Invasive Electrophysiology

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.

In the field of sequential mapping systems, multielectrode mapping has been introduced to shorten the time required for mapping of a given arrhythmia. However, it is critical for these systems that the arrhythmia is relatively stable with little cycle length variation. Also, because direct contact is required, the risk of mechanical alteration or termination is higher. Fig. 18.4 shows an example of the Rhythmia system (Boston Scientific, Marlborough, Massachusetts), which collects a large number of points with a dedicated multielectrode basket catheter. Comparison of neighboring points and various other stability criteria (including cycle length stability) allows rapid mapping of several thousand points on a 3D reconstruction. No data are yet available using this technology in a patient cohort with ACHD.