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Percutaneous Mitral Balloon Valvotomy for Mitral Stenosis


Percutaneous Mitral Balloon Valvotomy for Mitral Stenosis

Mitral stenosis (MS) is a ,disabling and eventually lethal disease. Significant symptoms such as, fatigue and dyspnea and serious complications such as pulmonary hypertension pulmonary edema and systemic embolism may result if this progressive disease is left untreated.

Rheumatic heart disease is the major cause of this disease in adults, with symptoms appearing 16 to 40 years after the acute rheumatic fever episode. Medical therapy doesn’t affect the obstruction to flow, despite the fact that it can relieve symptoms. Because of this, MS could be corrected with either surgical commissurotomy, or open valvuloplasty for many years. However, the treatment of this disorder was revolutionized thanks to the development of PMBV (percutaneous mitral balloon valvotomy) by Inoue in 1984 and Lock in 1985. In this article, we will review the efficacy of PMBV, including comparison with surgery, and the management of patients with MS undergoing PMBV.

 

CHOICE OF PMBV:

Rheumatic MS:

Patients for PMBV are selected on the basis of hemodynamic and echocardiographic criteria. Usually, PMBV is performed in chronically symptomatic patients but it could also be performed in patients who present emergently with cardiac arrest, pulmonary edema, or cardiogenic shock. This surgery could also be performed in asymptomatic patients who plan on childbearing or major noncardiac surgery. Prophylactic valvotomy for the prevention of systemic emboli or atrial fibrillation isn’t a firmly established criterion.

 

In cases when intervention is warranted, the 2006 ACC/AHA guidelines have recommended that PMBV is preferred to surgery in case the valve morphology is favorable and the patient doesn’t have moderate to severe (3+ to 4+) mitral regurgitation or left atrial thrombus. The main indication of PMBV among asymptomatic patients was evidence of pulmonary hypertension at rest or with exercise, and moderate to severe MS (valve area ≤ 1.5 cm2). In 2007, the European Society of Cardiology made similar recommendations.

 

In patients with multiple comorbidities or other conditions that preclude surgical valve replacement, consensus guidelines haven’t addressed patient selection for PMBV to palliate symptoms. In these circumstances, meaning in the absence of left atrial thrombus or moderate to severe mitral regurgitation, PMBV is usually performed in spite of moderate to advanced deformity of the valve that would otherwise be considered inappropriate or suboptimal for the procedure.

 

The role of MS in the patient’s clinical condition, the goals of therapy in the palliative setting, technical constraints, and the patient’s own preferences for symptom relief are some of the factors that could influence the decision to perform PMBV in such patients.

 

Congenital MS:

Patients who have rheumatic MS are usually the ones that undergo PMBV. The efficacy of PMBV is limited in patients with significant stenosis of the subvalvular apparatus and the catheterization procedure is potentially dangerous. Additionally, there’s only little experience with PMBV in congenital MS. Only at centers with established experience and skill and only in selected patients should PMBV be considered.

 

MS due to mitral annular calcification:

Mitral annular calcification (MAC) could result in mitral regurgitation and in rare cases, mitral stenosis; but generally, MAC is a benign process that is commonly seen in the elderly. When the calcification extends into the mitral inflow, a gradient may be produced resulting in mitral stenosis, but usually, annular calcification alone doesn’t cause mitral stenosis. Mitral annular calcification won’t be amenable to balloon valvotomy in case it has caused mitral stenosis.

 

Echocardiography:

In patients who seem to be candidates for PMBV, echocardiography is an essential screening procedure.

 

Valvular anatomy:

After evaluating the extent of valvular and subvalvular deformity, the likelihood of a successful result after PMBV can be assessed by assigning a score of 0 to 4 for each of these four factors:

 

  • Degree of leaflet rigidity
  • Severity of leaflet thickening
  • Amount of leaflet calcification
  • Extent of subvalvular thickening and calcification

 

The maximum score is 16; more severe anatomic disease and a lower likelihood of a successful balloon valvotomy with durability is indicted by higher scores.

 

Intracardiac echocardiography (ICE):

In this procedure, an ultrasound-tipped catheter is inserted intravenously and is manipulated within the heart. A preliminary observations study has suggested that ICE may detect more extensive subvalvular disease than suggested by TTE or TEE and therefore may improve patient selection for PMBV versus surgery; however, this currently isn’t an accepted part of the diagnostic strategy for the evaluation of patients with mitral stenosis. During a valvotomy procedure, this technique could be used for monitoring.

 

Left atrial thrombus:

Due to the risk of dislodging the thrombus during the procedure, the presence of left atrial or left atrial appendage thrombus is a contraindication to PMBV. In patients with MS, such thrombi aren’t uncommon. Partly, it seems that the prevalence is related to whether or not the patients have been treated with warfarin. Because of this, in a study from Scotland in which almost all patients had been treated with warfarin, the prevalence of left atrial thrombus was 13% in two series of patients referred for PMBV, compared to the 32% in a report from Thailand that excluded patients who had been treated with warfarin more than 72 hours before study entry.

 

We agree with the 200 AHA/ACC valvular disease guideline and the 2008 ACCP (American College of Chest Physicians) guideline recommendation to perform preprocedural transesophageal echocardiography (TEE) to exclude left atrial thrombus in patients who are being considered for PMBV.  We recommend postponement of the procedure and administration of anticoagulant therapy (target INR 3.0, range 2.5 to 3.5) until thrombus resolution is documented by repeat TEE in case the preprocedural TEE reveals left atrial thrombus. We also recommend that PMBV not be performed if surgery is feasible in case left atrial thrombus doesn’t resolve with anticoagulant therapy.

 

Transesophageal echocardiography (TEE):

This procedure is more sensitive than transthoracic echocardiography (TTE) for the detection of left atrial thrombus. In a series of 474 patients undergoing mitral valve surgery in which the sensitivity and specificity of TTE were 32 and 94%, this difference was illustrated. In contrast, the sensitivity and specificity of left atrial cavity thrombi was 81% and 99%, and for left atrial appendage thrombi were 98% and 98%. TEE is recommended prior to PMBV as a result to this.

 

Six months of anticoagulation and then repeat TEE to evaluate for resolution of thrombus should be included in the treatment of patients in whom left atrial thrombus is seen on TEE. In a report of 219 patients from Thailand, the frequency with which this occurs was assessed. Oral anticoagulation was initiated to maintain an INR of 2.0 to 3.0. Thrombus was no longer detectable in 53 patients (24%), after six months. Better NYHA functional class (I or II), thrombus size ≤ 1.6 cm2 and confined to the left atrial appendage, less marked left atrial spontaneous echocardiographic contrast, and maintenance of a mean INR ≥ 2.5 were some of the variables that predicted thrombus resolution. There was a 94% incidence of complete thrombus resolution in the patients who had all of these predictors. In a study from India, oral anticoagulation was given for up to six months to 66 patients who had MS and left atrial thrombus. Complete resolution of thrombus was seen on TEE in 22 patients (33%) and organization in 38 (58%); only six patients (9%) had no change in thrombus appearance.

 

Some of the patients with left atrial appendage thrombus that were found on TEE immediately prior to planned PMBV are too symptomatic to wait six months. A shorter duration of anticoagulation could be tried in these patients prior to repeat TEE. In patients who are unable to tolerate an adequate duration of anticoagulation, surgical mitral valve repair or replacement with left atrial appendage ligation may need to be considered.

 

TECHNIQUE:

A transseptal puncture is used to gain access to the mitral valve from the left atrium during cardiac catheterization. A single deflated balloon or a double-balloon is advanced from the venous circulation to the right atrium, across the interatrial septum to the left atrium, and then across the stenotic mitral valve. Through separation of the fused commissures, inflation and rapid deflation of the balloon opens the stenotic valve. This is a similar mechanism to that of surgical commissurotomy. Improved leaflet mobility and leaflet separation could be contributed to by fracture of calcific deposits in the leaflet tissue.

 

The standard approach to monitoring PMBV is transthoracic echocardiography with measurement of mitral valve area and assessment of mitral regurgitant severity after each balloon dilation, in addition to direct measurement of the transmitral pressure gradient. If an adequate valve area has been achieved or if there’s a significant increase in mitral regurgitant severity, the procedure should be stopped.

 

To guide the procedure and monitor for complications, transesophageal echocardiography (TEE) could be performed during PMBV. However, general anesthesia may be required due to the length of the procedure, which is one of the disadvantages of TEE. Most centers use transthoracic and/or intracardiac echocardiography.

 

The extent of valvular deformity can be delineated by intracardiac echocardiography, which can also be useful in visualizing several key steps of the valvotomy procedure, including:

 

  • Exclusion of thrombus from the left atrial appendage
  • Transseptal puncture of the interatrial septum
  • Initial assessment of the results of dilatation
  • Optimizing balloon placement across the valve orifice

 

Increased cost and, with current transducers, an inability to accurately measure mitral valve area or adequately assess mitral regurgitation are some of the disadvantages of this approach.

 

Some specialists have suggested that three-dimentional echocardiographic reconstruction from the TEE study could be valuable. In 2007, real-time 3D TEE became commercially available, and is being used in some centers to guide PMBV. Despite the fact that improved outcomes from a 3D approach haven’t yet been reported, but this method enables improved visualization of catheter manipulations, a more comprehensive assessment of the mitral valve before and after PMBV, and a more visually intuitive guidance. The commissural splitting and leaflet tears that aren’t visible on a 2-dimensional study can be identified by 3D TEE.

 

OUTCOMES:

Short-term outcomes:

PMBV has excellent early or immediate results. Most investigators have reported that the valve area increases from a critically stenotic value of 1.0 cm2 to approximately 2.0 cm2; this change is associated with a rapid reduction in left atrial pressure. Even though this is sufficient to produce substantial hemodynamic improvements including a reduction in pulmonary artery pressure, a decrease in left atrial pressure and the transmitral pressure gradient, and an increase in cardiac output; however, it is still smaller than the normal valve area of 3 to 5 cm2. A reduction in left atrial stiffness is yet another benefit of this approach, which results in an increase in left atrial pump function in patients in sinus rhythm and an increase in left atrial reservoir function in people who have atrial fibrillation.

 

Long-term results:

Several hymodynamic parameters show continued improvement twelve months after valvotomy, including increases in cardiac output and further reductions in pulmonary artery systolic pressure. In many patients, pulmonary vascular resistance declines and normalizes. However, there was a progressive reduction in the mitral valve area in a long-term follow-up of 561 patients, which by seven years was ≥ 0.3 cm2 in 27% of patients. In comparison, mild to moderate mitral regurgitation after the procedure didn’t progress in 81%; the progression was generally by one grade when it occurred.

 

One of the reviews from the NHLBI Balloon Valvuloplasty Registry evaluated 736 patients over the age of 18 who were followed for four years; the actuarial survival rate at one, two, three, and four years was 93, 90, 87, and 84%, respectively. The event free survival (freedom from death, mitral valve surgery or repeat PMBV) at one, two, three, and four years was 80, 71, 66, and 60%, respectively.

 

Functional tricuspid regurgitation may develop in patients with MS and pulmonary hypertension. In some patients, successful PMBV with decrease in pulmonary artery pressure is associated with improvement in tricuspid regurgitation.

 

The expected long-term benefits of the various treatment options, the goals of treatment and the anticipated risks of surgery are some of the factors that the decision of referring a patient for PMBV vs. surgical valve replacement is influenced by. PMBV introduces greater uncertainty than in many other medical conditions because the precision of its outcome prediction is somewhat limited. Because of this, careful consultation before the procedure with an open discussion with the patient and his/her family is quite important.

 

As a doctor, you should know that eventual surgical valve replacement is likely to be necessary in the long term, especially in young patients, even in the cases of very successful percutaneous procedures. Additionally, depending on the individual patient, the benefit of postponing surgery for as long as a decade or more can be significant.
 

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Prepared By: Dr. Mehyar Al-khashroum
Edited By: Miss Araz Kahvedjian


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