Junctional ectopic tachycardia (JET) is one of those rare narrow QRS tachycardias with atrioventricular dissociation. JET is often an arrhythmia seen in the intensive care unit after surgery for congenital heart disease, usually within the first 24 to 48 hours. There is also a congenital variety of JET. Prenatal diagnosis of JET is possible with Doppler flow recordings from the fetal superior vena cava and ascending aorta which can document AV dissociation.
The occurrence of JET following surgery for congenital heart disease ranges from 5-10%. Higher body temperature, longer cardiopulmonary bypass time and evidence of myocardial necrosis are associated with higher incidence of JET. These patients also need longer ventilatory support in intensive care stay, adding to the overall morbidity. Neonates are more prone for JET after cardiac surgery.
Induction of hypothermia has been the sheet anchor of therapy for JET. It may be achieved by infusion of cold saline in addition to surface cooling, aiming at a core temperature in the range of 32 to 34 degrees centigrade. Though usually JET will not respond to atrial pacing, hypothermia reduces the rate so that overdrive atrial pacing to get AV synchrony with reasonable rates is feasible. Additional measures used are magnesium supplementation and amiodarone infusion and occasionally intravenous flecainide. Dexmedetomidine and nifekalant have been reported to be useful in some instances. Propranolol given preoperatively has been associated with a lower incidence of JET post operatively. Radiofrequency catheter ablation has been resorted to in refractory cases of JET with success rates of about 80%.