Eclipsed Functional Mitral Regurgitation Destabilizing Hypertrophic Cardiomyopathy: An Unusual Case Treated With MitraClip

MitraClip (Abbott Laboratories, Abbott Park, IL) is validated in high-risk patients with severe degenerative mitral regurgitation (MR); however, it is not well established for functional MR in hypertrophic cardiomyopathy (HCM). We share a case of a 68-year-old man with HCM hospitalized for multiple incidents of acute pulmonary edema caused by a dynamic MR and successfully treated with the MitraClip device. Novel teaching points emerging from this case are that MRs in HCM can often be explained by mixed mechanisms, and properly identifying the MR mechanism is essential to choose optimal treatment. Furthermore, MitraClip can simultaneously treat MR secondarily to annular dilation and systolic anterior motion.


R ESUM E
In 2014, the MitraClip device was used for the first time in obstructive hypertrophic cardiomyopathy (HCM) to treat systolic anterior motion (SAM) and the associated MR. In a small case series, the use of MitraClip showed a significant reduction in MR and left-ventricular outflow tract (LVOT) obstruction and has recently been used in the management of patients with obstructive HCM who are not candidates for septal reduction. 4 We present an interesting case of a dynamic and unstable MR on annular dilation caused by left-atrial (LA) enlargement and a SAM causing LVOT obstruction and significant hemodynamic destabilization. The patient has been successfully treated with the MitraClip device.

Case
A 68-year-old man, known for HCM and nonsevere functional MR, suffered 2 incidents of acute pulmonary edema, following his atrial fibrillation ablation, in 2018 and 2019, the last of which was complicated by cardiogenic shock requiring transient mechanical support with an IMPELLA device (Abiomed, Danvers, MA). Transthoracic echocardiography (TTE) at that time showed a sudden deterioration of the MR, quantified as severe, with a centrally directed jet, possibly caused by procedural volume overload and the appearance of a SAM, causing the hemodynamic instability. The patient was stabilized and discharged with mild MR on the TTE. In January of 2020, the patient was hospitalized for another cardiac decompensation and transferred to our centre

Novel Teaching Points
Properly identifying the initial MR mechanism is essential in choosing the optimal treatment. MitraClip can simultaneously treat MR on annular dilation and SAM.
for evaluation. After diuretic treatment, transesophageal echocardiography (TEE) showed a mild-to-moderate central MR on an annular dilation (41 mm) caused by LA enlargement and no SAM. Despite optimized medical therapy, the patient had another fulminant cardiac decompensation in our centre that required respiratory support. A combination of a severe functional MR with a centrally directed jet and a subvalvular apparatus SAM causing LVOT obstruction was confirmed by TTE. The visualization of a central MR jet on the TTE is in favour of a severe functional MR caused by an annular dilation and not completely explained by the subvalvular apparatus SAM (Fig. 1).
Facing this "eclipsed" MR and the fragility of the patient, the heart team estimated the risk of mortality or morbidity to be more than 15% and proposed the least invasive intervention. The unstable MR being explained by a mixed mechanism (annular dilation and a SAM), the team opted for a MitraClip procedure rather than an advanced surface ablation to treat both mechanisms at the same time. We proceeded with the installation of 2 NTR clips under general anaesthesia and 3-dimensional TEE guidance. The first clip was installed in zone 2 (A2-P2), leaving a moderate residual, posteriorly directed MR jet on an incomplete subvalvular apparatus SAM, where a second clip was installed (Fig. 2). The procedure was successful, with a postprocedural TTE showing mild residual MR. The patient's symptoms were significantly improved, and he was discharged to a rehabilitation centre. At 6-month follow-up, the patient has not been readmitted, and the TTE showed stable MitraClips with residual mild MR.

Discussion
This case underlines how MR, caused by annular dilation, in which the coaptation length of the mitral valve leaflets is reduced, can become unstable rapidly under minimal hemodynamic change in afterload/preload and can lead to the appearance of a SAM, secondary to the tachycardia and the increased cardiac inotropy. LVOT obstruction can therefore lead the patient into profound cardiogenic shock. We emphasize that MR on annular dilatation in the HCM population seems to have a much less predictive evolution with a sometimes fulminant presentation. MRs in HCM are not all caused SAM and are often explained by mixed mechanisms.