Patients with ischemic ventricular tachycardia (VT) are frequently treated with radiofrequency catheter ablation. The efficacy of catheter ablation is limited for various reasons; one of those being incomplete myocardial and inhomogenous scar tissue damage due to suboptimal ablation lesions.

The aim of our study is to reassess initially ablated endocardial areas in a repeated mapping procedure. Initial lesion parameters will be studied in areas with conduction recovery at repeated mapping procedure. Also, VT inducibility will be correlated to the extent and characteristics of areas with recovered conduction.

Patients with ischemic ventricular tachycardia and implanted defibrillatior (ICD) will be sent to catheter ablation according to current guidelines (ESC and/or HRS). At the initial procedure the scar will be mapped with an ablation catheter and a high density catheter and all abnormal endocardial electrical potentials will be marked on a three-dimensional electro-anatomical (3DEAM) map; late potentials, local abnormal ventricular activity and decrement evoked electrical potentials. Afterwards, programed ventricular stimulation will be performed with an intent to induce sustained ventricular tachycardia. Imaging derived three-dimensional reconstructions of the ischemic scar will be used according to the operator's discretion.

All regions with abnormal endocardial electrical potentials will be ablated with an irrigated, contact force enabled catheter with a power setting of 30-50W. The aim during each energy delivery will be near-field electrical signal dissapearance or absence of myocardial capture at high energy local electrical stimulation. All ablated regions will be re-mapped during the same procedure with a high density mapping catheter. Additional ablation will be performed until all near-field electrical signals are be abolished.

The endpoint of each procedure will be absence of near-field electrical signals in the ablated areas and noninducibility of sustained ventricular tachycardia at the repeated programed ventricular stimulation.

After 1-3 months all patients will have a re-mapping procedure with a high density catheter. Programmed ventricular stimulation will be performed. If any sustained ventricular tachycardia will be induced or if any residual abnormal endocardial electrical potentials will be found in previously ablated regions, additional ablations will be performed with identical ablation settings and endpoints as in the initial procedure.

All areas previously ablated and with recovered electrical conduction will be identified, marked on the 3DEAM map and used for analysis with inclusion of ablation parameters and findings at the initial procedure and (non)inducibility of the sustained ventricular tachycardia at the repeat procedure.

Patients will be followed-up ICD interrogation at scheduled ambulatory visits or reports from emergency or other department using recorded electrocardiograms (ECG).

Inclusion Criteria:

• ischemic heart disease,
• sustained ventricular tachycardia,
• implanted (or scheduled for implantation) cardiac electrical device with ability to record and store intracardiac electrograms

Exclusion Criteria:

• nonischemic cardiomyopathy,
• need for epicardial access to the substrate for treatment of ventricular tachycardia,
• any severe acute organ damage beyond cardiomyopathy that could potentialy omit remapping procedure after 3 months,
• any terminal disease with expected survival of less than one year

Patients with ischemic cardiomyopathy with a clear indication to undergo catheter ablation for treatment of sustained ventricular tachycardia according to recognized and current guidelines (ESC and/or HRS).