Fibrillatory Factor in Ventricular Tachycardia

This study involves recording electrical signals inside the heart during an ablation procedure. It is thought that by studying these electrical signals in detail the investigators may be able to better identify and treat patients at risk of Ventricular Tachycardia (VT). VT is where the lower chambers (ventricles) of your heart beat fast and this condition can be life-threatening. An ablation procedure is performed in patients who have VT despite the best treatment available with tablets. Cardiac ablation involves interrupting the abnormal electrical signals, which cause VT, by applying a type of electrical energy through a catheter. An important part of the ablation procedure is the identification of the exact part of the heart muscle responsible for causing the VT. This typically involves sampling the electrical signals in lots of different areas of the heart, which allows the construction of computer generated 3 dimensional pictures of the structure and the electrical circuits inside the ventricle. Recent research has identified a new method to interpret these electrical signals (called Fibrillatory Factor - FF), which may allow better identification of the area within the ventricle that should be ablated. A standard VT ablation will often involve us controlling the heart-beat by pacing the heart through 1 of the investigators catheters within the heart. The electrical response to pacing at different heart rates can often provide your doctor with information to help the ablation. This study will involve an additional period of pacing at different heart rates, during which the electrical response is measured in different areas around the ventricle. This will allow us to calculate areas of the ventricle, which the investigators new measure FF would predict to be the source of the VT. In the future this may then allow us to better identify patients who are at risk of VT, and to better locate the area that needs to be ablated.

During sinus rhythm these patients will undergo a simple pacing protocol to allow us to calculate FF, which is an area we would predict is mod likely to be the origin of their VT.

To identify the proportion of clinical VT circuits which could be predicted during sinus rhythm from the calculation of fibrillation factor. The number of FF derived VT exit points which are successfully predicted blindly by the investigators (using the clinically derived VT exit point based on electrophysiology assessment and ablation) will be the primary endpoint.

Having established that fibrillatory factor (FF) can predict VT circuits we will then develop our software further so that we can calculate FF in real-time. This will then be used in further research studies to guide invasive mapping.

Inclusion Criteria: Age 18 or above, and capable of giving informed consent Scheduled for a clinically indicated cardiac ablation for the treatment of ventricular tachycardia Exclusion Criteria: Moderate or severe aortic stenosis or mitral stenosis Active infection Presence of thrombus, cardiac tumour, interatrial Baffle patch (a specific form of congenital cardiac surgery) or prior septal occluder device Subjects who cannot be anticoagulated of infused with heparinized saline A history of heparin induced thrombocytopenia Pregnant or actively breast feeding