CTI-dependent Atrial Flutter Research Articles

Three-dimensional bipolar voltage map demonstrating electrical activity of a single muscle bundle along the cavotricuspid isthmus

Ablation of the cavotricupsid isthmus (CTI) for the prevention of atrial flutter has traditionally been guided anatomically (1). Recently, an atrial electrogram (EGM) voltage-guided approach was described (2,3). It has been hypothesized that muscle bundles in the CTI are predominantly responsible for conduction through this area, and targeted ablation of those muscle bundles is an efficient and effective means to achieve bidirectional conduction block across the CTI. The muscle bundles can be identified by the highest-amplitude local atrial bipolar EGM recorded along any given ‘line’ between the tricuspid annulus and the inferior vena cava. A voltage map of the CTI bipolar atrial EGM was generated with a 4 mm, steerable irrigated-tip ablation catheter (Cool Path; St Jude Medical Inc, USA) during CTI-dependent atrial flutter (cycle length 243 ms) using a three-dimensional mapping system (NavX; St Jude Medical Inc). Figure 1 shows a caudal left anterior oblique view of the three-dimensional bipolar voltage map. A discrete line of high voltages was seen, demonstrating electrical activity of a single muscle bundle along the CTI. Figure 1) Three-dimensional bipolar voltage map (caudal left anterior oblique veiw). A discrete line of high voltages (purple colour, arrows) is seen, demonstrating electrical activity of a single muscle bundle along the cavotricuspid isthmus. The voltages corresponding ... In voltage maps, the voltages corresponding to the colour codes are indicated on the colour bar. Voltages higher than 1.8 mV (set arbitrarily) are shown in purple. The lowest voltages are shown in red. In the present voltage map, the region of the His potential was indicated by red dots. A duodecapolar catheter was in the right atrium, the ablation catheter was in the inferior vena cava and a reference catheter was in the coronary sinus. Visualization of the high-voltage area of the CTI with endocardial voltage mapping supports the muscle bundle hypothesis and helps with the understanding of the voltage-guided ablation approach for CTI-dependent atrial flutter.

Atrial Fibrillation–Atrial Flutter Interactions

An appreciation of the article by Moreira et al in the current issue of Circulation 1 requires an understanding of the close interrelationship between atrial fibrillation (AF) and atrial flutter (AFL). These authors have understood this interrelationship and applied it to their data to advance the approach to both AF and AFL ablation. Key to this understanding is the recognition that cavotricuspid isthmus (CTI)–dependent AFL almost always develops from antecedent AF of variable duration.2–5 This is because in almost all instances, it is during the AF that a functional line of block (LoB) necessary for the development of AFL forms between the superior and inferior vena cavae. This LoB acts as a critical lateral boundary that prevents short-circuiting of the AFL reentrant circuit. Thus, in the vast majority of instances, without preceding AF, there can be no AFL. The most recent additional support of this concept comes from the report by Ellis et al,6 which found that of 363 patients who presented with only CTI-dependent AFL and who underwent CTI ablation, long-term follow-up (mean of 39±11 months) demonstrated newly recognized AF in 82%. It also should be noted that, as Moreira et al1 recognize, in some patients, a LoB between the vena cavae may be fixed (ie, anatomic) rather than functional. In such patients, AF may not be required for AFL to develop. Article p 2786 As Moreira et al1 further recognize, their report does not answer all the questions about the interrelationships of AF and AFL as they relate to AF ablation, …

Abstract 2644: High Prevalence of a Novel Conduction Pattern Around the Coronary Sinus in Cavotricuspid Isthmus Dependent Right Atrial Flutter

Objective : We tested our hypothesis that, in atrial flutter (AFL) dependent on the cavotricuspid isthmus (CTI), lower loop reentry (LLR) is the common pathway route at the coronary sinus (CS) posterior site, and thus, dual loop reentry (DLR) is a common circular pattern. Methods and result s: We studied 25 patients with CTI-dependent AFL, 16 with chronic counterclockwise atrial flutter (CCW-AFL) and 9 with clockwise atrial flutter (CW-AFL) and determined the precise reentry circuitry, especially for conduction patterns around the CS orifice, using electroanatomical mapping. We measured post pacing interval and tachycardia cycle length during entrainment from sites within the flutter circuit. In 16 of the 25 CCW-AFL patients, the CS anterior pacing site was within the AFL circuit in 13. The CS anterior pacing site was within the AFL circuit in 6 of the 9 CW-AFL patients. In 8 each of 16 CCW-AFL and 9 CW-AFL patients, both the CS anterior and posterior sites were within the AFL circuit. Results of 3-Dimensional (3D) activation mapping suggest that all of these patients had a DLR circuit, and that CS posterior conduction broke through the eustachian valve/ridge. Conclusion : CS posterior conduction consisted of the flutter circuit and appeared to be critical for maintaining AFL. Almost all AFL patients had DLR formed within the LLR or the superior RA circuit constituted from CS posterior conduction and in the anterior loop around the tricuspid annulus.

Clinical Prediction of Cavotricuspid Isthmus Dependence in Patients Referred for Catheter Ablation of “Typical” Atrial Flutter

Typical atrial flutter (AFL) can be cured by catheter ablation of the cavotricuspid isthmus (CTI). The surface electrocardiogram (ECG) is not always diagnostic of isthmus dependence of AFL. The aim of this study was to evaluate clinical parameters for the prediction of isthmus-dependent AFL. Sixty consecutive adult patients without suspected atriotomy-related AFL, congenital heart disease, or previous AFL ablation, referred for catheter ablation of presumed typical AFL were studied. All patients had distinct flutter waves in the inferior leads, suggestive of CTI-dependent AFL, either on presentation to the electrophysiology (EP) lab or documented on prior ECG. Electrophysiology study was performed in the standard fashion. Patients who presented to the EP laboratory not in AFL underwent arrhythmia induction with a burst pacing protocol. A clinical history of persistent AFL (P = 0.0001) and existence of AFL on presentation to the EP laboratory (P = 0.0001) were strong predictors of CTI dependence. History of atrial fibrillation (P = 0.19), structural heart disease (P = 0.6), hypertension (P = 0.4), and previous cardiac surgery (P = 0.5), as well as the nature of AFL-related symptoms (P = 0.5), were not predictors of CTI-dependent AFL documented during EP study. In patients with ECG suggestive of typical AFL, the presence of persistent rather than paroxysmal AFL and presentation to the EP laboratory in AFL are strong predictors of CTI-dependent AFL. A paroxysmal pattern of AFL predicts noninducibility of CTI-dependent AFL during EP study. CTI ablation may therefore be less effective in these patients.

Performance of a New Cardiac Cryoablation System in the Treatment of Cavotricuspid Valve Isthmus‐Dependent Atrial Flutter

We sought to evaluate prospectively the safety and efficacy of cryothermal energy to ablate typical atrial flutter (AFL). Ablation of cardiac tissue using cryothermal energy has recently been developed as an alternative to radiofrequency energy, which may offer certain advantages in the treatment of AFL. This prospective, multicenter nonrandomized study of a new catheter-based system for the treatment of cavotricuspid isthmus (CTI)-dependent AFL enrolled patients between 18 and 75 years of age. The CTI dependence of AFL was confirmed at electrophysiologic study with activation mapping and/or entrainment. Patients with atrial septal defect, recent myocardial infarction, left ventricular ejection fraction <0.30, or prior AFL ablation were excluded. Cryoablation of AFL was performed in 48 patients from 11 centers. The procedure was immediately successful in 45 patients (94%), and effective in 30 of 40 patients with complete data available at 6 months. Cryoablation is a promising new treatment of CTI-dependent AFL refractory to medical therapy. Further improvements in catheter design and intravascular sheaths will be tested in a larger multicenter trial.