Frequency Content of Unipolar Electrograms May Predict Deep Intramural Excitable Substrate

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.

Catheter ablation of ventricular tachycardia: strategies to improve outcomes

Catheter ablation of ventricular arrhythmias has evolved considerably since it was first described more than 3 decades ago. Advancements in understanding the underlying substrate, utilizing pre-procedural imaging, and evolving ablation techniques have improved the outcomes of catheter ablation. Ensuring safety and efficacy during catheter ablation requires adequate planning, including analysis of the 12 lead ECG and appropriate pre-procedural imaging. Defining the underlying arrhythmogenic substrate and disease eitology allow for the developed of tailored ablation strategies, especially for patients with non-ischemic cardiomyopathies. During ablation, the type of anesthesia can affect VT induction, the quality of the electro-anatomic map, and the stability of the catheter during ablation. For high risk patients, appropriate selection of hemodynamic support can increase the success of VT ablation. For patients in whom VT is hemodynamically unstable or difficult to induce, substrate modification strategies can aid in safe and successful ablation. Recently, there has been an several advancements in substrate mapping strategies that can be used to identify and differentiate local late potentials. The incorporation of high-definition mapping and contact-sense technologies have both had incremental benefits on the success of ablation procedures. It is crucial to harness newer technology and ablation strategies with the highest level of peri-procedural safety to achieve optimal long-term outcomes in patients undergoing VT ablation.

Wavefront directionality and decremental stimuli synergistically improve identification of ventricular tachycardia substrate: insights from personalized computational heart models

AIMS

Multiple wavefront pacing (MWP) and decremental pacing (DP) are two electroanatomic mapping (EAM) strategies that have emerged to better characterize the ventricular tachycardia (VT) substrate. The aim of this study was to assess how well MWP, DP, and their combination improve identification of electrophysiological abnormalities on EAM that reflect infarct remodelling and critical VT sites.

METHODS AND RESULTS

Forty-eight personalized computational heart models were reconstructed using images from post-infarct patients undergoing VT ablation. Paced rhythms were simulated by delivering an initial (S1) and an extra-stimulus (S2) from one of 100 locations throughout each heart model. For each pacing, unipolar signals were computed along the myocardial surface to simulate substrate EAM. Six EAM features were extracted and compared with the infarct remodelling and critical VT sites. Concordance of S1 EAM features between different maps was lower in hearts with smaller amounts of remodelling. Incorporating S1 EAM features from multiple maps greatly improved the detection of remodelling, especially in hearts with less remodelling. Adding S2 EAM features from multiple maps decreased the number of maps required to achieve the same detection accuracy. S1 EAM features from multiple maps poorly identified critical VT sites. However, combining S1 and S2 EAM features from multiple maps paced near VT circuits greatly improved identification of critical VT sites.

CONCLUSION

Electroanatomic mapping with MWP is more advantageous for characterization of substrate in hearts with less remodelling. During substrate EAM, MWP and DP should be combined and delivered from locations proximal to a suspected VT circuit to optimize identification of the critical VT site.

Newer Methods for VT Ablation and When to Use Them

Radiofrequency (RF) catheter ablation has long been an important therapy for ventricular tachycardia and frequent symptomatic premature ventricular beats and nonsustained arrhythmias when antiarrhythmic drugs fail to suppress the arrhythmias. It is increasingly used in preference to antiarrhythmic drugs, sparing the patient drug adverse effects. Ablation success varies with the underlying heart disease and type of arrhythmia, being very effective for patients without structural heart disease, less in structural heart disease. Failure occurs when a target for ablation cannot be identified, or ablation lesions fail to reach and abolish the arrhythmia substrate that may be extensive, intramural or subepicardial in location. Approaches to improving ablation lesion creation are modifications to RF ablation and emerging investigational techniques. Easily implemented modifications to RF methods include manipulating the size and location of the cutaneous dispersive electrode, increasing RF delivery duration, and use of lower tonicity catheter irrigation (usually 0.45% saline). When catheters can be placed on either side of culprit substrate RF can be delivered in a bipolar or simultaneous unipolar configuration that can be successful. Catheters with extendable/retractable irrigated needles for RF delivery are under investigation in clinical trials. Cryoablation is potentially useful in specific situations when maintaining contact is difficult. Transvascular ethanol ablation and stereotactic radioablation have both shown promise for arrhythmias that fail other ablation strategies. Although substantial clinical progress has been achieved, further improvement is clearly needed. With ability to increase ablation lesion size, continued careful evaluation of safety, which has been excellent for standard RF ablation, remains important.

Radiofrequency Ablation Strategies for Intramural Ventricular Arrhythmias

Catheter ablation is an established treatment strategy for ventricular arrhythmias. However, the presence of intramural substrate poses challenges with mapping and delivery of radiofrequency energy, limiting overall success of catheter ablation. Advances over the past decade have improved our understanding of intramural substrate and paved the way for innovative treatment approaches. Modifications in catheter ablation techniques and development of novel ablation technologies have led to improved clinical outcomes for patients with ventricular arrhythmias. In this review, we explore mapping techniques to identify intramural substrate and describe available radiofrequency energy delivery techniques that can improve overall success rates of catheter ablation.