Surgical treatment for degenerative mitral stenosis associated with aortic valve stenosis: A case report

Abstract

We report a 73-year-old female who underwent mitral valve replacement for degenerative mitral stenosis (DMS) and aortic valve replacement for aortic valve stenosis. She was transferred to our hospital because of congestive heart failure. Transthoracic echocardiogram demonstrated severe mitral valve stenosis and aortic valve stenosis. Transesophageal echocardiogram (TEE) revealed severe mitral annular calcification (MAC) and calcification of the anterior mitral leaflet without commissure fusion. The diagnosis of DMS associated with MAC and aortic valve stenosis was made. Since she did not have other significant comorbidities except diabetes mellitus and hypertension, open-heart surgery for double valve replacement was scheduled by our heart team. Complete resection of the calcium bar and annulus reconstruction with an autologous pericardium allowed safe mitral valve replacement with a mechanical valve. Concomitant aortic valve replacement with a mechanical valve was carried out for aortic valve stenosis. Intraoperative TEE demonstrated good left ventricular function without perivalvular leakage in both mitral and aortic prosthetic valves. The postoperative course was uneventful, and the patient was discharged from the hospital. Surgical intervention may be one of the alternative treatments for elderly patients with degenerative mitral stenosis and MAC.

Learning objective

Degenerative mitral stenosis (DMS) associated with mitral annular calcification (MAC) is a severe heart valve disease in the elderly population in developed countries. The prognosis of patients with severe DMS is poor, and open-heart surgery for elderly patients with MAC is especially challenging from a surgical point of view. We report a surgical treatment for a patient with DMS and aortic valve stenosis considering the patient's comorbidities and extent of MAC.

Introduction

Degenerative mitral stenosis (DMS) associated with mitral annular calcification (MAC) is recognized as a severe heart valve disease in the elderly population in developed countries. Kuyama et al. documented the clinical characteristics of patients with DMS in Japan [1]. Common characteristics of the patients with DMS are old age, female sex, diabetes mellitus, hypertension, and aortic valve stenosis (AS). The prognosis of patients with severe symptomatic DMS is poor, but open-heart surgery for elderly patients with MAC is especially challenging from a surgical point of view. Moreover, elderly patients with DMS have several comorbidities, and medical treatment is a mainstay of therapy as the first step. In the case of severely symptomatic patients with DMS, the selection of invasive treatment is important. We report the surgical treatment for a patient with DMS and AS considering the patient's comorbidities and extent of MAC.

Case report

A 73-year-old female presenting with congestive heart failure was transferred from the outpatient clinic because of sudden onset of orthopnea. Chest X-ray demonstrated pulmonary congestion. Her heart had a normal sinus rhythm. Transthoracic echocardiogram demonstrated a normal left ventricular ejection fraction of 72 % [left ventricular end-diastolic (systolic) diameter (LVEDD) 34 mm, LVESD 18 mm], moderate to severe AS [peak velocity 3.9 m/s, max pressure gradient (PG) 61 mmHg, mean PG 33 mmHg] and severe mitral stenosis (MS) (peak velocity 2.9 m/s, max PG 34 mmHg, mean PG 15 mmHg, pressure half time 270 msec). After medical treatment for congestive heart failure, her chest computed tomography (CT) and coronary angiogram were studied. Coronary angiogram demonstrated severe calcification of both the left and right coronary arteries without significant stenosis. Chest CT demonstrated severe MAC along the posterior mitral annulus (Fig. 1a). Transesophageal echocardiography (TEE) demonstrated MAC of the posterior annulus and anterior leaflet calcification without commissure fusion (Fig. 1b). The diagnosis of DMS was made. Although surgical intervention is challenging, one of our authors, Yukikatsu Okada, has experienced >10 cases of mitral surgeries with MAC since 2002 [2], mitral valve replacement (MVR) associated with MAC resection followed by annulus reconstruction with a treated autologous pericardium and concomitant aortic valve replacement were scheduled. Median sternotomy and moderate hypothermic cardiopulmonary bypass were established. After aortic cross-clamping and aortotomy, calcified aortic valve cusps were gently resected. Then, the left atrium was entered through the interatrial groove. As the right half of the anterior mitral leaflet was calcified without calcification of the aortic curtain, the anterior leaflet was resected easily. As noted by Carpentier et al., decalcification was started by using a knife to incise the atrial endothelium around the borders of the calcium bar [3]. The base of the posterior leaflet was incised at the edge of the calcium bloc. Keeping the edge of the dissecting knife blade against the calcium allowed the attachment of the annulus to be sharply removed from the surrounding fibrous sheath. The mitral annulus was then reconstructed with a strip of a treated autologous pericardium by suturing it to the delimiting fibrous tissue of the left ventricle and atrium with a 4–0 monofilament suture in a mattress fashion [4,5] (Fig. 2, Fig. 3). After reconstruction of the mitral annulus, the left ventricular cavity was thoroughly washed with saline. The annulus size was measured carefully by a prosthetic sizer. As the annulus was 25 mm, a mechanical valve was selected to avoid left ventricular outflow obstruction and for prosthetic valve function. An SJM mechanical valve (Abbott, St. Paul, MN, USA) of 25 mm was implanted by using everting 2–0 pledget sutures. The left atrial appendage was closed by continuous mattress suture from the inside of the left atrium. Closure of the left atrium and aortic valve replacement using an SJM mechanical valve (Abbott) of 21 mm was also carried out safely. The aortic cross-clamp lasted 222 min. Intraoperative TEE demonstrated good function of the left ventricle and prostheses, without perivalvular leakage. The postoperative course was uneventful, and the patient was discharged from the hospital under insulin control.

Fig. 1.

(a) Chest CT demonstrated severe mitral annular calcification

(b) 3D color image of a mitral valve by transesophageal echocardiography

CT: computed tomography

AML: anterior mitral leaflet

PML: posterior mitral leaflet.

Fig. 2.

Keeping the edge of the dissecting knife blade against the calcium allowed the attachment of the annulus to be sharply removed from the surrounding fibrous sheath.

The mitral annulus was then reconstructed with a strip of a treated autologous pericardium (treated with 0.625 % glutaraldehyde, 15 min).

Fig. 3.

Intraoperative photographs at mitral annular reconstruction.

Discussion

DMS is a unique and newly recognized cause of mitral valve stenosis in developed countries. DMS patients are generally elderly, with multiple comorbidities, and are often high-risk candidates for open-heart surgery. Pasca and colleagues reported that DMS is a marker of poor survival [6]. The 5-year survival rate was 47 %, and worse with higher DMS grades. The patients are often elderly women (73 %) and often have coronary artery disease (49 %) or diabetes mellitus (50 %). Risk factors for higher mortality include greater age, atrial fibrillation, and renal insufficiency. Sud and colleagues reviewed DMS in terms of its epidemiology, pathophysiology, risk factors, cardiovascular events, diagnosis, and management [7]. They concluded that there is an unmet need for MVR among patients with DMS. Many patients with DMS are currently left untreated because of the presence of multiple comorbidities that significantly increase the risk of mortality with surgical MVR. The mainstay of therapy, therefore, is medical management with diuretic therapy. Surgical intervention or alternative percutaneous approaches might be delayed until symptoms become severe.

Bedeir and colleagues recently reviewed current and evolving strategies in the management of severe MAC [8]. They categorized the strategies concerning mitral annulus with MAC into 2 types: (1) decalcification with annular reconstruction – the “resect strategy” – and (2) avoiding annular decalcification – the “respect strategy”. The “respect” approach in valve replacement, including transcatheter mitral valve replacement (TMVR), has the disadvantage of higher perivalvular leaks that are less likely to heal. In the current era, the presence of MAC alone, regardless of severity, is independently associated with increased operative mortality and adverse postoperative outcomes, according to an analysis of the STS adult cardiac surgery database [9]. Kaneko and colleagues noted that centers with fewer than 50 mitral valve procedures per year were associated with increased operative mortality. Since our surgical team fortunately has experienced >10 cases of mitral surgery with MAC resection or respect approach since 2003 [2,6], our heart team decided to perform open-heart surgery. Patients with mitral stenosis, however, require valve replacement to enlarge the mitral orifice area with or without decalcification. MVR leaving calcium in the annulus brings a risk of developing significant perivalvular leakage even when making a suture of the sewing ring collar to the left atrial wall. Carpentier and colleagues noted that how to remove the calcium bar en bloc and how to reconstruct the mitral annulus systematically depend on the extent of the calcium bar [3]. David and colleagues reported using a strip of autologous pericardium or xenopericardium to reconstruct the mitral annulus after removal of the calcium bar [4]. We believe that mitral annulus reconstruction using an autologous pericardium is helpful to reduce the suture tension at the new mitral annulus [2,6]. A redundant autologous pericardium is essential to apply this technique to avoid perivalvular leakage as well. Carpentier and colleagues noted that the MAC was located in an encapsulated way along the posterior annulus in 78 % of patients. In such cases, the extent of MAC, compared with that in previous cases, was judged to be limited and encapsulated, and calcium removal and annulus reconstruction with an autologous pericardium were successfully carried out as expected. Although the “resect” approach is technically challenging, MVR associated with decalcification may be a good alternative procedure for selected patients with DMS in experienced centers, depending on the MAC extent. In this patient, we selected a mechanical valve. Aboul-Hassan and colleagues reviewed the patient–prosthesis mismatch (PPM) in mitral valve replacement [10].

They suggested that PPM (defined as indexed effective orifice area < 1.2 cm²/m²) in patients undergoing MVR was associated with increased postoperative mean and peak trans-mitral gradient and higher postoperative systolic pulmonary artery pressure. PPM may be associated with increased long-term mortality. This patient's mitral annulus diameter was 25 mm, and body surface area was 1.53 m². If a certain 25 mm bioprosthetic valve were used, indexed effective orifice area would have been approximately 1.07 cm²/m², which could have resulted in PPM.

Furthermore, the patient had a small left ventricle (LVEDD 34 mm, LVESD 18 mm). Considering hemodynamic performance through the mitral prosthetic valve and its stent post, we determined that a mechanical valve was preferable to a bioprosthetic valve in a patient with a small left ventricle.

Conclusions

We report the case of a patient who underwent surgical intervention for degenerative mitral stenosis and MAC. Total en bloc resection of MAC followed by annulus reconstruction and valve replacement is a reliable and safe surgical procedure. Surgical intervention may be one of the alternative treatments for elderly patients with degenerative mitral stenosis and MAC.

Consent statement

Written informed consent was obtained from the patient.

Declaration of competing interest

The authors declare that there is no conflict of interest.