Keywords:
Cardiac, MR, MR-Angiography, Ablation procedures, Comparative studies, Segmentation, Tissue characterisation
Authors:
G. Casagranda1, E. C. dal Piaz2, D. Ravanelli2, M. Del Greco2, U. M. Rozzanigo2, M. Centonze2; 1Trento, TN/IT, 2Trento/IT
DOI:
10.1594/ecr2013/C-0888
Conclusion
DISCUSSION AND LIMITS
- Results confirm that there is a good correlation between segments of LE-MR and areas of low voltage to the EAM [2-3].
Statistical analysis showed a VPN of LE rather high (93.8%) compared with a considerable number of false positives,
which resulted in a PPV of 73.3%; artifacts present in the MR images,
such as the often observed in the right inferior PV [4],
may have affected results,
leading to an overestimation of fibrosis.
- Some comparison studies [5-6] show an EAM spatial error of 5-10 mm; also EAM expresses mainly the voltage endocardial myocytes than epicardial,
it means that EAM could not provide accurate data relating to the whole thickness of the atrial wall.
So LE-MR could possess a power of identification fibrosis greater compared to EAM.
- There is a high percentage (18%) of uninterpretable images related to poor technical quality.
At present,
this limitation seems difficult to eliminate,
depending on patient compliance,
presence of arrhythmias during the examination and difficulty in choosing the correct Inversion Time (TI).
Determination of the TI value is carried out on left ventricular wall and not on the atrial wall,
because atrial wall is too thin (1-3 mm).
Furthermore,
long duration of GRE 3D IR Turbo Flash sequence (20 min) makes impossible to change the TI value,
which remains bound to the initial choice.
- Study was affected by the "learning curve" in the execution of the sequence of LE-RM and in interpretation of the images and limited sample size of patients.
- The significance of this method has recently been underlined in the Expert Consensus Statement of the Heart Rhythm Society [1].
In fact as proposed by other Authors [2] to quantify the accurate extension of the atrial fibrosis allows to stratify patients in terms of treatment and prognosis.
CONCLUSIONS
Despite the small sample size,
LE-MR sequence has proved to be useful for excluding the presence of atrial fibrosis,
but weaker for the confirmation of its existence.
The identification of the LE is important in the management of patients candidated to ablation even if further studies are needed to demonstrate the effective reproducibility of the method proposed and its reliability in clinical practice.