Journal of Arrhythmia Vol. 28(2012) No. 6
Special Issue: Current therapeutic standard for the treatment of atrial fibrillation

Pulmonary vein isolation (PVI) was the main strategy for catheter ablation of atrial fibrillation (AF) until a remarkable report was published by Nademanee et al. in 2004. The ablation targeting complex fractionated atrial electrograms (CFAE) achieved not only a high rate of AF termination but also excellent outcomes in both paroxysmal and persistent AF without isolating pulmonary veins. AF is thought to be caused by random or spiral reentry, as the fixed circuit to maintain AF may not exist, although the CFAE-guided ablation strategy is based on the theory that AF is not entirely random. CFAEs play an important role in identifying AF substrates, and have temporal and spatial stability, thus representing desirable targets for AF ablation; however, CFAE-guided ablation has not been fully replicated by others. In reports showing that CFAE ablation did not yield a good outcome either alone or combined with PVI, the AF termination rates were extremely low. Although AF termination is not mandatory in CFAE-ablation, terminating AF in the majority of patients appears to be necessary to yield good outcomes; therefore, this review will discuss AF ablation guided by CFAE with or without PVI, with particular emphasis given to practical aspects of achieving AF termination.

Cardioembolic stroke accounts for 20–30% of acute brain infarctions in Japan. This condition is often severe and has poor outcomes. Non-valvular atrial fibrillation (NVAF) is the most common cardiac source of emboli in cardioembolic stroke. Anticoagulants are recommended for preventing stroke in patients with NVAF, and these patients were usually treated with warfarin. However, the use of warfarin has many limitations. Approximately half of the patients with NVAF, who show indications for warfarin treatment, are treated with warfarin. Bleeding complications, including intracranial hemorrhages, are common during warfarin treatment; this is a huge concern of warfarin treatment. Warfarin-associated intracranial hemorrhage is often severe and devastating. Several novel anticoagulants that can overcome the limitations of warfarin have been introduced in the market or are under development. In this review, we discuss the pharmacological properties of novel anticoagulants and current strategies of anticoagulation therapy for preventing stroke in patients with NVAF.

Atrial fibrillation (AF) is the most common arrhythmia in persons of advanced age, and it is a potent risk factor for cardiogenic ischemic stroke. The overall prevalence of AF is less than 1%, but in people aged 80 years or older the rate is approximately 7–14% in Western countries and 2–3% in Japan. The number of people with AF has been increasing worldwide as the population has aged, and continued increases in the prevalence and incidence of AF are expected with the aging of society. It is predicted that 5–16 million in the United States and more than 1 million in Japan will be affected by 2050. Therefore, AF is one of important diseases that needs to be managed because it is a common disease in aged populations.

The development and introduction of radiofrequency ablation devices allowed maze procedure to be performed safely and easily, further enabling off-pump pulmonary vein isolation through mini-thoracotomy or thoracoscopy. The outcomes of the maze procedure include the prevention of stroke and other complications related to atrial fibrillation (AF), improvement in cardiac performance, and relief of symptoms. The indications for the maze procedure have been discussed on the basis of available evidence. Pulmonary vein isolation has been shown to be effective in most patients with paroxysmal AF, and can be performed with both endocardial catheter ablation and minimally invasive epicardial ablation. These 2 modalities should be compared in terms of the success rate, occurrence of cerebral microembolic signals, capability adding other lesions indicated for persistent or long-standing persistent AF, and closure of the left atrial appendage. Noncontinuous or nontransmural lines of conduction block as a result of incomplete ablation can result in the recurrence of AF and induction of atrial tachycardia. Intraoperative verification of a conduction block across the ablation lines is recommended to prevent these complications. Volume reduction of the enlarged left atrium or a box lesion to isolate the entire posterior left atrium may be effective in patients with a dilated left atrium, but the potentially impaired atrial transport function should be considered. Mapping of active ganglionated plexi and their ablation may improve the outcome of the procedure; however, the long-term effect on AF and autonomic nerve activities should be examined. Because the mechanism underlying AF varies in each patient, a tailor-made therapy, using a stepwise approach, with a hybrid procedure combining epicardial and endocardial ablation offers promising prospects in the nonpharmacological treatment of AF.

Background: There is limited data regarding the outcomes after stepwise ablation for persistent atrial fibrillation (AF) in patients with heart failure (HF).
Methods and results: Patients without structural heart disease undergoing stepwise ablation for persistent AF (continuous AF≤1 year) were studied (n=108; age, 61±10 years) and 32 patients had a history of HF. The HF patients were further grouped on the basis of left ventricular ejection fraction (LVEF)≤45% (n=15) and >45% (n=17). During a median follow-up period of 2.2 years, repeated ablations were necessary in 65 patients. The proportion of patients that were arrhythmia free 1 year after the last ablation was 67% in patients with LVEF≤45%, 86% in LVEF>45%, and 91% in no HF (p=0.0009). In patients with LVEF≤45%, the AF burden was reduced to less than one paroxysmal episode per month, and patients with and without recurrences both showed significant increases in LVEF over the follow-up period (38±7% to 60±10% and 37±6% to 53±10%, respectively).
Conclusions: HF patients with LVEF≤45% had lower chances to remain free from arrhythmias after stepwise ablation for persistent AF than those with LVEF>45%. Nevertheless, LVEF also improved in patients with recurrences, reflecting the observed reduction in AF burden and emphasizing the benefits of ablation.

A 58-year-old man, in whom an implantable cardiac defibrillator (ICD) had been implanted for Brugada syndrome, suffered rapidly progressive general paralysis. Various diagnostic imaging techniques were performed, but the cause could not be determined. Magnetic resonance imaging (MRI) scanning was performed. A 1.5-Tesla MRI system was used, and the ICD was programmed to ODO mode and all tachycardia detection was turned off. MRI was performed safely under electrocardiogram and pulse oximeter monitoring, and appropriate precautions were taken in preparation for an emergency. ICD parameters did not change in post-imaging investigations. MRI revealed an apparent tumor in the patient's medulla and upper cervical spinal cord, which was diagnosed as high-grade astrocytoma. When performing MRI procedures in patients with an ICD under urgent conditions, it is necessary to have complete knowledge of the procedure and to make careful preparations.

An 82-year-old female with a history of hypertrophic cardiomyopathy (HCM), sick sinus syndrome (SSS), and an implanted DDD pacemaker was admitted to our hospital for congestive heart failure caused by rapid atrial fibrillation. After administration of amiodarone, atrial fibrillation (AF) became atrial flutter (AFL). Electrophysiological investigation revealed counterclockwise AFL. Catheter ablation of the cavotricuspid isthmus was performed. Burst pacing from the coronary sinus ostium to confirm the block line of the isthmus induced rapid, regular, ventricular pacing at a rate of 110 bpm. The differential diagnosis of this tachycardia included ectopic atrial tachycardia and pacemaker-mediated, endless loop tachycardia (ELT). We diagnosed this arrhythmia as ELT, because temporary reprogramming of the pacemaker mode from DDD to VVI terminated the tachycardia. In this patient, pacing parameters favored ELT (long atrioventricular delay [AVD] and short postventricular atrial refractory period [PVARP]), and atrioventricular and ventriculoatrial conduction time was prolonged as a result of amiodarone administration.
The ELT continued because the rate was lower than the programmed upper tracking rate. Reprogramming the parameter (decreasing AVD and increasing PVARP) resulted in termination of ELT.

Andersen-Tawil syndrome (ATS), also known as long QT syndrome type 7, is a rare autosomal dominant disease caused by a KCNJ2 mutation. The characteristic triad of ATS is periodic paralysis, dysmorphic features, and ventricular arrhythmia. We describe a case of a woman with Andersen-Tawil syndrome and a history of syncope whose pregnancy was complicated with frequent premature ventricular contractions (PVCs) and nonsustained ventricular tachycardia (NSVT). Her PVCs and NSVT were significantly decreased during the peripartum period, especially during labor. We treated her with beta-blockers throughout her pregnancy, and she experienced no complications. Although the mechanism underlying the decreased PVCs and NSVT in pregnancy has not been elucidated, women with ATS may have less arrhythmic event risk during pregnancy.

Successful implantation of implantable cardioverter-defibrillators (ICDs) that is performed to avoid surgery in patients with atypical vasculature is still problematic. Acute angulations and significant tortuosity of the venous vasculature may influence both procedural success and periprocedural complications. We successfully implanted an ICD in a patient with deformed vasculature caused by tuberculosis-induced lung destruction by using a flexible coiled sheath instead of a friable peel-away sheath. This report highlights an alternative maneuver that may be an option in patients who have an acute angle between the brachiocephalic vein and the superior vena cava.