Clinical Investigation
Atrial Dysrhythmias
Usefulness of Pre-Procedure Cavotricuspid Isthmus Imaging by Modified Transthoracic Echocardiography for Predicting Outcome of Isthmus-Dependent Atrial Flutter Ablation

https://doi.org/10.1016/j.echo.2011.06.007Get rights and content

Background

Anatomic characteristics of the cavotricuspid isthmus (CTI) have been reported to be related to the outcome of atrial flutter ablation therapy. However, preprocedural evaluation of CTI anatomy using modified transthoracic echocardiography to guide atrial flutter ablation has not been well described.

Methods

Transthoracic echocardiography was prospectively performed before atrial flutter ablation in 42 patients with typical CTI-dependent atrial flutter. A modified apical long-axis view was designed to visualize and evaluate anatomic characteristics of the CTI and Eustachian ridge (ER). A prominent ER, extending from the inferior vena cava to the interatrial septum, is defined as an extensive ER.

Results

Twenty-eight patients had straightforward ablation procedures, and 14 patients had difficult ablation procedures. Two patients with difficult procedures had unsuccessful ablation. Multivariate analysis (using CTI length, the presence of a pouch or recess, ER morphology, and significant tricuspid regurgitation as variables) showed that the presence of extensive ER was the only independent predictor of a difficult ablation procedure. The ablation time in patients with extensive ER (n = 13) was significantly longer than in those patients with nonextensive ER (n = 29) (1,638.4 ± 1,548.3 vs 413.8 ± 195.5 sec, P = .015). The incidence of difficulty in achieving bidirectional isthmus block was also higher in patients with extensive ER (10 of 13 vs four of 29, P < .001).

Conclusion

Preprocedural transthoracic echocardiography using a modified apical long-axis view is useful to characterize the morphology of the CTI and the ER. An extensive ER is a strong predictor for difficult ablation of CTI-dependent atrial flutter.

Section snippets

Study Population

This prospective study included 42 consecutive patients (30 men, 12 women; mean age, 62 ± 14 years) who underwent electrophysiologic evaluation and RF catheter ablation for recurrent or refractory symptomatic CTI-dependent atrial flutter. Nineteen patients (45%) had structural heart disease, including coronary artery disease (n = 11), hypertensive cardiovascular disease (n = 3), valvular heart disease (n = 1), dilated nonischemic cardiomyopathy (n = 3), and congenital heart disease (n = 1). One

Ablation Time and Ablation Outcomes

Complete bidirectional isthmus block was achieved within 10 min of RF application in 28 patients (straightforward group) but could not be achieved with 10 min of ablation in 14 patients (difficult group). The ablation time in the difficult group was significantly longer than that in the straightforward group (1,638.6 ± 1,461.3 vs 369.9 ± 138.5 sec, P = .006). Baseline characteristics were similar between the two groups (Table 1).

ER Morphology and Ablation Outcomes

The echocardiography images of the 42 patients were of sufficient

Discussion

The CTI plays a critical role in the reentrant circuit of CTI-dependent atrial flutter and is the target for catheter ablation. Linear RF catheter ablation across the CTI can achieve bidirectional conduction block across the CTI and abolish the reentrant circuit and thereafter eliminate the isthmus-dependent atrial flutter.1, 2, 5, 6, 7, 8 However, complete bidirectional isthmus conduction block may be difficult to achieve after a prolonged ablation procedure in some patients with CTI-dependent

Conclusions

Transthoracic echocardiography using a modified apical long-axis view is useful to evaluate the anatomy of the CTI before ablation procedures for CTI-dependent atrial flutter. The presence of an extensive ER on echocardiography is a strong predictor for a difficult ablation procedure. Early decision and the selection of a more aggressive ablation strategy are suggested for these patients before the procedure, particularly in patients who are at high risk for developing procedure-related

Acknowledgments

We thank Hsiu-Chen Lu for her help in figure creation. We are also grateful to Pei-Chi Hung and the staffs of our echocardiography and electrophysiology laboratories for their kind support of this study.

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    Copyright © 2011 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.