Influence of atrial flutter ablation on right to left inter-atrial conduction

Aims Ablation of the atrial isthmus between the tricuspid annulus and the i nferior vena cava changes P-wave morphology during low lateral right atrial pacing. For better understanding of the mechanism of this alteration, the sequence of activation of the inter-atrial septum and the left atrium were compared before and after ablation of the isthmus between the inferior vena cava and the tricuspid annulus. Methods and Results In 13 patients, left atrial mapping was performed using a duodecapolar electrode catheter advanced to the far distal coronary sinu s. The inter-atrial septum was mapped using a right atrial duodecapolar ele ctrode catheter. Conduction times were measured during low lateral right at rial pacing from the pacing artefact and during sinus rhythm from the earli est right atrial electrogram to every intra-cardiac electrogram before and after the ablation. During low lateral right atrial pacing, isthmus ablatio n resulted in a significant delay in every left atrial lead. Changes were m aximal at the posterior aspect of the left atrium and minimal at its anteri or aspect. No significant change was discernible on the inter-atrial septum . During sinus rhythm, atrial activations remained unchanged. Conclusion Electrocardiographic changes of P-wave morphology result from al teration in the sequence of left atrial activation rather than that of the inter-atrial septum. (Europace 2001; 3: 64-72) (C) 2001 The European Societ y of Cardiology.