p.27 抽出テキスト

........................................................................................................................................................................ flutter and even the combination of AVN-blocking drugs (digoxin, beta-blockers, and calcium channel blockers)235238 may fail, making cardioversion to sinus rhythm necessary. Dofetilide and ibutilide, pure class III antiarrhythmic drugs, are generally effective in interrupting atrial flutter in i.v. administration (dofetilide may be also given orally for this purpose), while class IA and IC drugs have little or no effect.250257 Class IC antiarrhythmic drugs should not be used in the absence of AV-blocking agents because of the risk of slowing the atrial rate, which may result in 1:1 AV conduction.273,274 Amiodarone may not be very effective acutely to reestablish sinus rhythm, but it does help to control the ventricular rate if it is too fast.275,276 Low-energy electrical cardioversion is commonly used with haemodynamic compromise or after failure of previous actions, but it could be the first choice due to its high efficacy. Electrical cardioversion for atrial flutter is more effective and less energy is required, compared with AF.248,249 When atrial electrodes are in place, high-rate stimulation can be used to convert flutter, sometimes through AF.258,259 If pacing induces AF, this may allow better control of the ventricular rate than flutter. Atrial stimulation can also be done with percutaneous endocardial electrodes or from the oesophagus; this is mostly done in paediatrics.261 Pre-treatment with procainamide may facilitate conversion of atrial flutter by atrial pacing.277 Data on pre-cardioversion anticoagulation are lacking, but most probably patients should be treated the same as those with AF.4,278

11.1.4.1.4 Catheter ablation. Catheter ablation is the most effective therapy to maintain sinus rhythm, and is clearly superior to amiodarone.262,263 Ablation of CTI with confirmed bidirectional conduction block results in a <10% rate of recurrence.279 However, the incidence of AF is high in the long-term.280 When typical CTIdependent atrial flutter ensues during antiarrhythmic drug therapy (class IC or amiodarone) for AF, CTI ablation is a reasonable choice to ensure that antiarrhythmic drugs can be continued for AF control.262,263 Although no procedure-related mortality had been detected in early studies,203,204 in recent studies, mortality and stroke rates of 0.2 - 0.34 and 0.19 - 0.5%, respectively, have been reported (Table 11).12,206 In a recent registry, ablation for flutter had a higher mortality than that for AF (0.3 vs. 0.05%), but this might have been due to the comorbidities or advanced ages of patients referred for flutter ablation.207

11.1.4.1.5 Chronic therapy. Rate control is part of the therapeutic approach, using AV nodal blocking agents such as diltiazem, verapamil, or beta-blockers (Figure 12). When ablation is not feasible or the patient’s preference, antiarrhythmic drugs may also be used to maintain sinus rhythm. Dofetilide257 and sotalol281 are useful, but there are concerns about pro-arrhythmia. Amiodarone may have a role,263 but it should be restricted to cases of HF or significant structural heart disease.

11.1.4.1.6 Anticoagulation. Data about the embolic risk of atrial flutter have usually been derived in the presence of concomitant AF, thus making individualized risk stratification difficult. Left atrial (LA) appendage ‘stunning’ and thrombi seem to be lower compared with those in AF.247,282 The thrombo-embolic risk of atrial flutter, although lower than that of AF,246 is still significant.241244 That, together with the association with AF, justifies thromboprophylaxis, and anticoagulation has been recommended as in AF.2,3 These recommendations extend to the acute setting for cardioversion when flutter lasts for >48 h.278

However, it should be noted that there is a lack of prospective, dedicated, randomized studies on the subject. Furthermore, the value of the CHA2DS2-VASc [Cardiac failure, Hypertension, Age >_75 (Doubled), Diabetes, Stroke (Doubled)  Vascular disease, Age 6574 and Sex category (Female)] score in preventing ischaemic stroke in patients with atrial flutter has not been established,245 and in patients without concomitant AF the threshold for the initiation of anticoagulation appears to be higher than that for patients with AF.246

11.1.4.1.7 Other cavotricuspid isthmus-dependent macroreentrant atrial tachycardia. An atypical ECG pattern may not exclude CTI-dependent MRAT.283 Lower-loop re-entry refers to a circuit rotating around the inferior vena cava instead of around the tricuspid annulus. It may be clockwise or counter-clockwise.284,285 When rotating counter-clockwise, it might be considered a variant of typical counter-clockwise flutter with a caudal shift of the cranial turning point posterior to the entry of the superior vena cava, resulting in a similar ECG appearance. ‘Figure-of-eight double-loop reentry’ may also occur around the inferior vena cava and tricuspid annulus, and mimic typical clockwise atrial flutter.285 Other circuits using part of the CTI or even restricted inside it, are in essence CTIdependent with a similar ECG appearance to typical common flutter.286,287

11.1.4.2 Non-cavotricuspid isthmus-dependent macrore-entrant atrial tachycardia The terms non-CTI-dependent MRAT and atypical flutter are used interchangeably, and describe flutter waves in the ECG not suggestive of typical circuits. The pitfall with this use comes from the atypical ECG that may happen when typical circuits develop in diseased atria, most frequently after surgery or extensive ablation, or under the effects of antiarrhythmic drugs. Conversely, upperloop re-entry may mimic a typical flutter ECG pattern without being CTI-dependent.283 True atypical flutter is actually a post hoc diagnosis when the circuit has been outlined and dependence on CTI has been ruled out.

11.1.4.2.1 Right atrium macro2re-entrant atrial tachycardia. Atrial sutures and patches used for complex congenital heart disease surgery, together with progressive atrial damage, create multiple obstacles and protected isthmuses that constitute the substrate for complex and multiple MRAT.288,289 This usually happens around RA free wall scars. However, in patients with complex congenital heart disease, the presence of extensive atrial scars hinders the differential diagnosis of focal or MRAT.290 Figure-of-eight double-loop tachycardias mimicking the ECG pattern of a common atrial flutter may also occur following surgical atriotomy.291 Downloaded from academic.oup.com/eurheartj/article/41/5/655/5556821 by guest on 07 October 2026