Determining the Utility of Temporary Pacing Wires After Coronary ...

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Determining the Utility of Temporary Pacing Wires After Coronary Artery Bypass Surgery Brian T. Bethea, MD, Jorge D. Salazar, MD, Maura A. Grega, MSN, John R. Doty, MD, Torin P. Fitton, MD, Diane E. Alejo, BA, Louis M. Borowicz, Jr, MS, Vincent L. Gott, MD, Marc S. Sussman, MD, and William A. Baumgartner, MD Division of Cardiac Surgery, The Johns Hopkins Medical Institution, Baltimore, Maryland

Background. Temporary epicardial pacing wires are used routinely after coronary artery bypass graft (CABG) surgery and can cause rare, catastrophic complications. This study’s purpose was to identify patient characteristics predicting the need for pacing after CABG surgery with the potential to limit their utilization. Methods. This prospective observational study involved 290 consecutive patients undergoing CABG at our institution from August 2000 to January 2001. Sixty-eight patients were excluded for the following reasons: offpump CABG, preoperative pacemaker, no pacing wire placement, or incomplete follow-up. Among the remaining 222 patients, the incidence of pacing during the postoperative period was recorded. Univariate and independent multivariate predictors for postoperative pacing were determined using medical records, the Johns Hopkins Hospital cardiac surgery database and the Society of Thoracic Surgery database. Results. In the postoperative period, 19 of 222 patients

(8.6%) required pacing. Univariate analysis identified age, cardiomegaly, preoperative antiarrhythmic therapy, diabetes mellitus, preoperative arrhythmia, inotropic agents leaving the operating room, and pacing initialized at the separation from cardiopulmonary bypass as predictors of the need for postoperative pacing. Only diabetes mellitus, preoperative arrhythmia, and pacing utilized to separate from bypass were found to be significant on multivariate analysis. Using this model, if we exclude the patients with any of these three risk factors, only 2.6% of them would have required pacing. Conclusions. Few patients require temporary epicardial pacing after routine CABG. This study identified specific predictors for postoperative pacing requirements and provides criteria for the selective use of epicardial pacing wires after CABG.

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scribed such as retained pacing wires presenting as a bronchial foreign body [7]. Finally, patients may experience a delay in discharge awaiting wire removal, especially in the anticoagulated patient. Given these rare but significant complications, the aim of this study was to provide data identifying patient characteristics that could predict the need for pacing after routine coronary artery bypass grafting (CABG) with the potential to limit their utilization.

emporary epicardial pacing wires are routinely placed in patients undergoing cardiac surgery. In the early postoperative period, patients may suffer from hemodynamically significant arrhythmias and temporary pacing may be required to optimize cardiac function [1]. Pacing wires have been used for atrial or ventricular as well as atrioventricular pacing for bradyarrhythmias and to suppress both atrial and ventricular tachyarrhythmias [2, 3]. While temporary pacing wires are commonly used in most centers, they are associated with rare, and in some cases, catastrophic complications. The most common complication of temporary pacing wires is failure of atrioventricular sensing or capture [4]. More importantly, removal of pacing wires has been associated with injuries to saphenous vein grafts and atrial and ventricular lacerations, resulting in hemorrhage and cardiac tamponade [5, 6]. More unusual complications have been deAccepted for publication June 25, 2004. Presented at the Poster Session of the Fiftieth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 13–15, 2003. Address reprint requests to Dr Baumgartner, 618 Blalock Bldg, The Johns Hopkins Hospital, 600 North Wolfe St, Baltimore, MD 21287; e-mail: [email protected].

© 2005 by The Society of Thoracic Surgeons Published by Elsevier Inc

(Ann Thorac Surg 2005;79:104 –7) © 2005 by The Society of Thoracic Surgeons

Patients and Methods Patient Selection All patients undergoing isolated CABG surgery during a 6-month period from August 2000 through January 2001 were included in the data set. The Johns Hopkins Hospital Institutional Review Board approved the data collection. All patients were observed prospectively during their hospital stay. Patients having CABG were identified in the perioperative period. A total of 290 consecutive patients underwent isolated coronary artery bypass during the 6-month period of this study. Sixty-eight patients were excluded: 40 patients did not receive pacing wires, 18 patients had off-pump coronary artery bypass grafting, 0003-4975/05/$30.00 doi:10.1016/j.athoracsur.2004.06.087

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Table 1. Univariate Analysis of All Variables Examined Variable Demographics Mean age in years Male Medical History Diabetes mellitus Preoperative antiarrhythmicsa Cardiomegaly History of arrhythmias Stroke Carotid bruit Hypertension Pulmonary hypertension Chronic obstructive pulmonary disease Peripheral vascular disease Hypercholesterolemia Renal failure Cerebrovascular disease Myocardial infarction Thyroid disease Preoperative Beta blockers Mean Ejection fraction percentage PTCA Left Main disease ⬎50% LAD disease PDA disease Smoking history Current smoking Angina NYHA class I and II III IV Intraoperative Inotropes leaving the OR Pacing required to come off CPB Mean cardiopulmonary bypass time in min Mean aortic cross clamp time in min Intra-aortic balloon pump used Cardioversion required in OR Antiarrhythmics leaving the OR Prior to discharge outcomes In-hospital mortality Mean postoperative length of stay in days Stroke New onset atrial fibrillation Perioperative myocardial infarction a

No pacing required n ⫽ 203

Pacing required n ⫽ 19

p-value

64.2 ⫾ 10.8 92%

72.5 ⫾ 6.6 8%

0.0001

26.1% 2.0% 4.4% 13.3% 5.9% 12.0% 65.5% 5.4% 6.9% 16.3% 65.0% 6.4% 9.4% 60.1% 5.9% 62.1% 48.9 ⫾ 14.4 18.7% 8.9% 97.5% 40.9% 64.5% 14.8% 90.6% 12.3% 42.4% (mean EF ⫽ 49%) 44.3% (mean EF ⫽ 49%)

47.4% 15.8% 36.8% 57.9% 5.3% 21.1% 68.4% 10.5% 15.8% 26.3% 52.6% 15.8% 5.3% 68.4% 15.8% 47.4% 44.3 ⫾ 16.3 26.3% 5.3% 100% 57.9% 57.9% 15.8% 78.9% 0 52.6% (mean EF ⫽ 48%) 47.4% (mean EF ⫽ 40%)

0.04 0.015 0.0001 0.0001

63.5% 12.3% 101.5 ⫾ 29 70.6 ⫾ 23 6.4% 27.6% 3.0% 0.5% 6.7 ⫾ 8.2 1.5% 28% 1%

89.5% 44.4% 108.7 ⫾ 31 74.0 ⫾ 27 15.8% 21.1% 10.5% 10.5% 11.1 ⫾ 10.5 10.5% 21% 0

0.01 0.002

0.02 0.03

Antiarrhythmic drugs included amiodarone and digoxin.

CPB ⫽ cardiopulmonary bypass; LAD ⫽ left anterior descending artery; OR ⫽ operating room; ⫽ percutaneous transluminal coronary angioplasty; ⫾ indicates standard deviations.

9 patients had incomplete data, and 1 patient had a permanent pacemaker preoperatively. The Society of Thoracic Surgery (STS) database, the Johns Hopkins cardiac surgery database, and medical records were used

PDA ⫽ posterior descending artery;

PTCA

to compile the data. Postoperative complications were monitored for all patients while hospitalized. Patient information was obtained using the definitions as set forth by the STS database and the Johns Hopkins

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cardiac surgery database guidelines. A preoperative arrhythmia was defined as a bundle branch heart block, atrioventricular heart block, or atrial fibrillation. Preoperative sinus bradycardia was not considered to be a preoperative arrhythmia because many patients (61%) were taking beta blockers preoperatively. A preoperative 12-lead electrocardiogram was used to identify conduction problems. Preoperative myocardial infarction (MI) was defined as a history of MI and an acute or evolving MI was analyzed separately. Patients requiring temporary pacing in the postoperative period were included if either atrial, ventricular, or bichamber pacing was used leaving the operating room or in the immediate postoperative period.

Operative Procedures All patients underwent median sternotomy. Cardiopulmonary bypass was carried out using nonpulsatile flow to achieve a mean arterial pressure of 60 to 80 mm Hg. Moderate systemic hypothermia (28°C to 32°C), continuous topical cardiac hypothermia and antegrade crystalloid cardioplegia were used. At this institution, most patients receive only ventricular wires that are placed on the anterior or diaphragmatic surfaces of the right ventricle. Atrial wires are additionally placed when hemodynamic instability occurs after separation from cardiopulmonary bypass. Postoperatively, it is our clinical practice that patients are evaluated on an individual basis to determine if pacing is required. This may include significant bradycardia and associated hemodynamic instability. In addition, our anesthetic protocol is to start patients on epinephrine (0.05 mg · kg⫺1 · min⫺1) toward the end of cardiopulmonary bypass unless contraindicated or unless clinical judgment indicates a higher dose or additional inotropic agents are required. Our protocol focuses on a balanced approach (adequate preload, modest inotropic support, and optimal afterload) to maximize cardiac output.

Statistical Methods The univariate and multivariate regression analyses were made using the SPSS statistical software. Dichotomous variables were expressed as percentages, and continuous variables were expressed as the mean. For univariate analysis, ␹2 was used for dichotomous variables and the Student t test or the Mann-Whitney test (for nonnormally distributed data) was used for continuous variables. Factors significant at the univariate level were then entered into the multiple regression analysis. Variables with p values equal to or less than 0.05 were considered significant.

Results The data for the 222 patients who had pacing wires is summarized in Table 1. The patient population had a mean age of 64.9 (⫾11) years; and mean cardiopulmonary bypass time was 102.2 (⫾29) minutes. The patients were followed up for an average of 7.4 (⫾9.9) days (length of


Table 2. Multivariate Analysis of Variables Variables Analyzed History of arrhythmias Pacing required to come off CPB Diabetes mellitus Cardiomegaly Preoperative antiarrhythmics Inotropes leaving the OR Mean age CPB ⫽ cardiopulmonary bypass;

p value

Odds Ratio

0.001 0.01 0.04 0.44 0.13 0.14 0.06

8.7 4.7 3.7 1.8 4.8 3.9 1.0

OR ⫽ operating room.

hospital stay). Mean postoperative length of stay for the paced and nonpaced groups was 11.1 (⫾10.5) days and 6.7 (⫾3.3) days, respectively. In the immediate postoperative period, 19 of 222 patients (8.6%) required pacing. The indications for pacing included postoperative sinus bradycardia in 6, atrioventicular block in 4, atrial fibrillation in 3, bundle branch block in 3, cardiac arrest in 1, and not documented in 2 cases. Of the 19 patients who were paced in the postoperative setting, only 2 required a permanent implantable dual chamber pacemaker. One patient had persistent complete heart block; the second sustained asystole at the completion of cardiopulmonary bypass. There were 2 deaths in the early postoperative period in the paced group. One patient died of embolic brain stem infarct and the other died of multiorgan system failure. There was only 1 death in the 203 nonpaced patients. This patient died of overwhelming sepsis and multiorgan system failure in the late postoperative period. Univariate analysis identified preoperative arrhythmia, preoperative antiarrhythmic therapy, diabetes mellitus, age, cardiomegaly, pacing utilized at separation from bypass, and use of inotropic agents leaving the operating room as factors related to postoperative pacing. The multivariate analysis, shown in Table 2, identified three risk factors that were significantly associated with pacing. The odds ratio was 8.7 for preoperative arrhythmia, 4.7 for pacing utilized at separation from bypass, and 3.7 for diabetes mellitus. Using this model, if we exclude all the patients in our sample without any of the three risk factors (n ⫽ 113), only 2.6% of them would have required pacing.

Comment Currently, most cardiac surgical centers use some standard procedure of temporary postoperative pacing in patients undergoing isolated CABG. Standards of practice vary, however, with some centers using primarily ventricular wires whereas others use both atrial and ventricular wires. Temporary wires have been used in the perioperative period to improve patient hemodynamics as well as to suppress malignant arrhythmias. Most temporary pacing wires are considered to be associated with a low morbidity; however, there have been reported rare catastrophic complications. Given these rare but

significant complications, little research has been done to predict which patient populations are most likely to require the use of temporary pacing in the postoperative setting. The patient population in this study is consistent with a large academic medical institution; with a mean age of 64.9 years and a number of patients with significant comorbidities including diabetes mellitus, hypertension, chronic obstructive pulmonary disease, peripheral vascular disease, renal failure, and cerebrovascular disease. Of note, 68.4% of our patients had a history of a preoperative myocardial infarction and 86.7% were classified as either New York Heart Association heart failure class III or IV. All patients underwent standard isolated coronary artery bypass grafting utilizing cardiopulmonary bypass. In this study, 65.7% of patients in this study received lowdose inotropic support leaving the operating room, and this reflects our standard anesthetic protocol and guidelines for initiating pharmacological support. This practice could have made a difference in the number of patients who required pacing, as inotropic agents which activate ␤-adrenergic receptors will increase chronotrophy and would be predicted to decrease the need for pacing. Of the 19 patients who were paced, only 2 required placement of a permanent pacemaker. The first patient experienced complete heart block before surgery while being treated for hypertension with verapamil. Postoperatively, the patient continued to have hemodynamically significant bradycardia and a permanent pacemaker was placed. The second patient had an episode of asystole at the completion of cardiopulmonary bypass resulting in complete heart block requiring a permanent pacemaker. Both patients have done well otherwise. The remaining 17 patients received temporary pacing for bradycardia, to suppress tachyarrhythmias or to optimize their hemodynamic function while in the intensive care unit. Univariate and multivariate analysis identified specific patient risk factors that were associated with temporary pacing in the perioperative period. Importantly, only preoperative arrhythmia, pacing utilized at separation from bypass, and diabetes mellitus were found to be significant on multivariate analysis. Each of these three clinical entities was associated with significant odds ratios. Of note, there were not any major morbidities or mortalities related to temporary pacing wires in this patient population. There were two mortalities in the


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early postoperative setting; however, they were unrelated to the pacing wires. This study was limited by the small sample size and by the inherent design of observational studies, such that, patients were not randomized to receive pacing wires. This investigation does identify specific patient characteristics associated with postoperative utilization of pacing wires and based on this information, has brought about a change in practice at our institution, with fewer pacing wires being placed in the operating room. Currently, only 63% of isolated CABG patients at our institution receive pacing wires. Few patients require temporary epicardial pacing after standard isolated CABG. This study identified specific predictors associated with postoperative pacing requirements and provides criteria for the selective use of epicardial pacing wires after CABG. By selectively using temporary epicardial pacing wires, patient morbidity can be minimized and at the same time, decrease postoperative length of stay, thus improving institutional cost containment. This study was supported in part by the Mildred and Carmont Blitz Cardiac Research Fund. Doctor Brian Bethea is a Hugh R. Sharp Jr Research Fellow, and Dr Torin Fitton is an Irene Piccinini Investigator. The authors wish to thank Eileen Wright and Barbara Dobbs for their assistance in preparing the manuscript.

References 1. Khalighi K, Mantecon IJ, Tullo NG, et al. Natural history and predictors of temporary epicardial pacemaker wire function in patients after open heart surgery. Chest 1994;106:128. 2. Liebold A, Wahba A, Bimbaum DE, et al. Low-energy cardioversion with epicardial wire electrodes: new treatment of atrial fibrillation after open heart surgery. Circulation 1998; 98:883– 6. 3. De Belder MA, Malik M, Ward DE, et al. Pacing modalities for tachycardia termination. Pacing Clin Electrophysiol 1990;13: 231– 47. 4. Farhad E, Tullo NG, Khalighi K. Natural history and predictors of temporary epicardial pacemaker wire function in patients after open heart surgery. Cardiology 2002;98:175– 80. 5. Del Nido P, Goldman BS. Temporary pacing after open heart surgery: complications and prevention. J Card Surg 1989;4: 99 –103. 6. Gal ThJ, Chaet MS, Novitzky D. Laceration of a saphenous vein graft by an epicardial pacemaker wire. J Card Surg 1998;39:221–2. 7. Gentry WH, Hassan AA. Complications of retained epicardial pacing wires: an unusual bronchial foreign body. Ann Thorac Surg 1993;56:1391–3.

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