Paroxysmal supraventricular tachycardia with persistent ventriculoatrial block

Rare narrow QRS tachycardia with atrioventricular dissociation: A case report

BACKGROUND

Most Mahaim fibers are right free-wall atriofascicular accessory pathways with only antegrade conduction. Concealed Mahaim fiber is not very rare; however, concealed nodoventricular fiber is a very rare kind of retrograde accessory pathway in supraventricular tachycardia with atrioventricular (AV) dissociation. Only a few cases about successful ablation of the nodoventricular accessory pathway have been reported. We describe the case of a 32-year-old woman who underwent an electrophysiology study and radiofrequency (RF) ablation of a rare narrow QRS tachycardia with AV dissociation.

CASE SUMMARY

A 32-year-old woman with a history of paroxysmal palpitation was admitted to our hospital for RF ablation. Electrocardiography revealed a narrow QRS complex tachycardia with the same morphology in sinus rhythm. Echocardiography showed no structural heart disease. A right-sided concealed AV accessory pathway and a right-sided concealed nodoventricular accessory pathway were involved in the orthodromic atrioventricular reciprocating tachycardia. His bundle-ventricular interval during tachycardia was the same as that in sinus rhythm. The tachycardia could be initiated and entrained by ventricular pacing. Premature right ventricular stimulus introduced during the His-bundle refractory period when tachycardia occurred was able to advance the next atrial potential. The earliest atrial activation was mapped near the proximal slow AV nodal pathway. RF ablation of both accessary pathways was successfully performed under the guidance of a three-dimensional mapping system by recording the earliest retrograde atrial potential, and tachycardia could no longer be induced.

CONCLUSION

Narrow QRS tachycardia with AV dissociation is inducible by concealed nodoventricular fiber and ablated by recording the earliest retrograde atrial potential.

Reentrant and Nonreentrant Forms of Atrio-Ventricular Nodal Tachycardia Mimicking Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) manifests disorganized atrial activity and irregular R-R intervals on electrocardiogram (ECG). Variation in R-R intervals can also be seen with other supraventricular tachycardias that may mimic AF.

OBJECTIVE

We report our observations on three patients who were referred to our center to undergo pulmonary vein (PV) isolation for erroneously diagnosed AF in the setting of dual atrio-ventricular (AV) nodal pathways manifesting as AV nodal reentrant tachycardia (AVNRT) and/or double response during sinus rhythm.

METHODS AND RESULTS

These three subjects (two females) were derived from a group of 456 consecutive patients undergoing AF ablation at our center over a 3-year period. All three patients had been symptomatic for over 2 years, having failed two or more antiarrhythmic medications. In each case AF was initially diagnosed on ECG and/or recordings from ambulatory monitoring. However, in all three cases the correct diagnosis was established during the invasive electrophysiologic study. In one patient during the stimulation protocol, two narrow complex tachycardias were serially induced (cycle lengths: 305 and 360 msecs; VA time: 60 and 240 msecs). The latter was confirmed to be atypical AVNRT and during this tachycardia, block in upper pathway was observed. In the other two patients, sinus rhythm with repetitive runs of double response and isolated junctional beats were observed in the absence of retrograde conduction. Successful slow pathway modification was performed in each subject and all three patients have remained arrhythmia free over a mean follow-up of 31 +/- 16 months off antiarrhythmic medications.

CONCLUSIONS

AF can be erroneously diagnosed in patients with dual AV nodal pathways manifesting double response and/or AVNRT. Incorporating a stimulation protocol as a part of the AF ablation procedure may help in diagnosing these rare clinical presentations that can be cured by slow pathway modification alone.