Postoperative Junctional Ectopic Tachycardia in Children: Incidence, Risk Factors, and Treatment

Transcription

1 Postoperative Junctional Ectopic Tachycardia in Children: Incidence, Risk Factors, and Treatment Timothy M. Hoffman, MD, David M. Bush, MD, PhD, Gil Wernovsky, MD, Mitchell I. Cohen, MD, Tammy S. Wieand, MS, J. William Gaynor, MD, Thomas L. Spray, MD, and Larry A. Rhodes, MD Divisions of Cardiology and Cardiothoracic Surgery, The Cardiac Center at The Children s Hospital of Philadelphia, and the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Background. Junctional ectopic tachycardia (JET) occurs commonly after pediatric cardiac operation. The cause of JET is thought to be the result of an injury to the conduction system during the procedure and may be perpetuated by hemodynamic disturbances or postoperative electrolyte disturbances, namely hypomagnesemia. The purpose of this study was to determine perioperative risk factors for the development of JET. Methods. Telemetry for each patient admitted to the cardiac intensive care unit from December 1997 through November 1998 for postoperative cardiac surgical care was examined daily for postoperative JET. A nested case-cohort analysis of 33 patients who experienced JET from 594 consecutively monitored patients who underwent cardiac operation was performed. Univariate and multivariate analyses were conducted to determine factors associated with the occurrence of JET. Results. The age range of patients with JET was 1 day to 10.5 years (median, 1.8 months). Univariate analysis revealed that dopamine or milrinone use postoperatively, longer cardiopulmonary bypass times, and younger age were associated with JET. Multivariate modeling elicited that dopamine use postoperatively (odds ratio, 6.2; p 0.01) and age less than 6 months (odds ratio, 4.0; p 0.02) were associated with JET. Only 13 (39%) of the patients with JET received therapeutic interventions. Conclusions. Junctional ectopic tachycardia occurred in 33 (5.6%) of 594 patients who underwent cardiac operation during the study period. Postoperative dopamine use and younger age were associated with JET. It may be speculated that dopamine should be discontinued in the presence of postoperative JET. (Ann Thorac Surg 2002;74: ) 2002 by The Society of Thoracic Surgeons Postoperative arrhythmias occur frequently after cardiac operations in pediatric patients [1]. Junctional ectopic tachycardia (JET) has been commonly observed in the early postoperative period and has been associated with increased risk of morbidity and mortality [2 4]. Several treatment strategies to lower the ventricular rate and reestablish atrioventricular synchrony with atrial pacing have been reported [5 10]. Additionally, a paired ventricular pacing protocol has been used with success [11]. Treatment variations are wide and include hypothermia, amiodarone, propafenone, or a staged therapy approach using a combination of procainamide and cooling [5, 7 10, 12 17]. Studies have implicated the nature of the congenital heart disease and its repair (ventricular septal defect closure, tetralogy of Fallot repair, complete atrioventricular canal repair, and the Fontan operation) as a major contributor to the genesis of JET [3, 18 23]. One recent study associated hypomagnesemia with the occurrence of JET [24]. Despite these studies, the exact cause of JET in any particular patient often remains unknown. The purpose of this study was to ascertain Accepted for publication July 12, Address reprint requests to Dr Hoffman, Columbus Children s Hospital, Division of Cardiology, Room 628ED, 700 Children s Dr, Columbus, OH 43205; thoffman@chi.osu.edu. perioperative factors associated with development of JET in the immediate postoperative period. Material and Methods All patients admitted to the cardiac intensive care unit at The Children s Hospital of Philadelphia from December 1, 1997, through November 30, 1998, were consecutively entered into the study. All patients were followed daily from cardiac intensive care unit admission through hospital discharge. The patient population is a subset of a larger study conducted during the same period of time [1]. All patients were monitored using full-disclosure telemetry (Hewlett Packard, Andover, MA) during their hospitalization until discharge. This system stores the information for 24 hours and allows a beat-by-beat analysis for each patient. All alarms as well as heart rate trends were examined. The recordings were reviewed every 24 hours by one of the investigators, with the final coding of JET being accomplished by an attending electrophysiologist. Junctional ectopic tachycardia was defined as a heart rate greater than 170 beats per minute with the baseline QRS complex, atrioventricular dissociation, and a ventricular rate faster than the atrial rate [17]. In all cases of JET, the diagnosis was confirmed either by 2002 by The Society of Thoracic Surgeons /02/$22.00 Published by Elsevier Science Inc PII S (02)

2 1608 HOFFMAN ET AL Ann Thorac Surg POSTOPERATIVE JUNCTIONAL ECTOPIC TACHYCARDIA IN CHILDREN 2002;74: using more than one lead on the telemetry system or an electrocardiogram or by performing an atrial electrocardiogram if temporary pacing wires were available. Depending on the surgical procedure and intraoperative course, not all patients had temporary atrial wires placed during the study period. A record review was accomplished to determine patient and procedure-related data. The operative note was reviewed to determine the details of the procedure and cardiopulmonary bypass (if used). This study was not designed to determine efficacy of management strategies; however, pharmacologic treatment and pacing strategies for JET in a given patient were recorded. Treatment was determined by the attending physician on the basis of the physiologic status of the patient and the hemodynamic impact of the rhythm disturbance. Patients were treated in light of physiologic signs of low cardiac output that would be manifested by one or more of the following findings: hypotension, oliguria, metabolic acidosis, or poor peripheral perfusion. Each patient who experienced postoperative JET was defined as a case. The postoperative period was defined as up to 60 days after operation or hospital discharge, whichever was the earliest. From the remainder of the cohort, a control was randomly selected for each case (allocation ratio 1:1), using a random number table. The cases and controls were matched on date of cardiac surgical admission. Perioperative variables were examined in a case-control fashion by means of univariate and multivariate analyses to determine associations with the development of JET. These variables are represented in Table 1. A univariate analysis to determine odds ratios was accomplished using a 2 test or Fisher s exact test (for small expected observances) to judge statistical significance. Selected factors found to be significant predictors were modeled using unconditional logistic regression. Odds ratios were again used as the measure of association, with significance judged using the Wald test. In the analysis of electrolytes and inotropic support, only data in the first 72 hours after operation were included and analyzed to ascertain an association with JET. Inotropic support was analyzed as a discrete variable (yes/no) for each drug listed. Results During the study period, 789 admissions (629 patients) to the cardiac intensive care unit occurred. Of these, 594 (75.3%) were for cardiac operations (602 procedures). Cardiopulmonary bypass was used in 482 of the operations. The age range of the total group of postoperative patients is from 1 day to 45.5 years (median, 6.7 months). Thirty-three of the 594 surgical admissions (5.6%) met criteria for the diagnosis of postoperative JET; the age range of these patients was 1 day to 10.5 years (median, 1.8 months). Features of the patients experiencing JET are summarized in Table 2. The incidence of JET for a particular surgical procedure has been previously published [1, 25]. In our cohort, JET was noted in 36.4% of Table 1. Variables Examined for Association With Development of Junctional Ectopic Tachycardia Demographics 1. Age 3. Sex 2. Age 6 mo 4. Syndrome Preoperative anatomy 1. Atrial level anomaly 2. Ventricular level anomaly 7. Non-heterotaxy single ventricle 3. Great vessel anomaly 8. Single ventricle 4. Atrioventricular valve 9. Tetralogy of Fallot and anomaly variants 5. Semilunar valve anomaly 10. Transposition of the 6. Heterotaxy syndrome great arteries and variants Previous operation 1. Prior atrial suture line 3. Previous heart operation 2. Prior ventricular suture line Operation 1. Atrioventricular valve repair 5. Atrial level suture line 2. Ventricular septal defect 6. Ventricular level suture closure line 3. Konno procedure for 7. Ventriculotomy subaortic stenosis 4. Total anomalous pulmonary venous connection repair Intraoperative variables (continuous and discrete for support times) 1. Cardiopulmonary bypass time 4. Number of weaning attempts 2. Cross-clamp time 5. Modified ultrafiltration 3. Deep hypothermic circulatory arrest Postoperative variables (postoperative day 1 3 with concomitant event) 1. Hyperkalemia ( 6.0) 7. Dobutamine 2. Hypokalemia ( 2.5) 8. Dopamine 3. Hypocalcemia ( 7 or ionized 9. Epinephrine calcium 0.85) 10. Isoproterenol 4. Hypomagnesemia ( 1.5) 11. Milrinone 5. Acidosis (ph 7.25) 6. Alkalosis (ph 7.60) patients with anomalous pulmonary venous connection repair (n 11), 14.3% of those with repair of tetralogy of Fallot (and anatomic variants) (n 35), 13.2% of those after ventricular septal defect repair (n 53), 9.1% in those who had an isolated Blalock-Taussig shunt (n 11), 7.1% after a stage 1 palliation (n 42), 6.6% of those after Fontan operation (n 45), and 2.5% after bidirectional Glenn or hemi-fontan operation (n 40) [1]. Our general staged therapeutic approach is the avoidance of hyperthermia (antipyretic agents and removal of external sources of radiant warming), sedation, and minimizing catecholamines. Of the 33 cases, 13 (39.4%) of the patients received additional therapy to that described above. Three patients received amiodarone alone, 4 received pacing strategies alone, 6 received a combination of amiodarone and pacing, and 1 of these patients also had active cooling. Four of the 33 patients died during the study period; in all 4 patients, JET had resolved before

3 Ann Thorac Surg HOFFMAN ET AL 2002;74: POSTOPERATIVE JUNCTIONAL ECTOPIC TACHYCARDIA IN CHILDREN 1609 Table 2. Features of Patients Who Experienced Junctional Ectopic Tachycardia Age at Operation Diagnosis Surgical Procedure Postoperative Day for Initial Occurrence of JET (number of days of JET total) Additional Intervention a 3.1 mo TOF Repair 1 (1) None 10.4 mo TOF Repair 1 (1) None 3.9 mo TOF Repair 1 (1) None 1.8 mo TOF Repair 1 (1) A 1d b TOF/APV Repair 2 (1) A, P, C 10.5 y TOF/PA RV-PA conduit 1 (1) None 9.7 mo TOF/PA s/p Residual VSD closure 4 (1) None unifocalization 6.6 mo TOF/CAVC Repair 4 (1) None 8d b TGA/VSD/CoA Repair/ECMO 1 (1) A, P 2.0 mo TGA/VSD/CoA Repair 3 (1) P 4 d Single ventricle (H) Stage 1 1 (1) None 2 d Single ventricle (H) Stage 1 2 (1) None 6 d Single ventricle (H) Stage 1 1 (1) P 2.4 mo Single ventricle (H) BTS 3 (1) None 4.9 mo Single ventricle Hemi-Fontan/SVC plasty 2 (3) A, P 1.0 y Single ventricle Extracardiac Fontan 5 (1) A, P 1.8 y Single ventricle Extracardiac Fontan 1 (1) None 1.5 y Single ventricle Extracardiac Fontan 4 (4) A 11 d TAPVC Repair 1 (1) None 7 d TAPVC Repair 1 (1) None 7 d TAPVC Repair 1 (3) A, P 2 d TAPVC Repair 1 (1) P 1.3 mo PAPVR/CDH Repair 2 (2) P 20 d VSD/CoA Repair 1 (1) None 14 d VSD/CoA Repair 1 (1) A, P 3.7 mo VSD/PS Repair 1 (2) A 8.0 mo VSD/PV stenosis Repair 1 (1) None 1.2 mo VSD Repair 2 (2) None 1.2 mo VSD Repair 8 (10) None 19 d DORV/IAA s/p repair Residual VSD closure 1 (4) None 6.3 mo b IP of infancy Lung Tx 50 (1) None 1.4 mo AS/MS/MR Heart Tx 28 (1) None 2.4 mo b CHD/PHTN H/L Tx 1 (1) None a Interventions are in addition to active avoidance of hyperthermia, minimized exogenous catecholamines, and optimal sedation and pain control. b Died. A amiodarone; APV absent pulmonary valve; AS aortic stenosis; BTS Blalock-Taussig shunt; C active cooling; CAVC complete atrioventricular canal; CDH congenital diaphragmatic hernia; CHD congenital heart disease; CoA coarctation; DORV double outlet right ventricle; ECMO extracorporeal membrane oxygenation; (H) heterotaxy; H/L heart lung; IAA interrupted aortic arch; IP interstitial pneumonitis; MR mitral regurgitation; MS mitral stenosis; P pacing; PA pulmonary atresia; PAPVR partial anomalous pulmonary venous return; PHTN pulmonary hypertension; PS pulmonary stenosis; PV pulmonary vein; RV-PA right ventricle to pulmonary artery; SVC superior vena cava; TAPVC total anomalous pulmonary venous connection; TGA transposition of the great arteries; TOF tetralogy of Fallot; Tx transplant; VSD ventricular septal defect. the patient died and was not believed to be the direct cause of mortality. The initial onset of JET occurred in the first 24 hours in 19 of 33 patients, and in the 5 days after the operation in 30 of 33 patients. The latest onset of JET was on postoperative day 50 in a lung transplant recipient. Of the 2 remaining patients in whom the onset of JET was late, one experienced JET, which lasted inconsistently for 10 days, on postoperative day 8 after ventricular septal defect repair, and in the other patient, JET occurred on the 28th postoperative day after heart transplant. None of these 3 patients received active additional therapy. Table 3 represents those variables that were associated with JET by univariate analysis. Younger age, longer cardiopulmonary bypass times, and the presence of dopamine or milrinone in the first 72 hours after the operation were all factors associated with genesis of JET. Discrete variable analysis revealed an increased risk of experiencing JET with a cardiopulmonary bypass time of at least 75 minutes (odds ratio, 3.1) and age less than 6 months (odds ratio, 5.3). A dopamine infusion at a dose range of 3 to 7.5 g/kg/min was present in 30 of 33 (91%) of those patients who were diagnosed with JET as compared with 18 of 33 (55%) in the control group.

4 1610 HOFFMAN ET AL Ann Thorac Surg POSTOPERATIVE JUNCTIONAL ECTOPIC TACHYCARDIA IN CHILDREN 2002;74: Table 3. Variables Associated With Junctional Ectopic Tachycardia: Univariate and Multivariate Analysis Results Variable Odds Ratio p Value Univariate analysis Dopamine Milrinone Age (mo) a Age 6 (mo) CPB (min) a CPB 75 (min) Multivariate analysis Dopamine Age 6 mo a Odds ratio relates to increases in the unit measured. CPB cardiopulmonary bypass. Similarly, 17 of 33 (52%) patients diagnosed with JET were receiving milrinone as compared with 5 of 33 (15%) in the control group. Multivariate modeling (Table 3) revealed that the use of dopamine in the first 72 hours postoperatively remained as a risk factor for JET that occurred in the same time frame, and additionally, age less than 6 months was also associated with the occurrence of JET. Comment Despite the lack of knowledge concerning the cellular or macroscopic cause of JET, the presence of this arrhythmia in the postoperative period is viewed as a marker of untoward effects of the surgical procedure. In prior reports, the cause of JET is thought to be a result of a combination of factors, including underlying heart disease, type of surgical procedure, hemodynamic instability, and electrolyte imbalance, namely hypomagnesemia [3, 18 24]. The anatomic mechanism is believed to be a result of direct trauma to the atrioventricular node and bundle of His, although JET occurs in patients in whom there is no operation near the atrioventricular node (eg, transplantation, extracardiac Fontan operation, Blalock- Taussig shunt). Furthermore, 2 of the patients who had no intracardiac surgical procedure whatsoever (1 after Blalock-Taussig shunt and 1 after an extracardiac Fontan operation) had no perioperative hemodynamic instability or adverse cardiopulmonary physiology to explain the occurrence of JET. In our cohort, JET occurred in 5.6% of admissions for surgical procedures (n 594). Some of the operations did not involve intracardiac surgical procedures, and additionally, some did not require cardiopulmonary bypass. Electrolyte disturbances in the first 72 hours after operation were not associated with JET in our cohort. In our study, most patients experienced JET in the immediate postoperative period (range, 1 to 50 days; median, 1 day); however, 3 patients had JET documented greater than 1 week after the surgical procedure. Although the univariate analysis revealed that the use of dopamine or milrinone, young age, and longer cardiopulmonary bypass times were associated with the genesis of JET, multivariate modeling revealed that only dopamine use and age less than 6 months were significant predictors. We did not record the dosing strategy of dopamine at the exact time of the arrhythmia event initiation, termination, or recurrence. However, dopamine dosing strategies ranged from 3 to 7.5 g/kg/min in all patients (both the cases and controls if used). This finding suggests that dopamine, even at low doses, may be related to the development of JET in some patients secondary to its catecholamine-related properties. In contrast, milrinone acts independently of the -adrenergic receptor through phosphodiesterase inhibition and therefore does not cause increased myocardial oxygen consumption or catecholamine stimulation to the heart. Milrinone may have been significant in the univariate analysis simply as a marker of a more ill patient and acted as a colinear variable to other markers of a more complex surgical procedure. Milrinone use was not related to JET in the multivariate analysis. Several studies have implicated various clinical, surgical, and therapeutic associations with the genesis of JET. Our study included a large pediatric population with a myriad of diagnoses and surgical procedures. Our study, as does others, suggests that the cause of postoperative JET still remains largely unknown in any individual patient. For example, several patients did not have intracardiac surgical procedures and still experienced JET the procedures included the extracardiac Fontan operation, the hemi-fontan operation, and a Blalock-Taussig shunt performed without cardiopulmonary bypass. In addition, neither ventricular septal defect closure nor hypomagnesemia were associated with JET in our analysis, both of which are reported associations in other studies [23, 24]. In a contemporary study of 343 patients either with tetralogy of Fallot, ventricular septal defect, complete atrioventricular canal, or truncus arteriosus, 10.8% had documented postoperative JET; however, none of those with truncus arteriosus experienced JET. Injury to the conduction system was the proposed mechanism either by resection or excision of muscle bundles or relief of the right ventricular outflow tract through the right atrium commonly associated with a repair of tetralogy of Fallot [23]. Despite these important findings, it is plausible that the described surgical substrate is more a risk in those with tetralogy of Fallot and not in those with other diagnoses. Therefore, by reviewing the available literature and our study, the genesis of postoperative JET continues to be difficult to identify. If the ventricular rate is not adequately controlled or atrioventricular synchrony not achieved by means of pacing strategies, JET may beget further postoperative problems (ie, low cardiac output and hypotension). A recent study noted that the cardiac intensive care unit stay increased from 4.5 days to 8.8 days when comparing those without and with postoperative JET; respectively, as did mean mechanical ventilation time (3.5 to 7.8 days) [4]. In our study, the management of JET was determined on the basis of the hemodynamic impact and the clinical status of the patient. In 13 of the 33 patients (39%),

5 Ann Thorac Surg HOFFMAN ET AL 2002;74: POSTOPERATIVE JUNCTIONAL ECTOPIC TACHYCARDIA IN CHILDREN 1611 additional interventions were accomplished. Our current treatment strategy includes the active avoidance of hyperthermia, optimal sedation and pain control, minimized exogenous catecholamines, and the use of amiodarone or atrial pacing to optimize hemodynamics. Active cooling was only used once in combination with amiodarone and pacing in our series. During the study, our practice did not include discontinuing dopamine or substituting another inotropic medication for dopamine when JET was ongoing. However, in light of the analysis, it might be speculated that dopamine may be discontinued in the presence of JET to alleviate any unnecessary catecholamine stimulation. In conclusion, of 594 patients who underwent cardiac surgical procedures in our institution, 33 (5.6%) experienced JET. Multivariate analysis revealed that the use of dopamine in the immediate postoperative period and age less than 6 months were associated with JET. Only 39% of the patients had active therapeutic interventions for this dysrhythmia. It may be speculated that dopamine should be discontinued in the postoperative period in those patients with JET. References 1. Hoffman TM, Wernovsky G, Wieand TS, et al. The incidence of arrhythmias in a pediatric cardiac intensive care unit. Pediatr Cardiol 2002;23(6). 2. Braunstein PW, Sade RM, Gillette PC. Life-threatening postoperative junctional ectopic tachycardia. Ann Thorac Surg 1992;53: Dietl CA, Cazzaniga ME, Dubner SJ, Perez-Balino JA, Torres AR, Favaloro RG. Life-threatening arrhythmias and RV dysfunction after surgical repair of tetralogy of Fallot. Comparison between transventricular and transatrial approaches. Circulation 1994;90(Suppl 2):II Dodge-Khatami A, Miller OI, Anderson RH, Gil-Jaurena JM, Goldman AP, de Leval MR. 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