Transseptal Mitral Valve Replacement after Transcatheter Aortic Valve Implantation

Abstract

We report a case of mitral valve replacement in a patient who had previously undergone transcatheter aortic valve implantation. A transseptal approach was used to avoid displacing the aortic prosthesis. Because of the small mitral annulus, a bioprosthetic aortic valve was used in reverse position for mitral valve replacement. The procedure did not interfere with the existing prosthesis, and a follow-up echocardiogram showed that both prosthetic valves were functioning well.

To the best of our knowledge, this is the first report of mitral valve replacement in a patient who had a preceding transcatheter aortic valve implantation. We believe that the transseptal approach is promising for mitral valve replacement in such patients. Moreover, using a bioprosthetic aortic valve in reverse position is an option for mitral valve replacement when the mitral annulus is too small for placement of a standard bioprosthetic mitral valve.

Transcatheter aortic valve implantation (TAVI) is currently emerging as a valuable option to treat high-risk patients with severe, symptomatic aortic stenosis.¹ The number of patients receiving TAVI has increased dramatically over a short period of time because of the promising advances in this new technology and the growing number of high-risk, elderly patients with multiple comorbidities, who are better suited for a minimally invasive procedure. Consequently, cardiac surgeons must care for an increasing number of patients who have undergone TAVI. Subsequent cardiac procedures in the setting of previous TAVI pose a challenge due to the risks of procedural interference with—and postprocedural functional impairment of—the previous aortic prosthesis. The following case illustrates an effective method of performing a mitral valve replacement in the setting of previous TAVI.

Case Report

In January 2011, an 85-year-old woman presented at the hospital with symptoms of chest pain, fatigue, and shortness of breath. Her medical history consisted of atrial fibrillation, hypertension, coronary artery disease, congestive heart failure with normal left ventricular function, mitral regurgitation (MR), and aortic stenosis treated by TAVI six weeks earlier. On echocardiography before TAVI, the patient had shown moderate MR due to calcification in the medial aspect of the posterior mitral valve annulus. This calcification between the P2 and P3 scallops restricted movement, as seen on preoperative transesophageal echocardiography (Fig. 1). The MR had been stable on a postoperative echocardiogram before she was discharged after TAVI.

Fig. 1 Transesophageal echocardiograms before transcatheter aortic valve implantation. A) Three-dimensional view shows thickened mitral leaflets before transcatheter aortic valve implantation. Mid-esophageal 4-chamber views with color-flow Doppler show B) preoperative centrally directed moderate mitral regurgitation, which C) has not changed immediately after transcatheter aortic valve implantation.

During the acute presentation, a transesophageal echocardiogram (Fig. 2) revealed severe, acute MR attributed to a flail segment between the P1 and P2 scallops—the result of newly ruptured mitral chordae tendineae. The echocardiogram also revealed mild concentric left ventricular hypertrophy; however, left ventricular size was normal, and the left ventricular ejection fraction was >0.70. The left atrium was moderately dilated, and severe pulmonary hypertension was present. The aortic prosthesis was functioning normally. The patient's increasing shortness of breath and other signs of congestive heart failure were attributed to the ruptured chordae. A trial of medical therapy failed, and she was offered mitral valve replacement one month after her acute presentation.

Fig. 2 Transesophageal echocardiograms 6 weeks after transcatheter aortic valve implantation. A) Mid-esophageal 4-chamber view shows a flail mid-posterior mitral leaflet (arrow). B) Three-dimensional view shows a flail mid-posterior mitral leaflet (arrow). C) Three-dimensional view with color-flow Doppler shows anteriorly directed severe mitral regurgitation.

Surgical Procedure

With the patient under general anesthesia on standard monitoring, a full sternotomy was performed. Ablation therapy for atrial fibrillation was first performed using bipolar radiofrequency. Standard cardiopulmonary bypass was then initiated. The heart was arrested with cold-blood cardioplegic solution. An incision into the right atrium was carried onto the dome of the left atrium. We then made an extended transseptal incision, taking care not to displace the aorta² (Fig. 3). The mitral valve was exposed. Because of extensive calcification extending into the body of the left ventricle and a very small mitral annulus, the commercially available mitral prostheses were found to be too large. Consequently, a 23-mm Carpentier-Edwards Magna® bioprosthetic aortic valve (Edwards Lifesciences LLC; Irvine, Calif) was used in the reverse position. The native valve was left in place in order to avoid entry into the posterior wall, which was a major concern given the extent of calcification extending into the ventricular wall. The bioprosthetic valve displaced the native valve leaflets outward. Stitches were placed in the softest areas of the annulus, and great care was used neither to impale the aortic bioprosthesis with the needles nor to displace it with traction. After placement of the valve, the patient was weaned from cardiopulmonary bypass and decannulated. Transesophageal echocardiography performed in the operating room indicated no residual MR, a left ventricular ejection fraction of 0.60 postoperatively, and good conformity of the bioprosthetic valve with the mitral annulus. The echocardiogram also showed that the aortic prosthesis was functioning well (Fig. 4).

Fig. 3 Drawings show A) incision into the right atrium carried onto the dome of the left atrium, with care taken to preserve some tissue near the aortic root; B) the atrial septum opened in the fossa ovalis and carried up the septum; and C) traction sutures used to hold open the left atrium, with care taken not to displace the aortic root and bioprosthetic aortic valve.

AO = aorta; CS = coronary sinus; IVC = inferior vena cava; LA = left atrium; MV = mitral valve; RA = right atrium; RV = right ventricle; SVC = superior vena cava; TV = tricuspid valve

Fig. 4 Transthoracic echocardiogram (parasternal long-axis view) after the mitral valve replacement shows well-seated aortic and mitral prostheses with normal function.

The patient had an uneventful postoperative course except for needing temporary pacing for junctional bradycardia. A transthoracic echocardiographic reevaluation performed one month after surgery showed an ejection fraction of 0.50 to 0.55 and good functioning of both prosthetic valves.

Discussion

We describe a case in which we used a transseptal approach to mitral valve replacement, implanting an aortic valve in reverse position in a patient who had undergone TAVI two months earlier. To the best of our knowledge, this is the first report of mitral valve replacement in a patient who had a preceding TAVI. Mitral valve repair or replacement is the standard treatment option for a patient with severe, symptomatic MR.³ The standard surgical approach for a mitral valve replacement is via a left atriotomy; however, a transseptal approach via a right atriotomy has been favored for specific cases, such as patients with a small left atrium, friable tissues, heavily calcified mitral valves, or the need to undergo combined tricuspid and mitral procedures.^2,4,5 We believe that previous TAVI should be added to this list. The transseptal approach in this case enabled excellent visualization and successful replacement of the mitral valve without disrupting the aortic prosthesis. In addition, the lack of adhesions afforded by the previous TAVI facilitated our approach to the left atrium during mitral valve replacement.

The patient was initially considered for mitral valve replacement with a standard mitral bioprosthesis. However, due to the small mitral annulus, we decided to position a 23-mm Carpentier-Edwards Magna bioprosthetic aortic valve in reverse position. This resulted in marked hemodynamic and clinical improvement in comparison with the preoperative performance.

Mitral regurgitation is frequently associated with aortic stenosis. Moderate to severe MR has been reported in 18% to 48% of patients undergoing TAVI.^6–8 After surgical aortic valve replacement, MR has been shown to improve spontaneously in 27% to 82% of patients.^9–21 After TAVI, one study of 46 patients showed that MR remained unchanged in 61% of patients, improved in 17%, and worsened in 22%.⁸ A study of 35 patients found that mitral annular calcification that encroaches onto the leaflets, causing restricted leaflet motion, was the only variable associated with a lack of MR improvement after TAVI.²² More research is required to determine the relationship between TAVI and change in MR as well as to elucidate the exact factors that predict improvement in MR after TAVI. In our patient, it was not persistent MR but ruptured mitral valve chordae (which led to worsening MR 6 weeks later) that necessitated the mitral valve replacement.

In conclusion, the transseptal approach is a promising method for mitral valve replacement in a patient who has previously received an aortic prosthesis through TAVI. Moreover, using a tissue aortic valve in reverse is an option for mitral valve replacement when the size of the mitral annulus is not suitable for placement of a standard prosthetic mitral valve.

Acknowledgment

We wish to thank Mr. David Hayes for rendering the sketches of the surgical approach.