Research on this Topic

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Summary

Research on this Topic

We would like to briefly review some of the important contributions different groups have published on this topic. Special attention should be paid to the group based in the USA and led by Dr Spodick who investigated several aspects of IAB and specifically its relation to stroke and to the electromechanical dysfunction of the left atrium associated with IAB^24,25.

Daubert’s group from France, studied different aspects of atrial pacing associated with the presence of advanced IAB²⁶.

Garcia-Cosio’s group from Spain performed interesting studies using intracardiac mapping, demonstrating the retrograde activation of the left atrium in these patients²⁷.

Platonov and Holmqvist studied the characteristics of the P wave morphology according to the manner of atrial activation and the relation of this pattern to atrial fibrillation^28,29.

In the past three years, the groups of Baranchuk and Conde from Canada and Argentina have added to the knowledge of the syndrome. Those findings considered the most important are: a) the presence of advanced IAB was a strong predictor of new atrial flutter/fibrillation post-cavotricuspid isthmus ablation for typical atrial flutter¹⁶; b) the presence of advanced IAB in patients with Chagas disease implanted with defibrillators was a strong predictor of new AF in the follow-up¹⁷; c) the presence of advanced IAB is highly prevalent in patients with sleep apnoea and this probably could explain the higher incidence of AF in these patients; d) treatment with CPAP could induce reverse atrial remodelling and resolution of IAB; and e) the presence of advanced IAB predicts new onset AF in patients with severe heart failure and RT¹⁸.

Future Directions

It is our intention to highlight the association of advanced IAB, which can be easily recognised in a surface 12-lead ECG, with atrial arrhythmias (specifically AF). Future investigations (some of them ongoing studies of our international collaboration group) should be considered:

• To create an international register that would allow for longitudinal follow-up of these patients.
• To perform studies to evaluate the prevalence of IAB and its association with atrial arrhythmias in different clinical settings including: a) after electrical cardioversion (larger observational studies)(ongoing); b) cardiac surgery for aortic and mitral valve replacement (ongoing); c) in patients with heart failure (ongoing); d) in patients with hypertrophic cardiomyopathy and other forms of less frequent cardiomyopathies and e) in athletes.
• To determine the prevalence of IAB in special populations (i.e. atrial septum abnormalities, haemodialysis (ongoing), cryptogenec stroke, patients with fibrotic diseases).
• To study the correlation by cardiac MR between advanced IAB ECG pattern and extension of atrial fibrosis.
• To confirm the hypothesis that early intervention with arntiarrhythmic drugs may represent a reduction in the incidence of new AF.
• To determine whether patients with CHA2DS2-score > 3 and advanced IAB, regardless of the documentation of AF, would benefit from oral anticoagulation.
• To determine if there are any genetic influences.