Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction

This method can help answer key questions about how to successfully use 3D mapping for catheter ablation of ventricular tachycardia. The main advantages of this mapping system are that it can automatically assign heartbeats to different origins and can take into account only morphologies relevant for the map. Before beginning the procedure, apply self-adhesive electrocardiogram electrodes for the 12 lead ECG onto the front chest and the extremities of the patient in a standard arrangement.

Then apply surface patches, a neutral electrode, a system reference electrode compatible with the designated 3D mapping system and a neutral electrode for the ablation catheter to the patient's skin in the standard positions. Apply self-adhesive defibrillator patches to the skin below the right clavicle and at the left ventricular apex and switch on the defibrillator. Deactivate the tachycardia therapies at the implantable cardioverter-defibrillator with the appropriate programmer and use 75 percent propanol to disinfect the skin of both groins.

Then cover the patient up to the groins with a sterile cloth. Wearing hair protection and a mask, administer an appropriate local anesthetic to both groins by subcutaneous injection. Use the Seldinger technique to introduce a central venous catheter via the left femoral vein and one five, one six, and one 12 French catheter sheath via the right femoral vein.

Place a quadripolar catheter in the right ventricular apex and dawn the appropriate lead protection materials. Using fluoroscopy, insert an eight-polar steerable catheter into the coronary sinus and introduce a long steerable sheath via the right femoral vein into the right atrium of the heart. After performing transseptal puncture, according to standard procedures, advance the sheath over the dilator under fluoroscopy control and place the distal end of the long steerable sheath in the left atrium, pointing toward the left ventricle.

To reconstruct the left ventricle, introduce the multipolar catheter into the endocardial left ventricle via the steerable sheath and use the 3D mapping system to collect extensive anatomical and electrical data of the ventricle. Using the morphology matching feature to sort out unwanted ventricular complexes, define the ventricular signal voltage of the scar area under 0.5 millivolts, the low voltage area between 0.5 and 1.5 millivolts, and the normal voltage area above 1.5 millivolts. Pay close attention to the ventricular action potentials with more than one component and any second ventricular activation potentials clearly separated from the first ventricular action on a given electrode, annotating these potentials separately with special tags.

When all of the voltages have been defined, remove the multipolar mapping catheter and introduce an irrigated tip ablation catheter with a sensor connecting to a cooling pump into the left ventricle. Then use the ablation catheter to collect any electroanatomical points at places where the multipolar catheter could not be placed to add the missing anatomy and verify any zones of high interest to complete the electroanatomical map. Before beginning the programmed ventricular stimulation, make sure that the external defibrillator is ready to deliver a shock at any time during the procedure.

Next, use an electrophysiology stimulator to send a six feet drivetrain with a 500 millisecond cycle length through the catheter into the right ventricular apex, adding a 350 millisecond extra stimulus of coupling interval after the last stimulus of the drivetrain. If a ventricular tachycardia is induced, perform activation mapping via the catheter in the right ventricular apex if the ventricular tachycardia is hemodynamically stable. After programmed ventricular stimulation, in the case of a well-defined scar in ischemic cardiomyopathy, continue with the substrate modification.

To ablate the lesions, use the ablation catheter to start an irrigated radio frequency ablation with 35 to 45 watts and apply energy to each lesion for a forced time integral of 450 gram seconds, encircling the scar area by the ablation lesions. Then further modify the substrate by ablating all of the previously mapped abnormal potentials and matching the pace mapping in electrically interesting regions to previously marked ventricular tachycardia. Pay close attention to ablation catheter impedance, catheter temperature, and patient blood pressure compared to the initial value, immediately stopping ablation if the impedance drops or rises substantially compared to the initial value.

After the ablation, perform a second programmed ventricular stimulation. If ventricular arrhythmias can be induced, re-evaluate the substrate and continue the ablation. In this study, the simultaneous acquisition of numerous mapping points in a patient with ischemic heart disease after anterior myocardial infarction with occlusion of the proximal left anterior descendant artery allowed a rapid and precise electroanatomical reconstruction of the left ventricle.

The close electrode spacing of the multipolar catheter made possible the detection of critical signals, such as fragmented and late potentials. Additional pacing from the right ventricle clearly separated the late potential from the first ventricular activation, and thus identified the mapped area as a zone of slow conduction of high importance regarding the occurrence and maintenance of ventricular arrhythmias. Using this advanced 3D mapping system in combination with the multipolar mapping catheter and new mapping feature allows the quick generation of a very precise electroanatomical map.