Μαγνητική τομογραφία καρδιάς πριν από κατάλυση αρρυθμιών. Χρήσιμο εργαλείο ή περιττή πολυτέλεια;

Transcription

1 Μαγνητική τομογραφία καρδιάς πριν από κατάλυση αρρυθμιών. Χρήσιμο εργαλείο ή περιττή πολυτέλεια; Δημήτριος Τσιαχρής Διευθυντής Εργαστηρίου Ηλεκτροφυσιολογίας Ιατρικό Κέντρο Αθηνών

2 Points of interest Κατάλυση κολπικής μαρμαρυγής Κατάλυση κοιλιακών ταχυκαρδιών SVT ablation is and always be a matter of EP knowledge rather than imaging

3 Κατάλυση κολπικής μαρμαρυγής

4 MRI as a pre ablation tool MRI with late gadolinium enhancement (LGE) allows the detection and quantification of fibrotic tissue by slow washout kinetics of gadolinium in diseased tissue. While ventricular fibrosis assessment has achieved excellent results with CMR imaging, the challenge of atrial fibrosis assessment remains open because of limited image resolution and the thinness (1 2 mm) and unpredictable shape of the LA wall

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6 4 stages of atrial fibrosis DECAAF study

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8 Assessment of pulmonary vein encirclement. Identification of gap lesions in left- and right-sided pulmonary veins.

9 Methods to discriminate left atrial fibrosis in magnetic resonance imaging with late gadolinium enhancement Once the atrial myocardium is properly isolated, we detect fibrotic tissue, either visually or by automatic or semi-automatic thresholding techniques. Thresholding consists of applying a cut-off value to the image to distinguish viable from non-viable myocardium, based on the range of signal intensities. A major drawback of visual assessment as a technique for large studies is the subjectivity and non-repeatability of the results

10 Thresholding techniques Standard deviations above reference Histogram-based reference

11 Controversies and limitations Poor reproducibility of the results in different centres The prevalence of baseline LGE in patients submitted to a first AF ablation differs significantly across the published studies, and even across those conducted by a single group, varying from 8.7% of the recruited patients with mild MRI enhancement to 47 with at least moderate enhancement

12 Detection of the ablation induced fibrosis The RF-induced fibrosis has been identified with visual methods, reporting 100% sensitivity and specificity Others, using computational methods, found that the reliability of CMR in assessing the presence and distribution of ablation lesions ranged from as low as 28 to 54%.

13 Image acquisition Lack of standardized image acquisition protocols No consensus on the choice and dose of contrast agent, nor on the timing in acquisition of LGE sequences after contrast administration. The choice of the optimal TI for the LGE sequence is performed manually by a technician. This is a crucial step, as it can generate the appearance of more or less scar and so an over- or underestimation of the fibrosis.

14 The choice of the threshold from which tissue should be considered border zone or scar is still an open issue. Figure 4 shows how this choice can change the perception of presence or absence of pre-ablation atrial fibrosis and its quantification.

15 Figure 5 shows this same variability but with dense fibrosis, after an ablation procedure, depending on the thresholding technique and threshold chosen

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17 MRI for VT ablation Always perform cardiac MRI before ICD implant.

18 MRI as a pre VT ablation diagnostic tool

19 MRI as a pre VT ablation tool Two of the main challenges in current procedural planning for VT ablation are whether to proceed with an epicardial approach and identification of interventricular septal scar.

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23 Epicardial or not? Bogun et al performed CE-CMR in 29 patients with nonischemic cardiomyopathy; 14 patients were found to have scar. All 14 patients underwent catheter ablation, of which 9 had a successful outcome. In these 9 patients, 5 had only endocardial scar and required only endocardial ablation. In the other 4 patients, scar was either intramural and epicardial or epicardial alone. All 4 of those patients required an epicardial approach for effective therapy.

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