Magnetic Resonance Imaging Versus Computed Tomography for Characterization of Pulmonary Vein Morphology Before Radiofrequency Catheter Ablation of Atrial Fibrillation
OBJECTIVES: The accurate assessment of pulmonary vein (PV) anatomy is important in planning radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF). The aim of the present study was to perform a head-to-head comparison of magnetic resonance imaging (MRI) and multislice computed tomography (CT) for the evaluation of PV morphology before RFCA of AF.
METHODS: Contrast-enhanced MRI (on a 1.5-T system) and multislice CT (on a dual-source system) were performed for the evaluation of the PVs in 44 consecutive patients (31 men, mean age 56 +/- 10 years) admitted for RFCA of drug-refractory AF. Data on PV anatomy, ostial branching pattern, and ostial dimensions were compared between MRI and multislice CT.
RESULTS: Variant PV anatomy was observed in 21 patients (48%) with the 2 imaging approaches. The incidence of PV ostial branching, as assessed with MRI and multislice CT, was higher on the right and more common in the inferior than superior vein. Agreement between the 2 imaging modalities for the evaluation of variant PV anatomy (kappa = 0.87, 95% confidence interval 0.77 to 0.97) and ostial branching pattern (kappa = 0.84, 95% confidence interval 0.75 to 0.93) was nearly perfect. Assessment of PV ostial cross-sectional area as well as maximal and minimal ostial diameters resulted in strong agreement and correlation (r(2) = 0.75 to 0.99, p <0.001 for all) between the 2 imaging approaches.
CONCLUSIONS: In conclusion, MRI and multislice CT of the PVs appear to provide similar and detailed anatomic and quantitative information before RFCA of AF.
PMID: 19932789
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Phillip M. Young, MD on December 6th, 2009
This is the first direct comparison of MRA and CTA for the pre-procedural assessment of pulmonary veins, and it appears to confirm that they are equivalent in terms of diagnostic accuracy.
The choice between the two, as is typically the case, will likely be related to a patient-specific analysis of radiation risk, cost, renal function, institutional expertise, and availability.
Paul Schoenhagen, MD on December 6th, 2009
Also, it should be considered the need to image the left atrial appendage, and potential fusion of the CT and MRI derived dataset with the electroanatomical map.
Jacobo Kirsch, MD on December 12th, 2009
I read this article with great interest, as I have had the EP cardiologists in my Institution question the use of MRI for their RFCA procedures.
In this study, the authors show a high level of agreement between the 2 imaging modalities in the same patients – both for the determination of PV anatomy as for the assessment of ostial cross-sectional area.
In my opinion, interesting aspects of the study included:
1. Non-ECG gated nature of the MR images vs the ECG-gated CT exams. If we consider that the study cohort consisted of 44 patients with AF, did the non-gating of the MRI actually helped to avoid mis-registration artifact on the MR?
2. The radiation dose of the CT was significant at over 17 mSv. If the study was going to invariably be reconstructed at the 75% phase of the R-R cycle, why was it retrospectively acquired?
3. Why was 75% used – I use 65% in my studies as an educated decision rather than evidence-based. Any insight?
By the way; copies of this paper were personally delivered to my EP guys. Thanks!
Paul Schoenhagen, MD on December 12th, 2009
In response to Dr. Jacobo Kirsch’s comment:
- There is good experience both with prospectively triggered acquisitions, and also non-gated CT. This drops the radiation exposure significantly (below 5 mSv).
Jacobo Kirsch, MD on December 14th, 2009
That is the reason I asked; why the need of retrospectively gating the pre-ablation study? In our practice, we have decided on prospectively gating the pre-ablation studies; and not gating the follow-up exams when ordered.