Use of MitraClip for Postmyocardial Infarction Mitral Regurgitation Secondary to Papillary Muscle Dysfunction

Papillary muscle rupture after acute myocardial infarction (AMI) is a dreadful complication and it is associated with five percent of deaths following AMI. Surgery is the recommended treatment of choice; however, it is usually deferred due to the high risk of mortality. MitraClip implantation using a transcatheter approach is an alternative option for patients with severe mitral regurgitation (MR) following AMI or those with high operative risk. We report a case of a 68-year-old male patient who developed severe MR secondary to AMI and underwent successful mitral valve repair using the MitraClip device.


Introduction
Flail mitral valve (MV) leaflet after acute myocardial infarction (AMI) is a lethal complication associated with five percent mortality post-AMI [1][2]. MV repair showed a better outcome than replacement in terms of mortality, survival, ventricular function preservation, and risk of endocarditis for most cases. MitraClip implantation using a transcatheter approach is an alternative option for patients with severe mitral regurgitation (MR) due to flail MV following AMI who have a high operative risk [3]. The most effective current technique for MV repair is the double orifice MV configuration. Applying that technique percutaneously using the MitraClip system can result in lower mortality, morbidity, and recurrence of mitral regurgitation (MR) in most patients. We report a case of a 68-year-old male patient who developed severe MR secondary to AMI and underwent successful MV repair using the MitraClip device.

Case Presentation
A 68-year-old Caucasian male with a history of hypertension, hypercholesterolemia, coronary artery disease status post five vessel coronary artery bypass grafting presented to the emergency room with chest pain for four days which radiated to his jaw and along the left arm ( Figure 1).   The patient was electively intubated before urgent cardiac catheterization, which was performed within 12 hours of patient's arrival, and revealed 100% occlusion in right coronary, left main coronary, and the proximal portion of the circumflex artery as well as diffuse disease of the grafted vessels to circumflex. Furthermore, during catheterization, the patient was also noted to have hemodynamic compromise with blood pressure observed to be 86/63 mmHg and a heart rate of 115 beats per minute, which prompted emergency echocardiography (ECHO) showing partial disruption of medial papillary muscle with severely flail posterior MV leaflet and severe MR. He subsequently underwent venoarterial extracorporeal membrane oxygenation (ECMO) pump placement by cardiothoracic surgery for hemodynamic support accessing through the right common femoral artery and right femoral vein ( Figure 4). Heart team specialists thus discussed the possibility of performing an MV clipping, and it was decided in favor of proceeding with the transcatheter procedure as the patient had a history of median sternotomy and previous bypass surgery. The patient remained intubated and was taken to cath lab on the fifth day of hospitalization. The femoral vein was accessed using ultrasound guidance, and the transseptal puncture was performed using intraoperative transesophageal echocardiography. This was then followed by prepping the MitraClip using standard technique and positioning it across the interatrial septum and above the atrial valve. For this procedure, two clips were used, one was on the posterior segment P2 and just beside it to cinch up P2 and A2, and the second one for P2 and P1 laterally. Once the resulting MR reduction was regarded as adequate, clips were deployed ( Figures 5 and 6). The only complication noted was the transient Wenckebach heart block for which the patient subsequently received a pacemaker later in the hospital course. Thus, the patient underwent two successful MitraClip placements, and the severity of MR went down from 4+ to no more than 1+. The patient's left ventricular function improved postprocedure and ECMO was subsequently followed by extubation later on. Repeat ECHO on third postprocedure day showed mild MR and normal left ventricular ejection fraction. At the 30th day, the patient was followed up in the clinic and repeat ECHO at that time showed mild MR only.

Discussion
Acute myocardial infarction with associated papillary muscle dysfunction leads to MR, and concomitant cardiogenic shock carries high mortality risk and accounts for approximately 5% of deaths following AMI [1]. The most common culprit vessel is the right coronary artery, but the condition can involve the left circumflex artery as well, albeit less commonly [4]. Our case involved both the right coronary and left circumflex arteries. Pulmonary edema or signs and symptoms of cardiogenic shock in the following AMI should prompt urgent investigation. Once this catastrophe is identified, medical treatment is limited and associated with poor outcomes [5]. The standard therapy is surgical repair or replacement, a class I recommendation in severe MR [2]. Despite the decreased incidence of perioperative mortality associated with surgery, there is still a substantial risk associated with this procedure [6]. Prior to receiving this definitive treatment, patients require supportive treatment with vasodilator therapy and interval hemodynamic support using an intra-aortic balloon pump or ECMO [1]. We used venoarterial ECMO to provide hemodynamic support for our patient. Percutaneous transcatheter MV repair using the MitraClip is an emerging alternative option for patients with severe MR who are considered as high risk for open repair [3]. The common indications for the MitraClip procedure for MR repair include chronic degenerative or functional etiologies, and data on MitraClup use in acute settings are scarce. Nevertheless, both etiologies can present in the setting of AMI [7]. Degenerative MR is caused by an abnormality in the structural apparatus of the MV whereas functional MR occurs without any structural deformity. To our knowledge, ours is the 10th reported case of a mitral clip used in an acute setting. Our patient's severe MR was caused by posterior papillary muscle rupture as a complication of AMI. Currently, there are reservations for the use of MitraClip in the setting of AMI given the risk of papillary rupture with leaflet detachment and the lack of sufficient data in support of (and possible improvement of) MR severity following revascularization once the myocardium is revitalized [8]. The MitraClip consists of two arms that open and close using delivery system operated by an expert in structural heart disease [9][10]. Once approximated at the leaflet margin, the system is deployed ensuring a reduction in the severity of MR under fluoroscopic and transesophageal echocardiographic guidance.

Conclusions
Our case represents a successful treatment with a MitraClip using the double orifice technique and suggests that this minimally invasive technique may be useful for high-risk surgical candidates with cardiogenic shock and pulmonary edema following AMI. It also shows that using this technique percutaneously might result in lower mortality rate, higher survival rate, with a lower risk of endocarditis following the procedure. Additional studies are necessary to establish the long-term efficacy and safety of this procedure. Due to a lack of data, a multidisciplinary team consisting of experts in structural heart disease should make the decision based on risk assessment scores, clinical presentation, morphology of MV, and cardiac function. Our case represents a successful treatment involving a MitraClip using the double orifice technique and suggests this minimally invasive technique may be useful for high-risk surgical candidates with cardiogenic shock and pulmonary edema following AMI. It also shows that using this technique percutaneously might result in lower mortality rate, higher survival rate, with a lower risk of endocarditis following the procedure. Additional studies are necessary to establish the long-term efficacy and safety of this procedure. Due to a lack of data, a multidisciplinary team consisting of experts in structural heart disease should make the decision based on risk assessment scores, clinical presentation, morphology of MV, and cardiac function.

Additional Information Disclosures
Human subjects: Consent was obtained by all participants in this study.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.