LETTER TO THE EDITOR

P-Wave Duration or P-Wave Morphology? Interatrial Block: Seeking for the Holy Grail to Predict AF Recurrence Adrian Baranchuk, M.D., F.A.C.C., F.R.C.P.C.,∗ Diego Conde, M.D.,† Andres Enriquez, M.D.,∗ and Antoni Bay´es de Luna, M.D.‡ From the ∗ Division of Cardiology, Queen’s University, Kingston, Ontario, Canada; †Cardiovascular Institute of Buenos Aires. Buenos Aires, Argentina; and ‡Cardiovascular Research Center, CSIC-ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain Ann Noninvasive Electrocardiol 2014; 00(0):1–3 interatrial block; atrial fibrillation; P-wave duration.

Dear Editor, We read with interest the manuscript of Gonna et al. recently published in the journal.1 The authors evaluated a group of patients with persistent atrial fibrillation (AF) referred for electrical cardioversion. They manually measured the 12-lead electrocardiogram in sinus rhythm (single operator, semiautomatic calipers) to determine maximum P-wave duration and P-wave dispersion; two noninvasive markers previously associated with AF recurrence in many different clinical scenarios. The main finding of this study was that both measurements predicted AF recurrence at 1 month, evaluated by 12-lead ECG. We would like to comment on the terminology used (that to our understanding may impact on the results), the physiopathology of the prolonged Pwave duration and the interpretation and possible applicability of the results. For the past few decades, several investigators have done major contributions to the understanding of atrial physiology. Atrial synchronicity depends in great part to the connections (and conduction velocity) between the right and left atria. Bay´es de Luna et al. were the first to describe the physiopathology of interatrial block (IAB).2, 3 Delay and eventually block at the Bachman bundle

level results not only in prolongation of the P-wave duration but also in the development of a final negative component of the P wave in the inferior leads. A recent consensus reviewed all literature on this topic and defined IAB as partial (P-wave duration > 120 milliseconds) and advanced (Pwave duration >120 milliseconds with a negative final component of the P wave (±) in the inferior leads).4 This negative component is a reflection of caudal-cranial activation of the left atrium that happens in cases of block at the Bachman level, as it was demonstrated by Bay´es de Luna several years ago (Fig. 1).2 The addition of the morphological analysis, to the strict duration of the P wave, may help in understanding the physiopathological process that occurs during advanced IAB. These noninvasive findings were later on validated by using activation maps.5 One would like to know whether a morphological analysis in the interesting series of Gonna et al.1 may shed some light in understanding which patients with long P-wave duration are more prone to develop AF recurrence. This is even more interesting given that the journal is presenting a second paper from Blanche et al.6 analyzing a similar population (persistent AF, follow-up within the year) but using signal average P-wave analysis (only parameters of

Address for correspondence: Adrian Baranchuk, M.D., F.A.C.C., F.R.C.P.C., Cardiac Electrophysiology and Pacing, Kingston General Hospital, Queen’s University, Kingston, ON K7L 2V7, Canada. Fax: 613-548-1387; E-mail: [email protected]  C 2014 Wiley Periodicals, Inc. DOI:10.1111/anec.12156

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Figure 1. (A) Typical ECG of advanced IAB with P-wave duration of >120 milliseconds and biphasic morphology (±) in inferior leads. (B) Schematic representation of atrial activation, with conduction block in the upper and middle part of the interatrial septum and retrograde LA activation via muscular connections in the vicinity of coronary sinus. (C) Electroanatomic map of the LA during sinus rhythm in a patient with a IAB. Note the LA activation in a caudal-cranial direction. Reproduced with permission (Ref. 8). Modified from Refs. 2 and 5.

P-wave duration) but showing negative results to identify patients with AF recurrence. So the question that arises is: Is P-wave duration enough to deduct the loss of homogeneity in interatrial contraction or the morphology of the P wave should also be taking into account? Our group is now actively trying to answer this question, and it seems that in certain clinical scenarios, the morphological aspect of the P wave is essential to understand the anatomical substrate that could facilitate AF recurrence.7–10 In recognition to the one that has described the association between IAB and AF, its intrinsic physiopathological mechanisms and eventually demonstrated the association between IAB and atrial arrhythmias, we coined the term Bayes’ syndrome to describe this association.11 Our final comment refers to the applicability of Gonna’s results in clinical practice. The cutoff of 142 milliseconds is very difficult to apply in daily practice. Using the previously proposed cutoff of

120 milliseconds would allow the physician to comfortably measure the P-wave duration and have an initial estimation of risk of recurrence.4 We agree with Goona et al. that further research is needed before drawing final conclusions on the validity of these results.

REFERENCES 1. Gonna H, Gallagher MM, Guo XH, Yap YG, Hnatkova K, Camm AJ. P-wave abnormality predicts recurrence of atrial fibrillation after electrical cardioversion: A prospective study. Ann Noninv Electrocardiol 2014;19:57–62. 2. Bayes de Luna A, Cladellas M, Oter R, Torner P, Guindo J, Marti V, Rivera I, Iturralde P. Interatrial conduction block and retrograde activation of the left atrium and paroxysmal supraventricular tachyarrhythmia. Eur Heart J 1988;9:1112–1118. 3. Bay´es de Luna A, Guindo J, Vinolas ˜ X, Martinez-Rubio A, Oter R, Bay´es-Gen´ıs A. Third-degree inter-atrial block and supraventricular tachyarrhythmias. Europace 1999;1(1):43– 46. 4. Bay´es de Luna A, Platonov P, Cosio FG, Cygankiewicz I, Pastore C, Baranowski R, Bay´es-Genis A, Guindo J, Vinolas ˜ X, Garcia-Niebla J, Barbosa R, Stern S, Spodick D. Interatrial

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blocks. A separate entity from left atrial enlargement: A consensus report. J Electrocardiol 2012;45(5):445–451. 5. Cos´ıo FG, Mart´ın-Penato ˜ A, Pastor A, Nu´ nez ˜ A, Montero MA, Cantale CP, Schames S. Atrial activation mapping in sinus rhythm in the clinical electrophysiology laboratory: Observations during Bachmann’s bundle block. J Cardiovasc Electrophysiol 2004;15(5):524–531. 6. Blanche C, Tran M, Carballo D, Rigamonti F, Burri H, Zimmermann M. Usefulness of P-wave signal averaging to predict atrial fibrillation recurrences after electrical cardioversion. Ann Noninv Electrocardiol 2014 Jan 8 [Epub ahead of print]. 7. 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;39:131–138.

8. Enriquez A, Conde D, Hopman W, Mondragon I, Chiale PA, de Luna AB, Baranchuk A. Advanced interatrial block is associated with recurrence of atrial fibrillation post pharmacological cardioversion. Cardiovasc Ther 2014;32:52–56. 9. Conde D, van Oosten EM, Hamilton A, Petsikas D, Payne D, Redfearn DP, Hopman WM, Bay´es de Luna A, Baranchuk A. Prevalence of interatrial block in patients undergoing coronary bypass graft surgery. Int J Cardiol 2014;171:e98– 99. 10. Baranchuk A, Villuendas R, Bayes-Genis A, Goldwasser D, Chiale P, Bay´es de Luna A. Advanced interatrial block: a well-defined electrocardiographic pattern with clinical arrhythmological implications. Europace 2013;15(12):1822. 11. Conde D, Baranchuk A. Interatrial block as anatomical– electrical substrate for supraventricular arrhythmias: Bayes’ syndrome. Arch Mex Cardiol 2014 Feb 12. pii: S14059940(13)00140-7.

P-wave duration or P-wave morphology? Interatrial block: seeking for the Holy Grail to predict AF recurrence.

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