Slow pathway ablation provides curative treatment for patients with atrioventricular nodal re-entrant tachycardia (AVNRT). The major concern remains the induction of complete atrioventricular (AV) block.¹ To minimise the risk, many centres apply a stepwise approach, targeting initially inferoposterior sites of the septal annulus of the tricuspid valve.² If the first ablation attempts are unsuccessful, the catheter is positioned at more medial and finally anterosuperior sites. Thus, the longest possible distance from the AV node is kept during energy delivery.

Previous investigations suggest that the successful ablation site may be related to the conduction interval of the slow pathway.^3–5 Since this interval is a determinant of the tachycardia cycle length, we hypothesised that the successful ablation site may be related to the heart rate during tachycardia. Such a finding would be important, since it would possibly allow a rough prediction of the successful ablation site and, thus, an approximate stratification of the risk of AV block based on ECG documentation of the tachycardia.

METHODS

We studied 109 patients (44 men, 65 women, mean (SD) age 47 (16) years) with AVNRT undergoing slow pathway ablation.

After providing informed written consent, patients underwent the procedures in the fasting, non-sedated state. All antiarrhythmic agents had been discontinued for at least five drug elimination half lives.

The stepwise approach was applied as follows. The septal annulus of the tricuspid valve, extending from the most inferior area of the annulus adjacent to the coronary sinus ostium to the His …