Early Postoperative Arrhythmias After Cardiac Operation in Children

Early Postoperative Arrhythmias After Cardiac Operation in Children Emanuela Valsangiacomo, MD, Edith R. Schmid, MD, Rolf W. Schüpbach, MD, Daniel Schmidlin, MD, Luciano Molinari, PhD, Katharina Waldvogel, MD, and Urs Bauersfeld, MD Department of Pediatrics, University Children s Hospital Zurich, and Division of Cardiovascular Anesthesia, Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland Background. Arrhythmias are a recognized complication of cardiac operations. However, little is known about the incidence, treatment, and risk factors for early postoperative arrhythmias in children after cardiac operations. Methods. Diagnosis and treatment of early postoperative arrhythmias were prospectively analyzed in an intensive care unit in 100 consecutive children with a median age of 17 months (range, 1 day to 191 months) who had undergone cardiac operation. Patients were grouped in three different categories of surgical complexity. Results. During a median postoperative time of 1 day (range, 0 to 15 days), 64 critical arrhythmias occurred in 48 patients. Arrhythmias consisted of sinus bradycardia in 30, atrioventricular block II to III in 7, supraventricular tachyarrhythmias in 14, and premature complexes in 13 instances. Treatment of 52 arrhythmias was successful and included pacing in 41, intravenous amiodarone in 8, body cooling in 5, overdrive pacing in 3, and electrolyte correction in 2 cases, with more than one treatment modality in 8 cases. Risk factors for arrhythmias were lower body weight (p < 0.05), longer cardiopulmonary bypass duration (p < 0.05), and a category of higher surgical complexity (p < 0.001). Conclusions. Early postoperative arrhythmias occur frequently after cardiac operations in children. Sinus bradycardia, atrioventricular block II to III, and supraventricular tachyarrhythmias are the most frequent arrhythmias, which, however, can be treated effectively by means of temporary pacing, cooling, and antiarrhythmic drug therapy. Lower body weight, longer cardiopulmonary bypass duration, and a higher surgical complexity are risk factors for early postoperative arrhythmias. (Ann Thorac Surg 2002;74:792 6) 2002 by The Society of Thoracic Surgeons Accepted for publication May 13, 2002. Address reprint requests to Dr Bauersfeld, University Children s Hospital Zurich, Steinwiesstrasse 75, CH-8032 Zurich, Switzerland; e-mail: bauersfe@kispi.unizh.ch. Postoperative arrhythmias are a known complication after open heart operation for congenital heart disease [1]. Many reports have been published about arrhythmias as late complication after cardiac operations such as the Mustard or Senning operation for transposition of the great arteries, Fontan procedures, or tetralogy of Fallot repair [2 5]. However, data concerning rhythm disturbances in the immediate postoperative period after open heart operation in children are scarce [1, 6]. Factors that may cause or increase the risk of postoperative arrhythmias are preexisting myocardial compromise by the cardiac defect, complex operation with extensive scars and suture lines, consequences of myocardial ischemia, postoperative electrolyte disturbances, and an increased adrenergic tone or catecholamine stimulation [7]. Arrhythmias that may be tolerated in a normal heart can be a major cause of morbidity and mortality after cardiac operation for congenital heart disease [7]. The aims of this prospective study were to assess the incidence of early postoperative arrhythmias after cardiac operation in a pediatric population, to describe their management, and to analyze possible risk factors. Patients and Methods Patients Between November 1998 and January 2000, 108 consecutive patients with a congenital heart defect underwent open heart operation with cardiopulmonary bypass (CPB) at the University Hospital Zurich. There were 8 perioperative deaths (7%), none related to arrhythmias; these patients were not enrolled in the study. Thus, 100 patients were evaluated prospectively during the entire stay in the intensive care unit (ICU), ie, from postoperative admission to discharge from the ICU. For risk factor analysis, surgical procedures were classified as published previously into three categories of different operative complexity: low, moderate, and high (Table 1) [8]. The study was approved by the ethical committee of the University Children s Hospital Zurich. Electrocardiographic Monitoring Standard electrocardiograms (ECGs) were registered in all patients at the time of ICU admission. Continuous 2002 by The Society of Thoracic Surgeons 0003-4975/02/$22.00 Published by Elsevier Science Inc PII S0003-4975(02)03786-4

Ann Thorac Surg VALSANGIACOMO ET AL 2002;74:792 6 ARRHYTHMIAS AFTER CARDIAC OPERATION 793 Table 1. Surgical Procedures and Categories of Surgical Complexity Surgical Procedures Patients (n 100) Category I (low complexity) 19 Atrial septal defect closure 16 PDA ligation 0 Blalock Taussig shunt 0 Aortic coarctation repair 2 Aortopulmonary window 1 Category II (moderate complexity) 46 Ventricular septal defect closure 9 ASD VSD 3 Partial AVSD repair 3 Modified Glenn shunt 4 Partial abnormal pulmonary 4 venous connection Right ventricular outflow tract 12 augmentation Pulmonary artery augmentation 1 Aortopulmonary shunt with CPB 2 Mitral valve reconstruction or 0 replacement Tricuspid valve reconstruction 1 Conduit replacement 1 Resection of subaortic stenosis 5 Reimplantation left coronary artery 1 in aorta Category III (high complexity) 35 Arterial switch 8 Fontan procedure 1 Ross procedure 2 Repair with homograft 10 implantation Total AVSD repair 9 Truncus arteriosus repair 0 Interrupted aortic arch repair 1 Total abnormal pulmonary venous 4 connection ASD atrial septal defect; AVSD atrioventricular septal defect; CPB cardiopulmonary bypass; PDA patent ductus arteriosus; VSD ventricular septal defect. ECG monitoring was performed during the entire ICU stay with Marquette Hellige SMU 612, Hellige SMV 110 TP, or Marquette Solar 8000 monitors (Marquette- Hellige, Marquette, WI). These monitoring systems did not provide storage and retrospective printing of the monitored ECG. When an arrhythmia was detected on the ECG monitor, this was also documented with standard ECG. If standard ECG failed to provide adequate diagnostic information, an atrial ECG was recorded using the implanted temporary atrial pacing wires. Arrhythmia Definitions Sinus bradycardia, frequent premature atrial or ventricular complexes, atrioventricular (AV) blocks, and supraventricular and ventricular tachycardias were considered critical arrhythmias. Sinus bradycardia was defined as an inadequate sinus rate for the age and hemodynamic condition of the patient or as a junctional escape rhythm in the absence of AV block or junctional ectopic tachycardia. As estimated normal heart rates are not applicable to children with cardiac dysfunction and in the postoperative state, higher sinus rates than normal were defined as adequate for the postoperative patients [9]. A minimal sinus rate of 120 beats/min in children younger than 2 years of age, and sinus rate of 100 beats/min in children older than 2 years of age were defined as adequate. Premature atrial or ventricular complexes were defined as frequent if occurring more often than 1 per minute [9, 10]. Arrhythmia Management INDICATIONS. Indications for treatment were sinus bradycardia, the presence of second-degree or third-degree AV block, and sustained supraventricular or ventricular tachycardias. Frequent premature atrial or ventricular complexes were treated in case of hemodynamic impairment. Hemodynamic impairment was defined as deterioration of one or more of the following variables: mean arterial blood pressure, mixed venous saturation, central venous pressure, or occurrence of acidosis. TREATMENT. As potential causes of arrhythmias, electrolyte disturbances or adverse hemodynamic conditions were ruled out and corrected, if possible. Patients with sinus bradycardia and AV block were treated by pacing using the temporary stainless-steel wire electrodes, routinely sutured on the epicardium of the right atrium and the right ventricle at the end of the operation. Termination of supraventricular reentry tachycardia was attempted with atrial overdrive pacing by using atrial stimulation protocols published previously [11]. Automatic tachycardias were treated primarily with body surface cooling to a rectal temperature of 32 C to 34 C using a cooling blanket, with the patient sedated and mechanically ventilated [12, 13]. Amiodarone was our drug of choice for the treatment of ventricular and supraventricular tachycardias resistant to overdrive pacing and automatic tachycardias unresponsive to cooling. Amiodarone was chosen on the basis of its well-documented antiarrhythmic potency, limited hemodynamic side effects, and good tolerance in children [11, 14]. Amiodarone was started with a loading dose of 5 mg/kg intravenously for 1 hour and continued with a continuous infusion at 10 to 15 g/kg per minute. The oral administration was started with a 1-day to 2-day overlap with intravenous therapy [11]. Statistical Analysis Descriptive statistics are reported as median value and range. 2 analysis and logistic regression models were used for the determination of independent risk factors for arrhythmias. A p value of less than 0.05 was considered statistically significant. Categories of surgical complexity, CPB duration, weight, and use of catecholamines were

794 VALSANGIACOMO ET AL Ann Thorac Surg ARRHYTHMIAS AFTER CARDIAC OPERATION 2002;74:792 6 Table 2. Patient Characteristics and Perioperative Details a Characteristic Surgical Categories I II III Total Patients (n 100) 19 46 35 100 Age (mo) 79 (7 191) 18.5 (0.25 187) 6 (0 183) 17 (0 191) Weight (kg) 22.5 (6.8 65.3) 9.3 (3.6 55.4) 5.5 (2.2 48.5) 9 (2.2 65.3) Results CPB time (min) 52 (3.6 55.4) 80 (11 506) 118.5 (58 337) 87 (11 506) ICU stay (days) 3 (2 14) 6 (2 44) 11 (3 395) 7 (2 395) Catecholamine 6 (32%) 28 (61%) 32 (91%) 66% Arrhythmia 3 (16%) 20 (43%) 25 (71%) 48% Pacing 2 (10%) 19 (41%) 25 (71%) 46% a Data reported as median value and range or absolute number and percentage of patients. CPB cardiopulmonary bypass; ICU intensive care unit. analyzed as potential risk factors for postoperative arrhythmias. Results The patient characteristics and the perioperative data of the different surgical categories are summarized in Table 2. Table 3. Diagnosis and Frequency of Arrhythmias Diagnosis (n 64) a Patients Frequency (n 48/100) a (%) Sinus bradycardia with junctional 30 46 escape 7 Premature complexes 13 20 Atrial 9 Ventricular 4 Supraventricular tachycardia 9 15 AV block 7 11 AV block II 1 AV block III 6 Junctional ectopic tachycardia 5 8 a More than 1 arrhythmia occurred in some patients. Arrhythmias Sixty-four arrhythmias were observed in 48 patients during a median observation time in the ICU of 7 days (range, 2 to 395 days). The time of arrhythmia occurrence ranged from the same day of operation to 15 days after operation, with a median time of 1 day. Thirteen patients experienced two different types of arrhythmias, and four different arrhythmias were observed in 1 patient. Hemodynamic impairment was observed in 48 of 64 arrhythmias (75%). However, arrhythmias never represented life-threatening events, nor were they the cause of death in any patient. The diagnosis and frequency of arrhythmias are listed in Table 3. Supraventricular tachycardias consisted of intraatrial reentry tachycardias in 3 children, inappropriate sinus tachycardia in 1, ectopic atrial tachycardia in 2, and AV-reentry tachycardia in 1 patient. In 2 patients with supraventricular tachycardia we failed to make a more exact diagnosis as the tachycardia converted spontaneously before an ECG could be obtained. Ventricular arrhythmias were limited to isolated ventricular premature beats. We did not observe any ventricular tachycardia. All AV blocks II and III were transient in the 7 patients in whom they occurred, and no permanent pacemaker had to be implanted. Treatment Fifty-two arrhythmias, corresponding to 81% of all arrhythmias, were treated. Applied therapies for arrhythmias are summarized in Table 4. Combined treatment regimens were used in 8 patients. Pacing was performed in 57% of all observed arrhythmias and was therefore the most used therapy. Temporary pacing was performed during a median period of 5 days (range, 1 to 27 days). The most common indication for temporary pacing was sinus bradycardia. Pacing was used for suppression of premature beats in 2 patients with premature atrial complexes in bigeminy. In another case, pacing was required for sinus bradycardia caused by drug therapy with amiodarone used to convert an atrial ectopic tachycardia. Atrial overdrive pacing was successfully used for conversion of intraatrial reentry tachycardia in 3 cases. Table 4. Arrhythmia Therapies Therapy Applications a None 12 Pacing 41 Amiodarone 7 Surface cooling 6 Overdrive pacing 3 Electrolyte correction 2 a More than one therapy was used in 7 patients.

Ann Thorac Surg VALSANGIACOMO ET AL 2002;74:792 6 ARRHYTHMIAS AFTER CARDIAC OPERATION 795 Cardioversion and defibrillation were not necessary in any case. Body surface cooling was applied in 6 patients, including 2 with junctional ectopic tachycardia, 1 with atrial ectopic tachycardia, 1 with AV-reentry tachycardia, 1 with inappropriate sinus tachycardia, and 1 with intraatrial reentry tachycardia. Arrhythmia could be controlled with cooling alone in 3 cases of AV-reentry tachycardia, junctional ectopic tachycardia, and sinus tachycardia. Antiarrhythmic drug therapy with amiodarone was used in 7 patients, including junctional ectopic tachycardia in 3, atrial ectopic tachycardia in 2, and intraatrial reentry tachycardia in 1. Amiodarone was effective in 6 cases. In spite of drug therapy, the patient with intraatrial reentry tachycardia could be converted only with repeated overdrive pacing. Intravenous amiodarone was administered during a median period of 5 days (range, 3 to 14 days). All 3 patients with junctional ectopic tachycardia received amiodarone only transiently, whereas therapy was continued in oral form for further prophylaxis in the other patients. We did not observe any short-term adverse effects attributable to intravenous amiodarone such as hypotension during drug loading or proarrhythmic effects. No changes were seen in liver or thyroid laboratory values. Combined antiarrhythmic therapy was used in 7 patients. Body surface cooling and amiodarone were used in 1 case with junctional ectopic tachycardia, 1 with ectopic atrial tachycardia, and 1 with intraatrial reentry tachycardia. However, this last arrhythmia was finally converted by overdrive pacing. Overdrive pacing had to be performed additionally to drug therapy with amiodarone in another case with intraatrial reentry tachycardia. Antibradycardia pacing was applied after amiodarone therapy in the treatment of an ectopic atrial rhythm and together with body cooling in the treatment of 1 patient with junctional ectopic tachycardia. Finally, isoproterenol was given to a patient with sinus bradycardia, because of dysfunction of the pacing wires that were being used for 19 days. Risk Factor Analysis Independent risk factors for early postoperative arrhythmias were lower body weight (p 0.05), prolonged CPB duration (p 0.05), and a surgical category of high operative complexity (p 0.001). Long CPB duration was found to be a risk factor for arrhythmias in the overall group of patients studied and in the patient group with moderate operative risk. In contrast, differences in CPB duration were not significant in the group with surgical procedures of low complexity and generally short CPB duration, and in the group with surgical interventions of high complexity and long CPB duration. Comment A large number of studies have been written about late-onset arrhythmias after cardiac operation [1 5]. Some other authors have focused their interest on the immediate postoperative period for specific cardiac defects or specific arrhythmias and treatments [6, 15 22]. This study presents data regarding the incidence of arrhythmias, their course, and the performed treatment during the ICU stay in a pediatric population after cardiac operation. Our assessment was intentionally not focused on specific lesions to provide broader information about the overall spectrum of rhythm disturbances potentially encountered by the pediatric cardiologist, cardiac surgeon, and critical care specialist in the immediate postoperative period. Our results demonstrate that arrhythmias are a frequent early complication after open heart operation for congenital heart disease, despite the advances in surgical and CPB techniques as well as myocardial preservation. We observed an overall arrhythmia incidence of 48%, similar to the frequencies reported by other authors [6, 23, 24]. This high incidence, occurring in spite of all surgical technical improvements, can be explained by performance of more-complex surgical procedures in increasingly younger patients. The fact that we found lower body weight, long duration of CPB, and highcomplexity surgical procedures to be risk factors for arrhythmias supports this explanation. Pathophysiologic causes for early postoperative arrhythmias are various, including direct surgical injuries like myocardial incision, results of cannulation, sutures close to the conduction system, and acute changes of the intracardiac pressure caused by volume and pressure overload [1, 7]. Furthermore CPB with ischemia reperfusion and the related cellular biochemical effects as well as medical interventions such as electrolyte shifts and catecholamine administration may affect the stability of the cellular membrane and result in an increased myocardial irritability and automaticity [12, 13]. The degree of myocardial damage and the possibly associated risk for arrhythmia can be demonstrated by measuring myocardial metabolites like troponin I [25]. All arrhythmias we observed in this study were transient, and their adverse hemodynamic effects could be limited with the therapies used. Thus no life-threatening episodes or death were related to postoperative arrhythmias. By this means, the increased quality of the postoperative intensive care enables early recognition and immediate treatment of potentially lethal rhythm disturbances. Among all treatments, temporary pacing and drug therapy with amiodarone were the most frequently used. Temporary pacing is crucial as a therapy as well as a diagnostic tool in cases of complex arrhythmias [19]. Regarding drug therapy, this study confirms the efficacy, safety, and absence of negative inotropic effects of amiodarone compared with class I antiarrhythmic agents [14, 21, 22]. The size of the population studied was limited to 100 patients. Nevertheless, statistical rules of thumb suggest that in a sample size of 100 subjects, four covariates can certainly be analyzed with sufficient reliability. Thus, from our data, lower body weight, long duration of CPB, and complex operation can be considered to be risk factors for developing arrhythmia soon after operation.

796 VALSANGIACOMO ET AL Ann Thorac Surg ARRHYTHMIAS AFTER CARDIAC OPERATION 2002;74:792 6 In conclusion, early postoperative arrhythmias are still a frequent complication after cardiac operation in children. However, aggressive and expeditious management can reduce morbidity and mortality. Particularly temporary pacing and drug therapy with amiodarone are effective and safe treatments for early postoperative arrhythmias. References 1. Krongrad E. Postoperative arrhythmias in patients with congenital heart disease. Chest 1984;85:107 13. 2. Garson A. Chronic postoperative arrhythmias. In: Gillette PC, Garson A, eds. Pediatric arrhythmias: electrophysiology and pacing. Philadelphia: WB Saunders, 1990:667 78. 3. Deanfield J, Camm J, Macartney F, et al. Arrhythmia and late mortality after Mustard and Senning operation for transposition of the great arteries. An eight-year prospective study. J Thorac Cardiovasc Surg 1988;96:569 76. 4. Gelatt M, Hamilton RM, McCrindle BW. Risk factors for atrial tachyarrhythmias after the Fontan operation. J Am Coll Cardiol 1994;24:1735 41. 5. Vaksmann G, Fornier A, Davignon A, Ducharme G, Houyel L, Fouron JC. Frequency and prognosis of arrhythmias after operative correction of tetralogy of Fallot. Am J Cardiol 1990; 66:346 9. 6. Kürer C, Tanner C, Norwood W, Vetter V. Perioperative arrhythmias after Fontan repair. Circulation 1990;82(Suppl 4):190 4. 7. Herzog L, Lynch C. Arrhythmias accompanying cardiac surgery. In: Lynch C III, ed. Clinical cardiac electrophysiology. Philadelphia: JB Lippincott, 1994:231 58. 8. Manno CS, Hedberg KW, Kim HC, et al. Comparison of the hemostatic effects of fresh whole blood, stored whole blood and components after open heart surgery in children. Blood 1991;5:930 6. 9. Lawrence JH III, Kanter RJ, Wetzel RC. Pediatric arrhythmias. In: Nichols DG, Cameron DE, Greeley WJ, Lappe DG, Ungerleider RM, Wetzel RC, eds. Critical heart disease in infants and children. St. Louis: Mosby-Year Book, 1995: 221 32. 10. Garson A Jr. Arrhythmias and sudden death. In: Gillette PC, Garson A Jr, eds. Clinical pediatric arrhythmias. Philadelphia: WB Saunders, 1999:287 92. 11. Bauersfeld U, Pfammatter JP, Jaeggi E. Treatment of supraventricular tachycardias in the new millennium drugs or radiofrequency ablation? Eur J Pediatr 2001;160:1 9. 12. Balaji S, Sullivan I, Deanfield J, James I. Moderate hypothermia in the management of resistant automatic tachycardias in children. Br Heart J 1991;66:221 4. 13. Pfammatter JP, Paul T, Ziemer G, Kallfelz HC. Successful management of junctional tachycardia by hypothermia after cardiac operations in infants. Ann Thorac Surg 1995;60: 556 60. 14. Perry JC, Fenrich AL, Hulse JE, Triedman JK, Friedman RA, Lamberti JJ. Pediatric use of intravenous amiodarone: efficacy and safety in critically ill patients from a multicenter protocol. J Am Coll Cardiol 1996;27:1246 50. 15. Drago F, Turchetta A, Calzolari A, et al. Early identification of patients at risk for sinus node dysfunction after Mustard operation. Int J Cardiol 1992;35:27 32. 16. Weindling SN, Saul JP, Gamble WJ, Mayer JE, Wessel D, Walsh EP. Duration of complete atrioventricular block after congenital heart disease surgery. Am J Cardiol 1998;82:525 7. 17. Bonatti V, Agnetti A, Squarcia U. Early and late postoperative complete heart block in pediatric patients submitted to open heart surgery for congenital heart disease. Med Surg Pediatr 1998;20:181 6. 18. Walsh EP, Saul JP, Sholler GF, et al. Evaluation of a staged treatment protocol for rapid automatic junctional tachycardia after operation for congenital heart disease. J Am Coll Cardiol 1997;29:1046 53. 19. Yabek SM, Bechara F, Berman W, Neal JF, Dillon T. Use of atrial epicardial electrodes to diagnose and treat postoperative arrhythmias in children. Am J Cardiol 1980;46:285 9. 20. Takeda M, Furuse A, Kotsuka Y. Use of temporary atrial pacing in management of patients after cardiac surgery. Cardiovasc Surg 1996;4:623 7. 21. Figa FH, Gow RM, Hamilton RM, Freedom RM. Clinical efficacy and safety of intravenous amiodarone in infants and children. Am J Cardiol 1994;74:573 7. 22. Raja P, Hawker RE, Chaikitpinyo A, et al. Amiodarone management of junctional ectopic tachycardia after cardiac surgery in children. Br Heart J 1994;72:261 5. 23. Zhang N. Management of postoperative arrhythmia after open heart surgery in complex congenital heart disease. Chin J Cardiol 1991;19:91 3. 24. Hoffman TM, Wernovsky G, Wieand TS, et al. Predictors of arrhythmias in a pediatric cardiac intensive care unit. J Am Coll Cardiol 1999;33(Suppl A):539A. 25. Immer FF, Stocker F, Seiler AM, et al. Troponin-I for prediction of early postoperative course after pediatric cardiac surgery. J Am Coll Cardiol 1999;33:1719 23.