Junctional ectopic tachycardia (JET) has been observed in up to 11.4% of pediatric patients after cardiac surgery and is the most common tachyarrhythmia during the early postoperative period.1 Following surgery, the heart is vulnerable to the negative effects of a high heart rate and atrioventriular (AV) asynchrony, which can lead to hemodynamic instability, decreasing cardiac output. Accurate identification of JET is critical because it is not amenable to synchronized cardioversion and is an important factor in postoperative morbidity.1 The following case is an example of the cardioversion attempt of a perfusing tachyarrhythmia mistakenly identified as supraventricular tachycardia (SVT).
Case Report
A 5-month-old, 8.7-kg, female infant underwent surgical treatment of complete atrial-ventricular septal defect with a common atrium, left-looped ventricles, pulmonary atresia with confluent pulmonary arteries, and dextrocardia. A Glenn shunt and AV valvuloplasty was performed with a cardiopulmonary bypass time of 225 minutes and aortic cross-clamp time of 47 minutes.
Adenosine was successfully used in the operating room for SVT after cardiopulmonary bypass was discontinued. Intermittent tachycardia continued throughout the first postoperative night. The morning of postoperative day 1, the patient was tachycardiac (>200/min) with a variable arterial blood pressure. Supraventricular tachycardia was suspected, and the child was cardioverted using 0.5 J/kg of body weight (Figure 1). Immediately afterward ventricular fibrillation occurred without measurable blood pressure or detectable pulse. Defibrillation using 2 J/kg of body weight was immediately performed with restoration of tachyarrhythmia (220/min) with variable blood pressure present (Figure 2). Cardiologists were contacted and consultation identified the rhythm as JET, not SVT. The patient was cooled to a temperature of 35.5[degrees]C via environmental exposure. Potassium and magnesium levels were normalized and the child was given amiodarone 5 mg/kg body weight over 1 hour, with eventual restoration of sinus rhythm.
Discussion
Junctional ectopic tachycardia is associated with AV asynchrony, which may lead to hypotension. The rhythm does not respond to electrical cardioversion.2 The dysrhythmia has been commonly observed following cardiac surgery, and its presence may be a marker of an untoward effect of the surgical procedure.3 Risk factors for the development of JET include young age (<30 days), weight less than 4 kg, aortic cross-clamp time more than 60 minutes, cardiopulmonary bypass time more than 100 minutes, and postoperative magnesium and potassium levels that are lower than normal levels.4,5 Identification of JET is crucial for proper treatment. When AV dissociation is present, cannon A waves will be apparent in the waveforms of central venous pressure monitoring, such as right- and left-atrial lines, and P waves will not be apparent on continuous electrocardiographic monitoring.
Treatment of JET primarily involves support and restoration of hemodynamics. If the rhythm is slow and blood pressure is acceptable, then not treating the arrhythmia may be entertained. In cases of hemodynamic instability, treatment of JET includes overdrive pacing, avoidance of hyperthermia, optimization of sedation, pacer control, and administration of amiodarone.2-7 Optimizing electrolytes and decreasing inotropic therapy may also be indicated.4-7
Lessons Learned
Interdisciplinary teams caring for critically ill pediatric cardiac surgery patients in the postoperative period should be aware that JET is a common rhythm for patients undergoing repairs near the AV node. Supraventricular tachycardia also can occur during this same timeframe and had been successfully treated in the patient with chemical cardioversion (adenosine) in the immediate postbypass period. Although suspecting SVT as the tachyarrhythmia in the patient was reasonable, on reflection, seeking expert consultation before proceeding to cardioversion would have been preferable. The patient had a perfusing rhythm at the time that may have allowed time for a cardiology consult, assessment, and development of a treatment plan. A 12-lead electrocardiogram also could have aided the assessment.
Differences between SVT and JET could have served as cues to which rhythm was present. P waves are absent in both rhythms, and the rates are often more than 200/min in children younger than 1 year. Supraventricular tachycardia, however, usually has a fixed rate that is not changed by stimulation, temperature, or pain medications. The JET rate, on the contrary, can vary up and down on the basis of the patient's condition. Therefore, JET is treated with cooling, sedative agents, and interventions that decrease metabolic demands.6,7 Those who care for pediatric patients at risk of these arrhythmias can use this knowledge to help inform the collaborative decision-making process for interventions.
Proper and timely identification of JET is necessary to avoid morbidity and mortality of postoperative cardiac pediatric patients. Anticipating potential changes in the patient's condition is critical so that evidence-based interventions can be initiated. Interdisciplinary team members caring for this population of patients need expert assessment skills and collaborative processes in place when complexities arise to ensure excellent care for pediatric patients and positive patient outcomes.
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