Clinical review: clinical management of atrial fibrillation - rate control versus rhythm control

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the critically ill and is associated with adverse outcomes. Although there are plausible benefits from conversion and maintenance of sinus rhythm (the so-called 'rhythm-control' strategy), recent randomized trials have failed to demonstrate the superiority of this approach over the rate-control strategy. Regardless of approach, continuous therapeutic anticoagulation is crucial for stroke prevention. This review addresses the findings of these studies and their implications for clinical management of patients with atrial fibrillation.     

Relation between history of paroxysmal atrial fibrillation and electrophysiological abnormalities of atrial muscle

Although electrophysiological abnormalities of atrial muscle have been evaluated in patients with paroxysmal atrial fibrillation (PAF), no prior study has determined the contribution of the patient's history of PAF to electrophysiological abnormalities. The study population consisted of 108 patients (71 men; mean age, 57 ± 14 years) with symptomatic and idiopathic PAF who underwent electrophysiological study. Before electrophysiological study, histories of frequency, number of PAF episodes per month, and duration, a time interval from the first episode of PAF to electrophysiological study, were examined. At electrophysiological study, endocardial electrograms from 12 right atrial sites were recorded during sinus rhythm, and the right atrial effective refractory period was determined. Longest duration of atrial electrograms, maximal number of fragmented deflections, and number of abnormal atrial electrograms recorded at the right atrial sites were significantly greater in the frequent group (> 1 PAF episode per month, n = 57) than in the infrequent group (< 1 PAF episode per month, n = 51) (98 ± 18 ms vs 88 ± 16 ms, P < 0.005; 8.7 ± 2.6 vs 7.5 ± 2.6, P < 0.05; and 2.2 ± 2.2 vs 1.4 ± 1.6, P < 0.05, respectively). Indices of atrial vulnerability were also greater in the frequent group. Duration of PAF history was significantly correlated with longest duration r = 0.52, P < 0.0001), maximal number of fragmented deflections r = 0.51, P < 0.0001), and number of abnormal atrial electrograms r = 0.58, P < 0.0001). More frequent episodes and longer history of PAF significantly increased the electrophysiological abnormalities of the atrial muscle, suggesting that PAF results in gradual electrical remodeling of the atrial muscle.     

房颤射频消融治疗围术期护理的研究进展

节律控制是房颤临床治疗的重要环节,既往药物维持节律控制的有效性较低.目前以环肺静脉隔离为基础的房颤射频消融术成为主要方案,所以房颤患者围术期的规范化护理直接影响手术治疗的效果.本文回顾性分析近5年房颤患者射频消融治疗护理的相关资料,探讨保证房颤射频消融术成功率、降低并发症发生率的围术期护理策略.     

阵发性心房颤动的动态心电图研究

目的 探讨阵发性心房颤动(paroxysmal atrial fibrillation，PAF)发作、持续、终止的节律变化，及诱发PAF的可能因素。方法 采用动态心电图(DCG)检测，分析PAF各时段发作、终止的次数和持续时间的节律变化；研究PAF发作与窦性心室率、前5分钟窦性心律的心率变异、房性期前收缩及其配对间期的关系。结果 ①PAF的发作于凌展3：00增多，4：00～6：00达高峰，终止与发作的节律变化基本一致，持续高峰在11：00～16：00；②PAF发作前心率＜60次／min者78例次(32．09％)，伴低频成分／高频成分(LF／HF)＜1．5者68例次(87．18％)；心率＞90次／min者52例次(21．3％)，伴LF／HF＞2．0者43例次(82．69％)；③诱发PAF的房性期前收缩配对间期及配对间期＜500ms者与对照组比较尸＜0．05，＜0．01。结论 DCG对分析PAF发作、持续、终止的节律变化，PAF发作与窦性心率、自主神经介导、房性期前收缩及配对问期的关系，是一项十分有用的检查方法，能为临床预防PAF的发生及复律等治疗提供依据。     

The renin-angiotensin system: a therapeutic target in atrial fibrillation

There is growing evidence to suggest a role for the renin-angiotensin system (RAS) in the pathogenesis of atrial fibrillation (AF). Experimental animal data suggest RAS-dependent mechanisms for the development of a structural and electrophysiologic substrate for AF. This is consistent with clinical data demonstrating the effectiveness of RAS blockade in preventing new-onset or recurrent AF in a variety of patient populations including patients with hypertension and left ventricular hypertrophy, congestive heart failure, and those undergoing electrical cardioversion for AF. This review summarizes experimental and clinical evidence to date relating to the role of RAS in the pathogenesis of AF, and the efficacy of its inhibition in managing this common arrhythmia.     

Indices of electrical and contractile remodeling during atrial fibrillation in man

BACKGROUND: Atrial electrical and contractile remodeling have been demonstrated to coincide during atrial fibrillation (AF) in experimental studies. We explored whether electrical and contractile remodeling correlate in man and explored its clinical implications. METHODS: Forty-nine patients with persistent AF were studied. Electrical remodeling was assessed noninvasively using spectral analysis to estimate the average fibrillatory rate (AFR). Atrial contractility was assessed by transesophageal echocardiography (TEE) measurement of left atrial appendage outflow velocity (LAAOV). RESULTS: The AFR was 403+/-43 fibrillations per minute (fpm) and the LAAOV was 0.27+/-0.14 m/s. A significant correlation was found between AFR and LAAOV (r=-0.47, P=0.001). In patients with a LAAOV>or=0.25 m/s, the AFR was 387+/-48 fpm compared to 419+/-31 fpm among patients with LAAOV<0.25 m/s (P<0.01). CONCLUSIONS: This study demonstrates that indices of electrical and contractile remodeling are strongly correlated in persistent AF in man. The interindividual overlap, however, is too large to allow predictions of LAAOV based on fibrillatory frequency alone.     

Antiarrhythmic therapy following ablation of atrial fibrillation

Antiarrhythmic drugs (AADs) are often used after ablation for atrial fibrillation (AF); the drugs employed vary, but most common are the drugs that were unsuccessful prior to ablation since it seems that the efficacy of AADs might substantially increase after catheter ablation of AF. AADs reduce early recurrences of atrial tachyarrhythmias after AF catheter ablation, whereas they did not prevent arrhythmia recurrences occurring later. Several upstream therapies (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, statins, corticosteroids and colchicine) have been tested with conflicting results. To date, there is no sufficient evidence to support the use of any upstream therapy after AF catheter ablation. Larger registries and controlled clinical trials in well-defined patient groups and with well-defined outcome parameters are required to further elucidate the role of AADs after AF ablation.     

Effects of rosuvastatin on serum asymmetric dimethylarginine levels and atrial structural remodeling in atrial fibrillation dogs

Background: Circulating asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, is increased in atrial fibrillation (AF). The purpose of this study was to investigate the effects of rosuvastatin on serum ADMA levels and atrial structural remodeling in AF dogs induced by chronic rapid atrial pacing. Methods: Twenty dogs were randomly divided into the sham‐operated (n = 6), control (n = 7), or rosuvastatin (n = 7) groups. Sustained AF was induced by rapid pacing of the right atrium at 400 beats per minute for 6 weeks. Rosuvastatin was administered orally (1 mg/kg d) for 3 days before rapid pacing and was continued for 6 weeks. Transthoracic and transesophageal echocardiography were performed to detect left atrial structure and function. Serum levels of nitric oxide and ADMA were measured. Interstitial fibrosis and cardiomyocyte apoptosis in the atria were also identified. Results: After 6 weeks, compared with the control group, dramatic smaller left atrium and left atrial appendage volumes and higher atrial contractile function were observed in the rosuvastatin group. Serum nitric oxide concentration was increased, whereas ADMA was decreased in the rosuvastatin group compared with the control group. The percentages of interstitial fibrosis and atrial apoptosis in the control group were significantly higher than those in the sham‐operated group, and rosuvastatin attenuated these changes induced by atrial rapid pacing. Conclusion: A short course of rosuvastatin treatment decreased apoptosis and prevented atrial structural remodeling in association with a decrease in ADMA levels in AF dogs. PACE 2012; 35:456–464)     

Deglutition induced atrial tachycardia and atrial fibrillation

Deglutition induced supraventricular tachycardia is an uncommon condition postulated to be a vagally mediated phenomenon due to mechanical stimulation. Patients usually present with mild symptoms or may have severe debilitating symptoms. Treatment with Class I agents, beta blockers, calcium channel blockers, amiodarone and radiofrquency catheter ablation has shown to be successful in the majority of reported cases. We report the case of a 46-year-old healthy woman presenting with palpitations on swallowing that was documented to be transient atrial tachycardia with aberrant ventricular conduction as well as transient atrial fibrillation. She was successfully treated with propafenone with no induction of swallowing-induced tachycardia after treatment. This is also the first case to show swallowing-induced atrial tachycardia and atrial fibrillation in the same patient.     

Early hyperbaric oxygen therapy for cerebral air embolism during atrial fibrillation ablation

Cerebral air embolism is a potentially life‐threatening complication of left‐sided ablation procedures. We present a 51‐year‐old woman with cerebral air embolism during atrial fibrillation cryoballoon ablation. Taking a deep breath while removing the dilatator was the most likely mechanism in our case. The patient was successfully treated with hyperbaric oxygen therapy at early stage and was discharged without any neurological sequelae.     

Effect of cardiac resynchronization therapy on conversion of persistent atrial fibrillation to sinus rhythm

Background  Spontaneous conversion of persistent atrial fibrillation to sinus rhythm (SR) has anecdotally been reported following cardiac resynchronisation therapy. Objective  This monocenter observational study was designed to estimate the incidence of spontaneous conversion of persistent atrial fibrillation to SR in consecutive patients implanted with a cardiac resynchronisation device. Methods and results  A total of 46 patients with persistent atrial fibrillation (≥4 weeks pre-implant), left bundle branch block (QRS > 130 ms), left ventricular ejection fraction <0.35 and NYHA III or IV heart failure were implanted with a cardiac resynchronisation pacemaker or defibrillator and followed for at least 6 months between 6/2000 to 12/2006. During 22 ± 9 (7–34) months of follow-up, eight out of 46 patients (17%) converted to SR. Spontaneous conversion was encountered in seven cases, whereas one patient converted due to an ICD shock delivered for ventricular tachycardia; in the latter patient, previous ICD shocks had not converted atrial fibrillation. The time interval from device implantation to conversion was 12 ± 11 (3–31) months. In patients converting to SR, the duration of atrial fibrillation before device implantation was significantly shorter than in patients remaining in atrial fibrillation (15 ± 13 vs. 53 ± 58 months, P = 0.001). Echocardiographic parameters such as left ventricular ejection fraction, left ventricular enddiastolic diameter, left atrial diameter did not differ significantly between converting and non-converting patients. However, patients converting to SR showed a significant reduction in systolic pulmonary artery pressure on CRT vs. before CRT (45 ± 13 vs. 29 ± 5 mmHg, P = 0.008). Conclusions  This pilot study suggests that CRT favors spontaneous conversion of persistent AF to SR in a minority of patients. If confirmed by larger clinical studies, atrial lead implantation would be encouraged in these patients, in order to provide AV synchronous pacing in case of spontaneous conversion or successful cardioversion to SR on cardiac resynchronisation therapy. M. Hauck and A. Bauer contributed equally to this work.     

器质性心脏病心房颤动患者的药物治疗

心房颤动(房颤)是临床常见的心律失常之一,致残、致死率高。房颤的治疗策略包括抗凝预防血栓栓塞、转复和维持窦性心律、心室率控制,药物治疗是房颤治疗的基础,但器质性心脏病合并房颤的处理有其特殊性,本文对器质性心脏病合并房颤的药物治疗予以综述。     

Mechanism of spontaneous transition from typical atrial flutter to atrial fibrillation: role of ectopic atrial fibrillation foci

Paroxysmal AF has been known to be initiated by ectopic beats, especially in the pulmonary veins (PVs), and radiofrequency catheter ablation could cure it. We considered that the spontaneous transition from typical atrial flutter to AF also could be initiated by ectopic beats. Twenty patients (18 men, mean age 66 +/- 14 years) with episodes of spontaneous transition from typical atrial flutter to AF were included in this study. They underwent detailed mapping of both atria. All the patients had spontaneous AF initiated by ectopic beats, and all of them had typical atrial flutter and spontaneous transition from typical atrial flutter (12 patients with counterclockwise atrial flutter and 8 patients with clockwise atrial flutter) to AF. The transition was initiated by ectopic beats from the PVs (17 foci, 85%), crista terminalis (2 foci, 10%), and superior vena cava (1 focus, 5%). After successful ablation of AF foci, typical atrial flutter was induced again, but no spontaneous transition was found after at least 10 minutes of observation. We concluded that paroxysmal AF and spontaneous transition from typical atrial flutter to AF were initiated by ectopic beats, and successful catheter ablation of the ectopic foci can eliminate paroxysmal AF and spontaneous transition from typical atrial flutter to AF.     

Intravenous vernakalant for the rapid conversion of recent onset atrial fibrillation: systematic review and meta-analysis

Atrial fibrillation is the most common cardiac arrhythmia and is associated with increased mortality and morbidity. Conversion to sinus rhythm is usually appropriate in patients with acute, symptomatic atrial fibrillation in order to reduce symptoms and prevent complications. Electrical cardioversion is the most used and widespread technique, but requires deep sedation and a fasting state. Pharmacological alternatives are burdened by a delayed onset of action and potential proarrhythmic effects. Therefore, new therapeutic options are being sought. Among those, vernakalant, showed a good efficacy profile and a short onset of action, but with conflicting evidence regarding potential serious adverse events. This drug profile will summarize the pharmacology behind this new drug and review recent evidence in terms of safety and efficacy.     

Influence of age on atrial fibrillation inducibility

The prevalence of AF is known to increase in the elderly. Some electrophysiological changes were reported in these patients, but the effects of age on AF inducibility and other electrophysiological signs associated with atrial vulnerability are unknown. The purpose of the study was to evaluate the effects of age on atrial vulnerability and AF induction. The study consisted of 734 patients (age 16-85 years, mean 61 +/- 15 years) without spontaneous AF who were admitted for electrophysiological study. Study was indicated for dizziness or ventricular tachyarrhythmia. Programmed atrial stimulation was systematically performed. One and two extrastimuli were delivered in sinus rhythm and atrial driven rhythms (600, 400 ms). Univariate and multivariate analysis of several clinical and electrophysiological data were performed. AF inducibility, defined as the induction of an AF lasting > 1 minute, was paradoxically and significantly decreased in elderly (> 70 years) patients compared to younger patients (< 70 years) (P < 0.01). AF inducibility was present in 40% of 62 patients < 40 years, 39% of 99 patients age 40-50 years, 37% of 130 patients age 50-60 years, 38% of 222 patients age 60-70 years, and only 28% of 221 patients > 70 years. There was no significant correlation with the sex, the presence of dizziness, the presence or not of an underlying heart disease, the left ventricular ejection fraction, and the presence of salvos of atrial premature beats on 24-hour Holter monitoring. There was a significant correlation with a longer atrial effective refractory period in the elderly (226 +/- 41 ms) than in younger patients (208 +/- 31 ms) (P < 0.001). Other electrophysiological parameters of atrial vulnerability did not change significantly. Increased atrial refractory period and age >70 years were independent factors of decreased AF inducibility. Programmed atrial stimulation should be interpreted cautiously before the age of 70 years. AF induction is facilitated by the presence of a short atrial refractory period in these patients. Surprisingly, AF inducibility decreases in patients > 70 years because their atrial refractory period increases. Therefore, increased AF prevalence in these patients should be explained by nonelectrophysiological causes.