Flutter Wave Morphology Research Articles

Flutter Wave Morphology of Peri-Mitral Atrial Flutters Is Mainly Determined by Right Atrial Activation: Insights From High-Resolution Mapping.

Peri-mitral atrial flutters frequently develop post-atrial fibrillation ablation or postcardiac surgery. The determinants of the flutter wave morphology on surface ECG have been less studied. We retrospectively reviewed 24 patients with peri-mitral atrial flutters who underwent biatrial high-resolution mapping at 3 institutions with LUMIPOINT software. We analyzed the overlap between the right atrial (RA) activation time and flutter wave duration and compared the proportion of the endocardial area that was activated in both atria during the flutter wave duration. Biatrial activation patterns and interatrial conductions were also identified. The mean tachycardia cycle length was 264±60 ms, with RA activation time 155±45 ms (60.8±20.6% of the tachycardia cycle length), and the flutter wave duration 107±31 ms (41.6±11.7% of the tachycardia cycle length). The overlap between the RA activation time and the flutter wave duration was 102±29 ms, which takes 68.5±17.2% of the RA activation time and 95.7±9.1% of the flutter wave duration, respectively. Quantitative analysis also showed that during the flutter wave duration, more percentage of the endocardial area was activated in the RA than in the left atrium (73.0±12.7% versus 45.2±13.0%, P<0.001). We consistently observed that the RA anterior wall rightward activation corresponded to the positive component in V1 in both flutter patterns, and the RA downward activation corresponded to the positive component in the counterclockwise group or the upward activation corresponded to the negative component in the clockwise group in the inferior leads. The passive RA activation patterns were varied with spontaneous atrial scarring or previous linear ablation. ECG flutter wave morphology of peri-mitral atrial flutters is mainly dependent on RA activation patterns.

Surface ECG characteristics of right and left atrial flutter

Atrial tachycardia in virtually all areas of both atria has become more important in the clinical management of patients with previous complex atrial fibrillation ablation. Accurate interpretation of surface electrocardiogram (ECG) characteristics is of paramount importance to localize the origin of atrial tachycardia, particularly for planning interventional treatment. This article highlights the ECG features of different types of right and left atrial tachycardia. Typical right atrial flutter through the cavotricuspid isthmus conducts septally in a cranial direction and demonstrates sawtooth-like flutter waves which start negative in II, III and aVF and then show a steep slope upwards to the isoelectric line. The flutter rate typically ranges between 240-250 beats/min. In contrast, right atrial flutter in a clockwise rotation, flutter around the vena cava inferior or superior and around a scar (e.g. after cardiac surgery) show positive or biphasic flutter waves (lower or upper loop reentry). Left atrial flutter waves (e.g. around the mitral valve or around the pulmonary veins) are very heterogeneous and are typically positive in V1 as the left atrium is located in the posterior mediastinum. Specific knowledge of flutter wave morphology in surface ECG facilitates planning and performance of the ablation strategy.

Prevalence and Characteristics of Dual-Loop Reentrant Atrial Flutter of Incisional and Cavotricuspid-Isthmus Dependent Atrial Flutter after Open-Heart Surgery

Background: Patients after open-heart surgery may develop macroreentrant atrial flutter (AFL) related to the right atriotomy scar (incisional AFL; I-AFL), which occasionally forms a dual-loop reentry circuit with cavotricuspid-isthmus dependent AFL (CTI-AFL). Objective: To demonstrate the prevalence and characteristics of dual-loop reentrant AFL (DL-AFL) consisting of I-AFL and CTI-AFL after open-heart surgery. Methods and Results: Thirty-six consecutive patients (25 males, 61±13 years) with I-AFL (n=6), CTI-AFL (n=22), or both AFLs (n=8) who underwent radiofrequency catheter ablation were retrospectively studied. Four of the 8 patients with both AFLs had a DL-AFL. In all patients with DL-AFL, CTI-AFL was clinically predominant and had a shorter flutter cycle length than I-AFL (260±37 ms vs. 281±35 ms). The flutter wave polarities in the inferior leads and lead V1 on the 12-lead electrocardiogram were negative and positive in 2 patients, negative and negative in 1, and positive and positive in 1, respectively. Conclusion: DL-AFL occurred in 14% of the patients with macroreentrant right atrial flutter after open-heart surgery and had variation in the flutter wave morphology. Thus, entrainment mapping and three-dimensional electroanatomic mapping can help to identify and localize the reentry circuits and critical isthmuses as targets for ablation.

Mechanisms of atypical flutter wave morphology in patients with isthmus-dependent atrial flutter

Sixty-three episodes of isthmus-dependent atrial flutter (AFL) in 55 patients were studied to characterize variations in flutter wave morphology and to investigate the mechanisms of the atypical flutter waves on surface ECG. The activation patterns of coronary sinus (CS) and their relationship with flutter wave morphology on the ECG were analyzed. In 46 episodes of counterclockwise AFL (CCW-AFL), there were four types of flutter waves on ECG. Typical and atypical flutter waves were found in 47.8% and 13.0% of the episodes, respectively. Atypical flutter waves had broad positive terminal portion or entirely positive wave in the inferior leads and in V(1), with a distal-to-proximal or fused activation pattern in the CS, and an average activation time of 21.3 +/- 11.4 ms. In 17 episodes of clockwise AFL (CW-AFL), typical and atypical flutter waves were identified in 41.2% and 41.2%, respectively. Atypical flutter waves had negative waves in the inferior ECG leads and in V1, a proximal-to-distal activation pattern in the CS, and an average activation time of 42.4 +/- 14.4 ms. We conclude that atypical flutter waves are common in the isthmus-dependent AFL. The clockwise or counterclockwise conduction in the right atrium, and the activation patterns or conduction sequences between the right and the left atrium, are associated with the variations in the flutter wave morphology on body surface ECG.

Prediction of the atrial flutter circuit location from the surface electrocardiogram

Identification of atypical atrial flutter (AFL) (non-cavo-tricuspid isthmus-dependent) prior to the electrophysiology laboratory is potentially useful because it allows appropriate procedural planning and enables discussion of the likely success rates and risks of the procedure with the patient. Typical counterclockwise AFL has a stereotypic appearance, the electrocardiogram (ECG) is predictive of the diagnosis in the majority of cases, and ablation procedures are associated with a high degree of safety and success. Atypical right atrial and left AFLs have a highly variable flutter wave morphology and may appear atypical, resemble typical flutter or appear to be focal in origin. Targeting these complex and often multiple re-entrant circuits is aided by expertise and use of electroanatomic mapping systems. This review will address whether there are clues from the 12-lead ECG which assist in the localization of AFL circuits.

Change in Atrial Flutter Wave Morphology—Insight into the Sources of Electrocardiographic Variants in Common Atrial Flutter

Whether the activation sequence of the right or left atrium plays a role in the morphology of the flutter wave in common atrial flutter is not completely understood. We present two patients with common counterclockwise atrial flutter in whom changes in the left atrial activation sequence produced significant changes in flutter wave polarity (+ to - and - to -/+ biphasic) without a change in the activation sequence within the right atrium. These cases highlight the possible role of alterations of the interatrial connections in the genesis of atypical manifestations of common atrial flutter.

Lower loop reentry as a mechanism of clockwise right atrial flutter.

Right atrial reentrant tachycardia resulting from lower loop reentry (LLR) around the inferior vena cava (IVC) has been described recently. However, all reported cases of LLR in the literature have negative flutter waves on the inferior surface ECG leads similar to that of counterclockwise typical atrial flutter around the tricuspid annulus (TA). Right atrial flutter with positive flutter waves in the inferior ECG leads has been assumed to rotate as a single reentrant activation wave front around the TA, and the role of LLR in those patients is not known. Twelve consecutive patients with flutter wave morphology on surface ECG consistent with clockwise atrial flutter were studied. The endocardial activation pattern recorded from conventional multipolar electrode catheters was characteristic of clockwise atrial flutter around the TA. Entrainment pacing in all 12 patients and 3D activation sequence mapping in 7 patients, however, revealed clockwise LLR involving the lower right atrium around the IVC in 7 patients, figure-of-8 double-loop reentry around both the IVC and TA in 4, and single reentrant loop around the TA in 1. Linear radiofrequency ablation in the isthmus between the TA and IVC (TI isthmus) terminated the tachycardia in all patients. Surface ECG flutter wave morphology and limited recording intracardiac sites proved insufficient to delineate the precise mechanism of the TI isthmus-dependent clockwise right atrial flutters. Most right atrial flutters with positive flutter wave on surface ECG may be supported by a reentrant circuit around the IVC or a figure-of-8 double-loop reentry involving both the IVC and TA.

Different patterns of interatrial conduction in clockwise and counterclockwise atrial flutter.

The terms counterclockwise (CC) and clockwise (C) atrial flutter (Afl) are used to describe right atrial activation around the tricuspid valve in the left anterior oblique view. The manner in which the left atrium is activated, as reflected by coronary sinus (CS) recordings, has not been systematically evaluated. Nine patients with both CC and C Afl underwent electrophysiological study with CS recordings during both rhythms with the use of a decapolar catheter with the tip placed in the distal CS. Patterns of CS activation during each type of Afl as well as during during sinus rhythm were categorized into 1 of 3 patterns: sequential proximal-to-distal, sequential distal-to-proximal, and fused, indicating activation from different directions. In 7 of 9 patients, the pattern of CS activation in CC Afl and C Afl differed, with a proximal-to-distal pattern in CC Afl and a fused pattern in C Afl. In 2 patients, pacing the high right atrial septum near the presumed site of Bachmann's bundle in sinus rhythm showed a similar fused pattern of CS activation. These results demonstrate different patterns of CS activation in CC Afl and C Afl in the majority of patients and are consistent with a model in which the left atrium is activated predominantly over Bachmann's bundle during C Afl and over the CS os in CC Afl. These findings may have implications for maintenance of Afl, interpretation of flutter wave morphology on surface ECG, and left atrial mechanical function in Afl.

Alternation in the flutter wave morphology during radiofrequency catheter ablation for common atrial flutter.

A linear lesion created at the right atrial isthmus by radiofrequency current application can successfully eliminate common atrial flutter (AF). The mechanism of unsuccessful cases has not yet been well delineated. This study sought to investigate the cause of unsuccessful cases of radiofrequency catheter ablation of AF. Sixty-six patients with refractory common AF were referred for radiofrequency catheter ablation. Radiofrequency current was applied to the right atrial isthmus between the inferior vena cava and tricuspid annulus or between the coronary sinus orifice and tricuspid annulus. In 5 (8%) of the 66 patients, a morphological change of the flutter wave was observed in the 12-lead ECG concomitant with the change of the atrial excitation sequence during the delivery of radiofrequency energy without the termination of atrial flutter. In 8 (12%) patients, the morphology of the new AF wave, which was provoked electrically after the termination of the original AF, was different, and the average flutter cycle length also differed in 3 cases (2%). The results of radiofrequency application could be misinterpreted as unsuccessful when the occurrence of another, different type of AF has been overlooked following the elimination of the original AF during the radiofrequency catheter ablation procedure. It is possible that the flutter circuit can take an alternative pathway despite the complete conduction block at the right atrial isthmus.

Three-dimensional mapping of the common atrial flutter circuit in the right atrium.

The full circuit of common atrial flutter using conventional methods of sequential or multielectrode activation mapping is not completely understood. We performed three-dimensional right atrial endocardial activation mapping during common counterclockwise atrial flutter in 17 patients (16 men, 1 woman; mean age, 53+/-11 years) by using the Cordis-Biosense EP Navigation system and assessed the distribution of estimated conduction velocities and double and fractionated potentials. ECG flutter wave morphologies were compared with activation patterns. Points (91+/-29) were sequentially acquired covering 88+/-11% of the flutter cycle length of 239+/-22 ms. A wide and variable posterior zone of double and fractionated potentials coincided with blocking and colliding wave fronts and formed the posterior limit of the circuit. A progressively widening septal (sep) wave front ascending from just beyond the coronary sinus ostium, passed cranially as a broad front anterior to the superior vena cava (SVC) in 14 patients, whereas fusion around the SVC formed the superior (sup) limb of the circuit in 3. Bounded anteriorly by the tricuspid valve, the wave front descended down the lateral (lat) aspect of the right atrium before completing the circuit in all cases through the inferior vena cava-tricuspid annulus isthmus. The estimated conduction velocity in the medial isthmus (0.6+/-0.3 m/s) was lower than in the other limbs of the circuit (sup=1+/-0.5 m/s, lat=1+/-0.5 m/s, sep=0.9+/-0.4 m/s, P=.05). Double and fractionated potentials were constant and more prevalent in the posterior right atrium. ECG flutter wave morphology did not correlate with three-dimensional activation maps. Interindividual variations occur in the right atrial circuit of common atrial flutter, with constant activation through the cavotricuspid isthmus. A variable zone of block forms the posterior limit. Fusion around the SVC can occur, and ascending medial septal activation does not follow a consistent pattern.