Prevalence and characteristics of continuous electrical activity in patients with paroxysmal and persistent atrial fibrillation.

BACKGROUND: Complex fractionated atrial electrograms (CFAEs) may play a role in the genesis of atrial fibrillation (AF). One type of CFAE is continuous electrical activity (CEA). The prevalence and characteristics of CEA in patients with paroxysmal and persistent AF are unclear. METHODS AND RESULTS: In 44 patients (age = 59 +/- 8 years) with paroxysmal (25) or persistent (19) AF, bipolar electrograms were systematically recorded for > or =5 seconds at 24 left atrial (LA) sites, including 8 antral sites, and 2 sites within the coronary sinus (CS). CEA was defined as continuous depolarization for >1 second with no isoelectric interval. CEA was recorded at the LA septum (79%), antrum (66%), posterior (68%) and anterior walls (67%), roof (66%), base of the LA appendage (61%), inferior wall (61%), posterior mitral annulus (48%), CS (41%), and in the LA appendage (14%). Antral CEA was equally prevalent in patients with paroxysmal (63%) and persistent AF (70%, P = 0.12). In patients with paroxysmal AF, the prevalence of CEA was similar among antral and nonantral LA sites, except for the LA appendage. However, in patients with persistent AF, CEA was more prevalent at the nonantral (80%) than antral sites (70%, P = 0.03). CEA at nonantral sites except the CS was more prevalent in persistent than in paroxysmal AF (80% vs 57%, P < 0.001). The mean duration of intermittent episodes of CEA was longer in persistent than in paroxysmal AF (P < 0.001). CONCLUSIONS: The higher prevalence and duration of CEA at nonantral sites in persistent than in paroxysmal AF is consistent with a greater contribution of LA reentrant mechanisms in persistent AF. However, the high prevalence of CEA at nonantral sites in paroxysmal atrial fibrillation (PAF) suggests that CEA alone is a nonspecific marker of appropriate target sites for ablation of AF. The characteristics of CEA that most accurately identify drivers of AF remain to be determined.

Body mass index, obstructive sleep apnea, and outcomes of catheter ablation of atrial fibrillation.

BACKGROUND: Obesity and obstructive sleep apnea (OSA) are associated with atrial fibrillation (AF). The effects of a large body mass index (BMI) and OSA on the results of radiofrequency catheter ablation (RFA) of AF are unclear. OBJECTIVE: To evaluate the effect of BMI and OSA on the efficacy of RFA for AF. METHODS: RFA was performed in 324 consecutive patients (mean age = 57 +/- 11 years) with paroxysmal (234) or chronic (90) AF. OSA was diagnosed by polysomnography in 32 of 324 patients (10%) prior to ablation. Among the 324 patients, 18% had a normal BMI (<25 kg/m(2)), 39% were overweight (BMI >/= 25 kg/m(2) and <30 kg/m(2)), and 43% were obese (>or=30 kg/m(2)). RFA was performed to eliminate complex fractionated atrial electrograms (CFAE) in the pulmonary vein antrum and left atrium. RESULTS: At 7 +/- 4 months after a single ablation procedure, 63% of patients without OSA and 41% with OSA were free from recurrent AF without antiarrhythmic drug therapy (P = 0.02). Multivariate analysis including variables of age, gender, type and duration of AF, OSA, BMI, left atrial size, ejection fraction, and hypertension demonstrated that OSA was the strongest predictor of recurrent AF (OR = 3.04, 95% CI: 1.11-8.32, P = 0.03). There was no association between BMI and freedom from recurrent AF. A serious complication occurred in 3 of 324 patients, with no relationship to BMI. CONCLUSIONS: OSA is a predictor of recurrent AF after RFA independent of its association with BMI and left atrial size. Obesity does not appear to affect outcomes after radiofrequency catheter ablation of AF.

Inducibility of paroxysmal atrial fibrillation by isoproterenol and its relation to the mode of onset of atrial fibrillation.

BACKGROUND: Isoproterenol has been used to assess inducibility during catheter ablation for paroxysmal PAF. However, no studies have determined the sensitivity and specificity of isoproterenol for the induction of AF. It also is not clear whether isoproterenol is equally effective in inducing AF in the clinical subtypes of vagotonic, adrenergic, and random AF. OBJECTIVE: To determine the sensitivity and specificity of isoproterenol for the induction of atrial fibrillation (AF). METHODS: Isoproterenol was infused at 5, 10, 15, and 20 microg/min at 2-minute intervals or until AF was induced in 20 control subjects with no history of AF and in 80 patients with PAF. RESULTS: Among the 20 control subjects, AF was induced by isoproterenol in one patient (5%). Among the 80 patients with PAF, persistent AF was induced in 67 patients (84%, P < 0.001). Isoproterenol induced AF in 15 of 17 patients (88%) with vagotonic AF, 11 of 11 patients (100%) with adrenergic AF, and 41 of 52 patients (79%) with random episodes of AF (P = 0.2). The yield of AF was 11% (9/80) after 5 microg/min, 28% (22/80) after 10 microg/min, 51% (40/78) after 15 microg/min, and 88% (67/76) after 20 microg/min of isoproterenol (P < 0.01). Isoproterenol had to be discontinued in four patients (5%) before reaching the maximum dose due to reversible chest pain or systolic blood pressure <85 mmHg. CONCLUSIONS: Isoproterenol at infusion rates up to 20 microg/min has a high sensitivity (88%) and specificity (95%) for induction of AF in patients with PAF, regardless of whether the clinical subtype is vagotonic, adrenergic, or random.

Mechanism of recurrence after radiofrequency catheter ablation of atrial fibrillation guided by complex fractionated atrial electrograms.

BACKGROUND: A better understanding of the mechanisms of recurrent atrial fibrillation (AF) after radiofrequency ablation of complex, fractionated atrial electrograms (CFAEs) may be helpful for refining AF ablation strategies. METHODS AND RESULTS: Electrogram-guided ablation (EGA) was repeated in 30 consecutive patients (mean age = 59 +/- 8 years) for recurrent paroxysmal AF, 10 +/- 4 months after the first ablation. During the first procedure, CFAEs were targeted without isolating all pulmonary veins (PVs). During repeat ablation, all PVs and the superior vena cava (SVC) were mapped with a circular catheter and the left atrium was mapped for CFAEs. EGA was performed until AF was rendered noninducible or all identified CFAEs were eliminated. During repeat ablation, > or =1 PV tachycardia was found in 83 PVs in 29 of the 30 patients (97%). Among these 83 PVs, 63 (76%) had not been completely isolated previously. During repeat ablation, drivers originating in a PV or PV antrum were identified only after infusion of isoproterenol (20 mug/min) in 12 patients (40%). At 9 +/- 4 months of follow-up after the repeat ablation procedure, 21 of the 30 patients (70%) were free from recurrent AF and flutter without antiarrhythmic drugs. CONCLUSIONS: Recurrence of AF after EGA is usually due to PV tachycardias. Therefore, it may be preferable to systematically map and isolate all PVs during the first procedure. High-dose isoproterenol may be helpful to identify AF drivers.

Atrial tachycardia after circumferential pulmonary vein ablation of atrial fibrillation: mechanistic insights, results of catheter ablation, and risk factors for recurrence.

OBJECTIVES: The aim of this study was to determine the mechanism of atrial tachycardia (AT) that occurs after ablation of atrial fibrillation (AF). BACKGROUND: Patients who undergo catheter ablation of AF may develop AT during follow-up. METHODS: Seventy-eight patients underwent an ablation procedure for AT after circumferential pulmonary vein ablation (CPVA) for AF. The 3-dimensional maps from the AF and AT procedures were compared to determine whether AT arose from a prior ablation line. RESULTS: A total of 155 ATs were mapped, and the mechanism was re-entry in 137 (88%) and focal in 18 (12%). The most common left atrial (LA) ablation targets were the mitral isthmus, roof, and septum. The critical isthmus in 115 of the 120 LA re-entrant ATs (96%) traversed a prior ablation line, consistent with a gap-related mechanism. Catheter ablation was successful in 66 of the 78 patients (85%). After a mean follow-up of 13 +/- 10 months, 60 of the 78 patients (77%) were free of AT/AF without antiarrhythmic medications. Re-entrant septal AT was associated with recurrence (odds ratio 7.3; 95% confidence interval 1.5 to 36; p = 0.02), whereas PV isolation during the AT procedure was associated with a favorable outcome (odds ratio 0.17; 95% confidence interval 0.04 to 0.81; p = 0.03). CONCLUSIONS: Approximately 90% of ATs after CPVA are re-entrant, and nearly all are related to gaps in prior ablation lines. These findings suggest that the prevalence of these arrhythmias may be reduced by limiting the number of linear lesions, demonstration of linear block, and pulmonary vein disconnection during the initial AF procedure.

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 > or = 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.

Role of Purkinje fibers in post-infarction ventricular tachycardia.

OBJECTIVES: The objective of this study was to assess the role of Purkinje fibers in monomorphic, post-infarction ventricular tachycardia (VT). BACKGROUND: Ventricular fibrillation and polymorphic VT in the setting of acute myocardial infarction (MI) may be triggered by ectopy arising from Purkinje fibers. METHODS: From among a group of 81 consecutive patients with post-infarction monomorphic VT referred for catheter ablation, 9 patients were identified in whom the clinical VT had a QRS duration < or =145 ms. Mapping was performed focusing on areas with Purkinje potentials. RESULTS: A total of 11 VTs with a QRS duration < or =145 ms were induced and mapped in the 9 patients; 9 of the 11 VTs had a right bundle branch block/left-axis morphology that mimicked left posterior fascicular VT. The mean VT cycle length was 402 +/- 82 ms. Eight of 9 patients had a history of inferior MI involving the left ventricular septum. One patient had an anterior wall MI with septal involvement. Mapping during VT demonstrated re-entry involving the inferior left ventricular wall. In each of the VTs, a Purkinje potential was present at the exit site of the VT re-entry circuit. Single radiofrequency catheter ablation lesions were successful in eliminating these VTs in all patients. CONCLUSIONS: The Purkinje system may be part of the re-entry circuit in patients with post-infarction monomorphic VT, resulting in a type of VT with a relatively narrow QRS complex that mimics fascicular VT.

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 > or = 1 risk factor for stroke. All patients were anticoagulated with warfarin for > or = 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 > or = 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.

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 approximately 80% of patients.

Clinical perspectives on the role of anti-platelet and statin therapy in patients with vascular diseases.

Peripheral arterial disease (PAD) is a manifestation of systemic atherosclerosis and is associated with a several-fold increased risk of cardiovascular morbidity and mortality. Statins and anti-platelet therapy have been unequivocally shown to be beneficial in patients with coronary artery disease, but minimal data exist on the effectiveness of these agents in patients with PAD and those undergoing peripheral vascular interventions. One recent study has demonstrated that statins are very effective as secondary preventive measures in patients with PAD but continue to be underutilized in this cohort. In our institutional peripheral interventional database, after adjustment for demographics and comorbidities, statin therapy (OR=0.21, 95% CI 0.05-0.86, p=0.03) and clopidogrel therapy (OR=0.17, 95% CI 0.04-0.78, p=0.02) were both associated with a significant reduction of the composite event rate of death, myocardial infarction and stroke at 6 months. In this article, we critically review the existing literature on the role of anti-platelet and statin therapy in reducing cardiovascular events in patients with PAD. Appropriate use of these agents may significantly decrease the cardiovascular morbidity and mortality of patients with PAD.