Long-term outcome and mode of recurrence following noninducibility during noninvasive programmed stimulation after ventricular tachycardia ablation

BACKGROUND

Noninducibility of ventricular tachycardia (VT) at noninvasive programmed stimulation performed shortly following ablation (negative NIPS) predicts low risk of the medium-term recurrence. This study aimed to evaluate long-term rate and mode of recurrence following negative NIPS.

METHODS

We extended follow-up on patients in whom no VT could be induced at NIPS following ablation between 2008 and 2010. Recurrent VTs were categorized as "Original clinical" if they matched VT that had occurred spontaneously prior to the index ablation; "Original nonclinical" if they matched VT that was induced during the index ablation but had not occurred spontaneously; or "New." Among those undergoing repeat ablation, the area ablated to treat the recurrent VT was categorized as "Targeted initial scar" if it was targeted during the index procedure; "Untargeted initial scar" if it was present but not targeted during the index procedure; or "New scar" if it was not present during the index procedure.

RESULTS

Of 60 patients with negative NIPS, 18 (30%) had recurrent VT and nine underwent repeat ablation over (4.1 ± 3.2) years follow-up. Of 23 recurrent VTs, 18 (78%) were "New." During repeat ablations, six (46%) of the 13 recurrent VTs were ablated in "untargeted initial scar" and four (31%) in "new scar."

CONCLUSIONS

When spontaneous or inducible VTs are eliminated with ablation and no longer inducible during NIPS, these VTs are unlikely to recur during long-term follow-up. More commonly, new VTs occur, which are either associated with areas of scar not present or not targeted during the initial ablation.

Three-dimensional myocardial scar characterization from the endocardium: Usefulness of endocardial unipolar electroanatomic mapping

Epicardial ablation may be required to eliminate ventricular tachycardia (VT) in patients with underlying structural heart disease. The decision to gain epicardial access is frequently based on the suspicion of an epicardial origin for the VT and/or presence of an arrhythmogenic substrate. Epicardial pathology and VT is frequently present in patients with nonischemic right and/or left cardiomyopathies even in the setting of modest or no endocardial bipolar voltage substrate. In this setting, unipolar voltage mapping from the endocardium serves to help identify midmyocardial and/or epicardial VT substrate. The additional value of endocardial unipolar mapping includes its usefulness to predict the clinical outcome after VT ablation, to determine the irreversibility of myocardial disease, and to guide endomyocardial biopsy procedures to specific areas of intramural scarring. In this review, we aim to provide a guide to the use of endocardial unipolar mapping and its appropriate interpretation in a variety of clinical situations.

Utility of ripple mapping for identification of slow conduction channels during ventricular tachycardia ablation in the setting of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Ripple mapping displays every deflection of a bipolar electrogram and enables the visualization of conduction channels (RMCC) within postinfarction ventricular scar to guide ventricular tachycardia (VT) ablation. The utility of RMCC identification for facilitation of VT ablation in the setting of arrhythmogenic right ventricular cardiomyopathy (ARVC) has not been described.

OBJECTIVE

We sought to (a) identify the slow conduction channels in the endocardial/epicardial scar by ripple mapping and (b) retrospectively analyze whether the elimination of RMCC is associated with improved VT-free survival, in ARVC patients.

METHODS

High-density right ventricular endocardial and epicardial electrograms were collected using the CARTO 3 system in sinus rhythm or ventricular pacing and reviewed for RMCC. Low-voltage zones and abnormal myocardium in the epicardium were identified by using standardized late-gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) signal intensity (SI) z-scores.

RESULTS

A cohort of 20 ARVC patients that had undergone simultaneous high-density right ventricular endocardial and epicardial electrogram mapping was identified (age 44 ± 13 years). Epicardial scar, defined as bipolar voltage less than 1.0 mV, occupied 47.6% (interquartile range [IQR], 30.9-63.7) of the total epicardial surface area and was larger than endocardial scar, defined as bipolar voltage less than 1.5 mV, which occupied 11.2% (IQR, 4.2 ± 17.8) of the endocardium (P < 0.01). A median 1.5 RMCC, defined as continuous corridors of sequential late activation within scar, were identified per patient (IQR, 1-3), most of which were epicardial. The median ratio of RMCC ablated was 1 (IQR, 0.6-1). During a median follow-up of 44 months (IQR, 11-49), the ratio of RMCC ablated was associated with freedom from recurrent VT (hazard ratio, 0.01; P = 0.049). Among nine patients with adequate MRI, 73% of RMCC were localized in LGE regions, 24% were adjacent to an area with LGE, and 3% were in regions without LGE.

CONCLUSION

Slow conduction channels within endocardial or epicardial ARVC scar were delineated clearly by ripple mapping and corresponded to critical isthmus sites during entrainment. Complete elimination of RMCC was associated with freedom from VT.

Role of Cardiac Magnetic Resonance Imaging in Patients with Idiopathic Ventricular Arrhythmias

Ventricular Arrhythmias (VAs) may present with a wide spectrum of clinical manifestations ranging from mildly symptomatic frequent premature ventricular contractions to lifethreatening events such as sustained ventricular tachycardia, ventricular fibrillation and sudden cardiac death. Myocardial scar plays a central role in the genesis and maintenance of re-entrant arrhythmias which are commonly associated with Structural Heart Diseases (SHD) such as ischemic heart disease, healed myocarditis and non-ischemic cardiomyopathies. However, the arrhythmogenic substrate may remain unclear in up to 50% of the cases after a routine diagnostic workup, comprehensive of 12-lead surface ECG, transthoracic echocardiography and coronary angiography/ computed tomography. Whenever any abnormality cannot be identified, VAs are referred as to "idiopathic". In the last decade, Cardiac Magnetic Resonance (CMR) imaging has acquired a growing role in the identification and characterization of myocardial arrhythmogenic substrate, not only being able to accurately and reproducibly quantify biventricular function, but, more importantly, providing information about the presence of myocardial structural abnormalities such as myocardial fatty replacement, myocardial oedema, and necrosis/ fibrosis, which may otherwise remain unrecognized. Moreover, CMR has recently demonstrated to be of great value in guiding interventional treatments, such as radiofrequency ablation, by reliably identifying VA sites of origin and improving long-term outcomes. In the present manuscript, we review the available data regarding the utility of CMR in the workup of apparently "idiopathic" VAs with a special focus on its prognostic relevance and its application in planning and guiding interventional treatments.

Predictive Score for Identifying Survival and Recurrence Risk Profiles in Patients Undergoing Ventricular Tachycardia Ablation: The I-VT Score

BACKGROUND

Several distinct risk factors for arrhythmia recurrence and mortality following ventricular tachycardia (VT) ablation have been described. The effect of concurrent risk factors has not been assessed so far; thus, it is not yet possible to estimate these risks for a patient with several comorbidities. The aim of the study was to identify specific risk groups for mortality and VT recurrence using the Survival Tree (ST) analysis method.

METHODS

In 1251 patients 16 demographic, clinical and procedure-related variables were evaluated as potential prognostic factors using ST analysis using a recursive partitioning algorithm that searches for relationships among variables. Survival time and time to VT recurrence in groups derived from ST analysis were compared by a log-rank test. A random forest analysis was then run to extract a variable importance index and internally validate the ST models.

RESULTS

Left ventricular ejection fraction, implantable cardioverter defibrillator/cardiac resynchronization device, previous ablation were, in hierarchical order, identified by ST analysis as best predictors of VT recurrence, while left ventricular ejection fraction, previous ablation, Electrical storm were identified as best predictors of mortality. Three groups with significantly different survival rates were identified. Among the high-risk group, 65.0% patients were survived and 52.1% patients were free from VT recurrence; within the medium- and low-risk groups, 84.0% and 97.2% patients survived, 72.4% and 88.4% were free from VT recurrence, respectively.

CONCLUSIONS

Our study is the first to derive and validate a decisional model that provides estimates of VT recurrence and mortality with an effective classification tree. Preprocedure risk stratification could help optimize periprocedural and postprocedural care.

Clinical applications of feature-tracking cardiac magnetic resonance imaging

Cardiovascular diseases represent the leading cause of mortality and morbidity in the western world. Assessment of cardiac function is pivotal for early diagnosis of primitive myocardial disorders, identification of cardiac involvement in systemic diseases, detection of drug-related cardiac toxicity as well as risk stratification and monitor of treatment effects in patients with heart failure of various etiology. Determination of ejection fraction with different imaging modalities currently represents the gold standard for evaluation of cardiac function. However, in the last few years, cardiovascular magnetic resonance feature tracking techniques has emerged as a more accurate tool for quantitative evaluation of cardiovascular function with several parameters including strain, strain-rate, torsion and mechanical dispersion. This imaging modality allows precise quantification of ventricular and atrial mechanics by directly evaluating myocardial fiber deformation. The purpose of this article is to review the basic principles, current clinical applications and future perspectives of cardiovascular magnetic resonance myocardial feature tracking, highlighting its prognostic implications.

Epicardial ventricular tachycardia in ischemic cardiomyopathy: Prevalence, electrophysiological characteristics, and long-term ablation outcomes

INTRODUCTION

The characteristics of the epicardial (EPI) substrate responsible for ventricular tachycardia (VT) in ischemic cardiomyopathy (ICM) are undefined, and data on the long-term outcomes of EPI catheter ablation limited. We evaluated the prevalence, electrophysiologic features, and outcomes of catheter ablation of EPI VT in ICM.

METHODS AND RESULTS

From December 2010 to June 2013, a total of 13 of 93 (14%) patients with ICM underwent catheter ablation at our institution and had conclusive evidence of critical EPI substrate demonstrated to participate in VT with activation, entrainment and/or pace mapping during sinus rhythm (two other patients underwent EPI mapping but had no optimal ablation targets). The electrophysiologic substrate characteristics and activation/entrainment mapping data were compared with a reference group of ICM patients without evidence of critical EPI substrate (N = 44), defined as a complete procedural success (noninducibility of any VT at programmed stimulation) after endocardial (ENDO)-only ablation. Patients with failed EPI access (N = 2) or history of cardiac surgery (N = 92) were excluded from the study. All 13 patients had evidence of abnormal EPI substrate with fractionated/late/split electrograms and low-bipolar voltage areas. The critical VT ablation sites were all located within the EPI bipolar "dense" scar (<1.0 mV) opposite the ENDO bipolar scar in 77% of cases and extending beyond the ENDO bipolar scar (within the ENDO unipolar low-voltage area) in the remaining patients. Compared with the reference ENDO-only group, patients with EPI VT had a smaller ENDO bipolar scar area, 54.0 (37.1-84) vs 86.7 (55.6-112) cm² ; P = 0.0159, with a similar extent of ENDO unipolar low voltage. No other substrate characteristics or location differed between the two groups. After 35.2 ± 24.2 months of follow-up, VT-free survival was 73% in patients with EPI VT compared with 66% in the ENDO-only group (log-rank P = 0.56).

CONCLUSIONS

The presence of the critical EPI substrate responsible for VT can be demonstrated in at least 14% of patients with ICM. The majority of EPI critical ablation sites are distributed opposite the ENDO bipolar scar area and catheter ablation is effective in achieving long-term arrhythmia control.

Electrophysiologic Substrate, Safety, Procedural Approaches, and Outcomes of Catheter Ablation for Ventricular Tachycardia in Patients After Aortic Valve Replacement

OBJECTIVES

This study sought to investigate the substrate, procedural strategies, safety, and outcomes of catheter ablation (CA) for ventricular tachycardia (VT) in patients with aortic valve replacement (AVR).

BACKGROUND

VT ablation in patients with AVR is challenging, particularly when mapping and ablation in the periaortic region are necessary.

METHODS

We identified consecutive patients with mechanical, bioprosthetic, and transcatheter AVR who underwent CA for VT refractory to antiarrhythmic drugs and analyzed VT substrate, approach to LV access, complications, and long-term outcomes.

RESULTS

Overall, 29 patients (87% men, mean age 67.9 ± 9.8 years, left ventricular ejection fraction 39 ± 10%) with prior AVR (13 mechanical, 15 bioprosthetic, 1 transcatheter AVR) underwent 40 ablations from 2004 to 2016. Left-sided mapping/CA was performed in 27 patients (36 procedures). Access was retrograde aortic in 11 procedures (all bioprosthetic), transseptal in 24 (13 mechanical; 10 bioprosthetic; 1 transcatheter AVR), or transventricular septal in 1. Periaortic bipolar or unipolar scar was detected in all 24 patients in whom detailed periaortic mapping was performed. Clinical VT circuit(s) involved the periaortic region in 10 patients (34%), 2 (7%) had bundle branch re-entry VT, and 17 (59%) had substrate unrelated to AVR. There were 2 major complications (both related to vascular access). Only 2 patients (9.1%) had VT recurrence. Over median follow-up of 12.8 months, 11 patients died (none as a result of recurrent VT).

CONCLUSIONS

Whereas most patients undergoing CA for VT after AVR had VT from substrate unrelated to AVR, periaortic scar is universally present and bundle branch re-entry can be the VT mechanism. CA can be safely performed with excellent long-term VT elimination.

Outcomes of patients admitted with ventricular arrhythmias and sudden cardiac death in the United States

BACKGROUND

Mortality caused by ventricular arrhythmias (VAs) remains a problem of epidemic proportions. Understanding current trends on admission of VA, patient characteristics, morbidity, mortality, and health care utilization could help us improve allocation of health care resources and risk prediction.

OBJECTIVE

The purpose of this study was to investigate clinical outcomes of VA, including ventricular tachycardia (VT), implantable cardioverter-defibrillator (ICD) shocks, and sudden cardiac death (SCD); and to identify predictors of morbidity and mortality, patterns of utilization of ICD and VT ablation, and the impact of such metrics on overall health care utilization.

METHODS

From 2010-2015, we identified 290,998 VA hospitalizations, which were stratified into group 1: normal heart; group 2: ischemic heart disease (IHD); group 3: nonischemic heart disease (non-IHD); group 4: ICD shocks; and group 5: SCD (cardiac arrest without ICD shock).

RESULTS

The number of admissions for VA decreased during the study period (except for patients with SCD and ICD shock, which increased); in-hospital mortality in patients admitted with VA and SCD increased; utilization of VT ablation in patients with ICD shocks and IHD increased; ICD implantation decreased in non-IHD patients and IHD patients; and admission for SCD was the strongest predictor of in-hospital mortality, followed by patients with non-IHD, patients with ICD shocks, and all patients with a Charlson comorbidity index ≥2.

CONCLUSION

We report a decrease in admissions for VA, decreased ICD utilization, a change in pattern of VT ablation utilization, and an increase of in-hospital mortality in SCD patients. Predictors of adverse outcomes identified in our study should be considered when developing risk models for patients undergoing risk assessment for SCD.

Bundle branch reentrant ventricular tachycardia: review and case presentation

Bundle branch reentrant ventricular tachycardia (BBRVT) is characterized by a unique, fast (200-300 beats/min), monomorphic wide complex tachycardia (WCT) associated with syncope, hemodynamic compromise, and cardiac arrest. It is challenging to diagnose, requiring a His bundle recording and specific pacing maneuvers. The overall incidence has been reported to be up to 20% among patients with non-ischemic cardiomyopathy (NICM) undergoing electrophysiologic studies. We report a case of BBRVT in a patient with ischemic cardiomyopathy (ICM) presenting as a WCT with recurrent implantable-cardioverter-defibrillator (ICD) shocks. We describe all the characteristic features of BBRVT and discuss its differential. We also discuss the role of ablation for this condition.

Importance of the Interventricular Septum as Part of the Ventricular Tachycardia Substrate in Nonischemic Cardiomyopathy

OBJECTIVES

This study sought to characterize septal substrate in patients with nonischemic left ventricular cardiomyopathy (NILVCM) undergoing ventricular tachycardia (VT) ablation.

BACKGROUND

The interventricular septum is an important site of VT substrate in NILVCM.

METHODS

The authors studied 95 patients with NILVCM and VT. Electroanatomic mapping using standard bipolar (<1.5 mV) and unipolar (<8.3 mV) low-voltage criteria identified septal scar location and size. Analysis of unipolar voltage was performed and scars quantified using graded unipolar cutoffs from 4 to 8.3 mV were correlated with delayed gadolinium-enhanced cardiac magnetic resonance (DE-CMR), performed in 57 patients.

RESULTS

Detailed LV endocardial mapping (mean 262 ± 138 points) showed septal bipolar and unipolar voltage abnormalities (VAs) in 44 (46%) and 79 (83%) patients, most commonly with basal anteroseptal involvement. Of the 59 patients in whom the septum was targeted, bipolar and unipolar septal VAs were seen in 36 (61%) and 54 (92%). Of the 35 with CMR-defined septal scar, bipolar and unipolar septal VAs were seen in 18 (51%) and 31 (89%). In 12 patients without CMR septal scar, 6 (50%) had isolated unipolar septal VAs on electroanatomic mapping, a subset of whom the septum was targeted for ablation (44%). In the graded unipolar analysis, the optimal cutoff associated with magnetic resonance imaging septal scar was 4.8 mV (sensitivity 75%, specificity 70%; area under the curve: 0.75; 95% confidence interval: 0.60 to 0.90).

CONCLUSIONS

Septal substrate by unipolar or bipolar voltage mapping in patients with NILVCM and VT is common. A unipolar voltage cutoff of 4.8 mV provides the best correlation with DE-CMR. A subset of patients with septal VT had normal DE-CMR or endocardial bipolar voltage with abnormal unipolar voltage.