Epidemiology of Postoperative Junctional Ectopic Tachycardia in Infants Undergoing Cardiac Surgery

BACKGROUND

Junctional ectopic tachycardia (JET) complicates congenital heart surgery in 2% to 8.3% of cases. JET is associated with postoperative morbidity in single-center studies. We used the Pediatric Cardiac Critical Care Consortium data registry to provide a multicenter epidemiologic description of treated JET.

METHODS

This is a retrospective study (February 2019-August 2022) of patients with treated JET. Inclusion criteria were (1) <12 months old at the index operation, and (2) treated for JET <72 hours after surgery. Diagnosis was defined by receiving treatment (pacing, cooling, and medications). A multilevel logistic regression analysis with hospital random effect identified JET risk factors. Impact of JET on outcomes was estimated by margins/attributable risk analysis using previous risk-adjustment models.

RESULTS

Among 24,073 patients from 63 centers, 1436 (6.0%) were treated for JET with significant center variability (0% to 17.9%). Median time to onset was 3.4 hours, with 34% present on admission. Median duration was 2 days (interquartile range, 1-4 days). Tetralogy of Fallot, atrioventricular canal, and ventricular septal defect repair represented >50% of JET. Patient characteristics independently associated with JET included neonatal age, Asian race, cardiopulmonary bypass time, open sternum, and early postoperative inotropic agents. JET was associated with increased risk-adjusted durations of mechanical ventilation (incidence rate ratio, 1.6; 95% CI, 1.5-1.7) and intensive care unit length of stay (incidence rate ratio, 1.3; 95% CI, 1.2-1.3), but not mortality.

CONCLUSIONS

JET is treated in 6% of patients with substantial center variability. JET contributes to increased use of postoperative resources. High center variability warrants further study to identify potential modifiable factors that could serve as targets for improvement efforts to ameliorate deleterious outcomes.

Efficacy of Prophylactic Dexmedetomidine in Preventing Postoperative Junctional Ectopic Tachycardia After Pediatric Cardiac Surgery

BACKGROUND

Postoperative junctional ectopic tachycardia is one of the most serious arrhythmias that occur after pediatric cardiac surgery, difficult to treat and better to be prevented. Our aim was to assess the efficacy of prophylactic dexmedetomidine in preventing junctional ectopic tachycardia after pediatric cardiac surgery.

METHODS AND RESULTS

A prospective controlled study was carried out on 90 children who underwent elective cardiac surgery for congenital heart diseases. Patients were randomized into 2 groups. Group I (dexmedetomidine group): 60 patients received dexmedetomidine; Group II (Placebo group): 30 patients received the same amount of normal saline intravenously. The primary outcome was the incidence of postoperative junctional ectopic tachycardia. Secondary outcomes included bradycardia, hypotension, vasoactive inotropic score, ventilation time, pediatric cardiac care unit stay, length of hospital stay, and perioperative mortality. The incidence of junctional ectopic tachycardia was significantly reduced in the dexmedetomidine group (3.3%) compared with the placebo group (16.7%) with P<0.005. Heart rate while coming off cardiopulmonary bypass was significantly lower in the dexmedetomidine group (130.6±9) than the placebo group (144±7.1) with P<0.001. Mean ventilation time, and mean duration of intensive care unit and hospital stay (days) were significantly shorter in the dexmedetomidine group than the placebo group (P<0.001). However, there was no significant difference between the 2 groups as regards mortality, bradycardia, or hypotension (P>0.005).

CONCLUSION

Prophylactic use of dexmedetomidine is associated with significantly decreased incidence of postoperative junctional ectopic tachycardia in children after congenital heart surgery without significant side effects.

Junctional ectopic tachycardia after congenital heart surgery

PURPOSE

In this literature review, we try to give anesthesiologists a better understanding about Junctional Ectopic Tachycardia (JET), a narrow complex tachycardia that frequently occurs during and after surgery for congenital heart disease.

SOURCE

Information was found in the databases of Pubmed, Science Direct, Medline and the Cochrane Library, by using the mesh terms "Tachycardia, Ectopic Junctional", combined with "Diagnosis", "Etiology", "Physiopathology", "Complications" and "Therapy". The publication date of the articles ranged from 1990 to 2012.

PRINCIPAL FINDINGS

Risk factors for the development JET are surgery near the AV node, a duration of cardiopulmonary bypass longer than 90 minutes, young age, the use of inotropic drugs and hypomagnesaemia. The diagnosis of Junctional Ectopic Tachycardia can be made on a 12-lead ECG, demonstrating a narrow-complex tachycardia with inverted P-waves and VA dissociation. Adenosine administration and an atrial electrocardiogram can help to confirm the diagnosis. If JET has a minimal impact on the hemodynamic status of the patient, risk factors should be avoided and the adrenergic tonus should be reduced. Hemodynamic unstable JET can be treated by amiodarone, hypothermia and pacing. Extracorporeal membrane oxygenation (ECMO) and radiofrequency or cryoablation are treatment options for life-threatening and resistant JET.

CONCLUSION

JET is the most frequent arrhythmia during and after congenital cardiac surgery. The ECG is the only available method to diagnose JET, demonstrating inverted P-waves and VA-dissociation. Amiodarone seems to be the most effective treatment option, because it can restore sinus rhythm and reduces the JET rate.

Junctional ectopic tachycardia after congenital heart surgery in the current surgical era

To determine the incidence of postoperative junctional ectopic tachycardia (JET) in a modern cohort of pediatric patients, evaluate possible risk factors for JET, and examine the effects of JET on postoperative morbidity and mortality. JET is common after congenital heart surgery. JET-related mortality has been a rare event at our center, which is different from previous reports. We reviewed records for pediatric patients who had postoperative arrhythmias between January 2006 and June 2010 at a large tertiary-care children's hospital. We performed a matched case-control study to identify risk factors for JET and a matched-cohort study to compare outcomes between patients and controls. Whenever possible, each JET case was randomly matched to two controls on the basis of lesion, repair, and surgical period. We identified 54 patients with JET (incidence = 1.4 %). After multivariate logistic regression analysis, low operative weight, cardiopulmonary bypass (CPB) duration >100 min, and immediate postoperative serum lactic acid level >20 mg/dl were associated with increased odds of developing JET. Patients with JET had longer mechanical ventilation time, cardiac intensive care unit (CICU) stay, and hospital stay. There was only one death in JET group (1.8 %) with no significant difference compared with the control group. JET remains a relatively common postoperative arrhythmia, but it is less frequent than previously reported. JET occurs more commonly in smaller patients with longer CPB runs and significant postoperative lactic acidosis levels. Mortality associated with JET is lower than historically reported, but morbidity remains high.

Which parameters describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia?

OBJECTIVE

Atrioventricular nodal reentrant tachycardia (AVNRT) accounts for about 60% of the patients presenting with paroxysmal supraventricular tachycardia. The radiofrequency (RF) catheter ablation of the slow atrioventricular (AV) node pathway is the preferred therapeutic approach in patients with AV node reentrant tachycardia. The aim of our study was describe the electrophysiological properties of successful slow pathway RF ablation in patients with common atrioventricular nodal reentrant tachycardia.

METHODS

The study design was a retrospective analysis involving fifty consecutive patients (18 males; mean age of 39+/-22 years) who underwent slow pathway ablation because of AVNRT.

RESULTS

Slow junctional beats with a cycle length longer than 550 ms were observed in 39 patients (79%); the presence of rapid junctional beats with a cycle length less than 550 ms was showed in 5 patients (10%). Moreover, in 32 of 50 patients (65%) duration of atrial electrogram more than 40 ms was noticed. Analyzing data reported, we found the statistically significant presence of slow junctional beats (p=0.001) and atrial electrogram >40 ms (p=0.05) in successful RF ablation procedures.

CONCLUSION

In patients with AVNRT undergoing slow pathway ablation, the duration of atrial electrogram >40 ms and slow junctional beats with cycle length >550 ms during the application of RF energy describe the electrophysiological properties of successful slow pathway RF ablation.

Myocarditis presenting as junctional ectopic tachycardia

Junctional ectopic tachycardia (JET) is an unusual arrhythmia in children. It is usually described as a congenital tachycardia or as occurring in the postoperative setting. Here we report the case of an 8-year-old girl who presented with JET in the context of viral myocarditis and its later subsidence which could have been in response to Carvedilol therapy.

Isolated junctional tachycardia in a patient with pheochromocytoma: an unusual presentation of an uncommon disease

Pheochromocytoma is a rare disease, which often presents a diagnostic challenge due to a variable symptom presentation complex. We report the case of a child who presented with isolated symptoms of palpitations and was found to have junctional tachycardia with subsequent development of cardiomyopathy. Further evaluation revealed that she had an extra-adrenal pheochromocytoma, which was the cause of her arrhythmia and subsequent symptomatology.

Arrhythmia in early post cardiac surgery in pediatrics: Siriraj experience

OBJECTIVES

To determine the incidence, risk factors and outcome of early postoperative arrhythmias in pediatric patients with congenital heart disease.

MATERIAL AND METHOD

A prospective study was conducted in every pediatric patient who consecutively underwent open-heart surgery at Siriraj Hospital from January 1st to December 31st, 2006. The collected data were demographic data, diagnosis, pre-operative arrhythmia, cardiac surgical data and continuous electrocardiographic monitoring data throughout the post operative intensive care period.

RESULTS

A total of 191 pediatric patients underwent cardiac surgery. Forty-five cases (23.5%) developed early post operative cardiac arrhythmias i.e. junctional ectopic tachycardia 18 cases (40%), heart block 7 cases (15.6%), supraventricular tachycardia 2 cases (4.4%). Cardiac arrhythmia occurred mostly within 24 hours after the operation. Patients with single ventricle physiology repaired developed the highest incidence of acute post operative arrhythmia (36.4%). Longer, cardiopulmonary bypass time- and redo-operation were the risk factors. Thirty-nine cases were treated with medications, 7 cases with temporary pacing, and 1 case with electrical cardioversion. Four patients needed long-term anti-arrhythmic agents. Cardiac arrhythmia played role in the causes of death in 2 cases (1.1% of total cases).

CONCLUSIONS

Post operative arrhythmias remained common and important complications of pediatric open-heart surgery. Long cardiopulmonary bypass time and redo-operation were risk factors for early post operative arrhythmia.

[Successful administration of nifekalant hydrochloride for postoperative junctional ectopic tachycardia in congenital cardiac surgery]

Two episode of junctional ectopic tachycardia (JET) caused hemodynamic deterioration early after tetralogy of Fallot repair in an 8-month-old infant. Sinus rhythm resumed in each of the episodes immediately after intravenous administration of nifekalant hydrochloride (NIF), a newly developed Vaughan-Williams class III antiarrhythmic drug in Japan. Although QT interval was modestly prolonged with NIF, no life-threatening ventricular arrhythmia (i.e., torsades de pointes) occurred. NIF might be an effective alternative in the treatment of postoperative JET in congenital cardiac surgery.

Junctional ectopic tachycardia following complete heart block associated with viral myocarditis

We describe the case of an infant progressing from sinus rhythm to complete heart block, junctional ectopic tachycardia, and back to sinus rhythm as the only manifestation of viral myocarditis.

A prospective analysis of the incidence and risk factors associated with junctional ectopic tachycardia following surgery for congenital heart disease

This study was designed to evaluate the incidence and risk factors associated with the occurrence of junctional ectopic tachycardia (JET) in patients after congenital heart surgery. We prospectively analyzed cardiac rhythm status in 336 consecutive patients undergoing surgery for congenital heart disease at our institution during a 1-year period. The incidence of JET was 8% (27/336). Repairs with the highest incidence of JET were arterial switch operation (3/13, 23%), atrioventricular (AV) canal repair (4/19, 21%), and Norwood repair (2/10, 20%). Compared to patients with no arrhythmias, patients with JET were more likely to be younger (2.75 +/- 2.44 vs 5.38 +/- 7.25 years, p < 0.01), have had longer cardiopulmonary bypass times (126 +/- 50 vs 85 +/- 73, p < 0.01), and have a higher inotrope score (6.26 +/- 7.55 vs 2.41 +/- 8.11, p < 0.01). By multivariate analysis, ischemic time was the only factor associated with JET [odds ratio, 1.01 (confidence interval, 1.005-1.02); p = 0.0014). The presence of JET did not correlate with electrolyte abnormalities. JET is not necessarily related to surgery near the His bundle or hypomagnesemia. Longer ischemic time is the best predictor of JET. Patients undergoing arterial switch operation, AV canal repair, and Norwood repair are at highest risk of postoperative JET and should be considered for prophylactic therapy.

Documenting junctional ectopic tachycardia following pediatric open heart surgery

OBJECTIVE

To determine appropriated documentations for diagnosis junctional ectopic tachycardia (JET) before treatment in post-operative open heart surgery and identify risk factors for post-operative cardiac arrhythmias in children.

MATERIAL AND METHOD

The authors performed a retrospective chart review in 277 patients who underwent surgical corrections at British Columbia's Children Hospital from January 1st, 2000 to December 31st, 2001. History, clinical symptoms, complication of surgery and post-operative cardiac arrhythmias were reviewed from medical records. The authors investigated whether JET was being diagnosed accurately and whether it was being adequately documented prior to the initiation of therapy. The authors also identified risk factors that were associated with JET. All documentations before treatment were reviewed by Pediatric cardiologists to confirm diagnosis.

RESULTS

Although the diagnostic accuracy (84%), sensitivity (87%), and specificity (84%) are high, a significant number of patients with post-operative arrhythmias were treated without adequate documentation of the arrhythmia. The documentation of arrhythmias in the Intensive Care Unit was largely limited to rhythm strips, with very few 12-lead ECGs and wire studies performed to assist with the diagnosis.

CONCLUSION

The presented data indicates that, in this critically-ill population, there was an unacceptable number of patients with post-operative arrhythmias who may have been treated inappropriately. It is very important to emphasize the interpretation of wire studies, an investigation normally done in a critical care setting and whose interpretation is very important to the accurate diagnosis of pediatric arrhythmias.

Successful use of an intravenous infusion of flecainide and amiodarone for a refractory combination of postoperative junctional and ectopic tachycardias

After repair of an atrioventricular septal defect with common atrioventricular junction in a 2-month-old girl, rapid atrial tachycardia, in combination with junctional ectopic tachycardia, led to severe postoperative cardiovascular compromise. Intercurrent runs of ectopic atrial tachycardia made atrial pacing impossible, despite high doses of intravenous amiodarone. Following the addition of flecainide to the infusion, we were able to control the rhythm, and when combined with atrial pacing, this led to an immediate haemodynamic improvement. Treatment of refractory supraventricular tachycardias with amiodarone combined with flecainide can be very effective in the setting of postoperative cardiac intensive care.

Amiodarone for post-operative junctional ectopic tachycardia

BACKGROUND

Post-operative junctional ectopic tachycardia is a transient, but potentially life threatening, rapid automatic tachyarrhythmia that requires urgent and adequate treatment. In our study, we review retrospectively the use and efficacy of amiodarone for this arrhythmia over an 8-year period in our institution.

METHODS AND PATIENTS

Retrospective review revealed 15 patients who were administered amiodarone for post-operative junctional ectopic tachycardia during the period. The median age was 2.6 months, with a range from 8 days to 8.1 months. The median weight was 4.6 kilograms, with a range from 2.6 to 8.2 kilograms.

RESULTS

The median heart rate at diagnosis of the tachycardia was 192 beats per minute, and the range was 182 to 229 beats per minute. The biochemistry was essentially normal. The median length of time until the tachycardia was controlled was 4.5 hours, and the range was from 1 to 19.5 hours, with 13 of the 15 patients controlled within 12 hours. The median dose of amiodarone received by this time was 5.9 milligrams per kilogram, with a range from 1.0 to 25.0 milligrams per kilogram. Hypotension or bradycardia within 4 hours of commencing amiodarone were noted in 2 patients.

CONCLUSION

Experience in our institution, and a review of the literature, suggests that the most rapid control of post-operative junctional ectopic tachycardia will be obtained by a bolus of amiodarone followed by an intravenous infusion. Intravenous amiodarone is generally safe, with few side effects. Reported life threatening arrhythmias, however, suggest that intravenous amiodarone should be restricted to a setting where invasive monitoring and external cardiac pacing are available.

Postoperative junctional ectopic tachycardia (JET)

Postoperative junctional ectopic tachycardia (JET) is a potential life-threatening tachycardia that mainly occurs after surgical correction of congenital heart defects. The arrhythmia itself or the related treatment has significant clinical impact on the postoperative course and intensive care stay. In general, JET is a self-limiting disorder that usually resolves within one week. However, JET occurs usually within the first 24 to 48 hours after corrective surgery, when systolic and diastolic function of the heart is impaired. Thus, the rapid heart rate leads to an acute further deterioration of cardiac output that requires adequate treatment. The diagnosis of JET is made by the typical ECG-appearance with narrow QRS-configuration at a rate of 170 to 260 bpm and AV-dissociation. A variety of different therapeutic strategies have been tested in postoperative and congenital/spontaneous JET. Treatment success is usually defined as a stable decrease in the ventricular rate below 140-150/min, the possibility of atrial pacing and thereby the improvement of cardiac output. Optimal success is the reinstitution of sinus rhythm. Many of the treatment strategies reported are based on specific institutional treatment protocols. These include conventional supportive treatment, specific medical antiarrhythmic therapy, specific forms of pacing and surface cooling. Today, the administration of high doses of amiodarone usually leads to adequate control of the rate and enables pacing. Surgical intervention or catheter ablation of the HIS-bundle is rarely necessary. This article reviews the literature about JET over the past years and offers a specific treatment protocol.

Intravenous flecainide for the treatment of junctional ectopic tachycardia after surgery for congenital heart disease

BACKGROUND

Junctional ectopic tachycardia (JET) is a life-threatening arrhythmia producing severe hemodynamic dysfunction, which may complicate the postoperative course of surgery for congenital heart disease. Strict care and a fast and effective antiarrhythmic strategy are essential, because mortality largely depends on the duration of the arrhythmia.

METHODS

Seven consecutive neonates with postoperative JET without any evidence of myocardial ischemia received intravenous flecainide after conventional therapies proved ineffective. Atrial pacing at the minimal rate for atrioventricular synchrony was followed by a 10-min intravenous infusion of 1.6 mg/kg flecainide, then continuous infusion of 0.4 mg/kg flecainide per hour. Treatment was considered effective based on restoration of sinus rhythm or a JET rate no higher than 170 bpm within 4 hours of flecainide loading. Overall mean flecainide infusion lasted 31.2 hours (range 25 to 53 hours). Side effects were assessed by monitoring plasma flecainide levels, electrocardiogram, arterial pressure, and central venous pressure.

RESULTS

Flecainide was effective in all 7 patients after an infusion duration of 3.6 +/- 1.5 hours. Sinus rhythm was restored after 7.2 +/- 9.7 hours. After 4 hours of loading, heart rate fell from 219 +/- 14 to 136 +/- 7 bpm (p < 0.0001), arterial pressure increased from 69 +/- 8 to 93 +/- 10 mm Hg (p < 0.0001), while central venous pressure decreased from 8.0 +/- 1.6 to 5.2 +/- 1.9 mm Hg (p = 0.0007). No side effect or recurrence was noted.

CONCLUSIONS

Flecainide can exert a fast antiarrhythmic effect on postoperative JET, and its infusion can be modulated to maintain the concentration within the therapeutic range, thus avoiding toxicity. We propose further consideration of flecainide for treatment of JET in neonates without myocardial ischemia.

Use of intravenous amiodarone for postoperative junctional ectopic tachycardia in children

To assess the efficacy and safety of intravenous (IV) amiodarone for the treatment of postoperative junctional ectopic tachycardia (JET) in children, we retrospectively reviewed 11 patients treated with IV amiodarone for JET between 1/92 and 2/00. Data included heart rate and hemodynamics pre- and post-amiodarone, drug dosage, duration of therapy, and effect. Success was defined as reversion to sinus rhythm or slowing to a hemodynamically stable rate. The mean heart rate prior to amiodarone was 203 bpm, and the mean systolic blood pressure was 64 mmHg. Mean IV amiodarone loading dose was 8.2 +/- 4.0 mg/kg, followed by an infusion in 7 patients at a dose of 12.9 +/- 3.9 mg/kg/day for a duration of 74.3 +/- 46.9 hours. At 1 hour post-load, mean heart rate was 147 bpm and mean systolic blood pressure was 88 mmHg for the group. Three patients were in sinus rhythm, 4 in intermittent sinus rhythm with accelerated junctional rhythm, and 4 patients solely accelerated junctional rhythm. Control of JET persisted in 9 patients. Of the two patients requiring additional treatment, both had received a 5 mg/kg load and neither was on an infusion. Five patients were paced at some point following amiodarone: four to improve hemodynamics and one for late sinus bradycardia. Side effects included hypotension with loading (1) and late sinus bradycardia (1). One patient was discharged on oral amiodarone. Intravenous amiodarone given in doses of 10 mg/kg in two 5 mg/kg increments, followed by an infusion of 10-15 mg/kg/day for 48-72 hours, appears to be safe and effective for postoperative JET in patients who fail conventional therapy or who are hemodynamically unstable. Long-term oral therapy is usually not necessary.

Postoperative junctional ectopic tachycardia in children: incidence, risk factors, and treatment

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.

Junctional ectopic tachycardia in association with blunt abdominal trauma

Junctional ectopic tachycardia is recognized predominantly as a postoperative arrhythmia after surgery for congenital heart disease. Diagnosis and treatment distinguish it from more commonly observed mechanisms of supraventricular tachycardia. We present a case of junctional ectopic tachycardia that occurred in the setting of abdominal trauma caused by child abuse and then explore the significance of this arrhythmia in a patient with trauma.

Pharmacological and electrophysiological characterization of junctional rhythm during radiofrequency catheter ablation of the atrioventricular node: possible involvement of neurotransmitters from autonomic nervous system

Catheter ablation of the atrioventricular node (AVN) with radiofrequency current is closely associated with the short-term onset of a junctional rhythm. The origin of this rhythm was analyzed in Beagle dogs which were anesthetized with pentobarbital sodium. Atrioventricular (AV) conduction block was induced first using a standard catheter ablation technique for the AVN, so that the sinus automaticity could not override the junctional ectopy during the following energy delivery. The ablation catheter was kept in the initial position and the delivery of radiofrequency energy was repeated. The pattern of ECG changes suggests that the dominant pacemaker may shift from the distal portion of the AV junctional area to the proximal portion during the energy delivery. This enhanced junctional automaticity was suppressed by the beta-blocker esmolol, but was not affected by M-antagonist atropine. Moreover, the beta-agonist isoproterenol did not induce the same type of junctional tachycardia, but the pacemaker shift was induced by the increased sympathetic tone after transient asystole by ventricular overdrive pacing or acetylcholine administration. These results suggest that proximal portion of the AV junctional area has extremely slow pacemaker activity, but responds to locally released norepinephrine with an abrupt rise and fall in rate, resulting in a typical pattern of junctional tachycardia during the ablation of the AVN.

[The treatment of postoperative junctional ectopic tachycardia]

OBJECTIVE

To evaluate treatment of junctional ectopic tachycardia after cardiac surgery.

MATERIAL AND METHODS

Twenty-seven patients (5.5 % of 488 patients who underwent surgery) were treated for junctional ectopic tachycardia between 1994 and 1998. There were 14 boys and 13 girls with a mean age of 11 11 months. Seven suffered from tetralogy of Fallot, seven from ventricular septal defect, six from atrioventricular septal defect, three from transposition of the great vessels and the remaining four had other complex heart diseases. The mean initial frequency was 186 27 beats/min. Crystalloid cardioplegia was applied in 274 patients (1994-1996) and 20 patients (7.4 %) showed junctional ectopic tachycardia. Hematic cardioplegia was performed in 214 patients (1997-1998) and seven patients (3.2 %) developed junctional ectopic tachycardia. Of the 33 patients who were treated during the surgical procedure with high mean doses of sympathomimetic catecholamine agents, 27 (81 %) developed tachycardia. Tachycardia developed 8.24 7 hours after surgery (range: 1-24 hours) in 25 patients and after 4 and 5 days in the remaining two patients. The mean duration of tachycardia was 4 days.

RESULTS

In all patients rectal temperature was reduced to 32-34 C. Nineteen patients (70 %) showed a quick response (1-2 hours), although the technique was effective as an isolated procedure in only one patient. Sympathomimetic catecholamine level was reduced to 2-5 g/kg/min in 20 patients but this was effective in 14 (70 %). In 15 patients intravenous amiodarone was also administered and was effective in 11 patients (73 %). Finally, intravenous propafenone was administered to 5 patients. The most effective treatments were hypothermia with reduction of sympathomimetic catecholamine levels in 7 patients (100 %) or intravenous amiodarone in 4 (80 %). Tachycardia led to low cardiac output in 10 patients and only four recovered normal sinus rhythm. Eight patients died. Of these, hemorrhage in the junction area was confirmed in six patients.

CONCLUSIONS

Junctional ectopic tachycardia is favored by high levels of sympathomimetic catecholamines after surgery. On the other hand, myocardial protection with hematic cardioplegia reduces tachycardia. Moderate hypothermia with reduction of sympathomimetic agents or intravenous amiodarone reverses ectopic tachycardia.

Atrial activation sequence during junctional tachycardia induced by thermal stimulation of Koch's triangle in canine blood-perfused atrioventricular node preparation

Junctional tachycardia is observed during radiofrequency ablation of the slow pathway. The authors investigated the atrial activation sequence during junctional tachycardia induced with thermal stimulation in canine blood-perfused atrioventricular node (AVN) preparation. The canine heart was isolated (n = 7) and cross-circulated with heparinized arterial blood of the support dog. The activation sequence in the region of Koch's triangle (15 x 21 mm) was determined byrecording 48 unipolar electrograms. Atrial sites anterior to the coronary sinus ostium (site AN), close to the His-potential recording site (site N) and superior to site N (site F), were subjected to a continuous temperature rise from 38 degrees C to 50 degrees C with a heating probe. The temperature of the tissue adjacent to the heating site was monitored simultaneously. Junctional tachycardia at a rate of 92+/-12 beats/min with the His potential preceding the atrial one in the His-bundle electrogram was induced during thermal stimulation at site AN (temperature 42.1 degrees C+/-0.9 degrees C) in all seven preparations, whereas junctional tachycardia was induced during stimulation at site N in one and at site F in none. In each case, the temperature rose only at the site of stimulation. The earliest activation site during junctional tachycardia induced by site AN stimulation was at the His-potential recording site in five preparations and the middle of Koch's triangle in the other two. After creating an obstacle between sites AN and N, atrial tachycardia at a rate of 85+/-11 beats/min was induced during site AN stimulation. The earliest activation site during this tachycardia was site AN. Thus, junctional tachycardia induced by thermal stimulation was suggested to originate from the AN thermal stimulation site. The impulse from the stimulation site appeared to conduct via the posterior input to the compact AVN and junctional tachycardia was generated. When the posterior input was interrupted, atrial tachycardia was generated.

Surgical substrates of postoperative junctional ectopic tachycardia in congenital heart defects

BACKGROUND

Junctional ectopic tachycardia is a major cause of postoperative morbidity after surgery for congenital cardiac disease. To elucidate the mechanism of junctional ectopic tachycardia, surgical correlations were studied in four types of congenital heart defects involving closure of a ventricular septal defect, relief of right ventricular outflow tract obstruction, or both.

METHODS

Between 1997 and 1999, a total of 343 consecutive patients underwent repair of tetralogy of Fallot (n = 114), common truncus arteriosus (n = 10), ventricular septal defect (n = 161), and atrioventricular septal defect (n = 58). Variables studied included demographic and bypass data, surgical approaches toward ventricular septal defect closure and relief of right ventricular outflow tract obstruction, and resection as opposed to division of muscle bundles.

RESULTS

Junctional ectopic tachycardia occurred most frequently after repair of tetralogy of Fallot (n = 25; 21.9%), with no cases occurring after repair of common trunk, 6 occurring after repair of ventricular septal defect (3.7%), and 6 occurring after repair of atrioventricular septal defect (10.3%). Stepwise logistic regression revealed that resection of muscle bundles (P <.0001), higher bypass temperatures (P <.03), and relief of right ventricular outflow tract obstruction through the right atrium (P <.05) significantly and independently predicted postoperative junctional ectopic tachycardia.

CONCLUSIONS

Relief of right ventricular outflow tract obstruction appears to be more important in the causation of junctional ectopic tachycardia than does ventricular septal defect closure, which may explain the higher incidence of this complication after tetralogy of Fallot repair. Muscular resection seems to be more arrhythmogenic than is simple division. Increased traction through the right atrium for relief of right ventricular outflow tract obstruction would fit the hypothesis that enhanced automaticity of the His bundle, the morphologic substrate for junctional ectopic tachycardia, may result from direct trauma or infiltrative hemorrhage of the conduction system. When feasible, techniques avoiding both extensive muscle resection and excessive traction should be applied during resection of right ventricular outflow tract obstruction.

Morphological characteristics of P waves during selective pulmonary vein pacing

OBJECTIVES

We sought to assess the value of 12-lead electrocardiogram (ECG) P-wave morphology to recognize the paced pulmonary vein (PV).

BACKGROUND

Prediction of arrhythmogenic PVs producing ectopy or initiating atrial fibrillation (AF) using 12-lead ECG may facilitate curative ablation.

METHODS

In 30 patients P-wave configurations were studied during sinus rhythm and during pacing at six sites from the four PVs: top and bottom of each superior PV and both inferior PVs. The P-wave amplitude, duration and morphology were assessed, and predictive accuracies were calculated for the most significant parameters. An algorithm predicting the paced PV was developed and prospectively evaluated in a different population of 20 patients. RESULTS; Three criteria were used to distinguish right from left PV: 1) a positive P-wave in lead aVL and the amplitude of P-wave in lead I > or =50 microV indicated right PV origin (specificity 100% and 97%, respectively); 2) a notched P-wave in lead II was a predictor of left PV origin (specificity 95%); and 3) the amplitude ratio of lead III/II and the duration of positivity in lead V(1) were also helpful in distinguishing left versus right PV origin. In addition, superior PVs could be distinguished from inferior according to the amplitude in lead II (> or =100 microV). In prospective evaluation, an algorithm based on the above four criteria identified 93% of left versus right PV and totally 79% of the specific PVs paced.

CONCLUSIONS

Pacing from the different PVs produced a P-wave with distinctive characteristics that could be used as criteria in an algorithm to identify the PV of origin with an accuracy of 79%.

Cardiac rhythm disturbances in patients with left atrial isomerism

This long-term study sought to determine the clinical implication of defective sinus node and AV conduction tissue in patients with left atrial isomerism (LAI). From 1984 to 1998, a total of 22 patients were identified as LAI. Patient age at the last follow-up ranged from 2 to 276 months (90+/-70 months). Associated cardiac anomalies were interruption of the inferior vena cava (n = 18, 82%), common atrium (n = 9, 41%), AV canal (n = 14, 64%), double-outlet right ventricle (n = 8, 36%), and pulmonary stenosis (n = 15, 68%). Palliative interventions were performed in 16 patients (Fontan-type operation in 4 patients, shunt followed by Fontan-type operation in 2, repair of septal defect in 4, and extracardiac intervention in 6). During the follow-up, over half of the patients (n = 14, 64%) developed bradyarrhythmia (onset age: from 1 to 264 months; median 78 months): junctional rhythm (n = 11), sinus bradycardia (n = 8) (5 patients also had junctional rhythm), and AV block (n = 2, both also had junctional rhythm). The probability free from bradyarrhythmia was 80% and 46% at the age of 2 and 6 years, respectively. None of the bradyarrhythmias were directly related to open-heart surgery. Besides, junctional ectopic tachycardia occurred after Fontan-type operation in three of six patients. In two patients, a Mahaim-like pathway was identified during the electrophysiological study. The patients with LAI had a high probability of developing bradyarrhythmias due to abnormal sinus node function. Varied AV conduction abnormalities may include compromised AV conduction, junctional ectopic tachycardia after Fontan-type operation, and an association of Mahaim-like pathway.

A randomized comparison of the straight linear approach with electrogram mapping focal approach in selective slow pathway ablation

The aim of this study was to evaluate the efficacy and safety of the anatomic linear approach in selective AVN slow pathway ablation, in comparison to the widely used electrogram mapping focal approach. It remains undetermined whether or not anatomic linear ablation has a greater potential for eliminating slow pathway conduction than does focal ablation. Fifty consecutive patients (21 men, 29 women, age 56 +/- 14 years) with common type AVNRT were randomly assigned to the linear approach (25 patients) or local electrogram mapping approach (25 patients). A linear lesion was created between the tricuspid annulus, at the midlevel of the coronary sinus (CS) ostium, and the anterior aspect of the CS infundibulum. In 22 (88%) patients in the linear group, the AVNRT was successfully eliminated by 1.5 +/- 0.8 linear RF applications without any complications. All 25 patients in the focal group satisfied the endpoint criteria after 3.8 +/- 2.4 focal RF deliveries. The success rate did not significantly differ between the two groups. Out of the 22 patients with a successful outcome in the linear group, 17 (77%) attained complete abolition of the slow pathway conduction, whereas this was observed in only eight (32%) patients in the focal group (P < 0.005). The session time was significantly shorter in the linear group. Recurrence of the tachycardia was not documented in any patient during a mean follow-up of 18 +/- 8 months except one with residual slow pathway conduction in the focal ablation group. In conclusion, the anatomic linear approach can be performed safely and possesses a greater potential for slow pathway interruption compared to the electrogram mapping focal approach.

Magnesium supplementation in the prevention of arrhythmias in pediatric patients undergoing surgery for congenital heart defects

BACKGROUND

The efficacy of magnesium in the prevention of arrhythmias in pediatric patients after heart surgery remains unknown. Therefore we prospectively examined the effect of magnesium treatment on the incidence of postoperative arrhythmias in pediatric patients undergoing surgical repair of congenital heart defects.

METHODS AND RESULTS

Twenty-eight pediatric patients undergoing heart surgery with cardiopulmonary bypass were prospectively, randomly assigned in a double-blind fashion to receive intravenous magnesium (magnesium group, n = 13; 30 mg/kg) or saline (placebo group, n = 15) immediately after cessation of cardiopulmonary bypass. Magnesium, potassium, and calcium levels were measured at defined intervals during surgery and 24 hours after surgery. Continuous electrocardiographic documentation by Holter monitor was performed for 24 hours after surgery. Magnesium levels were significantly decreased below the normal reference range for patients in the placebo group compared with the magnesium group on arrival in the intensive care unit and for 20 hours after surgery. Magnesium levels remained in the normal range for patients in the magnesium group after magnesium supplementation. In 4 patients in the placebo group (27%), junctional ectopic tachycardia developed within the initial 20 hours in the intensive care unit. No junctional ectopic tachycardia was observed in the magnesium group (P =.026).

CONCLUSIONS

Although this study was originally targeted to include 100 patients, the protocol was terminated because of the unacceptable incidence of hemodynamically significant junctional ectopic tachycardia that was present in the placebo group. Thus low magnesium levels in pediatric patients undergoing heart surgery are associated with an increased incidence of junctional ectopic tachycardia in the immediate postoperative period.

Procainamide for rate control of postsurgical junctional tachycardia

This study was conducted to determine the efficacy of procainamide therapy for rapid rate control of postoperative junctional tachycardia (JT). Postoperative JT is one of the most difficult forms of tachycardia to manage. Reported success with a variety of treatments of JT in infants and children has been inconsistent and limited. Rate control using procainamide was achieved in 17 children having rapid JT (heart rate >200 beats/min) between 1986 and 1997. In the first 5 patients (protocol A), following a loading dose of 3 mg/kg over 20 minutes, a continuous procainamide infusion was initiated at a rate of 20 microg/kg/min. The infusion dose was increased in 10 microg/kg steps every 30 minutes to 40-120 microg/kg/min until the heart rate decreased below the target rate of 180 beats/min. In the other 12 patients (protocol B), after a higher loading dose of 10 mg/kg the infusion rate was increased every 10-15 minutes until the heart rate decreased below the target rate of 180 beats/min. Procainamide decreased JT rates in all patients but the response was significantly faster in protocol B. In the patients treated with protocol A, pretreatment JT rates ranged from 203 to 240 (213+/-17) beats/min and decreased to 195+/-10 beats/min at 2 hours (p = ns), 186+/-8.8 at 4 hours (p<0.02), and 179+/-8 at 6 hour postinitiation of PA. In protocol B, pretreatment JT rates ranged from 201 to 240 (218+/-17) beats/min and decreased to 183+/-20 beats/min at 2 hours (p<0.001) and 171+/-12 at 4 hours after starting the procainamide therapy. The mean duration to decrease JT rates below the target rate of 180 beats/min was 3.2+/-1.1 hours in protocol B compared to 6.4+/-3.8 hours in protocol A (p<0.02). Eight of 12 patients in protocol B achieved rate control below the target rate of 180 beats/min within 4 hours despite remaining on significant inotropic support. The procainamide infusion rates to maintain heart rates below 180 beats/min were 40-120 (68.4+/-22.1) microg/kg/min. No proarrhythmia, bradycardia, or significant hypotension was observed. In this series procainamide provided safe, effective, and rapid rate control of JT occurring in the immediate postoperative period.

Catheter ablation of atrioventricular junction via retrograde route in a patient with single ventricle

Radiofrequency catheter ablation of the atrioventricular junction (AVJ) was performed by the retrograde route in a 19-year-old woman with atrial fibrillation and single ventricle following the bidirectional Glenn procedure. Two energy applications resulted in complete atrioventricular block and dependence on an epicardial ventricular pacemaker.

Incidence and clinical significance of junctional rhythm remaining after termination of radiofrequency current delivery in patients with atrioventricular nodal reentrant tachycardia

The aim of this study was to elucidate the electrophysiologic characteristics and clinical significance of the accelerated junctional rhythm (JR) that remains after termination of radiofrequency (RF) current delivery during catheter ablation (CA) for atrioventricular nodal reentrant tachycardia (AVNRT). Fifty consecutive patients with AVNRT (21M, 29F, age 48 years) underwent RF-CA targeting the slow pathway. JR occurred at 124 out of a total of 236 ablation sites (53%) during the RF delivery. With 15 RF deliveries (6.4%, n=10), JR remained after termination of the RF delivery (Post-JR). The mean cycle length of the Post-JR immediately after termination of the RF delivery was 639+/-124 ms and its duration was widely distributed from 3 s to more than 1 h. The Post-JR exhibited a spontaneous rate deceleration and overdrive suppression by rapid atrial pacing. The JR during the RF delivery followed by Post-JR had a greater time span in which the JR appeared, compared with that without Post-JR. The Post-JR had less sensitivity(18 vs 96%), but greater specificity (97 vs 59%) and a positive predictive value (60 vs 39%) in predicting successful ablation compared with JR seen only during the RF delivery. It is concluded that the presence of Post-JR might be a reflection of the intense effect of RF energy on the nodal or peri-nodal tissue.

Amiodarone in the treatment of junctional ectopic tachycardia after cardiac surgery in children: report of two cases and review of the literature

Junctional ectopic tachycardia (JET) occurs most frequently after operative repair of congenital heart defects. The mechanism is thought to involve direct trauma to the atrioventricular node and His bundle resulting in an ectopic focus. Several therapeutic methods have been described in the pediatric literature with varying degrees of success and complication rates. Because heart rates may exceed 200 to 300 beats per minute, there may be inadequate time for ventricular filling. Ventricular filling can be further compromised because of the asynchrony between the atria and the ventricles. These factors can lead to significant compromise of cardiovascular function in the postoperative patient. We describe our experience with amiodarone in two patients who developed postoperative JET after repair of congenital heart defects. Dosing regimens and previous experience with amiodarone in patients with JET are reviewed.

Paired ventricular pacing: an alternative therapy for postoperative junctional ectopic tachycardia in congenital heart disease

Junctional ectopic tachycardia (JET) is one of the most life-threatening postoperative arrhythmias in children with congenital heart disease, and medical management is difficult. Paired ventricular pacing (PVP) may provide a safe alternative mode of management. We evaluated the safety and efficacy of PVP for the management of postoperative JET in patients with congenital heart disease. A retrospective collection of data was done from 1981-1995. PVP was successfully tried in five postoperative patients (age range: 37 days to 22 years, median: 10 months). Onset of JET was 3-60 hours (mean +/- SD, 19 +/- 23 hours) postoperatively. The maximal JET rate was 261 +/- 39 beats/min. PVP was used as the first line of management in three patients and was successful in all patients. It resulted in an instantaneous increase in blood pressure from 66 +/- 9 to 94 +/- 15 mmHg (42% increase) and was required for 12 +/- 14 hours (range 2-36 hours). No complications were noted. Therefore, in our experience, this is a safe alternative modality for the control of postoperative JET.

Atrial ectopy originating from the posteroinferior atrium during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia

Atrial ectopy sometimes appears during RF ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examine these issues, we analyzed 67 consecutive patients with AVNRT (60 with slow-fast AVNRT and 7 with fast-slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patients. During successful RF ablation, junctional ectopy with the activation sequence showing H-A-V at the His-bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A-H-V at the His-bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 patients) or without junctional ectopy (5 patients). Before RF ablation, retrograde slow pathway conduction induced during ventricular burst and/or extrastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.001). Successful ablation site in group A was distributed between the His-bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coronary sinus ostium. In group B, atrial ectopy also appeared in 21% of the unsuccessful RF ablations. In conclusion, atrial ectopy is relatively common during slow pathway ablation and observed in 8% of RF applications overall and 22% of RF applications that successfully eliminated inducible AVNRT. Atrial ectopy appears to be closely related to successful slow pathway ablation among patients with manifest retrograde slow pathway function.

Junctional tachycardia during radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia: effects of autonomic blockade

INTRODUCTION

The autonomic nervous system richly innervates the peri-AV nodal region and may be activated during radiofrequency (RF) ablation for AV nodal reentrant tachycardia, resulting in the generation of junctional tachycardia. The purpose of this prospective study was to determine the role of the autonomic nervous system in the genesis of junctional tachycardia.

METHODS AND RESULTS

We compared the characteristics of junctional tachycardia in patients with (n = 10) and without (n = 10) autonomic blockade undergoing RF ablation for AV nodal reentrant tachycardia. Intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg) were used to block the autonomic nervous system. There were no differences in clinical variables and baseline electrophysiologic characteristics between the two groups except for slightly longer effective refractory periods of the fast pathway and of the atrium in the autonomic blockade group. The autonomic blockade shortened the baseline sinus cycle length and effective refractory period of the ventricle only but not other electrophysiologic characteristics of the AV node. The junctional tachycardia was observed during ablation in each patient, but its occurrence and cycle length, as well as numbers of consecutive junctional beats, were not altered by the autonomic blockade.

CONCLUSION

Our results indicate that the muscarinic and beta-adrenergic components of the autonomic nervous system play no role in the genesis of junctional tachycardia.

Postoperative junctional ectopic tachycardia

PURPOSE

To report the management of junctional ectopic tachycardia after cardiac surgery in an infant. Postoperatively, the patient suffered profound cardiac decompensation secondary to the accelerated rhythm and required extracorporeal membrane oxygenation (ECMO) for haemodynamic support.

CLINICAL FEATURES

A 14-day-old, 3.5 kg boy exhibited junctional ectopic tachycardia after cardiopulmonary bypass. Left atrial pressure was 25-28 mmHg. No impact on the tachycardia was seen after rapid overdrive atrial pacing or after 20 micrograms fentanyl i.v., 45 micrograms digitalis, 100 mg magnesium or procainamide (loading dose 15 mg, then 30 mg.kg-1.min-1). Active cooling decreased the nasopharyngeal temperature to 35.2 degrees C, when the heart rate decreased below 180 bpm with a left atrial pressure of 8-10 mmHg. Dopamine (2 micrograms.kg-1.min-1) and dobutamine (5 micrograms.kg-1.min-1) were added to improve the cardiac output. Sodium nitroprusside (0.25 to 1 microgram.kg-1.min) maintained the systolic pressure < 100 mmHg. On arrival in ICU, heart rate increased to 200 bpm. The patient received cardiac massage for severe hypotension 75 min after surgery. Emergency ECMO was instituted for circulatory support. Procainamide, digoxin, dopamine, dobutamine, sodium nitroprusside and hypothermia were continued. Sinus rhythm resumed on the first postoperative day, but procainamide and induced hypothermia at 34 degrees C were maintained for 36 hr after normalization of the rhythm to prevent recurrence of the tachycardia. Total duration of ECMO was three and a half days. Recovery was uneventful.

CONCLUSION

The use of ECMO, as a first line of defence, is suitable for the emergency support of patients with JET because of the ease of support of circulation and precise control of hypothermia.

Early and late atrial dysrhythmias after modified Fontan operation

Occurrence of supraventricular tachycardia and sinus node dysfunction was investigated pre- and postoperatively by serial ECG and Holter monitors in 63 consecutive patients with univentricular circulation after modified Fontan operation (total cavopulmonary connection 39 patients, atriopulmonary connection 24 patients). Mean age at operation was 7.2 (0.1-20.3) years. Of the 63 patients, 14 (22%) had early (< 14 d) supraventricular tachycardia or sinus node dysfunction, which was not related to the type of operation. None of 9 patients with a preoperative mean right atrial pressure < or = 2.5 mm Hg had early supraventricular tachycardia or sinus node dysfunction in contrast to 16/54 patients (30%) with a preoperative mean right atrial pressure > 2.5 mm Hg. 6/63 patients died during the early (< 14 d) postoperative period. In only 1 child, death was related to a dysrhythmia (junctional ectopic tachycardia). During a mean follow-up of 2.5 years, 15/57 long-term survivors (21%) had late supraventricular tachycardia or sinus node dysfunction. Early supraventricular tachycardia/sinus node dysfunction was a predictor or late atrial dysrhythmias, as it occurred in 8 of the surviving 14 patients with early dysrhythmias in contrast to 4 children without early atrial dysrhythmias (p < or = 0.001). After creation of an atriopulmonary connection, 10/22 patients (45%) had late supraventricular tachycardia/sinus node dysfunction, but only 2/35 patients (6%) with a total cavopulmonary connection had late atrial dysrhythmias (p < 0.001).

CONCLUSIONS

Early atrial dysrhythmias after the Fontan operation were related to preoperative hemodynamics. Early supraventricular tachycardia/sinus node dysfunction and the atriopulmonary type of Fontan connection were significant risk factors for late atrial dysrhythmias.

[Immediate and late arrhythmia in patients operated on for tetralogy of Fallot]

Arrhythmias are a frequent complication after repair of tetralogy of Fallot (TOF). We present our experience with 97 patients with special consideration for early and late hyperkynetic arrhythmias. The most frequent, 4% of the patients, was in junctional tachycardia. Late arrhythmias can be atrial or ventricular. The incidence of ventricular arrhythmias in the literature range from 42 to 82%. In the Authors experience multiforme ventricular ectopy was present in 80% of the patients, 20 years after surgery. We suggest an exercise test and averaging ECG in all the patients. Thirty six percent of patients with supraventricular tachycardia were symptomatic.

CONCLUSION

as the incidence of arrhythmias after correction of TOF is high, it is very important to periodically reassess these patients. Antiarrhythmic treatment is indicated in all symptomatic patients, especially in those with major arrhythmias (SVT, AF and VT).

Spontaneous atrial flutter in a chronic canine model of the modified Fontan operation

OBJECTIVES

This study sought to 1) establish whether the atrial flutter (AFL) inducible acutely occurs spontaneously in a chronic canine model, and 2) characterize any reentrant circuits present chronically.

BACKGROUND

We previously demonstrated, in an acute canine model of the modified Fontan operation, that the lateral tunnel suture line creates a sufficient electrophysiologic substrate for AFL.

METHODS

Using cardiopulmonary bypass, a suture line was placed through a right atriotomy in adult dogs (n = 7) to simulate the lateral tunnel of the Fontan operation. Holter recordings were made preoperatively, on the first postoperative day and 2, 4 and 6 weeks postoperatively. At 6 to 8 weeks, through bilateral ventriculotomies, 253-point unipolar atrial electrodes were inserted. AFL was induced using atrial burst pacing, and endocardial activation sequence maps were created.

RESULTS

Preoperatively, all dogs were in sinus rhythm. Spontaneous AFL occurred in all dogs postoperatively, with a mean (+/-SD) cycle length of 192 +/- 22 ms. At 6 weeks postoperatively, of six dogs that survived, four had intermittent AFL, and two had incessant AFL. At reoperation, sustained AFL was inducible in six of six dogs, with a mean cycle length of 194 +/- 17 ms. Activation sequence maps demonstrated conduction block at the lateral tunnel suture line, which facilitated unidirectional conduction critical for propagation of the reentrant circuit. The AFL circuit was similar to that observed acutely.

CONCLUSIONS

In a chronic canine model of the modified Fontan operation, the lateral tunnel suture line alone, in the absence of atrial stretch or hypertension, provides an electrophysiologic substrate that promotes spontaneous AFL. This model may be useful for evaluating various forms of treatment and prevention of AFL after the Fontan operation.

Iatrogenically induced intractable atrioventricular reentrant tachycardia after verapamil and catheter ablation in a patient with Wolff-Parkinson-White syndrome and idiopathic dilated cardiomyopathy

In a patient with WPW syndrome and idiopathic dilated cardiomyopathy, intractable atrioventricular reentrant tachycardia (AVRT) was iatrogenically induced. QRS without preexcitation, caused by junctional escape beats after verapamil or unidirectional antegrade block of accessory pathway after catheter ablation, established frequent AVRT attack.

Evaluation of a staged treatment protocol for rapid automatic junctional tachycardia after operation for congenital heart disease

OBJECTIVES

This study sought to 1) develop an efficient treatment protocol for postoperative automatic junctional tachycardia (JT) using conventional drugs and techniques, and 2) identify clinical features associated with this disorder by analyzing a large study group.

BACKGROUND

Postoperative JT is a transient arrhythmia that may be fatal after operation for congenital cardiac defects. Its precise cause is unknown. A variety of palliative treatments have evolved, but because of a low incidence of JT, large studies of the most efficient therapeutic sequence are lacking.

METHODS

A protocol for rapid JT (>170 beats/min) was adopted in 1986, and was tested in 71 children between 1986 and 1994. Staged therapy involved 1) a reduction of catecholamines; 2) correction of fever; 3) atrial pacing to restore synchrony; 4) digoxin; 5) phenytoin or propranolol or verapamil; 6) procainamide or hypothermia; and 7) combined procainamide and hypothermia. Effective therapy was defined as a sustained reduction of JT rate <170 beats/min within 2 h. Clinical profiles of the study group were contrasted with all patients without JT from this same era to identify features associated with JT.

RESULTS

Of the multiple treatment stages, only correction of fever and combined procainamide and hypothermia appeared to be efficacious. By refining the protocol to eliminate nonproductive stages, the time to JT control was significantly shortened for the last 30 patients. Treatment was ultimately successful in 70 of 71 children. Postoperative JT was strongly associated with young age, transient atrioventricular block and operations involving ventricular septal defect closure.

CONCLUSIONS

A staged approach to therapy, with emphasis on combined hypothermia and procainamide in difficult cases, appears to be an effective management strategy for postoperative JT. These results may also serve as comparison data for evaluation of newer and promising JT options, such as intravenous amiodarone. Trauma to conduction tissue may play a central role in the etiology of this disorder.

Successful management of junctional tachycardia by hypothermia after a Fontan operation

We report herein the findings of a 2-year-old boy in whom junctional tachycardia developed 2 days after he underwent a modified Fontan operation and thereafter was successfully treated by hypothermia without paralyzing and artificially ventilating the patient. Chlorpromazine was useful in achieving moderate hypothermia by surface cooling without producing any unfavorable effects associated with topical cooling.