| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
J Thorac Cardiovasc Surg 2001;121:804-811
© 2001 The American Association for Thoracic Surgery
Surgery for Congenital Heart Disease |
From the Divisions of Cardiologya and Cardiothoracic Surgeryb and The Departments of Pediatrics and Surgery, The Children's Hospital of Philadelphia and The University of Pennsylvania School of Medicine, Philadelphia, Pa.
Presented in part at the 73rd Scientific Sessions of the American Heart Association, New Orleans, La, November 2000.
Received for publication Sept 13, 2000. Revisions requested Oct 25, 2000; revisions received Nov 10, 2000. Accepted for publication Nov 16, 2000. Address for reprints: Mitchell I. Cohen, MD, Division of Pediatric Cardiology, The Children's Hospital of Philadelphia, 34th & Civic Center Boulevard, Philadelphia, PA 19104 (E-mail: cohenmi{at}email.chop.edu).
Abstract
Objectives: There is an increasing incidence of sinus node dysfunction after the Fontan procedure. Inability to maintain atrioventricular synchrony after the Fontan operation has been associated with an adverse late outcome. Although pacing may be helpful as a primary or adjunct modality after the Fontan procedure, the effects of performing a late thoracotomy or sternotomy for epicardial pacemaker implantation are unknown. In addition, little is known about the long-term effectiveness of epicardial leads in patients with single ventricles. The purpose of this study was to compare the hospital course and follow-up of epicardial pacing lead implantation in patients with Fontan physiology and patients with 2-ventricle physiology.
Methods: We retrospectively reviewed all isolated epicardial pacemaker implantations and outpatient evaluations performed between January 1983 and June 2000.
Results: There was no difference in the perioperative course for the 31 Fontan patients (27 atrial and 41 ventricular leads [68 total]) compared with the 56 non-Fontan subjects (9 atrial and 61 ventricular leads [70 total]). The median length of stay in Fontan and non-Fontan patients was 3 and 4 days, respectively. There was no early mortality in either group. Pleural drainage for 5 days or longer was reported in 4% of the Fontan cohort and 3% of the non-Fontan group. Late pleural effusions were identified in only 2 patients in the Fontan group and 2 patients in the non-Fontan group. There was no significant difference in epicardial lead survival between the Fontan group and the non-Fontan group (1 year, 96%; 2 years, 90%; 5 years, 70%). The overall incidence of lead failure was 17% (24/138).
Conclusions: Epicardial leads can be safely placed in Fontan patients at no additional risk compared to patients with biventricular physiology. Sensing and pacing qualities were relatively constant in both the Fontan and non-Fontan groups over the first 2 years after implantation.
Bradyarrhythmias and tachyarrhythmias represent a cause of significant morbidity in patients after the Fontan operation.
1-4 Bradyarrhythmias consist of sinus node dysfunction, atrioventricular (AV) block, or both. Sinus node dysfunction has been reported in 15% to 45% of patients at midterm follow-up after the Fontan operation. 2-5 In addition, patients with L-loop (AV discordance) univentricular anatomy are prone to the development of AV block. 6-8 The inability to maintain AV synchrony both before 9 and after 10 the Fontan operation has been correlated with an adverse late outcome. The presence of bradycardia and multiple suture lines may further predispose patients to atrial flutter after the Fontan procedure, a cause of significant morbidity and mortality. Antibradycardia and antitachycardia pacing may be helpful as a primary or adjunct modality in patients after the Fontan operation. 10-13
In general, pacing leads may be implanted through an endocardial, transmural, or epicardial approach. However, endocardial lead implantation may be impossible in patients undergoing the Fontan operation because venous barriers limit access to the heart. In addition, endocardial or transmural pacing may result in thrombus formation and subsequent emboli to either the pulmonary or systemic circulation. 14,15 This is especially problematic in patients with a right-to-left shunt across a fenestrated Fontan repair. For these reasons, we have adopted the policy of only using epicardial pacing leads in patients after the Fontan operation. Although there are clear benefits to providing AV synchrony and rate support, in selected patients with Fontan physiology, there is little information on the effects of performing a late thoracotomy or sternotomy. Furthermore, there is little known about the long-term effectiveness of epicardial pacing leads in patients with a single ventricle compared with children with other forms of congenital heart disease. The objective of this study was to compare the early hospitalization and midterm follow-up of epicardial pacing systems in Fontan patients and patients undergoing similar lead implantation with 2-ventricle physiology.
Methods
A complete search of the cardiac surgical and pacemaker databases identified all patients who underwent epicardial pacing lead implantation from January 1, 1983, to June 30, 2000, at The Children's Hospital of Philadelphia. Patients having additional reparative or palliative cardiac operations within 30 days of the epicardial lead implantation were excluded to evaluate the effects of either an isolated thoracotomy or sternotomy on the perioperative course. In addition, patients who were admitted solely for a generator change without lead revision were excluded. All hospital and operative records, as well as pacemaker clinic charts, were retrospectively reviewed. The perioperative period, operative period, and follow-up of epicardial pacing systems were compared between patients with Fontan repair and all remaining patients with 2-ventricle physiology (hereafter referred to as non-Fontan).
Operative course
The epicardial leads were implanted by means of standard surgical techniques, either through a midline sternotomy, lateral thoracotomy, or subxiphoid approach on the basis of previous cardiac operation and morphologic cardiac position in the thorax. The subxiphoid approach was generally used for an isolated ventricular lead implantation. The ventricular lead was often fixed on the diaphragmatic ventricular surface. The atrial lead was positioned on either the right or left atrium, whichever afforded the best pacing and sensing thresholds. During the last 4 years, our current approach has generally been to place leads on the left atrial appendage through a lateral thoracotomy in patients with prior complex atrial operations. 12 The surplus of leads is addressed by creating loops of the electrode within the pericardium and the pacemaker pocket.
Hospital course
The following demographic and perioperative variables were compared between patients in the Fontan and non-Fontan groups: (1) anatomy; (2) age at pacemaker implantation; (3) weight at implantation; (4) indication for pacemaker; (5) anatomic chamber paced; (6) type of pacemaker and leads; (7) surgical approach; (8) pacing and sensing thresholds at implantation; (9) duration of ventilation; (10) chest tube drainage; (11) length of stay; (12) discharge pacing and sensing thresholds; and (13) frequency of readmission within 30 days. During lead implantation, the underlying P and R wave amplitudes, if present, were measured with a pacing system analyzer (5311; Medtronic, Minneapolis, Minn). The atrial and ventricular thresholds were analyzed with the same pacing system analyzer. These included the following: (1) the amplitude stimulation threshold (minimum voltage delivered at a fixed pulse width of 0.5 ms that consistently captured the tissue); (2) the measured current generated at this threshold voltage and pulse width; and (3) the lead impedance measured at a pulse width of 0.5 ms and 5 V. Acute pacing characteristics were defined as energy threshold (ET), lead impedance, and sensing at the time of implantation. Discharge pacing characteristics were assessed within 24 hours of hospital discharge.
Pacemaker follow-up
Pacing and sensing thresholds were evaluated at 1 month, 3 months, and subsequently at 6-month intervals. Outpatient evaluations consisted of real-time telemetry of battery and lead measurements. Sensing and pacing thresholds were determined by using either a Medtronic 5300, Pacesetter (Sylmar, Calif), Intermedics (Guidant, St Paul, Minn), or CPI (St Paul, Minn) pacing system analyzer. Implant and follow-up data were compared between the 2 patient groups (Fontan vs non-Fontan). Pacing and sensing thresholds were compared at the time of implantation, hospital discharge, 1 year, 2 years, 5 years, and the most recent pacemaker follow-up visit.
Lead failure was defined as the need for replacement or abandonment on the basis of the following: (1) fracture or insulation break; (2) increasing pacing or sensing thresholds; or (3) phrenic or myopotential stimulation. Infections were classified separately into (1) superficial infection (with or without positive blood culture) or (2) deep infection necessitating generator removal. Lead data were censored for elective change, death, or orthotopic heart transplantation.
Definitions
Lead current (I) was calculated by using Ohm's law:
I = V/R
where V is the programmed pulse amplitude in volts and R is the lead impedance measured in ohms. The ET is defined as the least amount of energy that produces a consistent capture outside the refractory period. The formula 16 used to calculate ET is as follows:
Statistical analysis
Exploratory data analysis was performed by using descriptive measures. Categoric variables were expressed in terms of percentages with associated SDs. Continuous variables were expressed in terms of means with SDs if the term was normally distributed; skewed variables were expressed as medians with ranges. The strength of a statistical association was measured by use of the 
2 test for categoric variables. When cell numbers were small, the Fisher exact test was used. Statistical significance of the difference between continuous variables was assessed by using a Student t test of the means of normally distributed variables and a Wilcoxon rank sum test for skewed distribution. A Cox proportional hazards model was used to assess confounding variables. Finally, Kaplan-Meier survival estimates were constructed for time-dependent variables by use of Stata 6.0 software (Stata Corporation, College Station, Tex). Statistical significance between curves was assessed by means of the log rank test.
Results
Subjects
During the study period, 48 patients in the Fontan group and 94 patients in the non-Fontan group underwent epicardial pacing lead implantation. Seventeen patients in the Fontan group and 38 patients in the non-Fontan group were excluded as a result of having had cardiac operations within the preceding 30 days. The remaining 31 patients in the Fontan group and 56 patients in the non-Fontan group met the inclusion criteria and were the basis for this study. Sixty-eight leads (27 atrial and 41 ventricular) were implanted in the 31 patients in the Fontan group during 65 operations. Seventy epicardial pacing leads (9 atrial and 61 ventricular) were implanted in the 56 patients in the non-Fontan group with 2 ventricles during 64 operations over the same time period. The anatomic diagnosis and indication for pacemaker implantation in the 2 study cohorts is shown in Table I. Of the 56 patients in the non-Fontan group, 24 (43%) had no structural heart disease.
|
Operative techniques
Epicardial leads were implanted with use of a thoracotomy (Fontan group, 37; non-Fontan group, 23), sternotomy (Fontan group, 24; non-Fontan group, 25), or a subxiphoid incision (Fontan group, 7; non-Fontan group, 22). There were no significant differences in the surgical approach between the 2 groups. The types of epicardial leads used were similar in the 2 groups. Steroid-eluting epicardial leads were used in 40% and 35% of the Fontan and non-Fontan lead insertions, respectively. The Fontan epicardial leads included 59 myocardial screw-in leads (Medtronic 4965, 5069, 5071, and 6917; Pacesetter 1043K; Cordis 325) and 9 fishhook leads (Medtronic 4951). The non-Fontan epicardial leads included 58 myocardial screw-in leads (Medtronic 4965, 5069, 5071, and 6917; Pacesetter 1043K) and 12 fishhook leads (Medtronic 4951).
Postoperative hospitalization
The perioperative course after epicardial lead implantation was similar between those patients with Fontan physiology and those with 2-ventricle physiology. There was no difference in the duration of intubation, chest tube drainage, or length of stay between the 2 groups (Table II). Chest tube drainage exceeding 5 days was observed in 3 (4.6%) patients in the Fontan group and 2 (3.1%) patients in the non-Fontan group. All 3 of these patients in the Fontan group underwent a thoracotomy for lead implantation and remained in the hospital for at least 1 week, receiving diuretics and pleurocentesis. The median stay after an isolated epicardial lead implantation was 3 days in both groups. One Fontan group patient was hospitalized for 45 days with a deep pacemaker pocket infection. One patient with dilated cardiomyopathy and congenital complete AV block remained hospitalized for 68 days because of a paralyzed diaphragm that required prolonged mechanical ventilation. This patient eventually had a successful diaphragm plication, resulting in extubation.
|
Pacing and sensing characteristics
Lead survival data are shown in Fig 1. Follow-up data from 6 months or longer were available in 77% of the Fontan and 71% of the non-Fontan epicardial leads. There was no significant difference in the duration of epicardial lead follow-up between the 2 study groups (Fontan group, 2.8 ± 2.4 years; non-Fontan group, 3.7 ± 4.4 years). The 1, 2-, and 5-year lead survival for all epicardial systems was 96%, 90%, and 70%, respectively. The presence of Fontan physiology did not significantly alter the lead survival curve (P = .2). The cause of lead failure was similar between the Fontan and non-Fontan groups (Fig 2) and was not confounded by the type of pacing lead, as determined with a multivariate model (P = .22).
|
|
Phrenic pacing was reported in 1 Fontan ventricular lead and 2 non-Fontan atrial leads. Lead fracture occurred in 3 Fontan and 3 non-Fontan ventricular leads and 1 additional Fontan atrial lead. Increasing pacing thresholds necessitating replacement was observed in 6 Fontan leads (1 atrial and 5 ventricular leads) and 5 non-Fontan ventricular leads. None of the 29 subxiphoid implanted leads have failed over an average follow-up of 2 years (1 month to 13.5 years). There was no difference in lead survival between those implanted through a thoracotomy or sternotomy.
Atrial epicardial leads
ETs were similar at implantation for the Fontan and non-Fontan systems (Fontan group, 2.2 ± 1.5 µJ; non-Fontan group, 2.3 ± 3.6 µJ; P = .57). There was a slight improvement in the ET for the Fontan leads at 2 years of follow-up (1.4 ± 0.3 µJ), without a significant change in the non-Fontan leads (3.4 ± 1.9 µJ). The lead impedances for patients in the Fontan and non-Fontan groups were not significantly different at implantation (Fontan group, 405 ± 127 
; non-Fontan group, 352 ± 86 ; P = .28) and at 2 years of follow-up (Fontan group, 408 ± 112 ; non-Fontan group, 338 ± 68 ; P = .27). Because the indication for pacing was sinus node dysfunction, in many of the patients in the Fontan group, P wave sensing could not always be performed. The sensed P wave amplitudes were similar in the Fontan and non-Fontan leads at implantation (Fontan group [n = 21/27], 3.1 ± 1.5 mV; non-Fontan group [n = 6/9], 5.5 ± 2.0 mV, and at 2 years of follow-up (Fontan group [n = 9/20], 2.6 ± 1.2 mV; non-Fontan group [n = 5/7], 2.9 ± 1.2 mV; P = .79).
Ventricular epicardial leads
The ETs at implantation and 2 years of follow-up were not significantly different between the Fontan and non-Fontan groups. Both groups had a significant increase in ET between implantation (Fontan group, 1.6 ± 1.3 µJ; non-Fontan group, 2.1 ± 3.3 µJ; P = .11) and 2 years of follow-up (Fontan group, 7.4 ± 6.5 µJ; non-Fontan group, 4.7 ± 4.4 µJ; P = .20). Similarly, the lead impedances for the Fontan and non-Fontan groups were not significantly different at implantation (Fontan group, 470 ± 155 ; non-Fontan group, 421 ± 130 ; P = .11) and 2 years of follow-up (Fontan group, 385 ± 78 ; non-Fontan group, 383 ± 103 ; P = .94). Patients with complete AV block and ventricular escapes of less than 30 beats/min were often unable to undergo intrinsic R wave assessment. The sensed R wave amplitudes were similar in the Fontan and non-Fontan leads at implantation (Fontan group [n = 37/41], 11.7 ± 5.3 mV; non-Fontan group [n = 53/61], 10.1 ± 5.1 mV) and at 2 years of follow-up (Fontan group, [n = 13/22], 8.6 ± 5.0 mV; non-Fontan group [n = 8/25], 7.3 ± 1.4 mV).
Steroid-eluting leads had similar ETs to non–steroid-eluting leads at implantation (steroid, 1.9 ± 1.91 µJ; nonsteroid, 2.0 ± 3.0 µJ). However, at 2 years of follow-up, steroid-eluting leads had significantly lower ETs than non–steroid-eluting leads (steroid [n = 20], 3.6 ± 3.7 µJ; nonsteroid [n = 41], 6.3 ± 5.8 µJ; P < .01). No significant difference in the lead impedance between steroid-eluting and non–steroid-eluting leads was noted at implantation (steroid, 438 ± 142 ; nonsteroid, 423 ± 135 ) or 2 years of follow-up (steroid, 336 ± 52 ; nonsteroid, 409 ± 98 ).
Long-term follow-up
Among the 31 patients in the Fontan group, there were 3 late deaths, and 1 patient received a heart transplant. Two of the deaths in the Fontan group were related to low cardiac output caused by ventricular dysfunction. The other death in the Fontan group occurred suddenly in a patient with a history of medically refractory atrial flutter. No patient in the Fontan group died during pacemaker implantation or as a result of pacemaker failure. Of the 3 deaths in the Fontan group, 2 had DDD generators, and 1 had a VVI pacemaker.
Among the 56 patients in the non-Fontan group with a pacemaker, 3 have ultimately died, and 1 underwent heart transplantation. None of the 3 deaths were pacemaker related. One patient with congenital AV block and hydrops died early in life. One patient with tetralogy of Fallot had aortic valve endocarditis and subsequent left ventricular dysfunction. This patient eventually died while awaiting a heart transplant. The third patient was a newborn with complete common AV canal and late-onset AV block who died as a result of bronchopulmonary dysplasia.
Six patients in the Fontan group and 12 patients in the non-Fontan group required generator revisions with the same epicardial lead or leads as a result of battery depletion. No patient in either cohort was lost to follow-up.
Discussion
Because the Fontan operation is increasingly used for a variety of lesions with a functional single ventricle, 6% to 10% of patients may require antitachycardia pacemakers, antibradycardia pacemakers, or both within the first 5 years after the operation. 1,5,10 Sinus node dysfunction and atrial flutter have been shown to increase in frequency with time from the Fontan operation. 3,5 Patients after the Fontan operation may have junctional rhythm with loss of AV synchrony, or alternatively, patients with L-loop univentricular hearts may acquire complete AV block. The inability to maintain AV synchrony limits atrial contribution to ventricular filling, a situation that can be remedied by cardiac pacing.
Although endocardial pacing is generally preferable to epicardial pacing because of lower current values and pacing thresholds, there are certain circumstances in which the use of transvenous leads is impractical or contraindicated. Disadvantages include the limited vascular access in small children, risk of venous obstruction, and the need for growth accommodation. It may be impossible to gain venous access to the ventricle in patients undergoing the Fontan operation who require ventricular pacing. Furthermore, newer modifications to the Fontan operation, such as the extracardiac conduit, may also exclude venous access to the atrium. Although successful transmural atrial pacing has been previously reported in patients undergoing the Fontan operation with the use of bipolar atrial leads, this approach continues to place patients at risk for systemic embolus, pulmonary embolus, or both, necessitating the use of warfarin. 11
With improvements in lead technology, such as steroid-eluting leads, the pacing thresholds are very similar to conventional endocardial leads. 17 In addition, positioning atrial epicardial leads on the left atrial appendage in patients who have previously undergone extensive right atrial operations has been shown to significantly lower ETs. 12 However, the disadvantage of epicardial lead placement relates to the extensive dissection often needed to achieve adequate sensing and pacing thresholds. Speculation has been raised that performing the lateral thoracotomy itself may result in a high incidence of pleural effusions, 12 a frequent finding before the use of the fenestrated Fontan procedure. 18 We undertook this study to address the acute hospitalization with placement of epicardial pacemakers in patients undergoing the Fontan operation, as well as to evaluate the long-term survival of epicardial leads in a large cohort of pediatric patients.
We observed no difference in the length of chest tube drainage or hospital stay after epicardial lead placement in patients in the Fontan group compared with patients in the non-Fontan group, regardless of the surgical approach. Additionally, having a prior thoracotomy or sternotomy did not alter the perioperative pacemaker implantation among the non-Fontan cohort. The median length of time that the chest tube was required after 68 epicardial lead placements in 31 patients in the Fontan group was 1 day. Furthermore, we observed no difference in the readmission rate or incidence of late effusions among the 2 groups. Only 2 patients in the Fontan group required readmission for late pleural effusions. On the basis of our study, a late thoracotomy or sternotomy for epicardial pacemaker implantation can be achieved with minimal risk of infection or effusion in all patients.
Lead failure occurred in 17% of all implanted epicardial leads and was typically a result of either a fracture or increasing pacing threshold. We observed no difference in the lead failure rate between those patients with biventricular anatomy and those with Fontan physiology. The 2-year survival of the leads was similar in patients in the Fontan group (90%) and patients in the non-Fontan group (89%). None of the 29 subxiphoid-implanted leads in this study failed. This approach generally minimizes the daily traction imposed by respiration and arm movement that might otherwise occur with leads implanted through a thoracotomy. Beyond the first few years of lead implantation, the failure rate was similar to that of previously reported epicardial pacing studies, achieving a probability of lead survival at 5 and 10 years of 70% and 65%, respectively. 7,19,20
The midterm pacing and sensing characteristics of the leads were comparable between the Fontan and non-Fontan groups. Exit block with increasing pacing thresholds occurred infrequently, although in all cases, the leads were nonsteroid eluting. No patient with a steroid-eluting lead had exit block. This is similar to a study by Cutler and colleagues, 21 who found no evidence of exit block in 22 patients with steroid-eluting epicardial pacing leads who were followed up for 6 years. The use of steroid-eluting leads in reducing the ET without significantly altering the lead impedance should prolong the battery life. Even in subjects in the non-Fontan group, epicardially pacing young children for as long as possible should reduce the risk of venous obstruction.
Limitations
This was a retrospective study. No patient in the Fontan group underwent endocardial or transmural lead placement for comparison. The earliest steroid-eluting lead was implanted in 1994, obviating long-term comparison between steroid-eluting and non–steroid-eluting epicardial leads.
Conclusions
We conclude that epicardial leads can be safely placed in patients having undergone the Fontan operation at no additional risk compared to non-Fontan subjects. The incidence of pleural effusions after a late thoracotomy in Fontan patients appears to be minimal. The use of epicardial leads is a reliable method of long-term pacing in children, has applicability in every child, and avoids the inherent risk of thromboembolism associated with transvenous leads.
References
This article has been cited by other articles:
|
|
 |
|
  H. Murayama, M. Maeda, H. Sakurai, A. Usui, and Y. Ueda Predictors affecting durability of epicardial pacemaker leads in pediatric patients. J. Thorac. Cardiovasc. Surg., February 1, 2008; 135(2): 361 - 366. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. M. Spotnitz Surgical Implantation of Pacemakers and Automatic Defibrillators Card. Surg. Adult, January 1, 2008; 3(2008): 1395 - 1428. [Full Text]
|
|
|
|
|
|
H. Laks, D. Marelli, M. Plunkett, and J. Myers Adult Congenital Heart Disease Card. Surg. Adult, January 1, 2008; 3(2008): 1431 - 1464. [Full Text]
|
|
|
|
 |
|
 M. I. Cohen, R. Jedeikin, S. Pfeiffer, and S. Pedersen Unipolar ventricular pacing reduces inappropriate shocks from a separate cardioverter defibrillator in a post-Fontan patient. Europace, April 1, 2006; 8(4): 293 - 296. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. J. Barber, A. S. Batra, G. H. Burch, I. Shen, R. M. Ungerleider, J. W. Brown, M. W. Turrentine, M. Mori, Y.-C. Hsieh, and S. Balaji Acute Hemodynamic Effects of Pacing in Patients With Fontan Physiology: A Prospective Study J. Am. Coll. Cardiol., November 15, 2005; 46(10): 1937 - 1942. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-L. Jansens, M. Jottrand, N. Preumont, E. Stoupel, and D. de Canniere Robotic-enhanced biventricular resynchronization: an alternative to endovenous cardiac resynchronization therapy in chronic heart failure Ann. Thorac. Surg., August 1, 2003; 76(2): 413 - 417. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Petko, R. J. Myung, G. Wernovsky, M. I. Cohen, J. Rychik, S. C. Nicolson, J. W. Gaynor, and T. L. Spray Surgical reinterventions following the Fontan procedure Eur. J. Cardiothorac. Surg., August 1, 2003; 24(2): 255 - 259. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. M. Spotnitz Pacemakers and Automatic Defibrillators Card. Surg. Adult, January 1, 2003; 2(2003): 1293 - 1326. [Full Text]
|
|
|
|
|
|
H. Laks, D. Marelli, M. Plunkett, J. Odim, and J. Myers Adult Congenital Heart Disease Card. Surg. Adult, January 1, 2003; 2(2003): 1329 - 1358. [Full Text]
|
|
|
|
 |
|
 M. I. Cohen, D. M. Bush, V. L. Vetter, R. E. Tanel, T. S. Wieand, J. W. Gaynor, and L. A. Rhodes Permanent Epicardial Pacing in Pediatric Patients : Seventeen Years of Experience and 1200 Outpatient Visits Circulation, May 29, 2001; 103(21): 2585 - 2590. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
