Background: Cardiac magnetic resonance (CMR) provides excellent temporal and spatial resolution, tissue characterization, and flow measurements. This enables major advantages when guiding cardiac invasive procedures compared with X-ray fluoroscopy or ultrasound guidance. However, clinical implementation is limited due to limited availability of technological advancements in magnetic resonance imaging (MRI) compatible equipment. A systematic review of the available literature on past and present applications of interventional MR and its technology readiness level (TRL) was performed, also suggesting future applications. Methods: A structured literature search was performed using PubMed. Search terms were focused on interventional CMR, cardiac catheterization, and other cardiac invasive procedures. All search results were screened for relevance by language, title, and abstract. TRL was adjusted for use in this article, level 1 being in a hypothetical stage and level 9 being widespread clinical translation. The papers were categorized by the type of procedure and the TRL was estimated. Results: Of 466 papers, 117 papers met the inclusion criteria. TRL was most frequently estimated at level 5 meaning only applicable to in vivo animal studies. Diagnostic right heart catheterization and cavotricuspid isthmus ablation had the highest TRL of 8, meaning proven feasibility and efficacy in a series of humans. Conclusion: This article shows that interventional CMR has a potential widespread application although clinical translation is at a modest level with TRL usually at 5. Future development should be directed toward availability of MR-compatible equipment and further improvement of the CMR techniques. This could lead to increased TRL of interventional CMR providing better treatment.

Radiofrequency (RF) catheter ablation has become a widely used therapeutic approach. However, long-term results in terms of arrhythmia recurrence are still suboptimal. Cardiac magnetic resonance (CMR) could offer a valuable tool to overcome this limitation, with the possibility of targeting the arrhythmic substrate and evaluating the location, depth, and possible gaps of RF lesions. Moreover, real-time CMR-guided procedures offer a radiation-free approach with an evaluation of anatomical structures, substrates, RF lesions, and possible complications during a single procedure. The first steps in the field have been made with cavotricuspid isthmus ablation, showing similar procedural duration and success rate to standard fluoroscopy-guided procedures, while allowing visualization of anatomic structures and RF lesions. These promising results open the path for further studies in the context of more complex arrhythmias, like atrial fibrillation and ventricular tachycardias. Of note, setting up an interventional CMR (iCMR) centre requires safety and technical standards, mostly related to the need for CMR-compatible equipment and medical staff’s educational training. For the cardiac imagers, it is fundamental to provide correct CMR sequences for catheter tracking and guide RF delivery. At the same time, the electrophysiologist needs a rapid interpretation of CMR images during the procedures. The aim of this paper is first to review the logistic and technical aspects of setting up an iCMR suite. Then, we will describe the experience in iCMR-guided flutter ablations of two European centres, Policlinico Casilino in Rome, Italy, and Haga Teaching Hospital in The Hague, the Netherlands.

Funding Acknowledgements Type of funding sources: None. Background Incomplete atrial lesion is related to high atrial fibrillation (AF) recurrence after Pulmonary vein antrum isolation (PVAI). Objectives The CALAMARI study is a single-center, prospective, observational study with a longitudinal design. The primary aim is to assess PVAI lesion and its development over time using cardiovascular magnetic resonance (CMR). The secondary objective is to identify possible predictors of AF recurrence. Methods 96 consecutive patients undergoing PVAI for paroxysmal AF will undergo four sequential CMR: 1) pre-PVAI CMR 2) post-PVAI CMR, immediately after the ablation 3) CMR one-day or one-week post-PVAI 4) CMR 3-months post-PVAI. Dark-blood short-inversion-time recovery (DB-STIR) will identify oedema. Pre- and post-contrast prepped inversion-recovery with long inversion time (IR-prep) and three-dimensional late gadolinium enhancement (3D-LGE) images will be used to visualize atrial lesion (AL). Qualitative and quantitative assessments of AL will be performed. Patients will be followed-up for 2 years to identify AF recurrence. Preliminary results Ten patients (63.1±5.7 years old, 80% male) completed a pre-PVAI CMR and a post-PVAI-CMR. The AL post-PVAI was visible in 9 patients (90%) using post-contrast IR-prep sequences and in 6 patients (60%) using pre-contrast IR-prep and 3D-LGE. Microvascular obstruction was identified in 7 (70%) patients using IR-prep-post-contrast. On DB-STIR, edema was visualized in all patients with a significant increase in the left atrium wall thickening in CMR post-PVAI vs. pre-PVAI CMR (6.4±2.9 vs. 3.4±1.5, p = 0.09). Conclusion Post-PVAI AL visualization with CMR is feasible in most patients. The CALAMARI study will better understand the AL modifications over time.