Pulmonary Vein Isolation Using the Visually Guided Laser Balloon: Results of the U.S. Feasibility Study

INTRODUCTION

Visually guided laser balloon (VGLB) ablation is unique in that the operator delivers ablative energy under direct visual guidance. In this multicenter study, we sought to determine the feasibility, efficacy, and safety of performing pulmonary vein isolation (PVI) using this VGLB.

METHODS

Patients with symptomatic, drug-refractory paroxysmal atrial fibrillation (AF) underwent PVI using the VGLB with the majority of operators conducting their first-ever clinical VGLB cases. The primary effectiveness endpoint was defined as freedom from treatment failure that included: Occurrence of symptomatic AF episodes ≥1 minutes beyond the 90-day blanking, the inability to isolate 1 superior and 2 total PVs, occurrence of left atrial flutter or atrial tachycardia, or left atrial ablation/surgery during follow-up.

RESULTS

A total of 86 patients (mean age 56 ± 10 years, 67% male) were treated with the VGLB at 10 US centers. Mean fluoroscopy, ablation, and procedure times were 39.8 ± 24.3 minutes, 205.2 ± 61.7 minutes, and 253.5 ± 71.3 minutes, respectively. Acute PVI was achieved in 314/323 (97.2%) of targeted PVs. Of 84 patients completing follow-up, the primary effectiveness endpoint was achieved in 50 (60%) patients. Freedom from symptomatic or asymptomatic AF was 61%. The primary adverse event rate was 16.3% (8.1% pericarditis, phrenic nerve injury 5.8%, and cardiac tamponade 3.5%). There were no cerebrovascular events, atrioesophageal fistulas, or significant PV stenosis.

CONCLUSIONS

This multicenter study of operators in the early stage of the learning curve demonstrates that PVI can be achieved with the VGLB with a reasonable safety profile and an efficacy similar to radiofrequency ablation.

The Effect of Direct Current Stimulation versus T-Wave Shock on Defibrillation Threshold Testing

INTRODUCTION

There are several methods to induce ventricular fibrillation (VF) during defibrillation threshold (DFT) testing. Delivering a shock at a critical time during the T wave (T-shock) is the conventional approach, while delivering a constant direct current voltage (DC stim) from the implantable cardioverter defibrillator is an alternative method. Only a few reports compare VF induction methods. The purpose of this study was to evaluate the effects and safety of DC stim versus T-shock.

METHODS

We retrospectively investigated 414 consecutive patients undergoing DFT testing. We compared the two groups (DC stim and T-shock) with respect to clinical characteristics, electrocardiogram (ECG) changes, and complications.

RESULTS

Ventricular arrhythmia, including ventricular tachycardia (VT) and VF, was induced by DC stim in 93 patients or T-shock in 321 patients. No more than three attempts were performed during one procedure. There was no significant difference in the baseline ECG, induced tachycardia cycle length (TCL), or complications between the two groups. However, the induced TCL was significantly shorter than the clinical TCL regardless of induction method (P = 0.001). Five patients suffered major complications (i.e., electromechanical dissociation or incessant VT). A history of atrial fibrillation was significantly greater in patients with major complications than the others (80% vs 24%, P = 0.004), and was an independent predictor on multivariate analysis.

CONCLUSIONS

There is no significant difference in induced TCL or complications between the DC stim and T-shock. The induced TCL is significantly shorter than clinical TCL regardless of induction method.

Idiopathic Ventricular Arrhythmia Originating From the Cardiac Crux or Inferior Septum

Background—

Idiopathic ventricular arrhythmia (VA) can arise from the epicardium near the posteroseptal region (cardiac crux). There are only 2 prior reports describing idiopathic VA from the cardiac crux. The purpose of this study was to characterize the clinical and the electrocardiographic features of idiopathic crux VA.

Methods and Results—

Crux VA was identified in 18 patients undergoing catheter ablation. We divided patients into 2 groups, those with VA originating from the apical crux (n=9) and the basal crux (n=9). We described the clinical and electrocardiographic characteristics of crux VA as well as the ablation results. Furthermore, we compared clinical features of crux VA with other sites of idiopathic VA. Fifteen crux VA patients (83%) had sustained ventricular tachycardia and 3 patients required implantable cardioverter defibrillator implantation because of syncope. All patients had a left superior axis and 16 patients had R>S wave in V2. In apical crux VA, all patients had a deep S wave in V6 and 8 patients (89%) had R>S wave in aVR. All apical crux patients underwent attempted ablation in the middle cardiac vein without success. In 4 of these patients, epicardial ablation with subxiphoid approach was performed successfully. All basal crux VA patients had either negative or isoelectric pattern in V1 and had R>S in V6. Patients had successful ablation within the middle cardiac vein.

Conclusions—

Apical versus basal crux VA is identified as a new category of idiopathic VA with distinctive electrocardiographic characteristics; ablation via the middle cardiac vein is effective for eliminating basal crux VA, whereas apical crux VA often requires a subxiphoid epicardial approach.

Use of a novel fragmentation map to identify the substrate for ventricular tachycardia in postinfarction cardiomyopathy

BACKGROUND

Substrate ablation is commonly performed in patients with postinfarction cardiomyopathy and ventricular tachycardia (VT). Recognition of fragmented and late potentials during sinus rhythm is a tedious process subject to operator fatigue.

OBJECTIVE

The purpose of this study was to assess the value of automated analysis to quantify electrogram fragmentation and to determine the relationship of fragmented regions to the VT isthmus.

METHODS

Detailed left ventricular (LV) mapping was performed in 2 groups: (1) 14 patients with previous myocardial infarction and tolerated VT and (2) 14 controls with structurally normal hearts. In patients with VT, mid-isthmus sites were identified using entrainment mapping. Sinus rhythm endocardial LV electrograms underwent time- and frequency-domain analysis and were displayed as fragmentation or frequency maps. The region of fractionated electrograms and their relation to the VT isthmus sites were determined.

RESULTS

Cutoffs for abnormal electrogram fragmentation were ventricular fractionation index ≥ 7 and fast Fourier transform ratio ≥ 14%, respectively. In the time domain, LV surface area with fractionated electrograms was significantly smaller than the total scar surface area (27.3% ± 7.1% vs 42.1% ± 12.3%, P <.001), yet contained 100% of VT isthmus sites. In the frequency domain, areas of abnormal fractionation occupied 9.7% ± 6.9% of total LV surface area and included only 60% of the VT isthmus sites.

CONCLUSION

Automated electrogram fractionation analysis represents an objective tool to rapidly quantify electrogram fragmentation and guide substrate-based ablation of VT. Empiric ablation of these regions may be a new strategy for substrate-guided VT ablation.

Catheter ablation of ventricular tachycardia in patients with post-infarction cardiomyopathy

Monomorphic ventricular tachycardia (VT) in patients with post-infarction cardiomyopathy (CMP) is caused by reentry through slowly conducting tissue with in areas of myocardial scar. The use of implantable cardioverter-defibrillators (ICDs) has helped to decrease the risk of arrhythmic death in patients with post-infarction CMP, but the symptomatic and psychological burden of ICD shocks remains significant. Experience with catheter ablation has progressed substantially in the past 20 years, and is now routinely used to treat patients with post-infarction CMP who experience VT or receive ICD therapy. Depending on the hemodynamic tolerance of VT, a variety of mapping techniques may be used to identify sites for catheter ablation, including activation and entrainment mapping for mappable VTs, or substrate mapping for unmappable VTs. In this review, we discuss the pathophysiology of VT in post-infarction CMP patients, and the contemporary practice of catheter ablation.

Coupling interval dispersion and body mass index are independent predictors of idiopathic premature ventricular complex-induced cardiomyopathy

INTRODUCTION

Patients with frequent premature ventricular complexes (PVCs) might be at risk for the developing or exacerbation of left ventricular (LV) dysfunction. However, some patients with a high-PVC burden do not develop cardiomyopathy, while other patients with low-PVC burden can develop cardiomyopathy. The purpose of this study was to evaluate the positive predictors of idiopathic PVCs-induced cardiomyopathy.

METHODS AND RESULTS

We investigated 214 patients undergoing successful ablation of PVCs who had no other causes of cardiomyopathy. We divided the study cohort into 2 groups: ejection fraction (EF) ≥ 50% (normal LV) and EF < 50% (LV dysfunction). We analyzed the clinical characteristics, including the electrocardiogram and findings at electrophysiology study. Among these patients, 51 (24%) had reduced LVEF and 163 (76%) had normal LV function. Patients with LV dysfunction had significantly longer coupling interval (CI) dispersion (maximum-CI-minimum-CI) and had significantly higher PVC burden compared to those with normal LV function (CI-dispersion: 115 ± 25 milliseconds vs. 94 ± 19 milliseconds; P < 0.001; PVC burden: 19% vs. 15%; P = 0.04). Furthermore, patients with LV dysfunction had significantly higher body mass index (BMI) compared to those with normal LV function (BMI > 30 kg/m(2) ; 37% vs. 13%; P = 0.001). Logistic regression analysis showed that CI-dispersion, PVC burden, and BMI (>30 kg/m(2) ) are independent predictors of PVC-induced cardiomyopathy.

CONCLUSIONS

In addition to the PVC burden, the CI-dispersion and BMI are associated with PVC-induced cardiomyopathy.

Cardiovascular applications of therapeutic ultrasound

Ultrasound (US) has gained widespread use in diagnostic cardiovascular applications. At amplitudes and frequencies typical of diagnostic use, its biomechanical effects on tissue are largely negligible. However, these parameters can be altered to harness US's thermal and non-thermal effects for therapeutic indications. High-intensity focused ultrasound (HIFU) and extracorporeal shock wave therapy (ECWT) are two therapeutic US modalities which have been investigated for treating cardiac arrhythmias and ischemic heart disease, respectively. Here, we review the biomechanical effects of HIFU and ECWT, their potential therapeutic mechanisms, and pre-clinical and clinical studies demonstrating their efficacy and safety limitations. Furthermore, we discuss other potential clinical applications of therapeutic US and areas in which future research is needed.

Randomized trial of conventional transseptal needle versus radiofrequency energy needle puncture for left atrial access (the TRAVERSE-LA study)

Background

Transseptal puncture is a critical step in achieving left atrial (LA) access for a variety of cardiac procedures. Although the mechanical Brockenbrough needle has historically been used for this procedure, a needle employing radiofrequency (RF) energy has more recently been approved for clinical use. We sought to investigate the comparative effectiveness of an RF versus conventional needle for transseptal LA access.

Methods and Results

In this prospective, single‐blinded, controlled trial, 72 patients were randomized in a 1:1 fashion to an RF versus conventional (BRK‐1) transseptal needle. In an intention‐to‐treat analysis, the primary outcome was time required for transseptal LA access. Secondary outcomes included failure of the assigned needle, visible plastic dilator shavings from needle introduction, and any procedural complication. The median transseptal puncture time was 68% shorter using the RF needle compared with the conventional needle (2.3 minutes [interquartile range {IQR}, 1.7 to 3.8 minutes] versus 7.3 minutes [IQR, 2.7 to 14.1 minutes], P=0.005). Failure to achieve transseptal LA access with the assigned needle was less common using the RF versus conventional needle (0/36 [0%] versus 10/36 [27.8%], P<0.001). Plastic shavings were grossly visible after needle advancement through the dilator and sheath in 0 (0%) RF needle cases and 12 (33.3%) conventional needle cases (P<0.001). There were no differences in procedural complications (1/36 [2.8%] versus 1/36 [2.8%]).

Conclusions

Use of an RF needle resulted in shorter time to transseptal LA access, less failure in achieving transseptal LA access, and fewer visible plastic shavings.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01209260.

Combination drug therapy for patients with intractable ventricular tachycardia associated with right ventricular cardiomyopathy

BACKGROUND

Drug therapy for patients with right ventricular (RV) cardiomyopathy refractory to single-drug therapy and ablation has not been well defined.

METHODS

We reviewed our entire RV cardiomyopathy database (31 patients) and found four patients presenting with ventricular arrhythmias of RV origin refractory to single-drug therapy. These patients underwent complete evaluation for arrhythmogenic right ventricular cardiomyopathy (ARVC).

RESULTS

Following the revised 2010 task force criteria, of these four patients, three were diagnosed with ARVC, and one with cardiac sarcoidosis. These patients proved to be refractory to drug monotherapy and either failed or deemed to not be candidates for endocardial ablation. Their arrhythmias were ultimately controlled with combinations of sotalol, flecainide, and mexiletine.

CONCLUSIONS

In our experience, combination drug therapy is an effective treatment strategy for patients with ventricular tachycardia refractory to monotherapy and, in some cases, ablation. In addition, flecainide appears to be safe and effective for those with RV cardiomyopathy without significant left ventricular dysfunction.

An electrocardiographic scoring system for distinguishing right ventricular outflow tract arrhythmias in patients with arrhythmogenic right ventricular cardiomyopathy from idiopathic ventricular tachycardia

BACKGROUND

Ventricular arrhythmias in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and idiopathic ventricular tachycardia (VT) can share a left bundle branch block/inferior axis morphology. We previously reported electrocardiogram characteristics during outflow tract ventricular arrhythmias that helped distinguish VT related to ARVD/C from idiopathic VT.

OBJECTIVE

To prospectively validate these criteria.

METHODS

We created a risk score by using a derivation cohort. Two experienced electrophysiologists blinded to the diagnosis prospectively scored patients with VT/premature ventricular contractions (PVCs) with left bundle branch block/inferior axis pattern in a validation cohort of 37 ARVD/C tracings and 49 idiopathic VT tracings. All patients with ARVD/C had their diagnosis confirmed based on the revised task force criteria. Patients with idiopathic VT were selected based on structurally normal hearts with documented right ventricular outflow tract VT successfully treated with ablation. The scoring system provides 3 points for sinus rhythm anterior T-wave inversions in leads V1-V3 and during ventricular arrhythmia: 2 points for QRS duration in lead I≥120 ms, 2 points for QRS notching, and 1 point for precordial transition at lead V5 or later.

RESULTS

A score of 5 or greater was able to correctly distinguish ARVD/C from idiopathic VT 93% of the time, with a sensitivity of 84%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 91%.

CONCLUSIONS

We describe a simple scoring algorithm that uses 12-lead electrocardiogram characteristics to effectively distinguish right ventricular outflow tract arrhythmias originating from patients with ARVD/C versus patients with idiopathic VT.

New unipolar electrogram criteria to identify irreversibility of nonischemic left ventricular cardiomyopathy

OBJECTIVES

This study sought to assess the value of left ventricular (LV) endocardial unipolar electroanatomical mapping (EAM) in identifying irreversibility of LV systolic dysfunction in patients with left ventricular nonischemic cardiomyopathy (LVCM).

BACKGROUND

Identifying irreversibility of LVCM would be helpful but cannot be reliably accomplished by bipolar EAM or cardiac magnetic resonance identification of macroscopic scar.

METHODS

Detailed endocardial LV EAM was performed in 3 groups: 1) 24 patients with irreversible LVCM (I-LVCM) but with no or minimal macroscopic scar (<15% LV surface) evidenced on bipolar voltage EAM and/or cardiac magnetic resonance; 2) 14 patients with reversible ventricular premature depolarization-mediated LVCM (R-LVCM); and 3) 17 patients with structurally normal hearts. LV endocardial unipolar electrogram amplitude and area of unipolar amplitude abnormality were defined after excluding macroscopic scar.

RESULTS

Unipolar amplitude differed in the 3 groups: median of 7.6 (interquartile range [IQR]: 5.5 to 9.7) mV in I-LVCM group, 13.2 (IQR: 10.4 to 16.2) mV in R-LVCM group, and 16.3 (IQR: 13.6 to 19.8) mV in structurally normal hearts group (p < 0.001). Areas of unipolar abnormality represented a large proportion of total LV surface in I-LVCM, 64.7% (IQR: 47.5% to 75.9%) compared with R-LVCM, 5.2% (IQR: 0.0% to 19.1%) and structurally normal hearts, 0.1% (IQR: 0.0% to 0.9%), groups (p < 0.001). A unipolar abnormality area cutoff of 32% of total LV surface was 96% sensitive and 100% specific in identifying irreversible cardiomyopathy among patients with LV dysfunction (I-LVCM and R-LVCM), p < 0.001.

CONCLUSIONS

Detailed unipolar voltage mapping can identify irreversible myocardial dysfunction consistent with fibrosis, even in the absence of bipolar EAM or cardiac magnetic resonance abnormalities, and may serve as valuable prognostic tool in patients presenting with LVCM to facilitate clinical decision making.

Use of a novel endoscopic catheter for direct visualization and ablation in an ovine model of chronic myocardial infarction

BACKGROUND

Defining the arrhythmogenic substrate is essential for successful ablation of scar-related ventricular tachycardia. The visual characteristics of endocardial ischemic scar have not been described in vivo. The goal of this study was (1) to quantify the visual characteristics of normal tissue, scar border zone, and dense scar in vivo with the use of a novel endoscopic catheter that allows direct endocardial visualization and (2) to correlate visual attributes of myocardial scar with bipolar voltage.

METHODS AND RESULTS

Percutaneous transient balloon occlusion (150 minutes) of the mid left anterior descending coronary artery was performed in an ovine model. Animals survived for 41.5±0.7 days. Detailed bipolar voltage maps of the left ventricle were acquired with the use of NavX. Video snapshots of the endocardium were acquired at sites distributed throughout the left ventricle. Visual tissue characteristics of normal (>1.5 mV), border (0.5-1.5 mV), and dense scar (<0.5 mV) were quantified with the use of image processing. Radiofrequency lesions (10-20 W, 30 seconds) were delivered under direct visualization. Mean white-threshold pixel area was lowest in normal tissue (189 969±41 478 pixels(2)), intermediate in scar border zone (255 979±36 016 pixels(2)), and highest in dense scar (324 452±30 152 pixels(2); P<0.0001 for all pairwise comparisons). Tissue whiteness, characteristic of scar, was inversely correlated with bipolar voltage (P<0.0001). During radiofrequency lesions, there was a significant increase in white-thresholded pixel area of the visual field after ablation (average increase, 85 381±52 618 pixels(2); P<0.001).

CONCLUSIONS

Visual characteristics of chronic infarct scar in vivo observed with the use of a novel endoscopic catheter correlate with bipolar electrogram voltage. Irrigated radiofrequency lesions in normal endocardial tissue and postinfarction zone can be visualized and quantified with the use of image processing. This technology shows promise for visually based delivery of radiofrequency lesions for the treatment of scar-based ventricular tachycardia.

ECG criteria for accurate localization of left anterolateral and posterolateral accessory pathways

BACKGround : Left lateral accessory pathway (AP) location along the mitral annulus (MA) can influence ablation strategy, including choice of a transseptal or retrograde aortic approach and the use of deflectable sheaths and/or bidirectional catheters. We aimed to develop electrocardiographic (ECG) criteria to accurately localize a left lateral AP, hypothesizing that the relationship of QRS amplitudes in limb leads II and III could be used to differentiate left anterolateral (LAL) from left posterolateral (LPL) AP locations.

METHODS

The ECGs from patients who underwent ablation of a left-sided AP between 2001 and 2008 were evaluated for the relationship of QRS amplitudes in limb leads II and III. A LAL-AP was defined by successful ablation between 12 and 3 o'clock on the MA, as seen in left anterior oblique (LAO) fluoroscopic projection. A LPL-AP was defined by successful ablation between 3 and 6 o'clock in the LAO projection.

RESULTS

In 249 consecutive patients undergoing AP ablation, 23 met the prespecified inclusion criteria: manifest preexcitation due to single AP, ablated successfully in a LAL or LPL location. The ratio of dominant QRS amplitude in lead II to lead III was ≥ 1 in 10/11 patients with LAL-AP, compared with 3/12 patients with a LPL-AP (P = 0.002). Using these criteria, two blinded reviewers predicted a LAL or LPL location with 87% accuracy and 100% interobserver agreement.

CONCLUSIONS

We report new ECG criteria that can be used to accurately predict the anterior and posterior location of a left lateral AP. Such localization may facilitate procedural planning.