Author's Reply

Abstract

To the Editor, We welcome the opportunity to reply to the letter by Drs Gul and Baranchuk regarding our paper “Advanced interatrial block predicts clinical recurrence of atrial fibrillation after catheter ablation” [[1]Wu J.T. Long D.Y. Dong J.Z. Wang S.L. Fan X.W. Yang H.T. Duan H.Y. Yan L.J. Qian P. Yang C.K. Advanced interatrial block predicts clinical recurrence of atrial fibrillation after catheter ablation.J Cardiol. 2015; https://doi.org/10.1016/j.jjcc.2015.10.015Abstract Full Text Full Text PDF Scopus (31) Google Scholar]. Baranchuk and colleagues have published a great deal of high-quality work on the role of interatrial block (IAB), all of which we have read, and much of which we cited in our own paper, apart from their paper “Prolonged P-wave duration is associated with atrial fibrillation recurrence after successful pulmonary vein isolation for paroxysmal atrial fibrillation” [[2]Caldwell J. Koppikar S. Barake W. Redfearn D. Michael K. Simpson C. Hopman W. Baranchuk A. Prolonged P-wave duration is associated with atrial fibrillation recurrence after successful pulmonary vein isolation for paroxysmal atrial fibrillation.J Interv Card Electrophysiol. 2014; 39: 131-138Crossref PubMed Scopus (82) Google Scholar]. In that study, they showed that the presence of pre-existent prolonged P-wave duration (PWD) ≥140 ms was associated with an increased risk of atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI). We completely agree with the comments of Drs Gul and Baranchuk regarding our own and their previous studies. IAB involves a conduction delay between the right and left atria, and is manifested in a 12-lead electrocardiogram by a PWD >120 ms. IAB was classified into partial (PWD >120 ms) or advanced IAB [PWD >120 ms with biphasic (±) morphology in inferior leads]. PWD indicates the total atrial activation time. Prolongation of PWD can result from a number of different mechanisms including atrial enlargement with lengthening of the activation pathway, increased atrial filling pressure, and overstretch of the atrium in conditions such as valvular disorders, congestive heart failure, and hypervolemia, actual Bachmann block, or slowing of atrial depolarization because of fibrosis, infarction, or atrial hypoplasia [3Song J. Kalus J.S. Caron M.F. Kluger J. White C.M. Effect of diuresis on P-wave duration and dispersion.Pharmacotherapy. 2002; 22: 564-568Crossref PubMed Scopus (34) Google Scholar, 4Boineau J. The prolonged P wave and interatrial block. Time to consider a broader concept and different terminology.J Electrocardiol. 2005; 38: 327-329Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar]. PWD was therefore not in complete accordance with the degree of IAB, as demonstrated in both these studies. In Caldwell et al.’s study referred to by Gul and Baranchuk, patients with PWD ≥140 ms included patients with first-degree IAB (partial IAB) and those with third-degree IAB (advanced IAB), while our study of advanced IAB only included patients with PWD ≥140 ms and <140 ms. These two studies therefore addressed issues in different populations. In addition, an electrocardiogram pattern of advanced IAB with PWD >120 ms and biphasic P-wave morphology in the inferior leads represents a higher degree of interatrial delay, with block of the electrical impulse in the Bachman bundle and caudo-cranial activation of left atrial through the coronary sinus, as demonstrated in a previous study [[5]Waldo A.L. Bush Jr., H.L. Gelband H. Zorn Jr., G.L. Vitikainen K.J. Hoffman B.F. Effects on the canine P waves of discrete lesions in the specialized atrial tracts.Circ Res. 1971; 20: 452-467Crossref Scopus (83) Google Scholar]. This inhomogeneous left atrial activation, evidenced by the biphasic P-wave, which cannot be identified by PWD alone, is probably more important in relation to AF recurrence than the total atrial activation time. This may explain why a PWD ≥140 ms demonstrated moderate sensitivity for the detection of post-PVI AF recurrence in Caldwell et al.’s study. Why were prolonged PWD (≥140 ms) and advanced IAB both predictors of AF recurrence after PVI? Prolonged PWD and advanced IAB are both likely to reflect underlying atrial remodeling, such as atrial fibrosis or atrial dilatation, which are associated with increased recurrence of AF after PVI. Additionally, the list of patients with longer PWD may include more patients with advanced IAB, with a higher degree of interatrial delay and longer PWD. In conclusion, we agree that prolonged PWD, as well as advanced IAB, is a predictor of AF recurrence after PVI, and PVI alone may be insufficient in patients with paroxysmal AF and prolonged PWD or advanced IAB. However, further studies are needed to assess the clinical efficacy of more extensive substrate ablation in these patients.