Interatrial Block (IAB)

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Interatrial Block (IAB)

• ANWER GHANI
• FIBMS
• IRAQ

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• It has been considered that an interatrial block
  exists when there is a delay of conduction in
  some part of the Bachmanns bundle zone.

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• The interatrial blocks are the most frequent and
  well-known blocks at atrial level.

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• Partial IAB (P-IAB) P wave duration that equals
  or exceeds 120 milliseconds and a bimodal
  morphology, especially in leads I, II, VL or
  inferior leads.

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• advanced interatrial block (A-IAB) P wave
  morphology in II, III, and VF with duration
  120 ms.

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• The prolonged P wave duration (P-wave duration
  120 milliseconds) may be present in the elderly
  but can also be a consequence of acute illness,
  such as pericarditis or acute myocardial
  infarction.

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• The combination of LAE with advanced interatrial
  block (A-IAB) is very common but isolated cases
  of A-IAB may be seen.

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• Cutting the Bachmanns bundle at either the right
  or left atrial side results in a typical ECG
  pattern with wide P wave with biphasic morphology
  in inferior leads.

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• The interatrial blocks may be of first (partial),
  second (transient interatrial block is part of
  atrial aberrancy), or third degree (advanced).

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.First-degree (Partial) Interatrial Block

• -The electrical impulse is conducted from the
  right to the LA through the normal propagation
  route but with a delay.
• -The ECG shows that a P wave of 120 milliseconds
  or more, usually bimodal, is especially visible
  in leads I, II, or III.

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Second-degree Interatrial Block

• Interatrial block occurs transiently on a beatby-
  beat basis or may be recorded momentarily.
• The morphology of the P wave may change in the
  same recording from interatrial block pattern
  (first or third degree) to normal pattern,
  usually transiently in relation to the preceding
  premature beats.
• These changes may be considered as atrial
  aberrancy.
• Atrial aberrancy may also present a transient
  bizarre P wave without the morphology of
  interatrial block. In these cases, the location
  of the block is usually the right atrium.

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Third-degree (advanced) Interatrial Block

• The electrical impulse is blocked especially in
  the upper and middle part of the interatrial
  septum, in the Bachmanns bundle zone, and/or in
  the upper part of LA.
• Retrograde left atrial activation occurs mainly
  via muscular connections in the vicinity of
  coronary sinus.
• In rare occasions, the right atrium and LA can
  demonstrate dissociated electrical activity.

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Third-degree (advanced) Interatrial Block

• The ECG shows that
• (a) P wave duration of 120 milliseconds or more.
• (b) the morphology of P wave is usually
  biphasic in leads II, III, and VF ( and also
  often in V1 to V3)
• The electrophysiological mechanism underlying
  this ECG pattern has been explained using
  deductive ECG-VCG data.

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Third-degree (advanced) Interatrial Block

• In dogs, the same biphasic morphology appears
  after cutting the Bachmanns bundle at the right
  and left sides of the septum.
• Atrial fibrosis is considered the anatomic
  substrate of A-IAB, which does not necessarily
  mean that the LA is enlarged.
• P wave (biphasic in inferior leads) that
  pinpoints that there is a retrograde activation
  of the LA.
• This type of block is very frequently accompanied
  by paroxysmal atrial arrhythmia.

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• .

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Inter-Atrial Block degrees

• 1st d pIAB prolonged P-wave durationgt120
  ms.
• 2nd d tIAB transient IAB, ( a, p)
• 3rd d aIAB prolonged P-wave durationgt120ms
  biphasic P-wave morphology.
• - Bayés syndrome The association of A-IAB and AF.

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• The prevalence of partial (P) and advanced AIAB
  is rare before the age of 50.
• The prevalence is much higher with advancing age.
• In patients with heart failure a prevalence of
  A-IAB of 10 .

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• The advanced IAB group presented a higher
  incidence of atrial flutter/fibrillation during a
  30-month follow-up compared with partial IAB.
• At one year of follow-up, the incidence of
  arrhythmias was 80 and 20 of AIAB and PIAB
  respectively.
• The prevalence of frequent premature atrial
  contractions (more than 60/h by Holter) was much
  more frequent in advanced (75 ) than in partial
  (25 ) IAB.

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Bayés syndrome

• The association of A-IAB and AF has been called
  Bayés syndrome.

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• The strong relationship between advanced IAB and
  atrial flutter/ fibrillation suggests the
  possible role of preventing atrial arrhythmias
  using antiarrhythmic drugs.
• A small comparative trial of patients with
  advanced IAB received either an antiarrhythmic
  drug or a placebo.
• A significant reduction of AF recurrences was
  observed at follow-up in the group receiving
  prophylactic antiarrhythmic medication.

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BAYÉS SYNDROME

• Bayés syndrome is a new clinical entity,
  characterized by the association of advanced
  interatrial block (IAB) on surface
  electrocardiogram with atrial fibrillation (AF)
  and other atrial arrhythmias. This syndrome is
  associated with an increased risk of stroke,
  dementia, and mortality. Advanced IAB is
  diagnosed by the presence of a P-wave 120ms
  with biphasic morphology () in inferior leads.
  The cause of IAB is complete Bachmann bundle
  blockade, leading to retrograde depolarization of
  the left atrium from areas near the
  atrioventricular junction. The anatomic substrate
  of advanced IAB is fibrotic atrial
  cardiomyopathy. Dyssynchrony induced by advanced
  IAB is a trigger and maintenance mechanism of AF.
  This alteration of the atrial architecture
  produces atrial remodeling, blood stasis and
  hypercoagulability, triggering the thrombogenic
  cascade. The presence of advanced IAB, even in
  patients without documented atrial arrhythmias,
  has also been associated with AF, stroke,
  dementia, and mortality. However, in these
  patients, there is no evidence to support the use
  of anticoagulation.
• What every clinician should know about Bayés
  syndrome Síndrome de Bayés. Lo que todo clínico
  debe conocer Antoni Bayés de Lunaa, Manuel
  Martínez-Sellésb, , Antoni Bayés-Genísc, Roberto
  Elosuad, Adrián Baranchuke
• Revista Española de Cardiología .2020.04.026

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BAYÉS SYNDROME

• In 1988, Bayés de Luna et al.1 reported that
  patients with advanced interatrial block (IAB)
  presented with supraventricular arrhythmia more
  often than patients with partial IAB. However,
  until a consensus article was published on IAB in
  2012,2 only a few authors had shown interest in
  the subject, mainly the groups led by Spodick,3
  García-Cosío,4 and Platonov,5 as well as our own
  group.6,7 Since this consensus article was
  published, there has been growing interest, and
  Conde and Baranchuk8 named this combination
  Bayés syndrome, a term quickly accepted by the
  scientific community.
• What every clinician should know about Bayés
  syndrome Antoni Bayés de Lunaa, Manuel
  Martínez-Sellésb, Antoni Bayés-Genísc, Roberto
  Elosuad, Adrián Baranchuke
• Revista Española de Cardiología .2020.04.026

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THANKS

• The reference Antoni Bayés de Luna,Albert
  Massó-van Roessel,Luis Alberto Escobar Robledo
  The Diagnosis and Clinical Implications of
  Interatrial Block.European Cardiology Review
  201510(1)549