Noncontact biventricular mapping and intramural ablation in a chronic ovine model of septal ventricular tachycardia

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Ventricular tachycardia (VT), an abnormal rhythm originating from the bottom portion of the heart is the major cause of sudden death in the community. Medications are not reliably effective. Expensive (costing about $40,000 every 5 years) implanted defibrillators are very effective in terminating VT, but frequently require painful shocks. Patients who require frequent treatment from their defibrillators are considered for mapping and ablation. About half of the patients with VT have the arrhythmia originating from the septum (heart muscle separating the two bottom portions of the heart). This area of the heart is difficult to map from an electrical point of view. A new type of mapping system called the Ensite 3000 system enables acquisition of 3,300 virtual electrical signals from within a heart chamber using an electrode array that does not have to be in direct contact with the heart muscle surface. Our evaluation of the Ensite system in one chamber of the heart has found it to be very good in identifying areas of abnormal electrical activity. It is possible that simultaneous mapping from both sides of the septum using Ensite might be useful in mapping VT originating from the septum. Destruction of the abnormal area, once identified, is generally done using a catheter, but is limited by its ability to destroy targets deep in the heart tissue. We have designed and developed a catheter that is equipped with a needle at its tip that can create deeper lesions. In this study we will be evaluating mapping using the Ensite electrodes in both ventricles in a chronic sheep model with VT originating from the septum. The Ensite mapping will be validated with detailed contact (conventional) mapping. The prototype catheter will be used to destroy the site of origin of VT, once identified. This study should enable more effective treatment of patients with VT and improve their quality of life.