Atrioventricular nodal reentrant tachycardia in patients with ventriculo-atrial conduction block.

OBJECTIVE

To demonstrate the reversibility of retrograde ventriculo-atrial block by isoproterenol in patients with atrioventricular nodal reentrant tachycardia (AVNRT).

DESIGN

Three case reports and their electrophysiological features.

PATIENTS

Three patients with documented or suspected paroxysmal supraventricular tachycardia.

INTERVENTIONS

At routine electrophysiology study, no supraventricular tachycardia was inducible in the baseline state. Infusion of isoproterenol (1 to 5 micrograms/min) was given and stimulation procedures were repeated.

RESULTS

At baseline, all three patients had discontinuous antegrade atrioventricular (AV) nodal conduction, but very poor (two patients) or absent (one patient) ventriculo atrial conduction prevented induction of AVNRT. During infusion of isoproterenol, retrograde conduction was enhanced so that 1:1 retrograde occurred to cycle lengths of 300, 340 and 260 ms. AVNRT was then inducible in all patients, reproducing their clinical symptoms.

CONCLUSION

Absent or poor ventriculo-atrial conduction in patients with suspected AV node reentry does not preclude the development of tachycardia with sympathomimetic enhancement. Isoproterenol should be given to attempt reversal of retrograde block in these patients.