# Impact of LGE-MRI in Arrhythmia Ablation
## 4 Use of the Processed LGE-MRI for Ablation Procedures
### LGE-MRI for VT Ablation  
The use of LGE-MRI in patients undergoing VT ablation is increasing, especially for the preprocedural assessment of the cardiac anatomy and myocardial scarring and for intraprocedural integration.  
On the one hand, the use of LGE-MRI provides accurate knowledge of the arrhythmic substrate, including the critical VT isthmuses, the BZ areas and CCs, supporting ablation strategies [52; 54; 58; 77]. The identification of these specific areas has been very useful in cases of ischaemic cardiomyopathyopathy [52; 54; 77]. Moreover, LGE-MRI is also very helpful in cases of nonischaemic cardiomyopathyopathy (NICM). In this sense, some studies have demonstrated that the location of scar in NICM, is also useful for the ablation procedure [78]. This is because the ablation technique and the type of tachycardia is related to the location of scar tissue. Similarly, the effectiveness of using MRI for selecting the appropriate ablation technique was demonstrated in a study involving 80 patients with both NICM and ischemic cardiomyopathy (ICM). In that study, the epicardial or endocardial access was chosen based on MRI. In addition, in case of the intramural substrate, the distance of the scar to the right and left endocardium was used to decided how to approach this substrate [79]. Figure 4 shows an example of the correspondence of LGE-MRI 3D reconstruction with an EAM map.  
On the other hand, in relation to EAMs, studies have not only demonstrated the feasibility of integration during the ablation procedure and a good correlation between 3D-LV reconstruction and EAMs [52; 79; 80], but have also shown that the scars in MRI scans were larger compared to those detected by EAMs. Moreover, some VT isthmuses were found in regions identified as scar by MRI, but were nonvisible in EAMs [65]. These kinds of studies underscore the value of integrating LGE and EAM for comprehensive scar characterization, particularly in the context of defining infarct BZs, nontransmural scars, and small sub epicardial scars [65]. This role of preprocedural MRI to aid procedural access  
Figure 4: Example of correlation of the 3D-VI reconstruction from LGE-MRI with electroanatomical voltage map. From left to right: LGE-MRI map (colour-coding: blue: healthy tissue, yellow: border zone and red: core scar) with two clear conducting channels (white line); and electroanatomical map high density voltage map showing septal scar (colour-coding: purple: healthy tissue, red: border zone and grey: core scar), with conducting channels at the same region as compared to the LGE-MRI.  
has also been related to a lower VT recurrence rate, improving the ablation results. A study in patients with ischemic heart disease and epicardial substrate identified prior to ablation by MRI showed that those patients that underwent ablation with epicardial access had better results in terms of VT recurrence, compared to patients who underwent exclusively the endocardial approach [80].  
Finally, there is a clear role of MRI in predicting the risk of VT recurrence, even without integration images into the EAM. In a study by [PERSON] et al. [81], 110 patients who underwent VT ablation with preprocedural LGE-MRI were analysed, identifying MRI-related factors that were clearly linked to a higher rate of VT recurrence, such as mass of border zone and total scar, septal substrate or midmural and transmural CCs. Similarly, in a smaller study [82], scar area was also linked to clinical outcomes, such as VT recurrence. Another study [83] involving 25 non ischemic patients, also verified that the extension of septal LGE was associated with a higher rate of VT recurrence.