ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA - A REVIEW

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of regular narrow complex tachycardia. It is due to dual atrioventricular nodal conduction over two pathways with different electrophysiological properties. The first pathway ('fast' pathway) conducts faster but has longer refractory period than the second pathway ('slow' pathway). OBJECTIVES: To review AVNRT. Clinically, AVNRT patients usually have palpitations in their neck during attacks. On the surface electrocardiogram, the diagnosis is suggested by the absence of P waves during tachycardia or very discrete P waves immediately after the QRS or an rSr' pattern in lead VI. Electrophysiologically, it can be reproducibly initiated or terminated by cardiac pacing. The reentrant circuit is limited to the atrioventricular node and a small amount of perinodal atrial tissue. Acute termination of tachycardia can be achieved by vagal manoeuvres or drugs. Adenosine compounds are excellent drugs, as are calcium channel blockers, for acute termination of the arrhythmia. If chronic therapy is indicated, digitaiis, calcium blockers and beta-blockers are effective and simple initial options. Catheter ablation, especially using radiofrequency energy, antitachycardia pacing and surgery are therapeutic alternatives for the resistant patient. CONCLUSION: Because of its high success rate and low incidence of complications, radiofrequency ablation is becoming the therapy of first choice for the treatment of AVNRT.