10įigure 1 Typical counterclockwise atrial flutter with variable atrioventricular transmission and alternating right and left bundle branch block. This gives an “overall impression of an upright flutter wave in V1 which becomes inverted by V6”. In lead V1, the flutter wave shows an initial isoelectric line followed by a positive component which typically falls later than the negative component of the inferior leads ( Figure 1). 7– 9 The characteristic “sawtooth” pattern is usually present in the inferior ECG leads. The tricuspid valve represents the anterior bound of the circuit, whereas the posterior one is a combination of anatomic obstacles (orifices of superior vena cava superiorly, IVC inferiorly, and Eustachian ridge posteriorly) and anatomo-functional barriers (region of the crista terminalis, see below). The mechanism is a macroreentrant circuit confined within the RA, with a descending wavefront in the lateral wall and an ascending wavefront on the septum with passive activation of the left atrium (LA). Typical AFLs Counterclockwise (CCW) typical flutter Non-CTI-dependent AFL will be excluded from this review. This article will focus on the clinical features of CTI-dependent AFL. the area bounded anteriorly by the inferior part of the tricuspid valve and posteriorly by the inferior vena cava (IVC) orifice. AFL is named typical if the inferior pivot point is the CTI, i.e. 6 Of note, all experts agreed to the fact that neither rate nor lack of isoelectric baseline was specific for the tachycardia mechanism. In 2001, an international group of experts proposed the definition of AFLs as follows: AFL refers to the ECG aspect of a regular AT with a rate ≥240 beats/min lacking an isoelectric baseline between deflections. 5 The most type of AFL was called “common” if negative biphasic flutter waves with a sawtooth pattern were present in the inferior ECG leads, and preceding the positivity in V1 AFL was named “atypical” or “rare” if a sawtooth pattern was observed in the frontal plane but now best seen in lead I. In 1970, a classification of AFL was proposed by Puech and Grolleau based upon the ECG morphology. 4 The macroreentrant mechanism was later proven by detailed mapping in the operating room, the use of steerable multipolar catheters, transient tachycardia entrainment and systems that allowed sequential or simultaneous recording of a large number of endocardial points acquired during the arrhythmia.ĪFL classically refers to the ECG pattern of an undulating wave with no electrical silence in at least one lead of the surface ECG. Lewis was the first to explain the mechanism of this arrhythmia by a single-wave circus movement. 2 The first ECG recording of AFL (with characteristic sawtooth waves in the inferior leads) appeared 23 years later with Jolly and Ritchie, using the Cambridge model of Einthoven’s string galvanometer. The term flutter was first used in 1887 by Mac William who described the visual phenomena resulting from “faradic stimulation of the auricles which sets them into a rapid flutter”. Definition and classification of CTI-dependent flutters A close follow-up of the patient will be suggested to detect the occurrence of atrial fibrillation (AF). 1 Once the diagnosis of CTI-dependent AFL is made (mainly based upon the surface ECG), the therapeutic strategy is well standardized, and radiofrequency (RF) catheter ablation (or with cryotherapy) may be performed with high success rate and low complications and recurrence rate. Our knowledge of CTI-dependent AFL has evolved from a relatively simple and unique electrocardiograph (ECG) pattern corresponding to a right atrial (RA) macroreentry to different forms of atrial tachycardias (ATs) propagating through the CTI (or even short-circuiting with epicardial connections). Since its first description more than a century ago, our understanding of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) has significantly improved, using recent advanced ultrahigh-resolution (UHR) mapping systems.
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