Rationale and Objectives
Catheter ablation of the cavotricuspid isthmus (CTI) is an effective treatment of right atrial flutter. The objective of this study was to evaluate the changes in CTI length and right atrial (RA) function after radiofrequency ablation of isthmus-dependent atrial flutter (isthmus ablation).
Materials and Methods
Magnetic resonance imaging was obtained in 14 patients (2 female, mean age 59 ± 9) before and after isthmus ablation (mean delay 80 ± 175 days) using steady-state free precession cine magnetic resonance imaging in right anterior oblique view orientation. Right atrial function (maximum/minimum right atrial volumes, stroke volume, ejection fraction) and maximum/minimum length of the CTI were measured.
Results
After isthmus ablation, maximum RA volume decreased by 13% ( P = .02) and minimum RA volume by 22% ( P = .01), whereas stroke volume and ejection fraction did not increase significantly ( P = .4 and .2, respectively). After ablation, the maximum length of the CTI showed a significant decrease of 19% ( P < .001) and the minimum length a decrease of 24% ( P < .001). A linear correlation between change in CTI length and number of energy applications during ablation could not be observed ( r = .605, P = .22 for minimum length; r = .384, P = .18 for maximum length). After eliminating the outliers in the number of energy applications, a significant correlation between energy applications and change in CTI systolic length was found ( r = .808, P = .008).
Conclusion
Magnetic resonance imaging to visualize right atrial size and function in right anterior oblique orientation was successfully performed and easy to evaluate for volumetric analysis and determination of CTI length. Scarring of the CTI with the use of catheter ablation leads to a significant and linear decrease in its length and to a subsequent reduction of right atrial volumes, whereas functional parameters such as stroke volume/ejection fraction did not change significantly.
Catheter ablation of the cavo-tricuspid isthmus (CTI) is an effective treatment of typical atrial flutter. The ablation aims to set a linear scar in the myocardium of the cavo-tricuspid isthmus to cut off macro-reentry mechanisms around the tricuspid valve . Although a single catheter ablation of the CTI cures about 90% of the patients with isthmus-dependent atrial flutter, reablation has to be performed in cases of recurrence and is usually successful . Anatomical characteristics can impair the ablation procedure , leading to longer ablation times and in theory to more extensive scarring of CTI . Several studies defining the right atrial isthmus either with echocardiographic or magnetic resonance imaging (MRI) have been published in the last decade, trying to address these anatomical difficulties .
In parallel to trials involving the imaging and detection of scars of the pulmonary veins after ablation, recent studies on the right atrium have analyzed changes of tissue in the ablation area of the cavo-tricuspid isthmus using MRI . Yokokawa et al studied the CTI morphology, looking at the anatomical variation of the isthmus and the prevalence of ablation-mediated tissue edema and scar formation. A postprocedural high T2-signal change and increase of wall thickness was noticed after 1 day, which resolved over the following month. The length of CTI was measured preprocedural but not after.
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Materials and methods
Patients
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Atrial Flutter RFA Technique
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MRI of the Cavo-tricuspid Isthmus
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Data and Statistical Analysis
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Results
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Table 1
Right Atrial Measurements Before and After Ablation
Right Atrial Measurements Preablation Postablation_P_ Value Maximum volume (mL) 148 ± 49 131 ± 42 .02 Minimum volume (mL) 111 ± 43 91 ± 31 .01 Stroke volume (mL) 38 ± 21 40 ± 20 .4 Ejection fraction (%) 26 ± 14 31 ± 10 .2 Maximum isthmus length (mm) 35 ± 8 29 ± 9 <.0001 Minimum isthmus length (mm) 22 ± 7 18 ± 6 <.001
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Discussion
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Conclusion
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