Contrast ICE for Myocardial Scar in VT Ablations

Contrast Enhanced Intracardiac Echocardiography (ICE) for Localization of Myocardial Scar During Ablation of Ventricular Tachycardia

There is a high correlation between scar areas identified by contrast-enhanced ICE and scar areas identified by conventional electroanatomic mapping. Therefore, the investigators will assess the utility of contrast-enhanced ICE to identify and localize myocardial scar real-time during VT ablation procedures.

Ventricular tachycardia (VT) is a life-threatening arrhythmia which occurs frequently in the setting of structural heart disease, most often as result of myocardial fibrosis or scar. Catheter ablation is often performed to treat recurrent VT, but is predicated on precise localization of myocardial scar, as scar is often the source of VT. Currently during VT ablation procedures the identification of scar is based on electroanatomic mapping where bipolar voltage criteria have been established (i.e., bipolar electrogram voltage < 1.5 mV is considered scar). However this definition is purely based on electrical signal information and so has significant limitations: 1) there has not been definitive establishment of the sensitivity and specificity of this threshold for defining scar in comparison with tissue; 2) a detailed 3-D map created by time-consuming movement of the mapping catheter must be obtained in order to assess the existence and location of the scar; 3) only scar on the surface in contact with the mapping catheter (most often endocardial) may be definitively identified, whereas there may be intramyocardial or epicardial scar that would not be identified unless the mapping catheter makes direct contact with those areas which may involve additional risky access (epicardial) or even impossible (intramyocardial). For these reasons it would be very helpful to have another method to identify and localize myocardial scar during a VT ablation procedure. Cardiac MRI has been validated for identifying and localizing scar, but would not be recommended for many patients due to presence of ICD (implantable cardioverter-defibrillator) devices in these patients. Contrast-enhanced echocardiography has been validated to identify myocardial scar (Montant 2010), and intracardiac echocardiography (ICE) is standardly used in VT ablation procedures. Therefore, the investigators will assess the utility of contrast enhanced ICE by identifying and localizing myocardial scar real-time during VT ablation procedures.

Perflutren echo contrast is infused to enhance intracardiac echo imaging recorded during catheter ablation of ventricular tachycardia. We will compare areas that appear to be myocardial scar on ultrasound with areas of abnormal electrical signals obtained by direct catheter mapping.

Perflutren 1.3mL diluted in 50 mL is infused intravenously, and intracardiac echo imaging is recorded to analyze for areas of possible myocardial scar, which is then compared with areas of abnormal electrical signal via direct catheter mapping which is performed during ablation of ventricular tachycardia.

Inclusion Criteria: Subject is 18 years of age or older Subject is undergoing catheter ablation of likely reentrant VT Planned use of intracardiac echocardiography (ICE) Subject is willing to sign and date the study informed consent form Exclusion Criteria: Contraindication to Perflutren (Optison) echo contrast Known right-to-left, bidirectional, or transient right-to-left cardiac shunts Known hypersensitivity to Perflutren, blood, blood products or albumin Subject has medical condition that would limit study participation (as per MD discretion) Subject is pregnant Inability to give informed consent