 11 devices were programmed to DDD and 11 to VVI pacing mode.

Echocardographic Measurements
Left ventricular dimensions were normal at implantation in 18 patients. Mild dilatation of the left ventricle was observed in 1 patient, and severe dilatation in 3 patients. Ventricular function was normal in 18 patients, mildly impaired in 2, moderately impaired in 1 patient, and severely impaired in 1. When present, left ventricular dilatation and decreased function occurred in all patients as a result of complex congenital heart disease necessitating cardiac surgery. There was no worsening of echocardiographic measurements over time.

Generator Service Life
During a median follow-up time of 4.6 years (range, 4 days to 12.8 years), 6 generators had to be replaced owing to end of battery life, at median of 4.5 years (range, 3.25 to 7.8). Freedom from generator replacement is shown in Figure 1. Small patient size necessitated positioning of the pulse generator within the abdominal cavity in 2 patients. In 1 of these patients, the generator was exchanged and repositioned electively after 1 year, when positioning in the rectus sheath became suitable to prevent any bowel complication (Fig 2).

View larger version (6K): [in this window] [in a new window]   Fig 1. Freedom from pacemaker replacement (n = 22 [solid line]); with 95% confidence intervals (dashed lines).

View larger version (95K): [in this window] [in a new window]   Fig 2. Dislocation of the pulse generator within the abdominal cavity. (A) Patient at age 2 weeks; (B) at 2.5 months of age; and (C) at 4 months of age.

In the whole study population, only one ventricular lead had to be replaced because of oversensing after 3.25 years. This was the only unipolar ventricular electrode used early in the series.

Measured Pacemaker Telemetry Data
Mean sensing and pacing thresholds as well as lead impedance were good and did not differ significantly during the whole observation period (Table 2).

Mortality
There were 4 deaths, none of which was related to the PM therapy. The median age at death was 3.6 months (range, 10 days to 6.3 months). All these children had complex congenital heart defects requiring surgery within their first days of life.

	Comment

Top Abstract Introduction Patients and Methods Results Comment References

 
The rate of perioperative complications in our series was surprisingly low, considering the small size of the patients, and the substantial number of complex cardiac anomalies and advanced heart failure. This may be the result of improved intraoperative and postoperative management, owing to increasing knowledge in the care of patients after cardiac surgery in particular.

In our study population, placement of PM leads was possible in all patients, with good initial measurements for sensing, pacing, and impedance, which remained satisfactory at follow-up. Only one ventricular lead failed and had to be repositioned early, and two atrial leads had a loss of sensing and could not be used for dual-chamber pacing. The need for reoperation is low compared with previous studies [13]. The complication rate in our study population was not increased by a dual-chamber approach. From this perspective, it is not justified to withhold this more physiologic option of PM therapy, especially for neonates and infants with complex congenital heart disease, who may benefit from atrioventricular synchronization. Moreover, the implantation of an atrial lead may be easier combined with the ventricular lead at first implant, as scar tissue may jeopardize a later atrial lead insertion, and may increase the risk of surgical damage of the ventricular lead.

Our study shows excellent atrial and ventricular pacing and sensing thresholds. As already shown in children [10, 11, 14], neonates and infants also show stable long-term characteristics of bipolar steroid-eluting epicardial pacing leads, with low energy pacing over time. The possibility of autocapture controlled pacing, which was applied in 12 patients, decelerates battery depletion and prolongs battery service life [12]. As a consequence, patient safety is increased, and reoperations for generator replacement are less frequent. The marked difference of battery service life reflects the different generators with various battery capacities, pacing modes, and capture management functions of the newer devices.

The position of the generator poses some challenge with small patients. In 2 patients, it was impossible to implant the generator in the submuscular rectus sheath. Thus, intraperitoneal implantation in the abdominal cavity was chosen. One of them showed a wide variability in its position from one follow-up to the next. With the possible risk of gut obstruction and erosion, it seems prudent to secure the generator to the internal abdominal wall with a suture.

In conclusion, our data suggest that the outcome of modern PM therapy is excellent in neonates and infants, using bipolar steroid-eluting epicardial pacing leads. Sensing and pacing properties are good and remain stable over time. Lead complications or dysfunctions are rare and usually do not require reinterventions. Generator service life is acceptable, considering the complete PM dependency at high pacing rates in most of these patients.

	References

Top Abstract Introduction Patients and Methods Results Comment References

 

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12. Bauersfeld U, Nowak B, Molinari L, Kampmann C, Schönbeck MH, Schüller H. Low energy epicardial pacing in children, the benefit of autocapture Ann Thorac Surg 1999;68:1380-1383.[Abstract/Free Full Text]
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ali Dodge-Khatami René Prêtre Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Aellig, N. C. Articles by Bauersfeld, U. Search for Related Content PubMed PubMed Citation Articles by Aellig, N. C. Articles by Bauersfeld, U. Related Collections Electrophysiology - arrhythmias Related Article