The patient was considered as a MINOCA case. He underwent a CMR.
CMR is a non-invasive imaging technique which gives a comprehensive overview of the cardiac function and myocardium characteristics. It is recommended in all MINOCA cases with no obvious cause (Class 1B) [1]. Prosthetic heart valves (bioprosthesis or mechanic) are not a contra-indication to CMR at 1.5T field and even at 3 T for most of them. In fact, forces exerted by the blood flow, gravity and heart beats to the prosthesis are more important than the magnetic field force. CMR can be performed within 24 hours after implantation when it is necessary. In case of doubt, practitioners should refer to the online site www.mrisafety.com and should adhere to recommendations [2].
In our case, CMR showed left ventricle myocardium thinning in the lateral, inferior and apical territories with akinesia (figure 1).
First pass perfusion showed slow reflow in the lateral and inferior walls. Late gadolinium enhancement (LGE) sequences showed typical ischemic subendocardial and transmural enhancement in the left descending artery, circumflex and right coronary arteries (figure 2).
Embolic origin of these myocardium infarcts was suspected. As the patient refused TEE, he underwent cardiac CT for the exploration of his prosthesis. Assessment of cardiac prosthesis dysfunction by cardiac CT is increasing. It is performed with the same technique as coronary CT angiography and with the same precautions (heart beat rate preferably < 70). Cardiac CT allows distinguishing structural deterioration of the prosthesis from non-structural abnormalities. These latters include thrombus and pannus. It helps evaluating opening and closing angles of monoleaflet and bileaflet prosthesis. In our case, cardiac CT showed hypodense formation (95UH) beneath the sewing ring of the prosthesis next to residual calcifications of the subvalvular apparatus, thought to be the cause of a local turbulence (figure 4).
Thrombi develop in focal areas of turbulence, most frequently on the non-ventricular side of the prosthesis and have generally an irregular shape. Their density is lower than 145 UH. The cut off has 87 % sensitivity of 96 specificity to distinguish between thrombus and pannus. When the density is <90UH, the thrombus is considered fresh and is more likely to respond to treatment [3].
References:
[1] Liang K, Nakou E, Del Buono MG, Montone RA, D’Amario D and Bucciarelli-Ducci C. The Role of Cardiac Magnetic Resonance in Myocardial Infarction and Non-obstructive Coronary Arteries. Front. Cardiovasc. Med. 2022;8:821067
[2] Theodoros D. Karamitsos, Haralambos Karvounis. Magnetic resonance imaging is a safe technique in patients with prosthetic heart valves and coronary stents. Hellenic Journal of Cardiology 2019;60(1):38-39.
[3] Prabhakar Rajiah, Alastair Moore, Sachin Saboo, Harold Goerne, Praveen Ranganath, James MacNamara, Parag Joshi, Suhny Abbara. Multimodality Imaging of Complications of Cardiac Valve Surgeries. RadioGraphics 2019; 39:932–956
