HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

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): Larry A. Rhodes Thomas L. Spray J. William Gaynor Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cohen, M. I. Articles by Gaynor, J. W. Search for Related Content PubMed PubMed Citation Articles by Cohen, M. I. Articles by Gaynor, J. W. Related Collections Electrophysiology - arrhythmias

Ann Thorac Surg 2004;78:197-202
© 2004 The Society of Thoracic Surgeons

---

Original article: cardiovascular

Efficacy of prophylactic epicardial pacing leads in children and young adults

^a Divisions of Cardiology, Philadelphia, Pennsylvania, USA
^b Cardiothoracic Surgery and Departments of Pediatrics and Surgery, The Children's Hospital of Philadelphia and The University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA

Accepted for publication February 3, 2004.

^* Address reprint requests to Dr Cohen, Director of Electrophysiology and Pacing, Phoenix Children's Hospital, Arizona Pediatric Cardiology Consultants, 1920 E Cambridge St, Phoenix, AZ 85006, USA
e-mail: mitchapcc{at}360express.com

	Abstract

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
BACKGROUND: Epicardial pacemakers are often required in children and young adults who cannot undergo a transvenous system because of patient size, vascular barriers, or significant residual intracardiac shunts. Prophylactic epicardial pacing leads, placed at the time of concomitant congenital heart surgery, may reduce a late thoracotomy or sternotomy. The efficacy of prophylactic epicardial leads in the pediatric population is unknown.

METHODS: A retrospective review of the cardiovascular surgery and pacemaker databases at The Children's Hospital of Philadelphia identified all patients less than or equal to 21 years of age, who underwent placement of an epicardial pacing lead between January 1, 1990 and December 31, 2002. Prophylactic epicardial pacing leads placed at the time of a concomitant congenital heart procedure were compared to standard epicardial leads that were connected to a simultaneous programable generator. Pacing and sensing threshold data were obtained in prophylactic epicardial leads at the time of lead retrieval and 6 month follow-up and compared to standard epicardial pacing leads.

RESULTS: Twenty-two (13 ventricular, 9 atrial) prophylactic epicardial pacing leads were retrieved in 13 patients at a median of 252 days (7 days to 3.98 years) from the time of initial implant and compared to 256 (164 ventricular, 92 atrial) standard epicardial leads placed in 142 patients. Nineteen (86%) prophylactic epicardial leads had acceptable pacing and sensing thresholds at lead retrieval. Only 1 patient with atrial and ventricular leads had poor pacing and sensing at retrieval and required a redo-sternotomy for placement of new atrial and ventricular epicardial pacing leads. For the remaining atrial (n = 7) and ventricular (n = 12) prophylactic epicardial leads, there was no significant difference in pacing (atrial, 1.59 ± 1.1 µJ; ventricular, 1.98 ± 1.9 µJ) or sensing (atrial, 3.6 ± 1.8 mV; ventricular, 13.8 ± 4.4 mV) compared to standard pacing (atrial, 2.1 ± 1.8 µJ; ventricular, 1.9 ± 3.4 µJ) and sensing (atrial, 3.3 ± 1.7 mV; ventricular, 11.3 ± 5.3 mV) epicardial leads. Six-month follow-up pacing and sensing thresholds were not significantly different between the prophylactic and standard epicardial pacing leads.

CONCLUSIONS: Prophylactic epicardial pacing leads can be successfully placed and retrieved in a subset of children and young adults who will likely require pacing at a later date. Prophylactic leads have comparable pacing and sensing qualities at lead retrieval and short-term follow-up compared to standard epicardial leads. Consideration for prophylactic epicardial pacing leads will likely reduce the need for a late thoracotomy or sternotomy.

	Introduction

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
Epicardial pacemakers are often required in children as a result of their small size, the presence of congenital heart defects with a right-to-left shunt, or because of an inability to pace the chamber-desired secondary to anatomic barriers. Epicardial pacemakers may be needed in children following reparative or palliative surgery for a variety of congenital heart lesions including ventricular inversion, complex left ventricular outflow tract obstruction, or heterotaxy syndrome. It is estimated that 15% to 45% of patients following the Fontan operation develop sinus node dysfunction, often necessitating pacemaker implantation to preserve atrioventricular (AV) synchrony [1–4]. Prophylactic epicardial leads, placed at the time of earlier open heart surgery, could theoretically simplify late pacemaker surgery by reducing the need for an additional sternotomy or thoracotomy. However, the efficacy of these leads at late generator implantation is unknown. This study sought to address the follow-up of prophylactic epicardial leads and the short-term pacing and sensing characteristics relative to epicardial leads that were placed with a simultaneous generator.

	Material and methods

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
A complete search of the pacemaker and cardiac surgical databases at The Children's Hospital of Philadelphia identified all patients who underwent placement of epicardial leads between January 1, 1990 and December 31, 2001. Patients aged more than 21 years of age were excluded in order to evaluate primarily a large pediatric cohort. Defibrillator and(or) atrial antitachycardia pacing leads were excluded from analysis. The database was queried for leads that were placed at a time remote from generator implantation. Only isolated leads placed at the time of an additional open or closed cardiac surgical case without connection to an implantable generator were deemed "prophylactic." An isolated epicardial lead implant (lead replacement) connected to a previously placed generator was not classified as a prophylactic implant. Prophylactic epicardial leads that have not yet required connection to a generator were excluded.

All hospital, operative, and outpatient charts were retrospectively reviewed. An active and prospective pacemaker database has been in place for the last 5 years. Records were abstracted for demographic data, cardiac malformation, type of congenital heart disease, presence or absence of single ventricle heart disease, cardiac surgical procedures (type and number), surgical approach, indication for pacing, mode of pacing, chamber placement, lead fixation method, steroid lead properties, pacemaker complications, and need for lead removal.

Operative course
Epicardial leads were implanted by standard surgical techniques either through a midline sternotomy, lateral thoracotomy, or subxiphoid approach. The surgical approach was based on the patient's underlying cardiac anatomy, morphologic cardiac position in situ, prior operation(s), and concurrent operation at the time of lead placement. 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. The surplus of lead was addressed by creating loops of the electrode within the pericardium and the pacemaker pocket. Leads were tunneled with care to avoid sites of potential injury along the rib margins to the generator implant site in the subrectus abdominal region. All prophylactic leads were placed at the time of a concomitant operation by a midline sternotomy.

For those leads implanted with a concomitant generator, implant measurements were obtained using a pacing system analyzer (Medtronic, 5311, Minneapolis, MN). Measurements included lead impedances at 0.5 msec/5 V, sensed P or R waves (if present), and amplitude stimulation threshold (minimum voltage delivered at a fixed pulse width of 0.5 ms that consistently captured the tissue), expressed as energy threshold (µJ = V(volts)² x pulse width (msec) x 10⁶/R (ohms) x 1,000 ms/s [5]). Consistent assessment of sensing and pacing thresholds was generally not performed at the time of prophylactic lead implantation. However, all prophylactically placed epicardial leads were tested for adequacy of pacing and sensing thresholds at the time of late generator connection by the previously described methods. The patient and his or her family were instructed that if, at the time of lead retrieval the lead(s) were not felt to have adequate thresholds, then additional sternotomy or thoracotomy may be required.

Pacemaker follow-up
Pacing and sensing thresholds were evaluated at 1 month and 6 month intervals. Outpatient evaluations consisted of real-time telemetry of battery and lead measurements. Sensing and pacing thresholds were determined by using a Medtronic 5300 or Pacesetter system analyzer. Threshold was determined by decreasing the pulse width until there was failure to capture. The threshold was considered to be the lowest programable pulse width at which there was consistent capture. For patients with slow ventricular escape complexes or absence of atrial activity, sensing tests could not always be performed.

Statistical analysis
Exploratory data analysis was performed using descriptive measures. Categorical variables were expressed in terms of percentages with associated standard deviations. Continuous variables were expressed in terms of means with standard deviations 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 ² for categorical variables. When cell numbers were small, the Fischer's exact test was employed. Statistical significance of the difference between continuous variables was assessed using the Wilcoxon rank sum test for skewed distribution.

	Results

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
Patient data
A total of 142 patients underwent implantation of 164 ventricular and 92 atrial epicardial leads at a median age of 3.6 years (1 day to 20.2 years). During the study period an additional 56 patients undergoing congenital heart surgery had implantation of at least one prophylactic epicardial pacing lead for possible use later. None of the 56 patients with a prophylactic epicardial lead required lead extraction secondary to infection. Of these 56 patients, 13 had eventual connection of an implantable pulse generator to their previously placed 13 ventricular and 9 atrial epicardial leads. The median age at the time of initial lead implant was 5.5 years (1 month to 19.4 years).

Complex congenital heart disease was present in all 13 patients with the majority having single ventricle physiology (Table 1). The surgical operation at the time of prophylactic lead implantation is shown in Table 1. The clinical indication for either a prophylactic atrial, ventricular, or both atrial and ventricular epicardial leads was related to one of the following: AV block occurring at some point during either the presurgical cardiac catheterization or the surgical procedure (n = 4); a concern about possibly developing AV block (n = 2); a history of atrial arrhythmias with the potential need for more aggressive antiarrhythmic drug therapy or antibradycardic pacing (n = 4); a history of isolated sinus node dysfunction (n = 2), or a history of syncope (n = 1) (Table 1). The composite clinical indication for prophylactic lead implantation in the other 43 patients (age at implant 6.3 years [4 months to 23.2 years]) who have not yet come to require a pacemaker was not significantly different in either anatomy (single ventricle heart disease, n = 18; complex biventricular repair, n = 20; status-post valve surgery, n = 5) or concern over sinus node dysfunction or AV block. No clinical factors allowed for an accurate prediction of which patients with prophylactic leads would eventually undergo pacemaker implantation.

Of the 22 prophylactically placed epicardial leads, 19 (86%) had acceptable pacing and sensing thresholds at the time of lead retrieval and generator attachment. For the 7 successful atrial lead retrievals, the pacing threshold was 1.59 ± 1.1 µJ with intrinsic P waves of 3.6 ± 1.8 mV. The prophylactic atrial lead retrieval thresholds were not significantly different than the implant data in the 92 standard atrial epicardial leads. The pacing and sensing thresholds for the 12 utilized prophylactic ventricular leads were not significantly different (1.98 ± 1.9 µJ; 13.8 ± 4.4 mV) than the implant data for the 164 routinely placed epicardial ventricular leads (previously mentioned).

Patient No. 5 had prophylactic epicardial atrial (Medtronic 4951) and ventricular (Medtronic 5069) leads placed at the time of the Fontan revision with hepatic vein inclusion, fenestration of the atrial baffle, and tricuspid valve replacement with a 23-mm pericardial bioprosthesis. Two weeks following the surgical procedure, the patient had progressed from Mobitz II AV block to complete heart block. At the time of lead retrieval the atrial pacing threshold was more than 5.0 V/0.5 msec though atrial sensing was acceptable (1 mV). The atrial and ventricular electrodes were connected to a dual chamber generator with adequate function in an atrial sensed-ventricular paced (VDD) mode. This patient did not require a "redo" sternotomy.

Patient No. 9, who had previously undergone a lateral tunnel Fontan, developed increasing common AV valve regurgitation. Prophylactic fishhook atrial (Medtronic 4951) and ventricular screw-in (Medtronic 5071) leads were placed at the time of the common AV valve replacement with a 33-mm St. Jude prosthesis (St Jude Medical, Inc, St. Paul, MN). Ten months later, as a result of increasing episodes of atrial flutter and slower ventricular rates on amiodarone, the previously placed epicardial leads were retrieved. Both the atrial and ventricular pacing thresholds exceeded 5 V/0.5 msec with no sensing of the atrial lead. At that time, the lower portion of the sternotomy was reopened and new atrial (Medtronic 5071) and ventricular (Medtronic 4965) epicardial leads were affixed with thresholds less than 1.0 V. Neither patient No. 5 nor patient No. 9 had testing of the leads at the time of prophylactic implantation. All 13 patients tolerated the lead retrieval and generator attachment without any development of infection or acute lead failure (median length of stay 4 days; 2 to 10 days).

Follow-up pacemaker data
Atrial sensing and stimulation thresholds at 6 months following lead implant were significantly comparable between the successfully retrieved prophylactic leads (n = 7, 2.2 ± 2.1 µJ; 2.7 ± 1.9 mV) and the available standard atrial epicardial leads (n = 59, 2.4 ± 2.3 µJ; 2.9 ± 1.4 mV). The atrial lead impedance between the two cohorts was not significantly different at 6 months post lead retrieval and standard implant (prophylactic: 321 ± 44 ; standard: 353 ± 93 ).

Six-month pacing threshold data were available for 9 of the 12 successfully retrieved prophylactic ventricular epicardial leads. Two of the patients moved and were lost to follow-up. One additional patient with sinus node dysfunction developed high ventricular stimulation thresholds and was changed to an AAI pacing mode with acceptable AV node conduction. Reoperation in this patient to place a new ventricular lead was not clinically indicated. For the 9 prophylactic ventricular leads there was no significant difference in pacing (2.7 ± 2.6 µJ) or sensing (12.2 ± 4.7 mV) compared to available data in the 115 available standard ventricular epicardial leads at 6 month follow-up (3.2 ± 2.3 µJ; 9.0 ± 4.7 mV)(p = NS). Measured ventricular lead impedance between each of the groups was also comparable (prophylactic: 389 ± 102 ; standard: 366 ± 107 ) (p = NS). None of the 19 successfully retrieved and utilized prophylactic epicardial leads had to be replaced or abandoned within the first year from fracture, insulation break, or phrenic nerve stimulation.

	Comment

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
Beause of an increasing incidence of sinus node dysfunction following the Fontan operation [1–4], and an incremental annual risk of AV block in patients with L-looped ventricles [6], there continue to be children and young adults who will require antibradycardic pacemakers. Despite improvements in pacing electrode design [7–9], a subset of patients with complex congenital heart disease cannot have a conventional endocardial implant either as a result of small size, persistent left-to-right shunt, lack of vascular access to the cardiac chamber of interest, and/or precluded by a mechanical tricuspid valve. However, identifying which individual patient will develop sinus node dysfunction, AV block, or AV nodal disease secondary to antiarrhythmics designed to prevent atrial arrhythmias is difficult and fraught with a great deal of uncertainty. Currently no study has addressed the utility and efficacy of prophylactic epicardial lead implantation in pediatric patients.

While prophylactic implantation of defibrillators have been recommended in certain high-risk patients [10, 11], prophylactic pacemakers for bradyarrhythmias have generally not been supported. Specific guidelines for the implantation of cardiac pacemakers in children and young adults have been published by various committees within the American College of Cardiology, the American Heart Association, and the NASPE, Heart Rhythm Society [12]. However, it would be beneficial to the patient if they could be identified as an individual likely to need pacing such that prophylactic epicardial leads could be placed at the time of concomitant heart surgery in order to avoid the need for an additional late sternotomy or thoracotomy. The decision to implant the programable generator should follow the same guidelines referenced above. In this study, prophylactic epicardial leads were placed in 56 patients over a ten-year period with 13 (23%) patients requiring lead retrieval and connection to a pacemaker. Furthermore, nearly 90% of the patients whose leads were successfully retrieved had comparable pacing and sensing thresholds to standard epicardial leads placed with a concomitant generator. While some of the patients with prophylactic leads required pacing in as short a time as 7 days, the average time to lead retrieval was 8.5 months. Only 1 of the 13 patients in our study required a "redo" sternotomy for high atrial and ventricular pacing thresholds at lead retrieval despite not testing the leads at the time of initial implant. Testing of epicardial leads immediately upon discontinuation of cardiopulmonary bypass may not truly reflect the pacing and sensing characteristics of that lead at a more physiologic state. While it has been our supposition that leads that have acceptable pacing and sensing thresholds at implant in theory should have acceptable pacing and sensing thresholds at retrieval, barring any scarring, the converse may not necessarily be valid. While it is possible that intraoperative testing of epicardial leads at implant would have identified pacing failure in the three leads at the time of retrieval, it is further possible that testing would have revealed unacceptable thresholds at implant in leads that would have otherwise performed well when the body was at a more physiologic state. Further testing of prophylactic leads may help answer some of these questions.

Aside from the immediate tests of lead reliability at retrieval was the observation that the 6-month follow-up pacing and sensing data were comparable to more routinely placed epicardial leads. Comparable to previously reported data on epicardial leads in children, only 1 ventricular lead developed exit block within the first 6 months following lead retrieval.

While the benefit of prophylactic lead insertion is the avoidance of a late sternotomy, thoracotomy, or even a subxiphoidal incision, the decision to implant a prophylactic lead must be weighed against the small risk of developing an infection with a foreign body [13] and the currently held belief that magnetic resonance imaging is clinically contraindicated in the presence of having a pacing electrode. It is important that for truly prophylactic pacing leads the indication and supposition that pacing may be required later be discussed with the patient and the family before the initial surgical operation. In addition, if it is at all possible that the patient is a reasonable candidate for an endocardial implant then prophylactic epicardial leads may not necessarily be warranted given the higher acute and chronic energy consumption associated with epicardial leads in comparison with endocardial leads. However, based on our institutional practice, all 13 patients in this study with successfully retrieved leads were deemed appropriate candidates for an epicardial implant.

Limitations
This was a retrospective study. Given the limited number of prophylactic epicardial leads retrieved and utilized, long-term pacing and sensing characteristics were not measured.

	Conclusions

Top Abstract Introduction Material and methods Results Comment Conclusions References

 
We conclude that prophylactic epicardial leads can be placed in a subset of children and young adults who may require permanent pacing at a later date. Prophylactic epicardial leads placed at the time of an earlier operation, even if not acutely tested at implant, appear to reduce the need for an additional thoracotomy, sternotomy, or subxiphoidal incision and have comparable short-term pacing and sensing characteristics to more routinely placed epicardial leads. Additional follow-up of these prophylactic epicardial leads will be required to see if they have longevity similar to standard epicardial leads.

	References

Top Abstract Introduction Material and methods Results Comment Conclusions References

 

1. Gentles T.L., Gauvreau K., Mayer J.E., Jr, et al. Functional outcome after the Fontan operation: factors that influence late morbidity. J Thorac Cardiovasc Surg 1997;114:392-403.[Abstract/Free Full Text]
2. Cohen M.I., Wernovsky G., Vetter V.L., et al. Sinus node function after a systematically staged Fontan procedure. Circulation 1998;98(Suppl II):352-359.
3. Manning P.B., Mayer J.E., Jr, Wernovsky G., Fishberger S.B., Walsh E.P. Staged operation to Fontan increases the incidence of sinoatrial node dysfunction. J Thorac Cardiovasc Surg 1996;111:833-840.[Abstract/Free Full Text]
4. Driscoll D.J., Offord K.P., Feldt R.H., et al. Five- to fifteen-year follow-up after Fontan operation. Circulation 1992;85:469-496.[Abstract/Free Full Text]
5. Hamilton R.M., Chiu C., Gow R.M., Williams W.G. A comparison of two-stab on unipolar epicardial pacing leads in children. PACE 1997;20:631-636.
6. Huhta J.C., Maloney J.D., Ritter D.G., Ilstrup D.M., Feldt R.H. Complete atrioventricular block in patients with atrioventricular discordance. Circulation 1983;67:1374-1377.[Abstract/Free Full Text]
7. Johns J.A., Fish F.A., Burger J.D., et al. Steroid-eluting epicardial pacing leads in pediatric patients. Encouraging early results. J Am Coll Cardiol 1992;20:395-401.[Abstract]
8. Cutler N.G., Karpawich P.P., Cavitt D., Hakimi M., Walters H.L. Steroid-eluting epicardial pacing electrodes: six year experience of pacing thresholds in a growing pediatric population. PACE 1997;20:2943-2948.
9. de Voogt W.G. Pacemaker leads: performance and progress. Am J Cardiol 1999;83:187-191.[Medline]
10. Moss A.J., Zareba W., Hall W.J., et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med 2002;346:877-883.[Abstract/Free Full Text]
11. Maron B.J., Shen W.K., Link M.S., et al. Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy. N Engl J Med 2000;342:365-373.[Abstract/Free Full Text]
12. ACC/AHA/NASPE 2002 Guideline update for implantation of cardiac pacemakers and antiarrhythmia devices. Circulation 2002;106:2145-2161.[Free Full Text]
13. Cohen M.I., Bush D.M., Gaynor J.W., Vetter V.L., Tanel R.E., Rhodes L.A. Pediatric pacemaker infections: twenty years of experience. J Thorac Cardiovasc Surg 2002;124:821-827.[Abstract/Free Full Text]

This article has been cited by other articles:

				L. A. Bockeria, A. Sh. Revishvili, and O. Y. Grygoryev eComment: Re: Intra-diaphragmatic pacemaker implantation in very low weight premature neonate Interactive CardioVascular and Thoracic Surgery, October 1, 2009; 9(4): 744 - 745. [Full Text] [PDF]

				A. E. Epstein, J. P. DiMarco, K. A. Ellenbogen, N.A. M. Estes III, R. A. Freedman, L. S. Gettes, A. M. Gillinov, G. Gregoratos, S. C. Hammill, D. L. Hayes, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) Developed in Collaboration With the American Association for Thoracic Surgery and Society of Thoracic Surgeons J. Am. Coll. Cardiol., May 27, 2008; 51(21): e1 - e62. [Full Text] [PDF]

				Writing Committee Members, A. E. Epstein, J. P. DiMarco, K. A. Ellenbogen, N.A. M. Estes III, R. A. Freedman, L. S. Gettes, A. M. Gillinov, G. Gregoratos, S. C. Hammill, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices): Developed in Collaboration With the American Association for Thoracic Surgery and Society of Thoracic Surgeons Circulation, May 27, 2008; 117(21): e350 - e408. [Full Text] [PDF]

				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]

				F. Bakhtiary, O. Dzemali, C. K. Bastanier, A. Moritz, and P. Kleine Medium-term follow-up and modes of failure following epicardial pacemaker implantation in young children Europace, February 1, 2007; 9(2): 94 - 97. [Abstract] [Full Text] [PDF]

				A. Dodge-Khatami, M. Rahn, R. Pretre, and U. Bauersfeld Dual Chamber Epicardial Pacing for the Failing Atriopulmonary Fontan Patient Ann. Thorac. Surg., October 1, 2005; 80(4): 1440 - 1444. [Abstract] [Full Text] [PDF]

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): Larry A. Rhodes Thomas L. Spray J. William Gaynor Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cohen, M. I. Articles by Gaynor, J. W. Search for Related Content PubMed PubMed Citation Articles by Cohen, M. I. Articles by Gaynor, J. W. Related Collections Electrophysiology - arrhythmias