Right Atrial Scar Detection after Catheter Ablation

Rationale and Objectives

To prospectively compare the diagnostic performance of two-dimensional (2D) and high spatial resolution three-dimensional (3D) late enhancement magnetic resonance imaging (MRI) for the detection of scar tissue caused by catheter ablation of the right atrium in patients with atrial flutter.

Materials and Methods

Forty-seven patients were enrolled. In 16 patients, imaging of the cavotricuspid isthmus was performed before and after catheter ablation, 16 subjects were imaged before, and 15 after catheter ablation, resulting in a total of 63 examinations. MRI included a standard 2D breathhold and a high-resolution navigator-gated 3D T1-weighted gradient-echo inversion-recovery sequence in right and left anterior oblique views. Two readers assessed the subjective image quality on a 4-point scale (1 = excellent) and the presence of late enhancement (blinded/ in consensus).

Results

The average image quality was 1.6 for both imaging approaches. In consensus reading, the sensitivity was 83% versus 100%, specificity 97% versus 89%, accuracy 90% versus 94%, positive predictive value 96% versus 89%, negative predictive value 86% versus 100% for 2D and 3D, respectively. The interobserver agreement was 0.86 for 2D and 0.78 for 3D imaging.

Conclusions

For the noninvasive identification of scars in the cavotricuspid isthmus after right atrial flutter, ablation 2D imaging was more consistent, whereas 3D sequences showed superior sensitivity for the depiction of late enhancement.

Introduction

Radiofrequency ablation (RFA) of the isthmus between the vena cava inferior and tricuspid annulus is the recommended therapy for isthmus-dependent (“typical”) atrial flutter, and catheter-based isolation of the pulmonary veins is a highly effective therapeutic option to prevent recurrent atrial fibrillation in symptomatic patients.

Although atrial fibrillation has a much higher prevalence and rising incidence among elder people, atrial flutter is less frequent. Ablation of the cavotricuspid isthmus (CTI) aims to generate linear scars in the atrial myocardium to cut off macro-reentry mechanisms around the tricuspid valve . A single catheter ablation of the CTI cures a high percentage (about 80%) of the patients ; reablation has to be performed in recurrent cases, which count up to approximately 40% including late recurrent cases .

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Materials and methods

Patients

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Atrial Flutter RFA Technique

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MRI of the Cavotricuspid Isthmus

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Data and Statistical Analysis

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Po=(both readers with positive finding+both readers with negative finding)/allfindings. Po

(

both readers with positive finding

both readers with negative finding

)

all

findings

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Ppos=(2× both readers’positive findings)/(2× both readers’positive findings+disagreeing findings) Ppos

(

× both readers

’

positive findings

)

(

× both readers

’

positive findings

disagreeing findings

)

Ppos estimates the conditional probability, given that one of the raters, randomly selected, makes a positive rating, the other rater will also do so.

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Kappa(K)=(Po−Pe)/(1−Pe) Kappa

(

)

(

)

(

)

and Pe defined as:

Pe=[(all positive findings of reader1/all findings)×(all positive findings of reader2/all findings)]+[(all negative findings of reader1/all findings)×all negative findings of reader2/all findings)]. Pe

[

(

all positive findings of reader

all findings

)

(

all positive findings of reader

all findings

)

]

[

(

all negative findings of reader

all findings

)

all negative findings of reader

all findings

)

]

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Results

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Table 1

Diagnostic Values for Two-dimensional Sequence Sets

Reader 1 (%) Reader 2 (%) Consensus (%) Specificity 90.6 95.3 96.8 Sensitivity 62.1 71.0 83.3 Accuracy 77.0 82.0 90.2 Positive predictive value 85.7 91.7 96.2 Negative predictive value 72.5 75.7 85.7

Table 2

Diagnostic Values for Three-dimensional Sequence Sets

Reader 1 (%) Reader 2 (%) Consensus (%) Specificity 82.1 93.1 89.3 Sensitivity 95.8 95.8 100 Accuracy 88.5 94.3 94.1 Positive predictive value 82.1 92.0 88.5 Negative predictive value 95.8 96.4 100

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Discussion

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Right Atrial Scar Detection after Catheter Ablation

Rationale and Objectives

Materials and Methods

Results

Conclusions

Introduction

Materials and methods

Patients

Atrial Flutter RFA Technique

MRI of the Cavotricuspid Isthmus

Data and Statistical Analysis

Results

Discussion

References

Further Reading

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