Abstract
Bayés syndrome is an under-recognized clinical condition characterized by inter-atrial block (IAB). This is defined electrocardiographically as P-wave duration > 120 ms and can be categorized into first, second and third degree IAB. It can be caused by inflammatory conditions such as systemic sclerosis and rheumatoid arthritis, abnormal protein deposition in cardiac amyloidosis, or neoplastic processes invading the inter-atrial conduction system, such as primary cardiac lymphoma. It may arise transiently during volume overload, autonomic dysfunction or electrolyte disturbances from vomiting. In other patients without an obvious cause, the predisposing factors are diabetes mellitus, hypertensive heart disease, and hypercholesterolemia. IAB has a strong association with atrial arrhythmogenesis, left atrial enlargement (LAE), and electro-mechanical discordance, increasing the risk of cerebrovascular accidents as well as myocardial and mesenteric ischemia. The aim of this review article is to synthesize experimental evidence on the pathogenesis of IAB and its underlying molecular mechanisms. Current medical therapies include anti-fibrotic, anti-arrhythmic and anti-coagulation agents, whereas interventional options include atrial resynchronization therapy by single or multisite pacing. Future studies will be needed to elucidate the significance of the link between IAB and atrial tachyarrhythmias in patients with different underlying etiologies and optimize the management options in these populations.
Highlights
The first case of inter-atrial block (IAB) was first described by Bachmann (1941), who recognized the significance of P-wave splitting on the ECG, some 25 years after he described the anatomy of Bachmann’s bundle (Bachmann, 1916)
Dr Bayés de Luna was the first who provided a clear description of atrial conduction block in 1979, classifying them into either inter- and intra-atrial (Bayés de Luna, 1979)
The cardiac conduction system starts at the sinoatrial node, which is the pacemaker responsible for initiating action potentials (APs) that are conducted through the right atrium via three distinct
Summary
The first case of inter-atrial block (IAB) was first described by Bachmann (1941), who recognized the significance of P-wave splitting on the ECG, some 25 years after he described the anatomy of Bachmann’s bundle (Bachmann, 1916). Similar to sinoatrial or atrioventricular block, it can be divided into first (partial), second (first degree with intermittent conduction through Bachmann’s bundle) or third degree (advanced; Figure 2; Bayes de Luna et al, 2012; Chhabra et al, 2014). As conduction via Bachmann’s bundle is completely blocked, the AP wave must pass through another pathway, such as the coronary sinus This may result in retrograde activation of the left atrium in the caudo-cranial direction, producing a negative terminal deflection It can be managed by interventional procedures, such as multi-site or single site pacing at the triangle of Koch or Bachmann’s bundle Atrial resynchronization therapy can be used to correct for left-sided atrioventricular dyssynchrony arising from IAB (Daubert et al, 2004)
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