Inappropriate shocks in patients with Fidelis® lead fractures: impact of remote monitoring and the lead integrity algorithm.

INTRODUCTION: The role of remote monitoring combined with lead integrity algorithm (LIA) in patients with Fidelis (Medtronic Inc., Minneapolis, MN, USA) lead fractures is not well defined. METHODS: We retrospectively identified patients with Fidelis lead fractures at our institution, documenting all pertinent data (remote monitoring use, clinical presentation, lead fracture diagnosis criteria). Patients were classified into subgroups based on the type of home monitoring and whether LIA was uploaded before lead fracture. Subgroups were compared based on delivery of inappropriate shocks (IS). RESULTS: A total of 131 patients (mean age 62 ± 16 years, 70% male, 69% primary prevention implants) were followed until lead fracture (average 32 ± 12 months). IS were delivered in 21% of patients (n = 11/52) with LIA versus 52% (n = 41/79) without LIA, P < 0.001. LIA significantly decreased the number of IS (2.1 ± 1.0 IS vs 7.9 ± 12 IS, P < 0.001) and significantly increased the number of patients diagnosed through audible alert (P < 0.001). Wireless monitoring significantly decreased the time interval to reprogram defibrillators OFF (mean 1.5 ± 1 days vs 15.6 ± 18 days with nonwireless CareLink [Medtronic Inc.] and 12.4 ± 20 days without CareLink, P < 0.001); 14% of patients with LIA and wireless monitoring combined received IS. Without LIA, 63% of patients with wireless monitoring received IS. CONCLUSION: This study confirms that LIA significantly decreases IS therapy in patients with Fidelis lead fractures. Wireless technology enhances LIA benefits by significantly shortening time to reprogram defibrillators. However, despite the "best scenario" of combining LIA and wireless monitoring, 14% of patients with lead fractures still get IS. Further refinements of detection algorithms are required to eliminate this significant clinical problem.

Cardiac Image Registration: Rotational Error Correction and Gated Stabilization for Cardiac Motion.

Background: Dynamic motion of the heart due to cardiac and respiratory cycles, and rotation from varying patient positions between imaging modalities, can cause errors during cardiac image registration. This study used phantom, patient and animal models to assess and correct these errors. Methods and Results: Rotational errors were identified and corrected using different phantom orientations. ECG-gated fluoro images were aligned with similarly gated CT images in 9 patients, and accuracy assessed during atrial fibrillation (AF) and sinus rhythm. A tracking algorithm corrected errors due to respiration; 4 independent observers compared 25 respiration sequences to an automated method. Following correction of these errors, target registration error was assessed. At 20 mm and 30 mm from the phantom model's center point with an in-plane rotation of 8 degrees, measured error was 2.94 mm and 5.60 mm, respectively, and the main error identified. A priori method accurately predicted ECG location in only 38% (p=0.0003) of 313 R-R intervals in AF. A posteriori method accurately gated the ECG during AF and sinus rhythm in 97% and 98% of 375 beats evaluated, respectively (p=NS). Tracking algorithm for ECG-gated motion compensation was identified as good or fair 96% of the time, with no difference between observers and automated method (chi-square=25; p=NS). Target registration error in phantom and animal models was 1.75±1.03 mm and 0 to 0.5 mm, respectively. Conclusions: Errors during cardiac image registration can be identified and corrected. Cardiac image stabilization can be achieved using ECG gating and respiration.

Incessant interfascicular reentrant ventricular tachycardia as a result of catheter ablation of the right bundle branch: case report and review of the literature.

A 72-year-old woman developed incessant interfascicular (IF) ventricular tachycardia immediately after successful right bundle branch (RBB) catheter ablation for the treatment of sustained bundle branch reentrant tachycardia. Catheter ablation of the left bundle branch and the left anterior fascicle was successful in eliminating the tachycardia (in 2 different sessions). This report discusses the direct link between the creation of an RBB block and the development of IF tachycardia, in our case, and in prior cases of IF reentry reported in the literature.

Periprocedural anticoagulation for atrial fibrillation ablation.

BACKGROUND: Catheter ablation for atrial fibrillation (AF) can increase risk of left atrial (LA) thrombi and stroke. Optimal periprocedural anticoagulation has not been determined. OBJECTIVE: We report the role of administering warfarin and aspirin without low molecular weight heparin in patients undergoing AF ablation. METHODS: A total of 207 patients underwent ablation for AF. Transesophageal echocardiography (TEE) guided transseptal puncture and ruled out clot in the LA. After first puncture, the sheath was flushed with heparin (5,000 Units/mL). After second puncture, a bolus of 80 units/kg of heparin was given, followed by an infusion to maintain activated clotting time (ACT) around 300-350 seconds. Warfarin was stopped and aspirin was started (325 mg/day) 3 days preprocedure. Warfarin was restarted on the day of the procedure. Both medications were continued for 6 weeks postablation. Warfarin was continued for 6 months in patients with prior history of persistent or recurrent AF. Thirty-seven patients who showed smoke in the LA on TEE were given low molecular weight heparin postprocedure until international normalized ratio (INR) was therapeutic. RESULTS: Thirty-two patients had persistent and 175 had paroxysmal AF; 87 were cardioverted during ablation. Two patients had transient ischemic attack (TIA) on the sixth and eighth days, respectively, following ablation, with complete recovery. Both had subtherapeutic INRs. CONCLUSION: In patients without demonstrable clot or smoke in the LA, starting aspirin 3 days prior and warfarin immediately post-radiofrequency ablation, without low molecular weight heparin, with meticulous anticoagulation during the procedure, appears to be a safe mode of anticoagulation.

Computed tomography-fluoroscopy image integration-guided catheter ablation of atrial fibrillation.

INTRODUCTION: This study examines the feasibility of atrial fibrillation (AF) ablation using registered three-dimensional computed tomography (CT) images of the left atrium with fluoroscopy. METHODS AND RESULTS: A total of 50 consecutive patients with symptomatic AF refractory to medical therapy (32 paroxysmal, 18 persistent, age 55 +/- 10 years) were randomized to undergo a catheter-based AF ablation procedure with or without the CT-fluoroscopy guidance system. All patients underwent preprocedural contrast-enhanced CT imaging and segmentation of the left atrium. For the CT-fluoroscopy group, circumferential lesions encompassing the pulmonary vein (PV) antrum and linear lesions along the roof of the left atrium between the superior PVs and the mitral isthmus were created on the CT image, which was registered with real-time fluoroscopy. The registered images were then used to navigate the ablation catheters to the sites of planned ablation. After the ablation sites were completed, any remaining PV potentials were isolated with electrophysiological guidance. In the control patients, the same technique was performed without using the CT-fluoro guidance system. CT scans were accurately registered to fluoroscopic images with minimal manual correction. Operators could navigate catheters on the registered images to preplanned, extraostial sites for ablation. CT-fluoroscopy guidance decreased procedure duration and fluoro times (P < 0.05). At a mean follow-up of 9 +/- 2 months, 21 patients (84%) in the CT-fluoro guidance group and 16 patients (64%) in the control group have had no recurrence of AF. CONCLUSION: CT-fluoroscopic-guided left atrial ablation is feasible and allows appropriate catheter manipulation in the left atrium.

Posterior left atrial-esophageal relationship throughout the cardiac cycle.

BACKGROUND: Radiofrequency energy delivered throughout the cardiac cycle has the potential to cause thermal injury to the esophagus if the anatomical relationship between the posterior left atrium and the esophagus changes during cardiac motion. OBJECTIVE: To assess the posterior left atrial-esophageal relationship throughout the cardiac cycle. METHODS: In this study, the anatomical relationship between the posterior left atrium and the esophagus was assessed throughout the cardiac cycle in 10 consecutive patients. All patients underwent contrast-enhanced, ECG-gated CT scanning. Left atrial volumes and the esophageal structure were generated from the reconstructed data at 10 phases of the cardiac cycle from 5% to 95% of the R-R interval. The posterior left atrial-esophageal anatomical relationship was measured at four levels, the superior pulmonary vein ostial site, and the upper, mid and lower left atrium. RESULTS: There were significant variations in the left atrial-esophageal relationship in the 10 patients. The relative movement between the esophagus and the posterior left atrium throughout the cardiac cycle in the anteroposterior and right-to-left orientations was 0.55 +/- 0.99 mm and 0.60 +/- 1.02 mm (95% confidence interval, 2.03 and 1.98 respectively). CONCLUSIONS: Under normal conditions, there is little change in the anatomical relationship between the posterior left atrium and the esophagus during the entire cardiac cycle. However, due to the interpatient variability at the esophageal location, identification of esophageal location may help prevent complications during catheter ablation procedures involving the left atrium.

Pulmonary vein isolation and linear lesions in atrial fibrillation ablation.

BACKGROUND: Various strategies have been used for atrial fibrillation (AF) ablation. It is unclear whether adding linear lesions to pulmonary vein (PV) isolation has significant advantages. OBJECTIVES: We assessed the clinical benefit of adding linear lesions in patients undergoing PV isolation for AF. METHODS: One hundred patients (63 male and 37 female; mean age of 59 +/- 11 years) with documented paroxysmal AF were included in the study. Patients were randomized into two groups. The first group underwent PV isolation alone. The second group underwent PV isolation and had two linear lesions created; one line between the superior PVs, and a second line from the left inferior PV to the mitral valve annulus. Patients' clinical progress after the ablation was evaluated and compared at 1, 3, and 9 months after their respective ablation procedures. RESULTS: The linear lesions group maintained sinus rhythm and had fewer symptoms than the lone PV isolation group (86 vs. 58%, respectively) (p < 0.05) at 1 month. At 9 months, when patients who reverted to AF underwent additional management to regain sinus rhythm (90 vs. 82%, respectively) (p = NS), there was no statistical difference between the groups regarding the use of antiarrhythmics, the need for electrical cardioversion, and subjective improvement. CONCLUSION: The addition of linear lesions to PV isolation more effectively achieved sinus rhythm initially and fewer patients required additional management to maintain their rhythm when compared to patients who underwent lone PV isolation. However, at 9 months, the overall results were similar in both groups.

The implantable cardioverter defibrillator: technology, indications, and impact on cardiovascular survival.

Since the introduction of the implantable cardioverter defibrillator (ICD) for the management of patients with high risk of arrhythmic SCD, there has been increasing use of this device. Its basic promise to effectively terminate ventricular tachycardia (VT)-ventricular fibrillation (VF) has been repeatedly met. In several randomized trials, the ICD has been shown to be superior to conventional anti-arrhythmic therapy, both in patients with documented VT-VF (secondary prevention) and those with high risk such as left ventricular ejection fraction and no prior sustained VT-VF (primary prevention). In both groups, the ICD showed overall and cardiac mortality reduction. The device now can more accurately detect VT-VF and differentiate these from other arrhythmias through a series of algorithms and direct-chamber sensing. Therapy options include painless antitachycardia pacing, low-energy cardioversion, and high-energy defibrillation. The technique implant is now simple as a pacemaker with one lead attached to an active (hot) can functioning as the other electrode. Among other improvements is its weight, volume, multiprogrammability, and storage of information,dual-chamber pacing and sensing, dual-chamber defibrillation, and addition of biventricular pacing for cardiac synchronization. It is anticipated that further improvement in ICD technology will take place and the list of indications will grow.