Continuing Education Activity
Mitral valve commissurotomy is the technique used to repair mitral valve stenosis. Mitral stenosis is most commonly due to rheumatic heart disease. There are multiple techniques used for the repair of mitral stenosis. The closed technique which does not use cardiopulmonary bypass was very popular in the past but this has been replaced with either open repair with cardiopulmonary bypass or the percutaneous method which uses balloon dilation of the valve. This activity reviews the procedure and indications of mitral valve commissurotomy and highlights the role of the interprofessional team in carrying out this procedure successfully.
Objectives:
- Identify the indications for performing mitral commissurotomy.
- Describe the equipment, personnel, preparation, and technique in regards to repair of mitral stenosis using mitral commissurotomy.
- Outline appropriate evaluation of the potential complications of mitral valve stenosis repair using mitral commissurotomy.
- Review interprofessional team strategies for improving care coordination and communication to advance the repair of mitral valve stenosis and improve outcomes.
Introduction
Mitral valve commissurotomy is a surgical technique used in the treatment of mitral stenosis. Mitral stenosis occurs from a multitude of different etiologies but is most commonly due to rheumatic heart disease, which leads to commissural fibrosis. The commissurotomy can be performed through many approaches, including an open, closed, and even percutaneous ballooning technique. The closed technique for repair was used for several years, but this has slowly changed to open repair and, more recently, to percutaneous technique. A skilled physician should have both techniques for mitral stenosis repair in their armamentarium but, most importantly, know when to use them throughout the evolution of mitral stenosis.
Anatomy and Physiology
The mitral valve (MV) is a very complex bicuspid valve that functions as the inlet to the left ventricle. The normal mitral valve consists of two leaflets, an anterior and posterior leaflet, which are attached by chordae tendineae to two papillary muscles. The papillary muscles are positioned in the superolateral and inferoseptal positions; they attach to the left ventricular walls and prevent the leaflets from prolapsing during ventricular systole. The anterior leaflet is short and covers around one-third of the valve orifice. The anterior leaflet is also called the aortic leaflet as it is in fibrous continuity with the aortic valve. The posterior leaflet, also known as the mural leaflet, covers two-thirds of the mitral orifice. The coronary sinus lies just to the right of the posterior leaflet while the circumflex coronary artery lies to the left of the posterior leaflet; these vessels can be easily damaged by the excessive force on the valve or improper placement of sutures.
Mitral Stenosis
- Mitral stenosis (MS) occurs most commonly due to rheumatic heart disease. The Western world has seen a drop over the course of the last several years, but it has recently been on the rise again due to immigration from non industrialized countries.[1] The prevalence of rheumatic heart disease remains persistent in developing countries, with nearly 7/1,000 children having this disease.[2] The main reason mitral stenosis occurs is due to commissural fusion, which causes the leaflets to become fused together, leading to mitral stenosis. Stenosis of the valve usually occurs years after the rheumatic heart disease has occurred. Rheumatic heart disease can cause deposits along with the mitral valve apparatus, which over time, causes thickening with calcifications, ultimately leading to commissural adhesions/fibrosis, which causes stenosis of the valve. One of the first consequences of mitral stenosis is increased mitral valve diastolic gradient, which depends on the valve area. The increase in the mitral gradient causes the left atrial pressure to increase, therefore overtime causing a dilated left atrium. A dilated left atrium can lead to an increased risk of atrial fibrillation. The other consequence of MS with a dilated left atrium is the risk of developing left atrial thrombus, especially in the appendage of the left atrium. Over time, chronic MS can lead to pulmonary hypertension due to elevated pulmonary artery pressures secondary to elevated left atrial pressure. Chronic pulmonary hypertension can lead to right heart failure with associated right ventricular hypertrophy with dilation and the possible involvement of the tricuspid valve. The tricuspid valve can be involved due to rheumatic involvement or secondary to the consequences of MS.
- MS can also be caused by congenital abnormalities which cause defects in the subvalvular apparatus such as a parachute mitral valve.
- Other etiologies of MS include infective endocarditis, systemic lupus erythematosus, carcinoid disease, rheumatoid arthritis, Whipple disease, Fabry disease, Hunter-Hurler mucopolysaccharidoses, endocardial fibroelastosis, chest radiation, and treatment with methysergide.
- Other valvular lesions such as degenerative aortic stenosis can cause calcific extension that extends into the mitral valve; this can cause mitral annular dilation with calcification of the leaflets, which can eventually cause nonrheumatic mitral valve stenosis.
- The presentation of other diseases can mimic mitral stenosis, such as Cor triatriatum can present as mitral stenosis in adults[3], left atrial myxoma, or pulmonary vein stenosis.
- There are several ways to assess the severity of mitral valve anatomy based on two different scoring systems. The Cormier score uses three groups to base the severity of the mitral valve anatomy while the Wilkins score uses four grades to assess the mobility, thickening, calcification, and subvalvular thickening of the mitral valve.
Presentation
- Patients often present with fatigue, dyspnea, orthopnea, or even paroxysmal nocturnal dyspnea. Patients may also present with a multitude of symptoms due to left atrial dilation, such as atrial fibrillation, dysphagia due to esophagus compression, and even more rare hoarseness consistent with Ortner syndrome (compression of the recurrent laryngeal nerve). Patients may also have peripheral edema or ascites due to chronic valve disease causing pulmonary hypertension.
Physical Exam
- MS may have an irregular low volume pulse, and when listening to cardiac sounds, one may hear a loud S1 with a mid-diastolic rumbling murmur heard best at the apex. The murmur intensity is based on the severity of the mitral valve gradient.
- EKG- MS may show normal sinus rhythm, but advanced MS may show wide p waves that are notched that appear M shaped.
Imaging
- CXR may show left atrial enlargement
- Cardiac echo is the mainstay of diagnosis. Echocardiography will allow the evaluation of the entire valve, leaflets, annular size, left atrium size, and left ventricular function. It will also assist in evaluating pulmonary hypertension and measuring the valve gradient. The parasternal short axis view gives the best viewpoint for planimetry, which allows measurement of the mitral valve area. This view also allows viewing for commissural fusion. Long axis views will give the best viewing of the subvalvular apparatus along with the best views of the anterior and posterior leaflets. The best view for evaluation of the MV is through the parasternal long and short-axis views.
- The “hockey stick” sign is seen when the anterior mitral leaflet has restricted leaflet motion.[4]
- The mitral valve area can also be assessed by measuring the pressure half time; this is best calculated using the four-chamber cardiac view. The apical view is best to measure the mean pressure gradient across the valve.
- When reviewing mitral valve parameters, one single value does not change the severity of the disease; all the values matter toward the overall valve morphology, including the mitral valve area, a mean gradient across the valve, and the systolic pulmonary artery pressure.[5]
Classifications of Mitral Stenosis
European Guidelines
- Mild
- Valve area >1.5 cm^2, mean gradient <5 mmHg, systolic pulmonary artery pressure <30 mmHg
- Moderate
- Valve area 1.0-1.5 cm^2, mean gradient 5-10 mmHg, systolic pulmonary artery pressure 30-50 mmHg
- Severe
- Valve area <1.0 cm^2, mean gradient >10 mmHg, systolic pulmonary artery pressure >50 mmHg
American Heart Association Guidelines
- Progressive MS
- Valve area >1.5 cm^2, diastolic pressure half-time <150 msec
- Severe MS
- Valve area ≤1.5 cm^2, diastolic pressure half time ≥150 msec
- Very Severe MS
- Valve area <1 cm^2, diastolic pressure half time >220 msec
Contraindications
Mitral valve commissurotomy is a surgical technique and cannot be carried out in patients who are unable to tolerate systemic anticoagulation or if there is an underlying bleeding disorder with coagulopathy.
Contraindications to percutaneous balloon valvotomy of the mitral valve include the following:
- Concomitant mitral valve regurgitation that is moderate to severe
- Excessive calcification of the mitral valve
- Commissural calcification
- Presence of thrombus in the left atrium
- Mitral valve area of more than 1.5 cm^2
- Concomitant severe aortic valve disease
- Coronary artery disease requiring coronary artery bypass grafting
- Combined tricuspid valve stenosis and regurgitation
- Cardiothoracic deformity
Equipment
The required equipment is largely based on the type of technique used. For percutaneous technique the following prerequisites are needed:
- Multiple wires and sheath sizes
- Cath lab/hybrid room with fluoroscopy
- Transthoracic echocardiography and transesophageal echocardiography machine
- Mitral valve repair device
- Code cart
- Sterile gown and gloves, sterile drape
- Anesthesia
- The operative cardiac surgical team and open surgical trays
- XRay lead
The open technique requires the following:
- The operative cardiac surgical team and open surgical instruments
- Transthoracic echo
- Transesophageal echo
- Code cart
- Anesthesia
- Sterile gown and gloves
Preparation
Before undergoing percutaneous or open mitral valve repair for mitral stenosis, the patient will need a complete workup with labs, imaging, and full history with a physical exam. The patient will need a 2-D cardiac transthoracic echo to evaluate the entire heart to rule out other possible surgical interventions while in the operating room. A transesophageal echo is mandatory prior to scheduling a percutaneous mitral valve balloon valvuloplasty to rule out any left atrial thrombus, the severity of any mitral regurgitation, or any other valve abnormality.
A cardiac structural specialist may be necessary to view the echo. You must review all echo studies and discuss the best approach for your patient not only based on the valve pathology but also on their lung function, pulmonary pressures, body surface area, and cardiac/non-cardiac functional disability. All surgical procedures, whether performed in the hybrid room or operating room, should be performed within a sterile field with all precautions taken to maintain sterility.
Technique or Treatment
Open Mitral Valve Commissurotomy
It has long been considered the gold standard for mitral valve stenosis repair.[6] The surgical outcomes of the percutaneous technique have not been around as long as open or closed techniques; therefore, multiple studies have shown that an open technique yields excellent results. This technique allows the surgeon to have direct visualization of the entire mitral valve. This technique uses cardiopulmonary bypass, whereas the closed technique can avoid going on bypass. Over the years, multiple studies have shown this to be a safe technique with excellent outcomes for open commissurotomy.[7]
Technique
The open technique uses a median sternotomy to gain access to the chest, but a right or left thoracotomy can be used to gain access to the mitral valve. A right thoracotomy incision and femoral cannulation will allow the surgeon to avoid midline sternal incision if there is a history of previous thoracic surgery via a sternotomy. After the chest is opened, the patient is placed on cardiopulmonary bypass with cannulation of the aorta, bicaval venous cannulation, and administration of cardioplegia. Once the cardiopulmonary bypass is established, the left atrium can be opened. Exposure of the mitral valve can be performed in many ways; there are three possible approaches: Interatrial groove approach, transatrial oblique approach, or transatrial longitudinal septal approach. Each approach to the mitral valve has its own pros and cons. Once the mitral valve is reached and properly exposed, two polypropylene sutures are placed to provide slight traction upward toward the superior left atrium. If sutures are not placed, nerve hooks can provide upward traction. This maneuver allows exposure of the mitral leaflets, which in return shows the line of mitral commissural fusion.
Once the line of mitral fusion is noted, one should try to examine the chords and papillary muscles through the mitral orifice. One should look for any evidence of calcification, shortening, or fusion to the subvalvular apparatus. A right-angle clamp can then be passed through the orifice and placed gently below the fused mitral commissures. The clamp can then be opened slightly so that a # 15 blade scalpel or # 11 blade scalpel can be used to cut on the commissures without damaging the structures below. With the clamp open, the first incision is made 5 mm from the annulus on top of the clamp, cutting downward into the fused chords and papillary muscle, this incision is extended toward the mitral orifice. If the incision does not enter the head of the papillary muscle, this can cause division of the papillary muscle, and repair or reimplantation would be necessary. The commissurotomy can not be overextended, or this may cause mitral valve incompetence. If valve incompetence is caused, then an annuloplasty of the ring or commissuroplasty may need to be performed. Once the commissurotomy is completed, the patient can be taken off bypass, and a post-procedure transesophageal echo can be obtained.
Closed Mitral Valve Commissurotomy
It was very popular for mitral valve stenosis repair since the 1920s. It has been widely used throughout the world and continues to be used in developing countries. Closed mitral valve commissurotomy is rarely performed in the United States due to the success of the open technique with cardiopulmonary bypass. This technique remains useful in select subgroups of patients even though there is no direct visualization of the mitral valve. Closed mitral commissurotomy remains a predominant technique in developing countries due to the low cost and the simplicity of the surgery compared to the open technique. The closed technique can now be performed through a small thoracotomy incision with port placement via guidance with transesophageal echo.[8]
Technique
A closed mitral valve commissurotomy is performed either through a left posterolateral or anterolateral thoracotomy at the level of the 5th rib. The lung is then retracted in the posteroinferior position. An incision is made parallel to the phrenic nerve, and the pericardium is opened then traction sutures are placed. The left atrial appendage is then excluded with a side biting clamp, and a left atrial polypropylene purse-string suture is placed. A second purse-string suture is placed with pledgets at the apex of the left ventricle.
The left atrial appendage is then opened, and the index finger is placed into the left atrium; the mitral valve is palpated to feel for any calcification, stenosis, or insufficiency. Prior to placing a finger into the left atrium, thrombus should be palpated; if the clot is palpated, then it should be excluded using the clamp. The thrombus can then be removed after exclusion with the clamp. If the thrombus can not be removed after the clamp is applied, this is a major indication to abort the closed technique and convert to an open technique with the initiation of cardiopulmonary bypass. When the finger is introduced into the left atrial appendage, it should not be placed for more than 2 to 3 cardiac cycles. If placed for longer than 2 to 3 cardiac cycles, this can produce dysrhythmia, which can lead to cardiac arrest. Once the index finger is placed into the left atrium, the heart can be elevated by bringing the apex of the left ventricle into view. A #11 blade scalpel is used to make a small ventriculotomy inside the purse-string suture, which was placed earlier in operation. Once the ventriculotomy is made, Hagar dilators are used until the Tubb valvulotome can be passed through the left ventricle passing through the mitral valve into the left atrium.
The Tubb valvulotome is opened quickly to an exact preset measurement of 3.5 to 4.5 cm, closed quickly, and then removed from the heart. After the finger is removed from the left ventricle, the purse string is tied down over pledgets. When passing the Tubb valvulotome, it must not be opened prematurely as this can cause damage to the mitral subvalvular apparatus and result in mitral insufficiency. If the Tubb dilator is not able to fully dilate the mitral valve, this is an indication for an open commissurotomy. Any time a patient is undergoing closed commissurotomy, the patient should have cardiopulmonary bypass at the bedside in the OR in case it is urgently needed. Once the procedure is completed, as all post-op valve procedures are done, a cardiac echo is needed to measure the valve area, pressures of the left atrium/pulmonary pressures, and the degree of mitral regurgitation that was caused.[9] Studies have shown excellent valve area that is gained with the added benefit of no cardiopulmonary bypass when using the closed technique.[10]
Percutaneous Mitral Valve Commissurotomy
The percutaneous mitral valve technique is the standard treatment used to treat MS patients with favorable valve anatomy. The technique was first introduced in the mid-1980s. Today it is now the standard first-line treatment for patients that meet the criteria for balloon dilation of the valve. Patient selection is very important when deciding which option to offer patients for repair, but one must always take into account the valve anatomy and experience of the surgical team. The percutaneous technique offers excellent 15-year outcomes when used in younger patients that had more valve area prior to intervention.[11]
The percutaneous technique had multiple options for balloon dilation of the mitral valve. In the past, a double-balloon technique has been used, but over the years, we have trended to the use of an Inoue balloon. The Inoue balloon is easier to use from a technical standpoint, and it has a lower complication rate compared to the double-balloon technique.[12] When patients are done with their percutaneous intervention, the majority have immediate hemodynamic benefits as the procedure offers an increase in the overall mitral valve area and a decrease in the overall mitral valve gradient. After the percutaneous intervention, the majority of patients that presented with an NYHA class 3 when reexamined at follow up appointments had an NYHA 2 classification. The percutaneous technique acts very similarly to the open technique in that the commissures are split open by opening the balloon inside in the stenotic valve.
- Pregnancy can often unveil a previously compensated MS. The pregnancy often increases the cardiac output and causes associated tachycardia, which increases during the second trimester. This major change in fluid status and worsening of the mitral valve stenosis can lead to heart failure symptoms in pregnant patients; this is why they should be treated with percutaneous mitral valve valvuloplasty.[13] The goal of mitral valve intervention is not for full repair but to overall improve the hemodynamic status of the patient.[14]
Technique
The groin is prepped/draped in the usual sterile fashion, and the femoral vein is accessed under ultrasound guidance. After access to the vein, the sheath and wire are placed with the placement of the wire into the right atrium. Transseptal catheterization into the left atrium is the most important step in the procedure. The Inoue balloon is then placed through the septum into the left atrium. The balloon itself has three different parts, all with different elastic strengths that can be inflated consecutively. The balloon ranges in size from 24 to 30 mm. The choice of balloon size is based on the patient's current height and body surface area or maximal size of the inter commissural distance.[15]
After the balloon is in position across the valve, the balloon is inflated under echocardiographic guidance. The balloon is inflated in a sequential fashion, starting with the smallest size of the balloon. Once the valve has been dilated, the balloon is withdrawn into the left atrium, and the valve is checked from any increase in the valve area and any degree of mitral regurgitation.[16]
If the valve area is not sufficient the balloon can be readvanced with further dilation of the valve. Once the valve has been dilated and the echo shows desirable results such as a mitral valve area of more than 1 cm^2/m^2 of body surface area, completely opening of at least one of the commissures, or an increase in the regurgitation across the valve, the procedure can be completed. The echo should be performed again in several days due to a slight valve area loss that occurs over the next 24 to 36 hours. This technique has shown through multiple studies that it provides excellent improvement of valve area, decrease in left atrial pressures, improves coronary flow, and can increase cardiac index.[17]
Complications
The complications associated with mitral valve repair are very similar in open repair or transcatheter percutaneous repair. Mortality of mitral valve repair in recent studies has shown zero deaths related to repair and overall less than 3% complication rate. The following are some important complications:
- Catheter-related complications to access the site, such as hematoma, arteriotomy, dissection, arteriovenous fistula
- Stroke
- Myocardial infarction due damage or irritation to the left coronary artery
- Perioperative bleeding and resulting blood products transfusion-related complications
- Mitral regurgitation
- Pericardial tamponade
- Arrhythmias and heart blocks
- Heart failure
- Drug reactions
- Surgical site infections
- Sepsis
- Pulmonary complications, such as pneumothorax, pneumonia, embolisms
- Renal failure due to concomitant use of contrast dye
Clinical Significance
Mitral stenosis is a significant disease process that affects millions of people worldwide. With more safe options for treatment and better overall operative rates with newer technology, we can now help treat patients with percutaneous intervention in those who have suitable valve anatomy. Untreated MS causes the patient's morbidity and mortality, especially when combined with other cardiac or pulmonary disease processes. When the finding of MS arises, it should be addressed if surgical intervention is warranted. We need to continue to monitor outcomes of both open vs. percutaneous mitral valve repairs to continue to gain knowledge of what changes we need to make to help guide the future of rheumatic mitral heart disease.
Enhancing Healthcare Team Outcomes
Mitral valve stenosis is a disease process usually caused by rheumatic fever. Mitral valve commissurotomy is the procedure of choice for the treatment of mitral valve stenosis. This entire disease process should be managed with a multidisciplinary team from the time the stenotic valve is diagnosed and, most importantly, throughout the entire surgical management. As mitral valve surgery advances, it is essential to have interprofessional teams that are close in communication with the management of patients to help advance the field and decrease morbidity and mortality.
An interprofessional team should include an anesthesia team, cardiologists, cardio-thoracic surgeons, and cardiac intensivists. Preoperative echocardiographic evaluation of the mitral valve requires coordination between the ultrasound sonographer and the cardiac surgery team. The intraoperative repair of the valve requires closed-loop communication between the cardiac surgeon, anesthesiologist, cardiologist, circulating nurse, and OR techs.
Nursing, Allied Health, and Interprofessional Team Monitoring
Nurses, technicians, and physicians of multiple specialties all play a major role in monitoring the patient. These roles require excellent interprofessional communication between all teams involved. The entire operative course from pre-operative, intra-operative, and post-operative management of the patient requires a skilled team.
Mitral Commissurotomy