Catheter Management Of Mitral Stenosis

The key to having a successful percutaneous mitral valve procedure is to have a trained interventional or structural cardiologist skilled in the techniques of mitral valve percutaneous transcatheter procedures. Other personnel includes a cardiac nurse, cardiac technician, and cardiothoracic surgeon. 

In patients undergoing mitral valvuloplasty for mitral stenosis, an echocardiographic scoring system called the Wilkins score can be used to predict the procedural outcome. Its basis is leaflet mobility, valve thickening, calcification, subvalvular thickening. Each item receives a grade from 1 to 4 which yields a score from 4 to 16. A score of 8 or less predicts a more favorable outcome than those with a higher score. However, a score higher than 8 does not exclude a patient from having a mitral valvuloplasty. Commissural calcification or fusion is another important predictor for poor outcome after mitral valvuloplasty. Not all operators use this scoring system to determine the viability of percutaneous transcatheter balloon mitral valvuloplasty intervention; however, it is useful as a tool in patients for whom procedural success is a question.

On the day of the surgery, patients will receive instructions to fast at least 6 to 8 hours before the procedure. Anticoagulation will also be held prior to the procedure. If the patient is on warfarin, it will need to be held, and an international normalized ratio (INR) of at least 1.7 is necessary prior to the day of the procedure. Before performing the percutaneous transcatheter balloon mitral valvuloplasty, a right heart catheterization is done to assess the pressures inside the heart and in the lungs. Also, a left ventriculogram is performed to evaluate concomitant mitral regurgitation.

Preparation for percutaneous transcatheter mitral valve replacement is very similar to PBMV. An echocardiogram is recommended, but there is no current scoring system available to determine procedure outcome. On the day of the procedure patient should be placed NPO and anticoagulation should be held. If not done recently, a right heart catheterization is also recommended prior to PMVR to determine the hemodynamics of the heart. 

Percutaneous Balloon Mitral Valvuloplasty

As in any percutaneous transcatheter procedure, to begin the procedure, vascular access must be obtained. Most operators use a femoral approach for this procedure. Upon obtaining vascular access, a transseptal puncture is performed to facilitate left atrial access. Heparin is then infused through the sheath (usually 5000IU). Care is made to avoid introducing any air bubbles into the heart. Hemodynamics of the left atrium is then taken to calculate the transmitral gradient. If the measurements meet criteria to continue the procedure, then a guide wire is advanced into the left atrium. The femoral vein and interatrial septum are both dilated to ease delivery of the of the balloon-tipped catheter. Once dilated, the balloon-tipped catheter is threaded over the guide wire in the left atrium and positioned at the site of the mitral valve. The tip of the balloon is dilated first, then the rest of the balloon is dilated to open the narrowed orifice of the mitral valve. Monitoring of this procedure is usually under transesophageal echocardiogram (TEE) and fluoroscopy. Following valvuloplasty, the results of the procedure undergo TEE evaluation for any residual mitral stenosis or new mitral regurgitation. If there is still significant stenosis with mild-to-moderate mitral regurgitation, the process is then repeated 1 mm below the maximal diameter and, if required, with maximal diameter balloon inflation. Once optimal results are obtained, the left atrial hemodynamics are repeated to calculate a new post-procedure residual transmitral gradient.

A right heart catheterization is then obtained to assess right-side of the heart hemodynamics along with a left ventriculogram to evaluate mitral regurgitation severity. Guidelines recommend obtaining an echocardiogram a few days after PBMV as the pressure half-time calculation for mitral valve area may be inaccurate due to post-procedure compliance changes in both the atrium and ventricle.

An assessment of mitral regurgitation and atrial septal defect should be performed as well. A yearly clinic review and echocardiographic assessment are required. Anticoagulation should be continued in patients with paroxysmal or chronic atrial fibrillation. If mitral stenosis recurs, PBMV can be repeated. At that time, if there are significant valvular anatomic abnormalities, the surgical mitral valve replacement would be recommended.

Percutaneous Transcatheter Mitral Valve Replacement 

Once the transeptal approach is complete, heparin is administered. A balloon-tipped catheter is then passed over the guide-wire and positioned at the site of the mitral valve. The balloon is inflated to open of the narrowed mitral opening. The balloon catheter is then deflated are removed from the guide-wire. The new artificial mitral valve is crimped onto a delivery catheter which makes the valve small enough to be transported through sheath and vasculature to the heart. Under fluoroscopy, the delivery catheter attached to the new valve is threaded over the guide-wire and positioned at the site of the degenerative mitral valve. The balloon on the delivery catheter is then inflated to expand the new valve inside the diseased valve replacing the diseased valve. This process is why the procedure is called "valve-in-valve." The balloon is then deflated, and the delivery catheter along with the guide-wire is removed. An intraoperative echocardiogram is then performed before closure. If the position of the valve is determined to be ideal, then the sheath is removed, and a compression device is placed to prevent hemorrhage or hematoma formation. 

The most common complication to the PBMV procedure is the development of mitral regurgitation when the valve opens excessively. Other complications are less common being that of iatrogenic Lutembacher syndrome with an atrial septal defect,[5] vascular complications, left ventricular perforation,[6] left ventricular pseudoaneurysm,[7] cerebral neurologic event, myocardial injury,[8]  arrhythmia, pacemaker dependence, cardiogenic shock, and possible death.[9]

The most common complication to the PMVR procedure is moderate-severe residual mitral regurgitation or left ventricular outflow tract (LVOT) obstruction. Other complications include valve malposition, arrhythmia, vascular complications, stroke, and death. Little data is available on long-term complications for this relatively new to the market procedure. 

The main advantages of PBMV and PMVR are the lower cost and avoidance of a thoracotomy and cardiopulmonary bypass. One study revealed that the pathophysiology of mitral stenosis results in a decrease in coronary flow reserve (CFR) and therapy with PTMC significantly improves CFR and subsequently leads to improved cardiac output from the right and left chambers.[10][11] Appropriate balloon sizing can help prevent PBMV complications.[12]

Percutaneous transcatheter mitral valve procedures are complex procedures requiring multiple specialties evaluation to determine the best procedural approach for the best outcome.[13] [level 1] This applies to all interventional and structural heart procedures. The recommendation is that all patients undergo evaluation by at least an interventional and/or structuralist in addition to a cardiothoracic surgeon. Other health professionals that may be involved other than the patient's own primary care physician, a cardiac nurse, a heart failure specialist, a pharmacist, and a cardiac surgeon. 

• The specialty-trained cardiology nurse should assist with patient and family education and monitoring of the patient throughout the procedure providing feedback to the clinician if untoward changes in vital signs or rhythms occur. They should also assist in providing follow-up care to the patient.
• The specialty-trained pharmacist should evaluate the medication use of the patient, making sure that drug-drug interactions that could complicate the procedure are avoided and communicate concerns with the clinical team.
• The clinical team should complete the procedure with surgical specialists readily available to assist with complications.

An interprofessional team approach will lead to the best outcomes. [Level 5]