Comparison of the Location of Slow Conduction Velocity in Cavotricuspid‐Dependent Atrial Flutter in Patients With and Without Prior Atriotomy: Different Arrhythmogenic Basis and Clinical Implications for Placement of Atriotomy

Slow Zone in CTI‐Dependent Flutter After Atriotomy. Introduction: Earlier studies have shown that the slow conduction zone in patients with cavotriscuspid (CTI)‐dependent atrial flutter without prior surgery (NS‐AFL) is the CTI. However, the location of this slow zone in patients with CTI‐dependent flutter and a prior atriotomy has not been formally studied. Identification of the slow zone in patients with prior atriotomy and CTI‐dependent atrial flutter (PA‐AFL) and comparison with NS‐AFL may have important clinical implications. Methods and Results: Seventeen consecutive patients with PA‐AFL and 17 consecutive patients with NS‐AFL were included. Conduction velocity (CV) was measured using 3‐dimensional mapping in 3 areas around the TVA. These regions were defined as the CTI area from lateral inferior vena cava orifice to coronary sinus ostium (region I), mid‐ to upper‐septum (S), and free wall (F). In region F, the CV was much slower in PA‐AFL than in NS‐AFL patients (0.43 ± 0.13 vs 0.76 ± 0.26 m/s, P < 0.01). However, region I was slower in NS‐AFL than PA‐AFL (0.57 ± 0.18 m/s vs 0.84 ± 0.24 m/s, P < 0.01). In all PA‐AFL patients, the slow zone was in region F. But in most (11/17) NS‐AFL patients the slow zone was in region I. There was no significant difference in CV in region S between the 2 groups. Conclusions: Unlike NS‐AFL, CTI in PA‐AFL displays relatively normal conduction but the slow zone is on the free wall. This arrhythmogenecity of atriotomy may perhaps be avoided if the incisional line were altered to extend to the TV. (J Cardiovasc Electrophysiol, Vol. 23, pp. 988‐995, September 2012)