Alan Wimmer

Risk of Thromboembolic Events After Percutaneous Left Atrial Radiofrequency Ablation of Atrial Fibrillation

Background— In patients with atrial fibrillation (AF), the risk of thromboembolic events (TEs) is variable and is influenced by the presence and number of comorbid conditions. The effect of percutaneous left atrial radiofrequency ablation (LARFA) of AF on the risk of TEs is unclear. Methods and Results— LARFA was performed in 755 consecutive patients with paroxysmal (n=490) or chronic (n=265) AF. Four hundred eleven patients (56%) had ≥1 risk factor for stroke. All patients were anticoagulated with warfarin for ≥3 months after LARFA. A TE occurred in 7 patients (0.9%) within 2 weeks of LARFA. A late TE occurred 6 to 10 months after ablation in 2 patients (0.2%), 1 of whom still had AF, despite therapeutic anticoagulation in both. Among 522 patients who remained in sinus rhythm after LARFA, warfarin was discontinued in 79% of 256 patients without risk factors and in 68% of 266 patients with ≥1 risk factor. Patients older than 65 years or with a history of stroke were more likely to remain anticoagulated despite a successful outcome from LARFA. None of the patients in whom anticoagulation was discontinued had a TE during 25±8 months of follow-up. Conclusions— The risk of a TE after LARFA is 1.1%, with most events occurring within 2 weeks after the procedure. Discontinuation of anticoagulant therapy appears to be safe after successful LARFA, both in patients without risk factors for stroke and in patients with risk factors other than age >65 years and history of stroke. Sufficient safety data are as yet unavailable to support discontinuation of anticoagulation in patients older than 65 years or with a history of stroke.

Radiofrequency Catheter Ablation of Chronic Atrial Fibrillation Guided by Complex Electrograms

Background— Radiofrequency catheter ablation of atrial fibrillation (AF) guided by complex fractionated atrial electrograms has been reported to eliminate AF in a large proportion of patients. However, only a small number of patients with chronic AF have been included in previous studies. Methods and Results— In 100 patients (mean age, 57±11 years) with chronic AF, radiofrequency ablation was performed to target complex fractionated atrial electrograms at the pulmonary vein ostial and antral areas, various regions of the left atrium, and the coronary sinus until AF terminated or all identified complex fractionated atrial electrograms were eliminated. Ablation sites consisted of ≥1 pulmonary vein in 46% of patients; the left atrial septum, roof, or anterior wall in all; and the coronary sinus in 55%. During 14±7 months of follow-up after a single ablation procedure, 33% of patients were in sinus rhythm without antiarrhythmic drugs, 38% had AF, 17% had both AF and atrial flutter, 9% had persistent atrial flutter, and 3% had paroxysmal AF on antiarrhythmic drugs. A second ablation procedure was performed in 44% of patients. Pulmonary vein tachycardia was found in all patients in both previously targeted and nontargeted pulmonary veins. There were multiple macroreentrant circuits in the majority of patients with atrial flutter. At 13±7 months after the last ablation procedure, 57% of patients were in sinus rhythm without antiarrhythmic drugs, 32% had persistent AF, 6% had paroxysmal AF, and 5% had atrial flutter. Conclusions— Modest short-term efficacy is achievable with radiofrequency ablation of chronic AF guided by complex fractionated atrial electrograms, but only after a second ablation procedure in >40% of patients. Rapid activity in the pulmonary veins and multiple macroreentrant circuits are common mechanisms of recurrent atrial arrhythmias.

A Tailored Approach to Catheter Ablation of Paroxysmal Atrial Fibrillation

Background— Because the genesis of atrial fibrillation (AF) is multifactorial and variable, an ablation strategy that involves pulmonary vein isolation and/or a particular set of ablation lines may not be equally effective or efficient in all patients with AF. A tailored strategy that targets initiators and drivers of AF is a possible alternative to a standardized lesion set. Methods and Results— Catheter ablation was performed in 153 consecutive patients (mean age, 56±11 years) with symptomatic paroxysmal AF with the use of an 8-mm tip radiofrequency ablation catheter. The esophagus was visualized with barium. The pulmonary veins and left atrium were mapped during spontaneous or induced AF. Arrhythmogenic pulmonary veins were isolated or encircled. If AF was still present or inducible, complex electrograms in the left atrium, coronary sinus, and superior vena cava were targeted for ablation. The end point of ablation was absence of frequent atrial ectopy and spontaneous AF during isoproterenol infusion and noninducibility of AF. Routine energy applications near the esophagus were avoided. During follow-up, left atrial flutter developed in 19% of patients and was still present in 10% at >12 weeks of follow-up. A repeat ablation procedure was performed in 18% of patients. During a mean follow-up of 11±4 months, 77% of patients were free from AF and/or atrial flutter without antiarrhythmic drug therapy. Pericardial tamponade or transient neurological events occurred in 2% of procedures. Conclusions— A tailored ablation strategy that only targets triggers and drivers of AF is feasible and eliminates paroxysmal AF in ≈80% of patients.

Fragmented QRS and mortality risk in patients with left ventricular dysfunction.

Background—Fragmented QRS (fQRS) has been shown to predict cardiac events in select patient populations. Whether fQRS improves patient selection for primary prevention patients eligible for implantable cardioverter-defibrillator (ICD) therapy remains unknown. Methods and Results—In a prospective, multisite cohort of 842 patients with left ventricular dysfunction (ejection fraction ⩽35%) representing both ischemic and nonischemic etiology, the presence of fQRS on ECG was assessed using standardized criteria. The association between fQRS and all-cause and arrhythmic mortality was evaluated overall and stratified by ICD status using multivariable Cox regression models, adjusted for demographic, clinical, and treatment variables. Fragmented QRS was present in 274 (32.5%) patients, and there were 191 (22.7%) deaths during a mean follow-up of 40±17 months. Rates of all-cause mortality did not differ between the fQRS+ (19.7%) and fQRS− (24.1%) groups; adjusted hazard ratio, 0.88; 95% confidence interval, 0.63–1.22; P=0.43. Additionally, rates of arrhythmic mortality were similar between the fQRS+ (9.9%) and fQRS− (12.7%) groups: adjusted hazard ratio, 0.77; 95% confidence interval, 0.49–1.31; P=0.38. Subgroup analyses found no association between fQRS and mortality when the cohort was further stratified by ICD status, etiology of left ventricular dysfunction, wide (≥120 ms) versus narrow (<120 ms) QRS duration, or fQRS myocardial territory. Conclusions—In this prospective, multisite cohort of primary prevention patients with left ventricular dysfunction, the presence of fQRS on ECG was not associated with a higher risk of either all-cause or arrhythmic mortality. These findings do not provide evidence that fQRS would be effective in risk stratifying primary prevention patients eligible for ICD therapy.

The Window of Slow pathway conduction after ablation and recurrence of atrioventricular nodal reentrant tachycardia

AbstractIntroduction: Slow pathway (SP) conduction often persists following radiofrequency (RF) catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT). An association between persistent SP conduction, as evidenced by discontinuous AV nodal conduction curves, and recurrent tachycardia has not been established. Of note, the segment of the curve attributable to SP conduction (the “window” of SP conduction) varies. This study examined whether the maximal post-ablation SP conduction window length differs in patients who later have recurrent tachycardia when compared with those who do not recur. Methods and Results: Electrophysiologic study data were compared in two groups who had undergone RF ablation of the SP for typical AVNRT at a single center from 1992–1998. The groups, consisting of seven known recurrences (Group A) and 50 non-recurrences confirmed through a follow-up survey and phone contact (Group B), were similar in gender proportion, age, baseline electrophysiologic data, and number of RF deliveries. Four patients (57%) from Group A and 26 (52%) from Group B exhibited discontinuous AV nodal conduction curves after ablation. The maximum post-ablation window lengths among patients with dual AV nodal physiology varied widely and similarly in the two groups, and the means did not significantly differ (53±47 msec in Group A vs. 36±31 msec in Group B; p=0.36). Conclusion: Persistent SP conduction post-ablation in this series was a common finding not predictive of recurrence. No difference in the maximum SP conduction window post-ablation was evident between recurrences and non-recurrences.

IMPACT OF MAGNETIC RESONANCE IMAGING IN NON-APPROVED CARDIAC DEVICES

For patients traditionally contraindicated for MRIs due to presence of non-MR-conditional cardiac implantable electronic devices (CIED), we established the Patient Registry Of Magnetic resonance imaging in Non-Approved Devices (PROMeNADe). This involves significant resources including research