Atrial fibrillation: Catheter ablation

Feasibility of fast MR-thermometry during cardiac radiofrequency ablation

Online MR temperature monitoring during radiofrequency (RF) ablation of cardiac arrhythmias may improve the efficacy and safety of the treatment. MR thermometry at 1.5 T using the proton resonance frequency (PRF) method was assessed in 10 healthy volunteers under normal breathing conditions, using a multi-slice, ECG-gated, echo planar imaging (EPI) sequence in combination with slice tracking. Temperature images were post-processed to remove residual motion-related artifacts. Using an MR-compatible steerable catheter and electromagnetic noise filter, RF ablation was performed in the ventricles of two sheep in vivo. The standard deviation of the temperature evolution in time (TSD) was computed. Temperature mapping of the left ventricle was achieved at an update rate of approximately 1 Hz with a mean TSD of 3.6 ± 0.9 °C. TSD measurements at the septum showed a higher precision (2.8 ± 0.9 °C) than at the myocardial regions at the heart-lung and heart-liver interfaces (4.1 ± 0.9 °C). Temperature rose maximally by 9 °C and 16 °C during 5 W and 10 W RF applications, respectively, for 60 s each. Tissue temperature can be monitored at an update rate of approximately 1 Hz in five slices. Typical temperature changes observed during clinical RF application can be monitored with an acceptable level of precision.

Towards optimized MR thermometry of the human heart at 3T

Catheter ablation using radio frequency (RF) has been used increasingly for the treatment of cardiac arrhythmias and may be combined with proton resonance frequency shift (PRFS) -based MR thermometry to determine the therapy endpoint. We evaluated the suitability of two different MR thermometry sequences (TFE and TFE-EPI) and three blood suppression techniques. Experiments were performed without heating, using an optimized imaging protocol including navigator respiratory compensation, cardiac triggering, and image processing for the compensation of motion and susceptibility artefacts. Blood suppression performance and its effect on temperature stability were evaluated in the ventricular septum of eight healthy volunteers using multislice double inversion recovery (MDIR), motion sensitized driven equilibrium (MSDE), and inflow saturation by saturation slabs (IS). It was shown that blood suppression during MR thermometry improves the contrast-to-noise ratio (CNR), the robustness of the applied motion correction algorithm as well as the temperature stability. A gradient echo sequence accelerated by an EPI readout and parallel imaging (SENSE) and using inflow saturation blood suppression was shown to achieve the best results. Temperature stabilities of 2 °C or better in the ventricular septum with a spatial resolution of 3.5 × 3.5 × 8mm(3) and a temporal resolution corresponding to the heart rate of the volunteer, were observed. Our results indicate that blood suppression improves the temperature stability when performing cardiac MR thermometry. The proposed MR thermometry protocol, which optimizes temperature stability in the ventricular septum, represents a step towards PRFS-based MR thermometry of the heart at 3 T.

Spatial relationship between left atrial roof or superior pulmonary veins and bronchi or pulmonary arteries by dual-source computed tomography: implication for preventing injury of bronchi and pulmonary arteries during atrial fibrillation ablation

AIMS

Bronchi or pulmonary arteries (PAs) could be injured during atrial fibrillation (AF) ablation. Therefore, the aim of the present study was to evaluate the spatial relationship between left atrial roof or superior pulmonary veins (PVs) and neighbouring structures of AF patients and provide anatomic guidance for AF ablation to avoid injuring bronchi or PAs.

METHODS AND RESULTS

A dual-source computed tomography (DSCT) scan was used to depict the left atrium (LA), PVs, and nearby structures including bronchi and PAs in 58 patients with drug-refractory AF (mean age, 64 ± 9 years). The distance between LA roof or superior PVs (SPVs) and bronchi or PAs was measured. The average minimal distances from the left, middle, and right points of the LA roof to the principal bronchi were 17.0 ± 6.4, 23.7 ± 5.1, and 23.2 ± 7.7 mm, respectively. The LA roof was closer to the right PA (RPA) than the left PA (LPA) for more than 90% of patients. The average minimal distances from the left, middle, and right points of the LA roof to the PAs were 8.3 ± 5.0, 5.9 ± 3.1, and 6.0 ± 2.8 mm, respectively. The average minimal distances between the left superior pulmonary vein and bronchi or LPA were 0.32 ± 0.79 or 0.4 ± 1.0 mm, respectively. The average minimal distances between the right superior pulmonary vein and bronchi or RPA were 0.27 ± 0.94 and 0.0 ± 0.1 mm, respectively. Both of the root parts of SPVs of most patients were in direct contact with branches of trachea and PAs.

CONCLUSION

Dual-source computed tomography provides important imaging information for determining the relationship between LA, PVs, and neighbouring structures. Use of pre-procedural cardiac CT scans may help avoid ablation-induced injury of bronchi and PAs.

Total costs and atrial fibrillation ablation success or failure in Medicare-aged patients in the United States

INTRODUCTION

This retrospective cohort study compared the direct medical costs of successful versus unsuccessful catheter ablation in Medicare-aged patients with atrial fibrillation (AF), using medical claims data.

METHODS

AF patients with > or = 12 months of continuous medical/pharmacy coverage pre- and postablation were identified from the MarketScan Medicare database (January 2003 to December 2006). For study inclusion, patients were required to have > or = 2 AF inpatient/outpatient visits within 6 months and to have received antiarrhythmic drug therapy within 12 months prior to the index ablation. Ablation success was defined as the absence of antiarrhythmic drug therapy 6-12 months postablation.

RESULTS

Of 135 patients identified (67% men, mean age 73 years), ablation was successful in 69 (51.1%); most patients (96%) underwent a single procedure. Patients with successful ablation discontinued antiarrhythmic drug treatment after (mean) 54 days. Use of rate-control and anticoagulant drugs decreased after successful ablation, from 87% to 67% and from 86% to 64% of patients, respectively. Among failed ablation patients, 74% versus 70% received rate-control drugs, and 88% versus 82% received anticoagulants pre- versus postablation. Mean +/- SD per-patient procedural costs were $13,655+/-$12,761 for successful compared with $17,294+/-$26,502 (P=0.21) for failed ablation, while AF-related medical costs over 12 months postablation were $2394+/-$642 and $2703+/-$1706, respectively (P<0.001). Overall costs tended to be lower for successful ($16,049+/-$12,536) than for failed ($19,997+/-$13,958) AF ablation (P=0.07). These findings are subject to the limitations imposed by a retrospective database analysis and a small sample size.

CONCLUSION

Outside the clinical-trial setting, catheter ablation for second-line treatment of AF proved unsuccessful in half of Medicare-aged patients. Direct medical costs did not differ significantly between patients with failed and successful ablations. The high rate and costs of AF ablation failure in the Medicare-aged population reinforce the need for better understanding of prognostic factors for ablation outcome.

Stroke risk associated with balloon based catheter ablation for atrial fibrillation: Rationale and design of the MACPAF Study

Background

Catheter ablation of the pulmonary veins has become accepted as a standard therapeutic approach for symptomatic paroxysmal atrial fibrillation (AF). However, there is some evidence for an ablation associated (silent) stroke risk, lowering the hope to limit the stroke risk by restoration of rhythm over rate control in AF. The purpose of the prospective randomized single-center study "Mesh Ablator versus Cryoballoon Pulmonary Vein Ablation of Symptomatic Paroxysmal Atrial Fibrillation" (MACPAF) is to compare the efficacy and safety of two balloon based pulmonary vein ablation systems in patients with symptomatic paroxysmal AF.

Methods/Design

Patients are randomized 1:1 for the Arctic Front^® or the HD Mesh Ablator^® catheter for left atrial catheter ablation (LACA). The predefined endpoints will be assessed by brain magnetic resonance imaging (MRI), neuro(psycho)logical tests and a subcutaneously implanted reveal recorder for AF detection. According to statistics 108 patients will be enrolled.

Discussion

Findings from the MACPAF trial will help to balance the benefits and risks of LACA for symptomatic paroxysmal AF. Using serial brain MRIs might help to identify patients at risk for LACA-associated cerebral thromboembolism. Potential limitations of the study are the single-center design, the existence of a variety of LACA-catheters, the missing placebo-group and the impossibility to assess the primary endpoint in a blinded fashion.

Trial registration

clinicaltrials.gov NCT01061931

Trends in catheter ablation for atrial fibrillation in the United States

BACKGROUND

There are few data on the use of catheter ablation for atrial fibrillation (AF) in the United States. We analyzed data from the National Hospital Discharge Survey (NHDS) to examine trends in the rate of catheter ablation for hospitalized patients with AF over a 15-year period.

OBJECTIVE

To examine rates of catheter ablation in patients with AF over time.

DESIGN

All adult patients in the NHDS with an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for AF from the years 1990 to 2005 were identified and assessed for the presence of a cardiac catheter ablation procedure code. Clinical characteristics associated with ablation were identified and multivariable logistic regression used to determine trends in the rate of ablation therapy over time.

RESULTS

We identified 269,471 adults with AF. The rate of catheter ablation in AF patients increased from 0.06% in 1990 to 0.79% in 2005 (P < 0.001 for trend). Compared to those not undergoing ablation, ablated patients were younger (mean age 66 versus 76 years; P < 0.001), more likely to be male (57% versus 43%; P < 0.001), have private insurance (22% versus 11%; P < 0.001), and have a none of the following stroke risk factors: congestive heart failure, hypertension, age >75 years, diabetes mellitus, or stroke/transient ischemic attack (37% versus 16%; P < 0.001). Catheter ablation in AF patients increased by 15% per year over the time period (95% confidence interval [CI], 13%-16%) and across all age groups, including in patients age > or =80 years (0.0% in 1990 and 0.26% in 2005; P < 0.001 for trend).

CONCLUSIONS

The rate of catheter ablation in patients with AF is increasing significantly over time, even in the oldest patients. Medicine.

Pulmonary vein contraction: characterization of dynamic changes in pulmonary vein morphology using multiphase multislice computed tomography scanning

BACKGROUND

The presence and extent of contraction within the pulmonary veins (PVs) have not been defined clearly.

OBJECTIVE

The purpose of this study was to determine whether PV contraction exists and can be visualized using multislice computed tomography (MSCT) scanning as this may indicate that this modality may be useful for monitoring patients after PV isolation procedures.

METHODS

Analysis was performed on 29 patients (mean age 57.5 +/- 12 years) undergoing MSCT for suspected coronary artery disease without structural heart disease or left atrial anatomical variants. Multiplane reconstructions were used to measure PV diameters at 0, 5, 10, and 15 mm from the ostium in two phases (maximum and minimum size). The ejection fractions of three 5-mm segments were calculated for each PV.

RESULTS

Right-sided and left-sided PV contraction and maximal atrial contraction occurred at a median of 85% and 95% of the cardiac cycle, respectively. The temporal concordance of minimal PV volume during peak atrial contraction indicated that the PV volume changes are secondary to active contraction rather than passive reflux and PV distension. The ejection fractions were highest in the superior veins: right superior PV (36.7%, 27.8%, and 16%, respectively, for the three segments from proximal to distal) and left superior PV (26.9%, 21.3%, and 12.1%), in comparison with the right inferior PV (21.1%, 6.6%, and -0.7%) and left inferior PV (15%, 9.3%, and 7.6%).

CONCLUSION

Volume changes related to active PV contraction occur extending up to 15 mm into the veins, and this effect is most pronounced in the superior veins.

Pilot study of transesophageal endoscopic epicardial coagulation by submucosal endoscopy with the mucosal flap safety valve technique (with videos)

BACKGROUND

We previously demonstrated that the thoracic cavity could be safely accessed by submucosal endoscopy with the mucosal flap safety valve (SEMF) technique.

OBJECTIVES

To evaluate the technical feasibility of transesophageal access to the heart and epicardial ablation.

DESIGN

One-week survival study with 5 porcine models.

SETTINGS

Animal laboratory with general anesthesia.

INTERVENTIONS

High-pressure carbon dioxide injection and balloon dissection created a large submucosal working space for insertion of a cap-fitted endoscope. A myotomy was performed inside the submucosal space. The thoracic cavity was endoscopically accessed through the myotomy site. A pericardial window was created with a needle-knife. A spot coagulation of the epicardium was performed with a heat probe and a hook-knife. The myotomy site was sealed with the overlying mucosal flap, and the mucosal entry site was closed with clips.

MAIN OUTCOME MEASUREMENTS

An endoscopy and a necropsy were performed to study the esophagus, mediastinum, pericardial space, and cautery locations on the epicardium one week after the procedure.

RESULTS

Epicardial coagulation was successfully performed within 30 minutes in 4 of the 5 pigs. Follow-up endoscopy demonstrated completely sealed myotomy sites by the overlying mucosal flap. There was no gross contamination or signs of contamination in the thoracic cavity. The pericardial space was normal in appearance. The epicardial coagulation sites were healing, without exudative ulceration.

CONCLUSIONS

The SEMF technique allowed endoscopic access to the upper mediastinum, the pericardium, and the epicardium via the esophagus, along with a minimal intervention on the epicardium.

Atrial fibrillation: insights from clinical trials and novel treatment options

Atrial fibrillation (AF) is the most common encountered sustained arrhythmia in clinical practice. The last decade the result of large 'rate' versus 'rhythm' control trials have been published that have changed the current day practise of AF treatment. It has become clear that rate control is at least equally effective as a rhythm control strategy in ameliorating morbidity as well as mortality. Moreover, in each individual patient the risk of thromboembolic events should be assessed and antithrombotic treatment be initiated. There have also been great advances in understanding the mechanisms of AF. Experimental studies showed that as a result of electrical and structural remodelling of the atria, 'AF begets AF'. Pharmacological prevention of atrial electrical remodelling has been troublesome, but it seems that blockers of the renin angiotensin system, and perhaps statins, may reduce atrial structural remodelling by preventing atrial fibrosis. Clinical studies demonstrated that the pulmonary veins exhibit foci that can act as initiator and perpetuator of the arrhythmia. Isolation of the pulmonary veins using radiofrequency catheter ablation usually abolishes AF. The most promising advances in the pharmacological treatment of AF include atrial specific antiarrhythmic drugs and direct thrombin inhibitors. In the present review we will describe the results of recent experimental studies, discuss the latest clinical trials, and we will focus on novel treatment modalities.

Esophagus imaging for radiofrequency ablation of atrial fibrillation using a dual-source computed tomography system: Preliminary observations

OBJECTIVE

The very recent introduction of dual-source computed tomography (DSCT) has significantly improved the temporal resolution of ECG-gated multidetector-row cardiac computed tomography (CT). The aim of the present study was to evaluate whether with a DSCT visualization of the esophagus is feasible without any use of contrast in the esophagus.

MATERIALS AND METHODS

A total of 20 patients were evaluated. Ten patients underwent examination with a DSCT scanner without a gastric tube. In another ten patients, which served as control group, a CT scan was performed with a radio-opaque gastric tube prior to circumferential pulmonary vein isolation (in seven patients with a 16-slice CT and in three patients with a DSCT).

RESULTS

In the control group the gastric tube and the left atrium were reconstructed and were well visualized in all ten patients in the electro-anatomic mapping system, independently whether 16-row CT or DSCT scan was used. In the study group integration of the esophagus into the electro-anatomic mapping system was not feasible, due to the lacking contrast counterpart the surrounding tissue.

CONCLUSIONS

Even with the newest generation of DSCT scanner it is not possible to integrate the esophagus image into the 3-D electroanatomic mapping system without contrast by whatever means. However placing a conventional gastric tube before performing the CT scan allowed visualization and integration of the esophagus into the 3-D electro-anatomical map in all patients.