A scan performed weeks before a mapping procedure may identify a chamber significantly larger than on the day of the procedure after a period of fasting. In addition, chamber size can vary significantly depending on the patient’s hydration status. This system depends on the quality of the digital images available (CT currently has a higher resolution than MRI) and the ease with which the images can be segmented. Detailed chamber anatomy is also helpful in pulmonary vein isolation procedures by delineating the location, size, and orientation of the pulmonary vein ostia. In the future, however, incorporation of electrodes into the shaft of catheters and long sheaths would offer a more complete view of the equipment within in the heart and would assist electrophysiologists still further in catheter positioning without the use of x-ray radiation.įIGURE 92-5 Posteroanterior and anteroposterior images of CARTO 3 (Biosense Webster) left atrial map, demonstrating simultaneous visualization of the circular mapping catheter, coronary sinus catheter and the ablation catheter, with pulmonary vein ablation lesions marked.Įlectroanatomic mapping with CT or MRI image integration is particularly useful in patients with complex anatomy, such as those with congenital heart disease. At present, electrodes of each catheter and their positions can be visualized. Although these lines are often performed by using conventional techniques alone, three-dimensional mapping systems truly allowed electrophysiologists to think in three dimensions within the left atrium.Īnother particular advantage of these systems is that they are nonfluoroscopic that is, x-ray radiation is not required to visualize catheters, which can be positioned and moved within a cardiac chamber or chambers solely by using the electroanatomic system. The advent of electroanatomic mapping has enabled the deployment of complex linear lesions within the left and right atria-most notably the roof line between left and right superior pulmonary veins and the mitral isthmus line, between the left inferior pulmonary vein and the mitral valve annulus. Over the past 10 years, there has been an escalation in the use of three-dimensional mapping systems, particularly for the ablation of AF. Sagittal, coronal, or transverse sections, or any other user-defined plane, can be mapped so the operator can view the chamber from the inside (Figure 92-3).įIGURE 92-3 CARTO Merge (Biosense Webster) image with a sagittal clipping plane to allow visualization of the antrum of left-sided pulmonary veins. Maps do not have to be viewed exclusively from the outside. In addition, these systems facilitate the encirclement of cardiac structures, the best example of which is the encirclement of pulmonary veins as part of the treatment for ablation of atrial fibrillation (AF). This may be between important scar boundaries (e.g., lines of ablation transecting the diastolic pathway in VT circuits) or between inert structures (e.g., linear ablation between the tricuspid valve annulus and the inferior vena cava in isthmus-dependent atrial flutter ). Once generated, the combination of voltage and activation maps can be very useful in guiding the electrophysiologist in placing focal ablation lesions or creating lines of ablation. FIGURE 92-2 CARTO XP (Biosense Webster) geometry of the left ventricle displaying a map of ventricular voltage, with areas of healthy myocardium in pink and colored areas depicting areas of scar.
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