Reciprocal impulses of junctional origin causing trigeminy.

Reciprocal impulses of junctional origin were seen in a patient with left isomerism who had undergone Kawashima repair in infancy. Heterotaxy syndromes are associated with disturbances in sinus node function. Junctional rhythm is hence common in this group. Junctional rhythm can conduct both anterogradely, to the ventricles, and retrogradely, back to the atrium. When it conducts retrogradely, it is termed as atrial echo, which can further conduct back to the ventricle. Our patient had a junctional rhythm with atrial echo beats that conduct to the ventricle, along with an ectopic atrial focus that does not conduct to the ventricle. This is due to variation in the RP interval [between R wave and subsequent P wave] of the echo beat and the atrial ectopic beat with respect to the preceding QRS complex. The timing of the P wave after the QRS complex determines the refractoriness of the atrioventricular node. This exhibits a trigeminal rhythm in our patient.