Patients who have undergone repair of congenital heart disease are at risk of atrial and ventricular tachyarrhythmias and sudden cardiac death (SCD), both because of their arrhythmia substrate and their altered hemodynamic response to it. While patients with even complex cardiac defects now have a realistic chance to survive into adulthood, cardiac arrhythmias are a very common source of morbidity and mortality in this patient group ( Table 18.1 ).
| Type of ACHD | IART | AP-Mediated Arrhythmia | Atrial Fibrillation | VT | SCD |
|---|---|---|---|---|---|
| Atrial septal defect | +++ | — | + | — | — |
| Ventricular septal defect | — | — | + | — | — |
| Ebstein anomaly of the tricuspid valve | + (RA isthmus-dependent flutter) | +++ | ++ | — | — |
| Tetralogy of Fallot | ++ | — | + | +++ | + |
| Transposition of great arteries (post Mustard or Senning) | +++ | — | — | + | + |
| Single ventricle (Fontan) | +++ | — | ++ | — | — |
| Total cavopulmonary connection | ++ | — | + | — | — |
Treating arrhythmias in this patient cohort is challenging for many reasons: the need to understand the patient’s anatomy at baseline and after surgical modification, further change of the anatomic substrate because of myocardial hypertrophy and fibrosis caused by chronic hemodynamic overload, and identification of the underlying tachycardia mechanism(s). Even if all these issues are taken into consideration, delivery of therapy (eg, catheter ablation or lead placement) can be challenging because of the sheer size or location of the target area.
Development of sophisticated mapping systems in recent years has allowed us to address catheter ablation with reasonable chances of success; devices to treat bradycardia and prevent SCD have improved equally, but still carry a significant risk of failure.
Invasive Electrophysiology in Adult Congenital Heart Disease Patients With Atrial Arrhythmias
The most common arrhythmia mechanism in patients with adult congenital heart disease (ACHD) involves a macroreentrant circuit within the atria (intraatrial reentry tachycardia [IART]). These IARTs occur most commonly around anatomic obstacles such as patches or suture lines (eg, at the bypass cannulation sites or atriotomies). Knowing the type of surgical procedure performed, including the presence of artificial material (such as patches or baffles), helps in narrowing down the potential reentrant circuits significantly. However, focal tachycardias are also not uncommon and can be difficult to map and understand, especially in patients with large scar areas. Detailed mapping and confirmation of the three-dimensional (3D) mapping data by conventional electrophysiology (EP) pacing maneuvers are key for a successful ablation procedure.
Understanding the Anatomy
In recent years, the accuracy and availability of 3D imaging modalities such as computed tomography (CT), cardiac magnetic resonance (CMR) imaging, or echocardiography have improved dramatically. Especially in the presence of ACHD, a 3D reconstruction of the individual anatomy of a given patient is very helpful ( Fig. 18.1 ). Familiarization with the underlying anatomy helps facilitate any electrophysiologic intervention and allows planning of optimal access routes (eg, retrograde through a hemiazygos continuation). Direct 3D imaging of scar tissue, for example, by late enhancement in CMR, might prove as valuable in ACHD patients as recently demonstrated in patients undergoing atrial fibrillation ablation. Knowing the dimensions of the target chamber helps in choosing the proper tools (eg, large curves or long guiding sheaths). In some instances, access to the target chamber might be obstructed by artificial valves, which might necessitate transseptal or transbaffle puncture.
Use of Three-Dimensional Mapping Systems for Catheter Ablation in Adult Congenital Heart Disease Patients
With the advent of 3D EP mapping systems, catheter ablation of IART experienced a “quantum leap.” These systems helped display the cardiac chambers in three dimensions, greatly facilitated understanding of the underlying mechanisms, and thereby reduced the total fluoroscopy exposure. Success rates reported for ACHD arrhythmias increased accordingly for acute and chronic results.
Integration of the pre-acquired 3D images is now standard for all 3D mapping systems, allowing the electrophysiologic information to be superimposed on the 3D contour ( Fig. 18.2 ).
Sequential Versus Simultaneous Mapping
In the last 5 years, simultaneous mapping systems have been introduced to the invasive EP arena (contact mapping using multielectrode baskets or noninvasive body surface mapping combined with 3D imaging). Data on patients with ACHD currently exist for noninvasive body surface mapping combined with 3D imaging. This system simultaneously records from 252 surface ECG electrodes and displays the electrical information of each cardiac activation on a 3D epicardial reconstruction of the biatrial or biventricular chambers ( Fig. 18.3 ). This allows mapping of multiple arrhythmias or even very rare arrhythmias (eg, ventricular ectopy triggering ventricular fibrillation) while the patient is still on the ward. Mapping can be performed for several hours, and provocation, such as physical exercise on a stationary bike or with various common stimulants (food, social interaction, pharmacologic, etc.), is carried out on the ward rather than in the catheterization lab.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
