Periaortic Ventricular Tachycardias in Nonischemic Cardiomyopathy: Substrate and Electrocardiographic Correlations

BACKGROUND

Periaortic fibrotic ventricular tachycardia (VT) substrate is common in nonischemic cardiomyopathy (NICM), often intramural, and difficult to ablate. We sought to better characterize normal and abnormal periaortic voltage map parameters and NICM periaortic VTs.

METHODS

In 15 patients without heart disease, the 5th percentile of endocardial voltage for increasing distance from the aortic valve ring was determined. In 53 consecutive patients with NICM (64±11 years; left ventricular ejection fraction 31±10%) undergoing ablation of recurrent VT, periaortic electrogram voltage and VT characteristics were analyzed.

RESULTS

In healthy patients, the fifth percentile of the bipolar voltage increased proportional to the distance from the aortic valve ring, from 1.0 mV at 1 cm to 1.5 mV at 1.5 cm; the corresponding unipolar voltage cutoffs were 5.0 and 7.5 mV. A total of 160 VTs were induced in 53 patients with NICM, of which 28 VTs in 20 patients had periaortic origins. Periaortic VTs were associated with similar periaortic bipolar voltage, but lower UVs consistent with intramural fibrosis as an important substrate. Periaortic VTs could be divided into left and right bundle branch block forms with mapping showing right septal and lateral exits. Left bundle branch block VTs were more often acutely abolished with ablation (100% versus 69%; P=0.034), but with a 23% incidence of heart block. Greater extent of low voltage was associated with more induced VTs and worse acute outcome.

CONCLUSIONS

Adjusting voltage parameters based on distance from the aortic valve may improve definition of left ventricular outflow tract arrhythmia substrate. Periaortic VTs are common in NICM, often associated with intramural substrate and can be divided into left bundle branch block and right bundle branch block types associated with different ablation outcomes and risks.

Renal Sympathetic Denervation as Upstream Therapy During Atrial Fibrillation Ablation: Pilot HFIB Studies and Meta-Analysis

OBJECTIVES

This study sought to determine the impact of adjunctive renal sympathetic denervation to catheter ablation in patients with atrial fibrillation (AF) and history of hypertension.

BACKGROUND

There are limited data regarding the impact of upstream adjunctive renal sympathetic denervation (RSDN) to pulmonary vein isolation (PVI) in patients with symptomatic atrial fibrillation (AF) and hypertension.

METHODS

The data for this study were obtained from 2 prospective randomized pilot studies, the HFIB (Adjunctive Renal Denervation to Modify Hypertension and Sympathetic tone as Upstream Therapy in the Treatment of Atrial Fibrillation)-1 (n = 30) and HFIB (Adjunctive Renal Denervation to Modify Hypertension and Sympathetic tone as Upstream Therapy in the Treatment of Atrial Fibrillation)-2 (n = 50) studies, and we performed a meta-analysis including all published studies comparing RSDN+PVI versus PVI alone up to January 25, 2020, in patients with AF and hypertension.

RESULTS

At 24 months, AF recurrence occurred in 53% and 38% in the PVI and PVI+RSDN groups (p = 0.43) in the HFIB-1 study, respectively, and 27% and 25% in the PVI and PVI+RSDN groups (p = 0.80) in the HFIB-2 study, respectively. When combined in a meta-analysis including 6 studies (n = 725), adjunctive RSDN significantly decreased the risk of AF recurrence (risk ratio [RR]: 0.68; 95% confidence interval [CI]: 0.55 to 0.83; p = 0.0002; I² = 0%) when compared with PVI. Six renal artery complications occurred in the HFIB-1 study and none occurred in the HFIB-2 study with RSDN. However, in the meta-analysis, there were no significant differences in overall complications between both groups (RR: 1.43; 95% CI: 0.63 to 3.22; p = 0.40; I² = 7%). When compared with baseline, RDSN significantly reduced the systolic blood pressure (-12.1 mm Hg; 95% CI: -20.9 to -3.3 mm Hg; p < 0.007; I² = 99%) and diastolic blood pressure (-5.60 mm Hg; 95% CI: -10.05 to -1.10 mm Hg; p = 0.01; I² = 98%) on follow-up.

CONCLUSIONS

The pilot HFIB-1 and HFIB-2 studies did not demonstrate a benefit with RSDN as an adjunctive upstream therapy during PVI. However, in the meta-analysis, adjunctive RSDN to PVI appears to be safe, and improves clinical outcomes in AF patients with a history of hypertension.

Conduction Recovery After Cavotricuspid Isthmus Ablation When Performed With or Without Concomitant Atrial Fibrillation Ablation

OBJECTIVES

This study sought to define the association between conduction recovery across the cavotricuspid isthmus (CTI) and typical atrial flutter (AFL) recurrence when CTI ablation is performed with pulmonary vein isolation (PVI) compared with a stand-alone procedure.

BACKGROUND

CTI ablation is commonly performed at the same time as PVI to treat AFL or as an empiric therapy. Conduction recovery is a recognized problem after linear ablation in the left atrium (e.g., mitral isthmus ablation) and is proarrhythmic. Less is known about conduction recovery after CTI ablation and possible differences in outcomes when performed at the time of PVI compared with at the time of a stand-alone procedure.

METHODS

Eligible participants who underwent stand-alone CTI ablation were compared with those who underwent a combined (CTI+PVI) procedure. CTI conduction recovery was assessed at the time of a second ablation. Conduction recovery across the CTI (primary outcome) and recurrence of typical AFL (secondary outcome) were studied using multivariable logistic regression.

RESULTS

Among 295 eligible participants (median age: 64 years [interquartile range: 55 to 69 years]; 33% women), recovery was assessed in 232 and was more common after combined versus stand-alone CTI ablation (52% [72 of 139] vs. 13% [12 of 93]; p < 0.001). In multivariable analysis, CTI ablation performed as a combined procedure increased odds of CTI conduction recovery 7.8-fold (odds ratio: 7.8; 95% confidence interval: 3.3 to 18.3; p < 0.001) and clinical AFL recurrence 4.1-fold (odds ratio: 4.1; 95% confidence interval: 1.0 to 16.9; p = 0.049).

CONCLUSIONS

CTI ablation performed at the time of atrial fibrillation ablation is associated with higher rates of conduction recovery and typical flutter recurrence.

Role of Contact Force Sensing in Catheter Ablation of Cardiac Arrhythmias: Evolution or History Repeating Itself?

Adequate catheter-tissue contact facilitates efficient heat energy transfer to target tissue. Tissue contact is thus critical to achieving lesion transmurality and success of radiofrequency (RF) ablation procedures, a fact recognized more than 2 decades ago. The availability of real-time contact force (CF)-sensing catheters has reinvigorated the field of ablation biophysics and optimized lesion formation. The ability to measure and display CF came with the promise of dramatic improvement in safety and efficacy; however, CF quality was noted to have just as important an influence on lesion formation as absolute CF quantity. Multiple other factors have emerged as key elements influencing effective lesion formation, including catheter stability, lesion contiguity and continuity, lesion density, contact homogeneity across a line of ablation, spatiotemporal dynamics of contact governed by cardiac and respiratory motion, contact directionality, and anatomic wall thickness, in addition to traditional ablation indices of power and RF duration. There is greater appreciation of surrogate markers as a guide to lesion formation, such as impedance fall, loss of pace capture, and change in unipolar electrogram morphology. In contrast, other surrogates such as tactile feedback, catheter motion, and electrogram amplitude are notably poor predictors of actual contact and lesion formation. This review aims to contextualize the role of CF sensing in lesion formation with respect of the fundamental principles of biophysics of RF ablation and summarize the state-of-the-art evidence behind the role of CF in optimizing lesion formation.

Substrate mapping for scar-related ventricular tachycardia in patients with resynchronization therapy-the importance of the pacing mode

PURPOSE

Targets for substrate-based catheter ablation of scar-related ventricular tachycardia (VT) include sites with fractionated and late potentials (LPs). We hypothesized that in patients with cardiac resynchronization therapy (CRT), the pacing mode may influence the timing of abnormal electrograms (EGMs) relative to the surface QRS complex.

METHODS

We assessed bipolar EGM characteristics in left ventricular low bipolar voltage areas (< 1.5 mV) from 10 patients with coronary disease and a CRT device undergoing catheter ablation for VT. EGMs at 81 sites were analyzed during three different pacing modes (biventricular (BiV), right ventricular (RV)-only, and left ventricular (LV)-only) pacing.

RESULTS

Stimulus to end of local electrogram duration (Stim-to-eEGM) depended significantly on the stimulation site (BiV, LV, or RV, p = 0.032). Single-chamber pacing unmasked LPs, not present during BiV pacing, in three patients. In another three patients, a concomitant increase in stimulus to end of surface QRS duration caused by single-site pacing compensated for the increase in Stim-to-eEGM duration, thereby prohibiting LP unmasking.

CONCLUSION

The sequence of ventricular activation, as determined by the pacing site in patients with CRT devices, has a major influence on the detection of late potentials during substrate-guided ablation. Further study is warranted to define the optimal approaches, including the rhythm, for substrate mapping, but our findings suggest that BiV pacing may be most likely to obscure detection of late potentials as compared to single-site pacing.

Family history of atrial fibrillation as a predictor of atrial substrate and arrhythmia recurrence in patients undergoing atrial fibrillation catheter ablation

Aims

A commonly held notion is that patients with a family history of atrial fibrillation (AF) have worse atrial substrate and higher rates of arrhythmia recurrence following ablation. We sought to examine differences in atrial substrate and catheter ablation outcomes in patients with a 1st degree family member with paroxysmal or persistent AF (PeAF) compared to those without.

Methods and results

A total of 256 consecutive patients undergoing their 1st ablation for AF (123 paroxysmal, 133 persistent) with >1 year follow up were included. The presence of one 1st-degree family relative was defined as a 'positive family history'. Clinical characteristics, electroanatomic map findings, ablation characteristics and outcomes were compared in patients with and without a positive family history of AF. Patients with paroxysmal fibrillation with a positive family history (n = 57; 46%) had similar clinical characteristics and arrhythmia recurrence after catheter ablation as those without. Of those that recurred, patients with a positive family history were more likely to have progressed to PeAF (P = 0.05). Patients with PeAF with a positive family history (n = 75; 56%) had similar clinical characteristics, electroanatomic mapping findings and ablation characteristics, but worse long term arrhythmia free survival (P = 0.04).

Conclusion

The presence of a 1st-degree family member with AF does not impact the clinical outcomes of catheter ablation for paroxysmal AF. However, a positive family history is associated with worse arrhythmia free survival in patients with PeAF. This finding is not explained by differences in clinical characteristics, atrial substrate assessed by voltage maps or ablation characteristics.

Catheter ablation of polymorphic ventricular tachycardia/fibrillation in patients with and without structural heart disease

BACKGROUND

Catheter ablation for polymorphic ventricular tachycardia and ventricular fibrillation (PMVT/VF) may target triggering premature ventricular contractions (PVCs). Targeting ventricular scar has also been suggested, but data are limited.

OBJECTIVE

The purpose of this study was to characterize the electrophysiological findings and ablation outcomes for patients with PMVT/VF and structural heart disease (SHD) compared to those with idiopathic VF.

METHODS

Data from 32 consecutive patients (13 idiopathic VF, 19 SHD) with recurrent PMVT/VF who underwent catheter ablation were reviewed.

RESULTS

A low-voltage area of myocardial scar was present in 15 of 19 patients with SHD. Sustained monomorphic ventricular tachycardia (SMVT) associated with scar was inducible and targeted in 8, 3 of whom had previous SMVT episodes separate from PMVT/VF episodes and 5 had no history of SMVT. Triggering PVCs were identified in 11 patients and arose from an area of endocardial scar in 6. Only scar ablation was performed in 8 patients who did not have triggering PVCs. All idiopathic VF patients underwent PVC ablation only. During a median of 540 days, 74% of SHD patients and 77% of idiopathic VF patients were free of recurrence, including 75% of those with only PVC ablation, 86% of those with scar plus PVC ablation, and 63% of those with only scar ablation.

CONCLUSION

Patients with recurrent PMVT/VF and SHD often have a low-voltage scar associated with PVCs or inducible SMVT, which may also be the substrate for PMVT/VF. When present, substrate ablation targeting scar is a reasonable option for treatment of PMVT/VF even if PVCs are absent.

Downstream overdrive pacing and intracardiac concealed fusion to guide rapid identification of atrial tachycardia after atrial fibrillation ablation

Aims

Atrial tachycardia (AT) related to atrial fibrillation (AF) ablation frequently poses a diagnostic challenge. Downstream overdrive pacing (DOP) can be used to rapidly detect reentry and assess proximity of a pacing site to an AT circuit or focus. We hypothesized that systematic DOP using multielectrode catheters would facilitate AT mapping.

Methods and results

DOP identified constant fusion when the post-pacing interval (PPI)-tachycardia cycle length (TCL) <40 ms and stimulus to adjacent upstream atrial electrogram interval >75% of TCL. Mapping was performed as follows: (i) CS DOP, (ii) DOP at left atrial (LA) roof, (iii) DOP at selected LA sites based on prior DOP attempts, and (iv) mapping and ablation at regions of fractionated electrograms in region of AT. Activation mapping was performed at operator discretion. AT diagnosis was confirmed by successful ablation or additional mapping when ablation was unsuccessful. Fifty consecutive patients with sustained AT underwent mapping of 68 ATs, of whom 42 (62%) were macroreentrant, 19 were locally reentrant (28%), and 7 (10%) were focal. AT was correctly identified with a median of three DOP attempts. All macroreentrant ATs were identified with ≤6 DOP attempts. One AT (1.6%) was terminated by DOP, and three ATs (4.8%) required activation mapping. Intracardiac concealed fusion was seen in 26 ATs (38%), each of which was successfully ablated.

Conclusion

Reentry could be demonstrated in a substantial majority of AF ablation-related AT. A stepwise diagnostic approach using DOP and recognition of intracardiac concealed fusion can be used to rapidly identify and ablate reentrant AT.

Temporal trends in safety and complication rates of catheter ablation for atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) ablation is increasingly common, but is associated with potential major complications. Technology, experience, and protocols have evolved significantly in recent times, and may have impacted procedural safety. We sought to compare AF ablation safety profiles, including complication rates and fluoroscopy times in a "modern" versus "historical" cohort.

METHODS AND RESULTS

We evaluated consecutive patients undergoing AF ablation from a modern cohort (MC) from 2014 to 2015 and a historic cohort (HC) from 2009 to 2011 for complications. Major complications were categorized according to Heart Rhythm Society guidelines. We included 1,425 patients, 726 in the HC and 699 in the MC. The MC was older, had more OSA and less valvular AF. Fifty-two (3.5%) procedures suffered major complications across the cohorts, with significantly fewer in the MC (5.0% vs. 2.3%, P  =  0.007). The largest reductions were seen in vascular, hemorrhagic, ischemic stroke, and perforation/tamponade related complications. Periprocedural antiplatelets drugs (aHR 2.1 [95 CI 1.1-3.9], P  =  0.02) and force-sensing catheters (aHR 0.4 [95 CI 0.2-0.9], P  =  0.03) were independently related to major complication rates. Direct oral anticoagulants and uninterrupted anticoagulation were not associated with complications. There was a decrease in both fluoroscopy (-17.4 minutes [95 CI 19.2-15.6], P < 0.0001) and radiofrequency ablation times (-561 seconds [95CI -750 to -371], P < 0.0001).

CONCLUSIONS

The safety profile of AF ablation has improved significantly in less than a decade.

Impact of Number of Oral Antiarrhythmic Drug Failures Before Referral on Outcomes Following Catheter Ablation of Ventricular Tachycardia

OBJECTIVES

This study sought to examine the relationship between the number of oral antiarrhythmic drug (AAD) failures before referral for ventricular tachycardia (VT) ablation and subsequent clinical outcomes.

BACKGROUND

Failure of AADs prompts referral for VT ablation.

METHODS

Consecutive patients (n = 669) with sustained VT who were referred for a first-time ablation were divided into 2 groups according to the number of oral Class 1 or 3 AAD failures before referral: single-drug failure (≤1 AAD; n = 256) or multidrug failure (>1 AADs; n = 413). Outcomes were stratified according to underlying disease type (no structural heart disease [SHD] [n = 87]; ischemic cardiomyopathy [ICM] [n = 368]; and ischemic cardiomyopathy [NICM] [n = 214]) and reported at a mean follow-up of 35 ± 46 months.

RESULTS

Patients with multidrug failure, compared with patients with single-drug failure, had more advanced SHD and required more extensive ablation to control arrhythmia. Multidrug failure, compared with single-drug failure, was associated with lower ventricular arrhythmia-free survival in ICM (46 ± 4% vs. 58 ± 6%; p = 0.03) and NICM (26 ± 5% vs. 49 ± 6%; p = 0.008), but not in the absence of SHD (71 ± 8% vs. 85 ± 7%; p = 0.10). Overall survival was lower in multidrug failure versus single-drug failure groups in patients with ICM (71 ± 3% vs. 84 ± 4%; p = 0.03) and NICM (70 ± 5% vs. 88 ± 4%; p < 0.001). Multidrug failure was independently associated with a higher risk of ventricular arrhythmia recurrence (hazard ratio: 1.6; p = 0.01) and mortality in NICM (hazard ratio: 2.6; p = 0.008), but not in ICM.

CONCLUSIONS

Patients with SHD and failure of multiple oral AADs before VT ablation referral have more advanced heart disease and worse clinical outcomes following ablation, especially in NICM.

Early Versus Late Referral for Catheter Ablation of Ventricular Tachycardia in Patients With Structural Heart Disease: A Systematic Review and Meta-Analysis of Clinical Outcomes

OBJECTIVES

This was a meta-analysis of published studies to examine the impact of early referral on outcomes after catheter ablation for ventricular tachycardia (VT) in patients with structural heart disease.

BACKGROUND

Patients are frequently referred for VT ablation after failure of antiarrhythmic drugs to control VT. Some studies have suggested that early referral might confer better outcomes.

METHODS

An electronic search was performed using major databases. The primary outcomes were long-term VT recurrence and total mortality. Secondary outcomes were acute procedural success and acute complications.

RESULTS

Three studies were included with a total of 980 patients (mean age 64 ± 12 years, 71% males). Mean follow-up was 29 ± 27 months. Early referral for VT ablation was associated with decreased VT recurrence and acute complications compared with late referral (relative risk: 0.69 [95% confidence interval: 0.58 to 0.82], p < 0.0001 and relative risk: 0.50 [95% confidence interval: 0.27 to 0.93], p = 0.03, respectively). There was no significant difference between early and late referral for total mortality and acute success.

CONCLUSIONS

Late referral for VT ablation was associated with worse outcomes (VT recurrence and acute complications) in patients with structural heart disease, which suggests that early referral for VT ablation might be a reasonable consideration in this patient population.

Significance of Inducible Nonsustained Ventricular Tachycardias After Catheter Ablation for Ventricular Tachycardia in Ischemic Cardiomyopathy

BACKGROUND

Noninducibility of sustained monomorphic ventricular tachycardia (SMVT) postablation does not insure absence of later recurrence in patients with ischemic cardiomyopathy. This study aims to determine the relation between inducible nonsustained VT postablation and VT recurrences.

METHODS AND RESULTS

One hundred sixty-five consecutive patients (156 male; age 68±9 years) underwent ablation for SMVT because of ischemic cardiomyopathy; 44 patients who did not have induction testing or in whom only ventricular fibrillation was induced after ablation were excluded. In 38 patients (23%), SMVT was inducible (group C). Of the 83 patients without inducible SMVT after ablation, nonsustained VT defined as ≥5 beats lasting for <30 s, was induced in 34 patients (group B, 21%), whereas the remaining 49 patients had no VT induced by the induction test (group A, 30%). Over a median follow-up of 18.7 months, freedom from recurrent VT at 24 months was 60% in group A, 45% in group B (P=0.017 versus group A), and 38% in group C (P=0.005 versus group A). In patients without inducible SMVT, inducible nonsustained VT and left ventricular ejection fraction was independently associated with VT recurrence (hazard ratio, 3.66 and 1.07; 95% CI, 1.3-11.1 and 1.01-1.14).

CONCLUSIONS

Inducible nonsustained VT postablation suggests the continued presence of functional arrhythmia substrate. Further trials are needed to assess whether additional ablation would improve outcome in this group.