Mapping for ventricular tachycardia

Mapping strategies for ventricular tachycardia (VT) have evolved significantly in the past 2 decades. This review discusses mapping techniques that can help in successful VT ablation. The electrocardiogram (ECG) remains a vital component of VT mapping and can help to identify the chamber of origin of VT. The ECG morphology of VT, however, is influenced by orientation of heart and location of the scar. Activation mapping during VT is an important technique that can help in further localization. Care has to be exercised to ensure that small signals are not ignored and far-field signals are recognized. Pace-mapping to mimic the VT is another way to map exit site for scar based reentrant VT or the site of origin of triggered and automatic VT in the absence of structural heart disease. For the latter group, this technique is widely used in determining the site of ablation. It is important to ensure a complete ECG match (12 out of 12 leads) of the pace-map to the clinical arrhythmia in these patients. In patients with structural heart disease, entrainment mapping remains the gold standard for defining the protected isthmus and other components of the VT circuit. Using this technique, successful ablation of reentrant VT can be achieved in 60–90% of patients. In order to perform entrainment mapping, the VT has to be hemodynamically tolerated; this is not the case in 25% of pts with scar based reentrant VT. The development of 3-dimensional mapping systems allows for more anatomically based linear ablation in patients with poorly tolerated uniform VT. Despite these advances, there are still about 10–20% VTs that cannot be ablated successfully with the above described techniques, especially in patients with structural heart disease. Other recent advances such as percutaneous closed chest epicardial mapping technique and cooled tip ablation catheter technology have the potential to enhance mapping and successful ablation of VT.     

Influence of Clinical and Procedural Predictors on Ventricular Tachycardia Ablation Outcomes: An Analysis From the Substrate Mapping and Ablation in Sinus Rhythm to Halt Ventricular Tachycardia Trial (SMASH‐VT)

Procedural Predictors in SMASH‐VT . Background: The Substrate Mapping and Ablation in Sinus Rhythm to Halt Ventricular Tachycardia (SMASH‐VT) trial is the largest randomized trial in substrate‐based ablation. We performed a retrospective analysis of patients randomized to prophylactic ablation of ventricular tachycardia to determine the predictive value of clinical and procedural variables on outcomes. Methods: In patients treated with catheter ablation, we examined predictors of ICD‐therapy free survival using Cox proportional hazards models. Procedural variables tested included the scar location, number of VT morphologies (VTs) induced, tachycardia cycle length, catheter irrigation, catheter approach, procedural duration, and VT inducibility after ablation. Clinical variables including age, index arrhythmia, NYHA class, ejection fraction, prior revascularization, and baseline medication use were also analyzed. Results: Among 64 patients randomized to ablation, 61 received the assigned therapy and complete procedural data were available for 54 patients. Thirteen percent (7 of 54) experienced ICD therapies during 2‐year follow‐up. Patients with subsequent ICD therapies had significantly more VTs induced during the ablation procedure than those without (3.9 ± 2.1 vs 1.9 ± 1.8, P = 0.05). The hazard ratio for each additional VT induced was 1.51 (95% CI 1.07–2.13, P = 0.02). Two‐year Kaplan–Meier event‐free survival rates were 96% for 0–1 VTs induced, and 78% for two or more. The use of irrigated catheters was not predictive of ablation success. Conclusion: In this small retrospective analysis, the number of VTs induced during the procedure was predictive of 2‐year outcomes. This likely reflects a more complex arrhythmia substrate in patients who fail ablation. (J Cardiovasc Electrophysiol, Vol. pp. 799‐803, July 2010)     

非接触标测在室性心动过速消融中的应用

非接触球囊标测系统以其独有的优势展现了全新的电生理标测方法,在多种心律失常的消融过程中,扮演着重要角色,尤其是室性心律失常的消融,现对非接触球囊标测系统的特点及在室性心动过速消融中的作用分别总结和叙述。     

Ultra High‐Density Multipolar Mapping With Double Ventricular Access: A Novel Technique for Ablation of Ventricular Tachycardia

Ultra High‐Density Multipolar Mapping With Double Ventricular Access . Background: Analogous to the use of circular loop catheters to guide ablation around the pulmonary veins, it may be advantageous to use a multipolar catheter in the ventricle for rapid mapping and to guide ablation. We describe a technique using double access into the left ventricle for multipolar electroanatomic mapping and ablation of scar‐mediated ventricular tachycardia (VT). Methods: Double access into the left ventricle was obtained via transseptal technique. Endocardial mapping was performed via the first transseptal sheath using a steerable duodecapolar catheter. Higher density mapping was performed in areas of dense scar (<0.5 mV) and border zone (0.5–1.5 mV). All late potentials (LPs) observed on the 20 poles were tagged and pacemapping was performed at these sites for comparison with the clinical or induced VT 12‐lead template. If VT was hemodynamically tolerated, entrainment mapping was attempted at sites demonstrating diastolic activity. Ablation was performed through the second transseptal sheath with an open‐irrigated catheter at target sites identified by LPs, pacemapping, and/or entrainment on the duodecapolar catheter. Results: Seventeen patients (88% ischemic cardiomyopathy) underwent electroanatomic mapping and ablation with double transseptal access. The mean number of endocardial mapping points was 819 ± 357 with an average mapping time of 31 ± 7 minutes. The mean number of VTs induced was 2.8 ± 1.6, mean cycle length 418 ms ± 101. LPs were seen in all patients during endocardial mapping with the duodecapolar catheter. Good (56%) and perfect (44%) pacemaps were seen in all patients when performed. Concealed entrainment, guided by the earliest diastolic activity seen on the duodecapolar catheter, was demonstrated in 4 patients (24%). Acute success was achieved in 94% of patients with complete success in 47% and partial success in 47%. The intermediate success rate (free of VT recurrence) was 69%, with an average follow‐up of 8 ± 3 months. Conclusion: Mapping and ablation of scar‐mediated VT using a multipolar catheter results in ultra high‐density delineation of the left ventricular substrate. A novel double ventricular access strategy has the potential to facilitate identification of LPs, pacemapping, and entrainment mapping. (J Cardiovasc Electrophysiol, Vol. 22, pp. 49‐56, January 2011)     

Anterior Q-Wave Infarction Complicating Attempted Catheter Electrode Ablation of Ventricular Tachycardia

This report describes an attempt to treat recurrent ventricular tachycardia by catheter electrode ablation. The procedure failed to control the arrhythmia and resulted in a Q-wave anteroseptal myocardial infarction. The potential complications of catheter electrode ablation in the normal ventricle are emphasized.     

Our Approach to Minimize Risk of Epicardial Access: Standard Techniques with the Addition of Electroanatomic Mapping Guidance

Epicardial mapping and ablation is increasingly being performed for the treatment of complex arrhythmias. Right ventricular (RV) puncture remains the most common complication, with damage to surrounding non‐cardiac structures also a concern. We describe the standard techniques used in our lab essential for safe epicardial access, as well as a novel technique incorporating electroanatomic mapping (EAM) guidance. In a series of 8 patients referred for ventricular tachycardia ablation, an RV endocardial voltage map was created using EAM systems. EAM images were fused with preprocedure CT scans when available. A 17G Tuohy needle was integrated with the EAM system by attaching the needle to sterile electrode clamps. EAM location points were used in conjunction with standard access techniques until epicardial access was obtained. Epicardial access was successfully obtained in 8/8 (100%) patients. Successful access without RV puncture was achieved in 7/8 (88%) cases. This proof of concept study demonstrates that EAM systems can be used as an adjunct to standard access techniques to visualize and facilitate pericardial access.     

Use of electrogram characteristics during sinus rhythm to delineate the endocardial scar in a porcine model of healed myocardial infarction

INTRODUCTION: Substrate-based catheter ablation of postmyocardial infarction (post-MI) ventricular tachycardia necessitates electroanatomic definition of the scarred endocardium. We sought to determine whether electrogram criteria during sinus rhythm could identify the location and extent of the myocardial scar by electroanatomic mapping. METHODS AND RESULTS: A porcine model of healed MI was generated by injecting agarose microspheres into the mid left anterior descending coronary artery. At least 4 weeks post-MI, the animals (n = 24) underwent detailed left ventricular endocardial electroanatomic mapping using a 4-mm-tip catheter (BioSense-Webster, Inc.). Based upon mapping data in normal animals, infarcted tissue was defined as bipolar electrogram amplitude < 1.5 mV and electrogram duration > or = 50 msec. Radiofrequency ablation lesions (2-10 per animal) were placed to tag the endocardial borders of the electroanatomic mapping-defined scar. The area of the scar defined by abnormal voltage amplitude was 25.9 +/- 15.4 cm2 (range 6.9-60.5). This area correlated well with that defined as scar by the electrogram duration criteria (26.4 +/- 16 cm2). Of those points remote from the infarct with falsely low voltage amplitude resulting from presumed poor catheter-tissue contact, 94% were correctly identified as normal when using the electrogram duration criteria. Late potentials were observed predominantly along the borders of the infarcted myocardium. The radiofrequency lesions placed to tag the scar borders were located along the scar periphery during gross pathologic examination. CONCLUSION: During normal sinus rhythm, both bipolar electrogram voltage amplitude and electrogram duration criteria are able to help differentiate normal from scarred myocardial tissue. Using these criteria, a detailed reconstruction of the endocardial scar can be rendered by electroanatomic mapping of the heart.     

Catheter Ablation of Repetitive Monomorphic Ventricular Tachycardia From Left Ventricular Outflow Tract Guided by Unipolar Mapping

Repetitive monomorphic ventricular tachycardia from the left ventricular outflow tract is an uncommon arrhythmia. Successful catheter ablation has been previously reported in a few cases, but a large number of applications were usually needed when an approach based on either activation mapping or pace mapping was used. In our patient, the selection of the target point for application was based exclusively on unipolar mapping criteria of the ectopic beats, resulting in a short procedure with successful outcome.