ABSTRACT
The electrophysiological mechanisms of a large number of cardiac arrhythmias are now well understood and amenable to ablation therapy. The prerequisite of this therapeutic approach requires accurate localization of critical regions of the arrhythmia circuit by mapping and the delivery of ablative lesions to prevent recurrence. Surgical ablation of arrhythmias is now seldom used, unless there are other reasons for surgical intervention, such as concomitant coronary artery bypass or valve surgery, due to the morbidity and mortality associated with this procedure [1,2]. For the majority of common cardiac arrhythmias, in which the pathological and electrophysiological abnormalities are well characterized, conventional mapping techniques are effective in localizing sites for ablation. However, it may not be possible to map complex cardiac arrhythmias using conventional techniques, because there are a number of limitations of conventional mapping. Contact catheters can only record changes of potential at a single point on the endocardium and there is a limit to the number of catheters that can be used. It is possible to obtain spatial information of activation by sequential point-to-point mapping from different sites and examine the temporal relationship to a reference electrode, but this is time consuming and requires the presence of continuous tachycardia for long periods. This approach may not be feasible for patients with poorly tolerated tachycardias such as fast ventricular tachycardias (VT) or if the arrhythmia is nonsustained. The
complex three-dimensional structure of the cardiac chamber, often in the presence of structural heart disease and geometric changes that occur during contraction, makes accurate endocardial mapping difficult. Multielectrode contact catheters have been developed in the form of expandable baskets. These have been limited to 64 electrodes, a proportion of which are functionally redundant due to inadequate endocardial contact, and resolution is limited by the interspline spaces [3,4].
