Development of an atrial esophageal

Development of an atrial–esophageal fistula is one of the most dreaded complications of AF ablation [78]. A relatively large-scale nonrandomized study revealed that the anatomical risk factor of a small LA-to-esophageal distance was the most important factor in esophageal ulceration when using an irrigation-tip catheter at an energy setting of ∼25W at the posterior left atrium. Most of the patients who developed an atrial–esophageal fistula in this study died (7/9 patients, 78%) [74], and it is vital to avoid this complication. The most common practice is to decrease power delivery, decrease tissue contact pressure, and move the ablation catheter every 10–20s when in close proximity to the esophagus. A number of other approaches are also used to avoid the development of an atrial–esophageal fistula [79–84], including temperature monitoring of the esophagus, use of pain as an assay for potential esophageal injury, the use of clemastine endoscopy after AF ablation, and mechanical displacement of the esophagus during the AF procedure. Yamasaki et al. showed that low body mass index is a predictor for esophageal injury even at low energy settings of radiofrequency delivery [85]. Because Asian people are generally thinner than people in other regions of the world, the risk of esophageal injury must always be considered in each patient undergoing ablation of AF.
Future direction
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Introduction Several clinical trials [1–4] such as MADIT II [3] and SCD-HeFT [4], have shown strong evidence regarding implantable cardioverter defibrillator (ICD) use in patients with a high risk of sudden cardiac death. Based on this evidence, the American College of Cardiology/American Heart Association/Heart Rhythm Society 2008 guidelines [5] and Japanese Circulation Society 2006 Guidelines for Non-Pharmacotherapy of Cardiac Arrhythmias, which was revised in 2011 [6], recommend ICD indications for primary prevention to include patients with ischemic or non-ischemic cardiomyopathy, a left ventricular (LV) ejection fraction ≤35%, and New York Heart Association (NYHA) function class III or IV Since the publication of these guidelines, more than 4000 patients have undergone implantation of ICD every year in Japan (Fig. 1). Although ICD improves survival when used in patients with heart failure (HF) and reduced LV function, a recent sub-analysis of major clinical trials of ICDs has revealed that ICD shock is associated with worsening HF or increase in mortality [7–10]. Accordingly, it is important to avoid ICD shock, particularly inappropriate shock, in patients with HF and reduced LV function.
Incidence of ICD shocks and association with mortality Current data suggest that about one third of HF patients with ICD for primary prevention receive ICD shock during their follow-up periods (Fig. 2). The MADIT II study showed that 20% of study subjects received ICD shock therapy with an annual shock rate of 5.6% and the incidence of inappropriate shock was 27%, with an annual shock rate of 7.5%. In the SCD-HeFT study, the incidence of appropriate shock was 21% of the ICD arm at 45 months and the incidence of inappropriate shock occurred in 17% of the ICD arm. After an ICD shock, either appropriate or inappropriate, it was reported that hospitalization for HF events and mortality rate increased. Moss et al. reported that mortality was increased 3-fold with frequent hospitalization for HF after an appropriate ICD shock and the survival rate after the first appropriate ICD shock was 80% at 1year, which was significantly lower compared with survival without ICD shock [7]. Moreover, the occurrence of an inappropriate ICD shock was associated with a hazard ratio for mortality of 2 [8]. Based on sub-analysis of the MADIT II study, ICD shock therapy was associated with a 39% increased risk of a first hospitalization for HF and a 58% increase in recurrent admission for HF [9]. In addition, according to the SCD-HeFT study, patients receiving an appropriate ICD shock had a 5-fold increase in risk of mortality and patients receiving an inappropriate ICD shock had a 2-fold increase in risk of mortality; these results are similar to the MADIT II sub-analysis data [10]. Based on these data, therapeutic shocks for spontaneous ventricular tachyarrhythmia are at increased risk. However, an adverse prognosis after shocked spontaneous ventricular tachyarrhythmia can only be related to underlying heart disease. As for inappropriate ICD shock, in the ALTITUDE study, which included 28,000 patients for primary prevention, inappropriate shock for sinus tachycardia or for noise oversensing was unrelated to increased mortality (HR 0.97; 95% CI 0.68–1.37 and HR 0.91; 95% CI 0.50–1.67, respectively) after adjustment for age, sex, and implantation data [11]. Underlying cardiac disease can cause ventricular arrhythmias or atrial fibrillation, in contrast to the shocks themselves, leading to increased mortality. Although ICD shocks in normal rhythm have adverse effects in experimental conditions, such as electrical shock trauma of irreversible electroporation of the cell membrane [12–14], Bhavnani et al. reported that there was no correlation between ICD shock delivered against induced ventricular arrhythmias and increased risk of all-cause mortality and hospitalization for HF, compared with patients without induction of ventricular arrhythmia; they concluded that ICD shocks for induced ventricular arrhythmias did not increase the risk of mortality or HF hospitalization significantly [15]. There is a room to argue whether correlation between ICD shocks and subsequent mortality is due only to a patient\'s underlying heart disease or whether ICD shocks themselves have an independent causal role. However, we must reduce ICD shocks as much as possible because they induce adverse psychosocial consequences, such as unpleasant anxiety and anticipation of the next shock.