Lars Lickfett

Pulmonary vein anatomy in patients undergoing catheter ablation of atrial fibrillation: lessons learned by use of magnetic resonance imaging.

Background—This study sought to define the technique and results of magnetic resonance imaging (MRI) of pulmonary vein (PV) anatomy before and after catheter ablation of atrial fibrillation (AF). Methods and Results—Twenty-eight patients with AF underwent ablation. Patients underwent gadolinium-enhanced MRI before and 6 weeks after their procedures. A control group of 27 patients also underwent MRI. Variant PV anatomy was observed in 38% of patients. AF patients had larger PV diameters than control subjects, but no difference was observed in the size of the PV ostia among AF patients. The PV ostia were oblong in shape with an anteroposterior dimension less than the superoinferior dimension. The left PVs had a longer “neck” than the right PVs. A detectable PV narrowing was observed in 24% of veins. The severity of stenosis was severe in 1 vein (1.4%), moderate in 1 vein (1.4%), and mild in 15 veins (21.1%). All patients were asymptomatic, and none required treatment. Conclusions—This study demonstrates that AF patient have larger PVs than control subjects and demonstrates the value of MRI in facilitating AF ablation. The benefits of preprocedural MRI of PVs include the ability to evaluate the number, size, and shape of the PVs. MRI also provides an assessment of the severity of PV stenosis.

Radiation Exposure During Catheter Ablation of Atrial Fibrillation

Background—The purpose of this study was to determine the radiation exposure during catheter ablation of atrial fibrillation (AF) using the pulmonary vein (PV) approach. Methods and Results—The study included 15 patients with AF and 5 patients each with atrial flutter and atrioventricular nodal reentrant tachycardia (AVNRT) who underwent fluoroscopically guided procedures on a biplane x-ray system operated at a low-frame pulsed fluoroscopy (7.5 frames per second). Radiation exposure was measured directly with 50 to 60 thermoluminescent dosimeters (TLDs). Peak skin doses (PSDs), effective radiation doses, and risk of fatal malignancies were all computed. Mean fluoroscopy durations for AF procedures were 67.8±21 minutes in the right anterior oblique (RAO) and 61.9±16.6 minutes in the left anterior oblique (LAO) projection, significantly different from that required for atrial flutter and AVNRT. The mean PSDs measured with the TLDs were 1.0±0.5 Gy in the RAO and 1.5±0.4 Gy in the LAO projection. The lifetime risk of excess fatal malignancies normalized to 60 minutes of fluoroscopy was 0.07% for women and 0.1% for men. Conclusions—The relatively small amounts of the patient’s radiation exposure in this study, despite the prolonged fluoroscopy durations, can be attributed to the use of very-low-frame pulsed fluoroscopy, the avoidance of magnification, and optimal adjustments of the fluoroscopy exposure rates. The resulting lifetime risk of fatal malignancy is within the range previously reported for standard supraventricular arrhythmias.

Predictors of Recurrence Following Catheter Ablation of Atrial Fibrillation Using an Irrigated‐Tip Ablation Catheter

Introduction: The aims of this study were to identify predictors of recurrence after catheter ablation of atrial fibrillation (AF) and to report the safety and efficacy of catheter ablation of AF using an irrigated‐tip ablation catheter.

Anatomic Stereotactic Catheter Ablation on Three-Dimensional Magnetic Resonance Images in Real Time

Background—Targets for radiofrequency (RF) ablation of atrial fibrillation, atrial flutter, and nonidiopathic ventricular tachycardia are increasingly being selected on the basis of anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures and is associated with radiation risk, other approaches to mapping may be beneficial. Methods and Results—An electromagnetic catheter positioning system was superimposed on 3D MR images using fiducial markers. This allowed the dynamic display of the catheter position on the true anatomy of previously acquired MR images in real time. In vitro accuracy and precision during catheter navigation were assessed in a phantom model and were 1.11±0.06 and 0.30±0.07 mm (mean±SEM), respectively. Left and right heart catheterization was performed in 7 swine without the use of fluoroscopy, yielding an in vivo accuracy and precision of 2.74±0.52 and 1.97±0.44 mm, respectively. To assess the reproducibility of RF ablation, RF lesions were created repeatedly at the identical anatomic site in the right atrium (n=8 swine). Average distance of the repeated right atrial ablations was 3.92±0.5 mm. Straight 3-point lines were created in the right and left ventricles to determine the ability to facilitate complex ablation procedures (n=6 swine). The ventricular lesions deviated 1.70±0.24 mm from a straight line, and the point distance differed by 2.25±0.63 mm from the pathological specimen. Conclusions—Real-time display of the catheter position on 3D MRI allows accurate and precise RF ablation guided by the true anatomy. This may facilitate anatomically based ablation procedures in, for instance, atrial fibrillation or nonidiopathic ventricular tachycardia and decrease radiation times.

Initial experience with a novel focused ultrasound ablation system for ring ablation outside the pulmonary vein

AbstractIntroduction: Atrial fibrillation has been shown to initiate from triggers within pulmonary veins. Several studies have documented that electrical isolation of those triggers can lead to maintenance of sinus rhythm. The complication of pulmonary vein stenosis has limited the utility of delivering ablation energy within the pulmonary vein. We utilize a focused ultrasound catheter ablation system for delivery of transmural ablation lines proximal to the pulmonary vein ostium. Methods: Nine dogs (weight 30–39 kg) were anesthetized and ventilated. Through a transseptal approach, pulmonary veins were engaged with the focused balloon ultrasound catheter. Ultrasound power was delivered at 40 acoustic watts outside the pulmonary vein ostium, focused 2 mm off the balloon surface, with a depth of approximately 6 mm, for 30–120 seconds. Following ablation, lesions were histopathologically analyzed. Results: Of nine animals studied, fourteen pulmonary veins were ablated. We found successful delivery of near circumferential and transmural ablation lines in 6/14 pulmonary veins. In each of the six circumferential ablations, successful alignment of the ultrasound transducer along the longitudinal axis of the parabolic balloon occurred. The final four ablations were conducted with an enhanced catheter design that assured axial alignment. Of these ablations, all four were circumferential. The remaining 8 pulmonary veins had incomplete delivery of lesions. In each of these veins the ultrasound transducer was misaligned with the balloon axis when therapy was delivered. Conclusion: Focused ultrasound ablation is a new means of performing pulmonary vein isolation. This method provides delivery of lesions outside the vein, limiting the risk of pulmonary vein stenosis for the treatment of atrial fibrillation.

Characterization of a new pulmonary vein variant using magnetic resonance angiography: incidence, imaging, and interventional implications of the "right top pulmonary vein".

Introduction: Catheter ablation of the pulmonary veins (PVs) for prevention of recurrent atrial fibrillation requires precise anatomic information. We describe the characteristics of a new anatomic variant of PV anatomy using magnetic resonance angiography.

Stereotactic magnetic resonance guidance for anatomically targeted ablations of the fossa ovalis and the left atrium

AbstractIntroduction: Targets for radiofrequency ablation (RFA) of atrial fibrillation are increasingly being selected based on anatomic considerations. Because fluoroscopy provides only limited information about the relationship between catheter positions and cardiac structures, we evaluated whether stereotactic catheter guidance might facilitate anatomical catheter navigation and RFA to the great vessels, the fossa ovalis and the left atrium (LA). Methods and Results: An electromagnetic catheters position system was superimposed on three-dimensional (3D) MR images using fiducial markers. This allowed the dynamic display of the catheter position on the true anatomy of previously acquired MRI in real-time. To assess the reproducibility of RFA, repeat ablations were created at the identical anatomic site in the inferior vena cava (IVC) in 5 swine. Average distance of the repeated ablations was 4.4 ± 2.4 mm.In five swine the catheter was anatomically guided with the MRI to the fossa ovalis and a single RFA was performed. On the pathological specimen all ablation sites were located within the fossa ovalis with an average distance of 3.9 ± 2.1 mm from its center. In two of the experiments the ablation catheter was passed into the left atrium and anatomically targeted ablation performed in the lateral wall of the left atrial appendage. Catheter location and ablation site were confirmed by autopsy and histology. Conclusion: Real-time display of the catheter position on 3D-MRI allows anatomically targeted catheter navigation and RFA in the IVC, the fossa ovalis, and the left atrium. This may facilitate anatomically based interventions like septal puncture or pulmonary vein ablation and decrease fluoroscopy times.

Influence of the point of origin on heart rate turbulence after stimulated ventricular and atrial premature beats

Abstract.Background:Heart rate turbulence (HRT) is a new and auspicious parameter for risk stratification in patients suffering from structural heart disease. The HRT parameters onset (TO) and slope (TS) are derived from Holter ECGs. Only a few studies have evaluated physiologic properties like age or prematurity of the ventricular beat on HRT. Until now, to our knowledge, little is known about the influence of the point of origin of the premature beat on HRT. Therefore, we conducted a study consisting of 25 patients (pts) with premature beats generating from 2 different sites in the atrium and ventricle.Methods:During an electrophysiologic study, premature extra beats were induced. The high right atrium (HRA) and the lateral part of the coronary sinus (CS) represented the atrial pacing sites, while the right ventricular apex (RVAP) and right ventricular outflow tract (RVOT) represented the ventricular pacing sites. Prematurity started at 450 ms and was decreased to the refractoriness of each site. TO and TS were computed and correlated to the site of origin and the coupling interval (CI).Results:Atrial TO was positive in 9 pts (HRA) and 7 (CS) as well as ventricular TO in 2 pts, respectively. TO induced in CS correlated with the CI (r = –0.50, p < 0.05). TS was negative, independent of the site of origin. Atrial TS showed no correlation with the CI. TO generated from both ventricular sites was positive in 2 pts. TO from RVAP correlated with the CI (r = –0.81, p < 0.005), but not with RVOT. TS from both ventricular sites exhibited no correlation with the pacing site, but correlated with themselves (r = –0.69, p < 0.03).Conclusion:The site of origin of the premature beat exhibits no influence on heart rate turbulence slope. The prematurity of the extra beat correlates with turbulence onset, but not with slope. Finally, the site of origin revealed no influence on HRT slope. Therefore, the calculation of heart rate turbulence derived from extra beats extracted from Holter ECG is reliable.

Total beta-adrenoceptor knockout slows conduction and reduces inducible arrhythmias in the mouse heart.

Introduction Beta-adrenoceptors (β-AR) play an important role in the neurohumoral regulation of cardiac function. Three β-AR subtypes (β1, β2, β3) have been described so far. Total deficiency of these adrenoceptors (TKO) results in cardiac hypotrophy and negative inotropy. TKO represents a unique mouse model mimicking total unselective medical β-blocker therapy in men. Electrophysiological characteristics of TKO have not yet been investigated in an animal model. Methods In vivo electrophysiological studies using right heart catheterisation were performed in 10 TKO mice and 10 129SV wild type control mice (WT) at the age of 15 weeks. Standard surface ECG, intracardiac and electrophysiological parameters, and arrhythmia inducibility were analyzed. Results The surface ECG of TKO mice revealed a reduced heart rate (359.2±20.9 bpm vs. 461.1±33.3 bpm; p<0.001), prolonged P wave (17.5±3.0 ms vs. 15.1±1.2 ms; p = 0.019) and PQ time (40.8±2.4 ms vs. 37.3±3.0 ms; p = 0.013) compared to WT. Intracardiac ECG showed a significantly prolonged infra-Hisian conductance (HV-interval: 12.9±1.4 ms vs. 6.8±1.0 ms; p<0.001). Functional testing showed prolonged atrial and ventricular refractory periods in TKO (40.5±15.5 ms vs. 21.3±5.8 ms; p = 0.004; and 41.0±9.7 ms vs. 28.3±6.6 ms; p = 0.004, respectively). In TKO both the probability of induction of atrial fibrillation (12% vs. 24%; p<0.001) and of ventricular tachycardias (0% vs. 26%; p<0.001) were significantly reduced. Conclusion TKO results in significant prolongations of cardiac conduction times and refractory periods. This was accompanied by a highly significant reduction of atrial and ventricular arrhythmias. Our finding confirms the importance of β-AR in arrhythmogenesis and the potential role of unspecific beta-receptor-blockade as therapeutic target.

Real-time three-dimensional transoesophageal echocardiography for guidance of interventional closure of paravalvular leakage

A 69-year-old female presented with increasing dyspnoea NYHA classes III–IV and peripheral cyanosis 10 years after mechanical mitral valve replacement (St Jude Medical, 27 mm) of a degenerated bioprosthesis. Transoesophageal echocardiography (TEE) revealed severe paravalular leakage of the mitral valve prosthesis (Panel A, colour Doppler jet indicating paravalvular regurgitation volume with apparent dehiscence). Repeated open heart …