Mapping of Atrial Arrhythmias in Complex Congenital Heart Disease

Mapping of Atrial Arrhythmias in Complex Congenital Heart Disease

Andreas Pflaumer, Gabriele Hessling, Naccarelli Gerald V
European Cardiovascular Disease 2007 - Issue II
Published: November 2007
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Advances in the treatment of complex congenital heart disease over the past 20 years have led to a dramatic improvement in long-term survival.1 However, the incidence of cardiac arrhythmias as a sequel of palliative heart surgery has also increased significantly in adolescent and adult survivors of congenital heart disease surgery.1,2 Cardiac arrhythmias are the leading cause of emergency admissions in adult congenital heart disease patients with or without surgical intervention.3
The incidence of late arrhythmias has been associated with long-term abnormal pressure–volume load, hypoxia, surgically created scars or suture lines.4–6 Residual haemodynamic problems are frequently encountered in these patients and may be aggravated by the arrhythmia, resulting in heart failure, acute collapse or cardiac arrest. The risk of sudden death is reported to be as high as 6–10% in long-term survivors after surgery for congenital heart disease.1

As patients with congenital heart disease form a heterogeneous population, an optimal treatment strategy for the individual patient has to be defined. This may include medical therapy, catheter ablation or implantation of a pacemaker or automatic internal defibrillator. Medical therapy is often insufficient to control the arrhythmia and exposes patients to the risk of serious side effects, especially with long-term treatment.7 Catheter ablation offers an alternative treatment strategy in many of these patients. New mapping and ablation techniques have improved the understanding of complex arrhythmia mechanisms.

There are some crucial steps to take when approaching an ablation therapy in patients with congenital heart disease. These include adequate preparation of the procedure, reliable identification of the tachycardia circuit and the appropriate ablation site and creation of an effective tissue-altering lesion. This article will focus on the identification of the intra-atrial tachycardia circuit by looking at the most recent developments in mapping, and will also present the two main patient populations that are encountered in the electrophysiology (EP) lab: patients after the Fontan procedure and patients with D-transposition of the great arteries after an atrial switch procedure (Mustard or Senning procedure).

The Use of Mapping Systems
In contrast to a ‘healthy’ atrium with defined anatomical structures, scarring, pressure overload or hypoxia-related changes can lead to the development of complex intra-atrial re-entrant tachycardias (IARTs) in patients after congenital heart disease surgery. Often, conventional mapping fails to depict these re-entrant circuits.8

In most cases IART is dependent on areas of surgical scarring, which function as lines of conduction slowing or block. Therefore, it is important to identify areas of absent or low voltage (<0.03mV), which are catalogued as incisional scars or patches (e.g. coloured grey on CARTO® maps). Other important insights into tachycardia mechanisms are given by ‘double potentials’ – two discrete electrocardiograms separated by at least 20msec. For example, a line of double potentials situated on the free wall of the right atrium (RA) may correlate with an atriotomy scar (a line of conduction block with asynchronous activation on either side). ‘Fractionated’ potentials show continuous low amplitude (<0.1mV) with more than two separate positive or negative deflections. These may also correspond to areas of slow or blocked conduction, or may indicate the site of origin of a focal atrial tachyardia.9

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