Intracardiac Echocardiography to Guide the Ablation of Parahisian Arrhythmias

Imaging to Facilitate Ventricular Tachycardia Ablation: Intracardiac Echocardiography, Computed Tomography, Magnetic Resonance, and Positron Emission Tomography

Catheter ablation is a well-established and effective strategy for the management of ventricular tachycardia (VT). However, the identification and characterization of arrhythmogenic substrates for targeted ablation remain challenging. Electrogram abnormalities and responses to pacing during VT provide the classical and most validated methods to identify substrates. However, the 3-dimensional nature of the myocardium, nonconductive tissue, and heterogeneous strands of conductive tissue at the border zones or through the nonconductive zones can prohibit easy electrical sampling and identification of the tissue critical to VT. Intracardiac echocardiography is critical for identification of anatomy, examination of catheter approach and contact, assessment of tissue changes during ablation, and even potential substrates as echogenic regions, but lacks specificity with regard to the latter compared with advanced modalities. In recent decades, cardiac magnetic resonance, computed tomography and positron emission tomography have emerged as valuable tools in the periprocedural evaluation of VT ablation. Cardiac magnetic resonance has unparalleled soft tissue and temporal resolution and excels at identification of expanded interstitial space caused by myocardial infarction, fibrosis, inflammation, or infiltrative myopathies. Computed tomography has excellent spatial resolution and is optimal for identification of anatomic variabilities including wall thickness, thrombus, and lipomatous metaplasia. Positron emission tomography excels at identification of substrates including amyloidosis, sarcoidosis, and other inflammatory substrates. These imaging modalities are vital for assessing arrhythmogenic substrates, guiding optimal access strategy, and assessing ablation efficacy. Although clearly beneficial in specific settings, further clinical trials are needed to enhance generalizability and optimize integration of cardiac imaging for VT ablation.

Innovations in ventricular tachycardia ablation

Catheter ablation of ventricular arrhythmias (VAs) has evolved significantly over the past decade and is currently a well-established therapeutic option. Technological advances and improved understanding of VA mechanisms have led to tremendous innovations in VA ablation. The purpose of this review article is to provide an overview of current innovations in VA ablation. Mapping techniques, such as ultra-high density mapping, isochronal late activation mapping, and ripple mapping, have provided improved arrhythmogenic substrate delineation and potential procedural success while limiting duration of ablation procedure and potential hemodynamic compromise. Besides, more advanced mapping and ablation techniques such as epicardial and intramyocardial ablation approaches have allowed operators to more precisely target arrhythmogenic substrate. Moreover, advances in alternate energy sources, such as electroporation, as well as stereotactic radiation therapy have been proposed to be effective and safe. New catheters, such as the lattice and the saline-enhanced radiofrequency catheters, have been designed to provide deeper and more durable tissue ablation lesions compared to conventional catheters. Contact force optimization and baseline impedance modulation are important tools to optimize VT radiofrequency ablation and improve procedural success. Furthermore, advances in cardiac imaging, specifically cardiac MRI, have great potential in identifying arrhythmogenic substrate and evaluating ablation success. Overall, VA ablation has undergone significant advances over the past years. Innovations in VA mapping techniques, alternate energy source, new catheters, and utilization of cardiac imaging have great potential to improve overall procedural safety, hemodynamic stability, and procedural success.

Best Practices for the Catheter Ablation of Ventricular Arrhythmias

Techniques for catheter ablation have evolved to effectively treat a range of ventricular arrhythmias. Pre-operative electrocardiographic and cardiac imaging data are very useful in understanding the arrhythmogenic substrate and can guide mapping and ablation. In this review, we focus on best practices for catheter ablation, with emphasis on tailoring ablation strategies, based on the presence or absence of structural heart disease, underlying clinical status, and hemodynamic stability of the ventricular arrhythmia. We discuss steps to make ablation safe and prevent complications, and techniques to improve the efficacy of ablation, including optimal use of electroanatomical mapping algorithms, energy delivery, intracardiac echocardiography, and selective use of mechanical circulatory support.