History and Physical Examination
History
In general, postoperative junctional ectopic tachycardia (JET) occurs in the hospital with rapid hemodynamic instability, whereas congenital JET may have a more insidious course before producing signs of congestive heart failure.
Postoperative JET usually begins 6-72 hours following cardiopulmonary bypass surgery for repair of congenital heart lesions. It is usually identified during monitoring in the ICU. A fall in blood pressure and cardiac output usually occurs concomitantly.
The onset of congenital JET is often insidious. The clinical presentation of congenital JET may occur from birth to age 4 weeks. However, sporadic cases of intrauterine tachycardia have been reported in infants who presented with JET at birth. Prolonged moderate tachycardia may not be recognized until myocardial dysfunction and signs of congestive heart failure ensue. Heart rate variability is decreased; the heart rate is very regular except for occasional sinus capture beats.
Physical examination
Patients with congenital JET present with moderate tachycardia and signs of congestive heart failure. If VA dissociation has occurred, which is usually the case, cannon waves may be present in the jugular venous pulse, and the intensity of the first heart sound varies.
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Lead II rhythm strip of a surface ECG from a patient with postoperative JET. Atrial activity (P) is marked with blue lines and ventricular depolarization (QRS) is marked in red. Note the narrow QRS complexes due to their origin at the AV junction. Also note the dissociation between atrial and ventricular depolarizations where some of the QRS complexes seem to "follow" the P waves. However, this is not possible because the PR intervals are exceedingly short to allow conduction. In addition, some of the P waves fall after the QRS.
