Reinserting Physiology into Cardiac Mapping Using Omnipolar Electrograms.

Omnipolar electrograms (EGMs) make use of biophysical electric fields that accompany activation along the surface of the myocardium. A grid-like electrode array provides bipolar signals in orthogonal directions to deliver catheter-orientation-independent assessments of cardiac electrophysiology. Studies with myocyte monolayers, isolated animal and human hearts, and anesthetized animals validated the tenets of omnipolar EGMs. The combination of information from omnipolar-based activation vectors and voltages may aid in localizing areas of scar, lesion gaps, wavefront disorganization, and fractionation or collision during arrhythmias. The goal of omnipolar EGMs is to better characterize myocardium through reintroducing electrogram direction related fundamentals of cardiac electrophysiology.

Characterising the difference in electrophysiological substrate and outcomes between heart failure and non-heart failure patients with persistent atrial fibrillation.

Aims: Characterizing the differences in substrate and clinical outcome between heart failure (HF) and non-heart failure (non-HF) patients undergoing persistent atrial fibrillation (AF) ablation. Methods and results: Using complex fractionated electrograms (CFE) as a surrogate marker of substrate complexity, we compared the bi-atrial substrate in patients with persistent AF with and without HF, at baseline and after ablation, to determine its impact on clinical outcome. In this retrospective analysis of two prospective studies, 60 patients underwent de-novo step-wise left atrial (LA) ablation, 30 with normal left ventricular ejection fraction (LVEF) ≥ 50% (non-HF group) and 30 with LVEF ≤ 35% (HF group). Multiple high-density bi-atrial CFE maps were acquired along with AF cycle length (AFCL) at each procedural stage. Change in bi-atrial CFE areas, AFCL and outcome data were then compared. In the non-HF group, higher CFE-areas were found at baseline and at each step of the procedure in the LA. In both LA and the right atrium (RA), baseline and final CFE area were also higher in the non-HF group. Single procedure, arrhythmia-free survival at 1 year was higher in the HF group compared with the non-HF group (72% vs. 43%, log rank P = 0.04). Final total bi-atrial CFE area was an independent predictor of arrhythmia recurrence. Conclusions: CFE represents an important surrogate marker of atrial substrate complexity. The atrial substrate in persistent AF differs between HF and non-HF with the latter representing a more complex 'primary' bi-atrial myopathy. LA focussed ablation results in more extensive substrate modification in HF and better clinical outcomes as compared with non-HF.

Catheter ablation vs electrophysiologically guided thoracoscopic surgical ablation in long-standing persistent atrial fibrillation: The CASA-AF Study.

BACKGROUND: Catheter ablation (CA) outcomes for long-standing persistent atrial fibrillation (LSPAF) remain suboptimal. Thoracoscopic surgical ablation (SA) provides an alternative approach in this difficult to treat cohort. OBJECTIVE: To compare electrophysiological (EP) guided thoracoscopic SA with percutaneous CA as the first-line strategy in the treatment of LSPAF. METHODS: Fifty-one patients with de novo symptomatic LSPAF were recruited. Twenty-six patients underwent electrophysiologically guided thoracoscopic SA. Conduction block was tested for all lesions intraoperatively by an independent electrophysiologist. In the CA group, 25 consecutive patients underwent stepwise left atrial (LA) ablation. The primary end point was single-procedure freedom from atrial fibrillation (AF) and atrial tachycardia (AT) lasting >30 seconds without antiarrhythmic drugs at 12 months. RESULTS: Single- and multiprocedure freedom from AF/AT was higher in the SA group than in the CA group: 19 of 26 patients (73%) vs 8 of 25 patients (32%) (P = .003) and 20 of 26 patients (77%) vs 15 of 25 patients (60%) (P = .19), respectively. Testing of the SA lesion set by an electrophysiologist increased the success rate in achieving acute conduction block by 19%. In the SA group, complications were experienced by 7 of 26 patients (27%) vs 2 of 25 patients (8%) in the CA group (P = .07). CONCLUSION: In LSPAF, meticulous electrophysiologically guided thoracoscopic SA as a first-line strategy may provide excellent single-procedure success rates as compared with those of CA, but there is an increased up-front risk of nonfatal complications.

Resolving Bipolar Electrogram Voltages During Atrial Fibrillation Using Omnipolar Mapping.

BACKGROUND: Low-voltage-guided substrate modification is an emerging strategy in atrial fibrillation (AF) ablation. A major limitation to contemporary bipolar electrogram (EGM) analysis in AF is the resultant lower peak-to-peak voltage (Vpp) from variations in wavefront direction relative to electrode orientation and from fractionation and collision events. We aim to compare bipole Vpp with novel omnipolar peak-to-peak voltages (Vmax) in sinus rhythm (SR) and AF. METHODS AND RESULTS: A high-density fixed multielectrode plaque was placed on the epicardial surface of the left atrium in dogs. Horizontal and vertical orientation bipolar EGMs, followed by omnipolar EGMs, were obtained and compared in both SR and AF. Bipole orientation has significant impact on bipolar EGM voltages obtained during SR and AF. In SR, vertical values were on average 66±119% larger than horizontal (P=0.004). In AF, vertical values were on average 31±96% larger than horizontal (P=0.07). Omnipole Vmax values were 99.9±125% larger than both horizontal (99.9±125%; P<0.001) and vertical (41±78%; P<0.0001) in SR and larger than both horizontal (76±109%; P<0.001) and vertical (52±70%; P value <0.0001) in AF. Vector field analysis of AF wavefronts demonstrates that omnipolar EGMs can account for collision and fractionation and record EGM voltages unaffected by these events. CONCLUSIONS: Omnipolar EGMs can extract maximal voltages from AF signals which are not influenced by directional factors, collision or fractionation, compared with contemporary bipolar techniques.

When Ventricular Safety Standby Does Not Work.

Dual chamber pacemakers have inbuilt advanced safety systems such as ventricular safety standby (crosstalk detection) to prevent ventricular oversensing resulting in inappropriate pacing inhibition. We describe a case where this safety mechanism does not reliably work and the management required to rectify the situation in an educational format.

Biomarkers in Persistent AF and Heart Failure: Impact of Catheter Ablation Compared with Rate Control.

BACKGROUND: To investigate the effects of catheter ablation and rate control strategies on cardiac and inflammatory biomarkers in patients with heart failure and persistent atrial fibrillation (AF). METHODS: Patients were recruited from the ARC-HF trial (catheter Ablation vs Rate Control for management of persistent AF in Heart Failure, NCT00878384), which compared ablation with rate control for persistent AF in heart failure. B-type natriuretic peptide (BNP), midregional proatrial natriuretic peptide (MR-proANP), apelin, and interleukin-6 (IL-6) were assayed at baseline, 3 months, 6 months, and 12 months. The primary end point, analyzed per-protocol, was changed from baseline at 12 months. RESULTS: Of 52 recruited patients, 24 ablation and 25 rate control subjects were followed to 12 months. After 1.2 ± 0.5 procedures, sinus rhythm was present in 22 (92%) ablation patients; under rate control, rate criteria were achieved in 23 (96%) of 24 patients remaining in AF. At 12 months, MR-proANP fell significantly in the ablation arm (-106.0 pmol/L, interquartile range [IQR] -228.2 to -60.6) compared with rate control (-28.7 pmol/L, IQR -69 to +9.5, P = 0.028). BNP showed a similar trend toward reduction (P = 0.051), with no significant difference in apelin (P = 0.13) or IL-6 (P = 0.68). Changes in MR-proANP and BNP correlated with peak VO2 and ejection fraction, and MR-proANP additionally with quality-of-life score. CONCLUSIONS: Catheter ablation, compared with rate control, in patients with heart failure and persistent AF was associated with significant reduction in MR-proANP, which correlated with physiological and symptomatic improvement. Ablation-based rhythm control may induce beneficial cardiac remodeling, unrelated to changes in inflammatory state. This may have prognostic implications, which require confirmation by event end point studies.

Relationship between contact force sensing technology and medium-term outcome of atrial fibrillation ablation: a multicenter study of 600 patients.

INTRODUCTION: Contact force sensing (CFS) technology improves acute pulmonary vein isolation durability; however, its impact on the clinical outcome of ablating atrial fibrillation (AF) is unknown. METHODS AND RESULTS: First time AF ablation procedures employing CFS from 4 centers were matched retrospectively to those without CFS in a 1:2 manner by type of AF. Freedom from atrial tachyarrhythmia was defined as the primary outcome measure, and fluoroscopy time the secondary outcome measure. Nineteen possible explanatory variables were tested in addition to CFS. A total of 600 AF ablation procedures (200 using CFS and 400 using non-CFS catheters) performed between 2010 and 2012 (46% paroxysmal, 36% persistent, 18% long-lasting persistent) were analyzed. The mean follow-up duration was 11.4 ± 4.7 months-paroxysmal AF 11.2 ± 4.1 CFS versus 11.3 ± 3.9 non-CFS (P = 0.745)-nonparoxysmal AF 10.4 ± 4.5 CFS versus 11.9 ± 5.4 non-CFS (P = 0.015). The use of a CFS catheter independently predicted clinical success in ablating paroxysmal AF (HR 2.24 [95% CIs 1.29-3.90]; P = 0.004), but not nonparoxysmal AF (HR 0.73 [0.41-1.30]; P = 0.289) in a multivariate analysis that included follow-up duration. Among all cases, the use of CFS catheters was associated with reduced fluoroscopy time in multivariate analysis (reduction by 7.7 [5.0-10.5] minutes; P < 0.001). Complication rates were similar in both groups. CONCLUSIONS: At medium-term follow-up, CFS catheter technology is associated with significantly improved outcome of first time catheter ablation of paroxysmal AF, but not nonparoxysmal AF. Fluoroscopy time was lower when CFS technology was employed in all types of AF ablation procedures.

Impact of stepwise ablation on the biatrial substrate in patients with persistent atrial fibrillation and heart failure.

BACKGROUND: Ablation of persistent atrial fibrillation can be challenging, often involving not only pulmonary vein isolation (PVI) but also additional linear lesions and ablation of complex fractionated electrograms (CFE). We examined the impact of stepwise ablation on a human model of advanced atrial substrate of persistent atrial fibrillation in heart failure. METHODS AND RESULTS: In 30 patients with persistent atrial fibrillation and left ventricular ejection fraction ≤35%, high-density CFE maps were recorded biatrially at baseline, in the left atrium (LA) after PVI and linear lesions (roof and mitral isthmus), and biatrially after LA CFE ablation. Surface area of CFE (mean cycle length ≤120 ms) remote to PVI and linear lesions, defined as CFE area, was reduced after PVI (18.3±12.03 to 10.2±7.1 cm(2); P<0.001) and again after linear lesions (7.7±6.5 cm(2); P=0.006). Complete mitral isthmus block predicted greater CFE reduction (P=0.02). Right atrial CFE area was reduced by LA ablation, from 25.9±14.1 to 12.9±11.8 cm(2) (P<0.001). Estimated 1-year arrhythmia-free survival was 72% after a single procedure. Incomplete linear lesion block was an independent predictor of arrhythmia recurrence (hazard ratio, 4.69; 95% confidence interval, 1.05-21.06; P=0.04). CONCLUSIONS: Remote LA CFE area was progressively reduced following PVI and linear lesions, and LA ablation reduced right atrial CFE area. Reduction of CFE area at sites remote from ablation would suggest either regression of the advanced atrial substrate or that these CFE were functional phenomena. Nevertheless, in an advanced atrial fibrillation substrate, linear lesions after PVI diminished the target area for CFE ablation, and complete lesions resulted in a favorable clinical outcome.

A randomized trial to assess catheter ablation versus rate control in the management of persistent atrial fibrillation in heart failure.

OBJECTIVES: This study sought to compare catheter ablation with rate control for persistent atrial fibrillation (AF) in heart failure (HF). BACKGROUND: The optimal therapy for AF in HF is unclear. Drug-based rhythm control has not proved clinically beneficial. Catheter ablation improves cardiac function in patients with HF, but impact on physiological performance has not been formally evaluated in a randomized trial. METHODS: In a randomized, open-label, blinded-endpoint clinical trial, adults with symptomatic HF, radionuclide left ventricular ejection fraction (EF) ≤35%, and persistent AF were assigned to undergo catheter ablation or rate control. Primary outcome was 12-month change in peak oxygen consumption. Secondary endpoints were quality of life, B-type natriuretic peptide, 6-min walk distance, and EF. Results were analyzed by intention-to-treat. RESULTS: Fifty-two patients (age 63 ± 9 years, EF 24 ± 8%) were randomized, 26 each to ablation and rate control. At 12 months, 88% of ablation patients maintained sinus rhythm (single-procedure success 68%). Under rate control, rate criteria were achieved in 96%. The primary endpoint, peak oxygen consumption, significantly increased in the ablation arm compared with rate control (difference +3.07 ml/kg/min, 95% confidence interval: 0.56 to 5.59, p = 0.018). The change was not evident at 3 months (+0.79 ml/kg/min, 95% confidence interval: -1.01 to 2.60, p = 0.38). Ablation improved Minnesota score (p = 0.019) and B-type natriuretic peptide (p = 0.045) and showed nonsignificant trends toward improved 6-min walk distance (p = 0.095) and EF (p = 0.055). CONCLUSIONS: This first randomized trial of ablation versus rate control to focus on objective exercise performance in AF and HF shows significant benefit from ablation, a strategy that also improves symptoms and neurohormonal status. The effects develop over 12 months, consistent with progressive amelioration of the HF syndrome. (A Randomised Trial to Assess Catheter Ablation Versus Rate Control in the Management of Persistent Atrial Fibrillation in Chronic Heart Failure; NCT00878384).