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February 27, 2017
Degenerative Disease Surgical Management & Results

Surgical Management & Results

Peri-operative management

Standard intraoperative monitoring lines including a radial arterial line and a central right internal jugular venous line are inserted in all patients. A Swan-Ganz catheter is particularly helpful in cases of complex mitral valve reconstructive surgery (which may be associated with a long ischemic time), multivalve surgery, and combined mitral and coronary artery bypass grafting surgery. Its use is also indicated in patients with increased operative risk such as those with left ventricular dysfunction, pulmonary hypertension, or undergoing reoperation. A Foley catheter with a bladder temperature probe is placed to monitor both the urine output and the systemic temperature throughout the procedure. Cerebral pulse oxymetry is used to assess the adequacy of brain perfusion. An external defibrillator is placed in the right thoracotomy approaches and in the reoperative setting. A double lumen endotracheal tube is used in right thoracotomy incisions. Transesophageal echocardiography (TEE) is performed in all patients prior to the institution of cardiopulmonary bypass, and after completion of bypass. Intraoperative echocardiography is vital to determine the mechanism of mitral regurgitation before repair, to identify and quantify any residual regurgitation after repair, and to assess left ventricular function, and deairing of cardiac chambers at the completion of the procedure. Epiaortic scanning of the ascending aorta is recommended in all patients, but particularly those with atherosclerotic risk factors.

Surgical incisions, cannulation and myocardial protection

Our preferred approach is a small skin incision with a midline sternotomy in complex reconstructive valve surgery, mainly in patients with Barlow's disease and bileaflet prolapse. An alternative surgical incision is the partial upper or lower hemi-sternotomy in selected patients. The sternum is partially divided from the sternal notch to the left 4th intercostal space (upper hemi-sternotomy) and from the xyphoid to the 2nd right intercostal space (lower hemi-sternotomy). Central arterial and venous cannulation is usually possible with these approaches. Video directed and robotic mitral valve surgeries are performed through a right mini-thoracotomy in the 4th intercostal space. Multi-port access is obtained by additional keyhole incisions. Peripheral vessels are used to initiate cardiopulmonary bypass. Additional adjunctive techniques such as port access instrumentation, CO2 insufflation, and vacuum assisted venous drainage are commonly used to facilitate these surgical procedures.

Myocardial protection is achieved with intermittent antegrade or a combined antegrade and retrograde infusion of high potassium cold blood cardioplegia. Further myocardial protection can be obtained by moderate systemic hypothermia between 28-30 oC. The myocardial temperature should be assessed continuously throughout the procedure and maintained below 15 oC with additional administration of cardioplegia as required.

Mitral valve exposure

Perfect exposure of the mitral valve is essential before undertaking mitral valve reconstructive surgery. We favor the interatrial approach through the Sondergaard's groove. The interatrial groove is incised and the two atria are dissected and divided up to the fossa ovalis. This dissection exposes the roof of the left atrium, which is opened close to the mitral valve.

Intraoperative valve analysis

The entire mitral valve apparatus is carefully examined to confirm the functional type of mitral regurgitation, to establish a detailed inventory of valvular lesions, and to plan the exact operative strategy. Jet lesions on the endocardium of the left atrium usually indicate leaflet prolapse of the segment opposite the jet lesion. Annular dilatation is assessed and the presence and extent of calcification carefully identified as this can dictate operative strategy. The extent and the severity of leaflet prolapse is evaluated segment by segment using Carpentier's reference point technique. The P1 segment constitutes the reference point, as it is not usually affected by the disease process.

Gross morphology and analysis of Barlow's valve

The Barlow's valve is characterized by marked excess tissue with typically thick leaflets. The size of the anterior leaflet measures classically about 40mm in transverse diameter and greater than 30mm in antero-posterior diameter. All segments of the posterior leaflet present with excess tissue and the height of P2 segment typically covers the entire antero-posterior diameter of the mitral orifice. The excess tissue is responsible for the billowing of the belly of the leaflets into the left atrium. The chordae are thickened, elongated, and may be ruptured. The attachment of the marginal and secondary chordae to the ventricular aspect of the leaflets is disorganized forming a trabeculated mesh surrounding pockets of billowing tissue. Papillary muscles are occasionally elongated and appear bulky. The annulus is severely dilated and sometimes calcified. Most Barlow's valves present with the prolapse of multiple segments. Bileaflet prolapse is present in about 30% of patients.

 

Stephen Hales
Stephen Hales
Stephen Hales

Gross morphology and analysis of Fibroelastic deficiency

Mitral valve leaflets are often thin and transparent with no excess tissue except in the prolapsing segment. Chordae are thin, frail, elongated, and often ruptured. The annulus is often mildly dilated, and may be calcified at its posterior segment. Most patients present with isolated P2 prolapse, although anterior or bileaflet prolapse is diagnosed in about 20 to 30% of patients. The posterior leaflet indentations have usually a normal aspect and are often spared in patients with P2 prolapse.

 

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
Stephen Hales
Stephen Hales

Fundamentals of mitral valve reconstructive surgery

Reconstructive valve surgery using Carpentier's techniques is the procedure of choice in patients with degenerative disease. The three goals of reconstructive surgery are firstly achieving normal leaflet motion, secondly providing a large surface of coaptation, and finally stabilizing the whole annulus with a remodeling annuloplasty.

 

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010

The choice of the reconstructive procedure depends upon the localization of the prolapse (anterior leaflet vs. post vs. commissure), the extent and severity of the prolapse, and the lesions causing the prolapse. Following this analysis, the appropriate technique is selected according to Carpentier's one-lesion- one-technique principle.

Posterior leaflet prolapse

Limited posterior leaflet prolapse, involving less than one third of the free margin of a segment, is treated by triangular resection followed by a primary repair of the defect. In patients with fragile and thin tissue, leaflet resection should be avoided and alternative techniques such as chordae transposition or artificial chordoplasty should be employed to correct leaflet prolapse.

Extensive Posterior leaflet prolapse is corrected by a quadrangular resection of the prolapsed area. Stay sutures are placed around the normal chordae in order to delineate the prolapsed area. The latter is then removed by performing a perpendicular incision from the free edge toward the annulus, resecting a quadrangular portion of the leaflet. It is important to preserve the indentations if they are not involved in the prolapse as they facilitate the opening motion of the posterior leaflet.  Plication sutures are placed along the posterior annulus in the resected area to approximate the leaflet remnants. Leaflet continuity is resorted by closing the gap between the two remnants. Finally, a remodeling annuloplasty with a prosthetic ring is performed.

 

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010

When excessive posterior leaflet tissue is present, such as in Barlow's disease, it is important to reduce the height of the posterior leaflet to less than 15 mm to prevent postoperative systolic anterior motion. A sliding leaflet technique is performed following quadrangular resection. In patients with severe excess tissue, an additional triangular resection at the base of P1 and P3 may be necessary. Following the detachment of P1 and P3 segments from the mitral annulus; compression sutures are placed in the posterior segment of the annulus. A sliding plasty of the P1 and P3 segments is performed and the gap between the 2 scallops is closed with interrupted sutures.

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010

Sliding plasty is also indicated if a large segment of the posterior leaflet is resected leaving a gap of greater than 2 cm between the two remnants. In this scenario, posterior annular plication must be avoided because of the increased risk of circumflex artery kinking. Finally, sliding leaflet plasty is a valuable technique in elderly patients with posterior leaflet prolapse and extensive annular calcification in whom the risk of decalcification is considered to be prohibitive.

Following leaflet resection and reconstruction, the procedure is completed with the implantation of a remodeling prosthetic ring. In patients with Barlow's disease the size of the ring, based on the size of the anterior leaflet, is usually equal or greater than 36 mm. Following the measurements, if the surgeon hesitates between two sizes, it is strongly recommended to select the larger size in patients with Barlow's disease.

 Anterior leaflet prolapse

Several techniques are available to correct anterior leaflet prolapse depending upon the extent of the prolapse and the lesions (Chordae elongation vs. rupture).

Triangular resection

Limited prolapse of the anterior leaflet, involving less than one fourth of the total length of the free edge, can be treated by a small triangular resection of the prolapsed area. This is followed by direct closure with interrupted monofilament sutures. The triangular resection must not be extended to the body of the anterior leaflet and should not involve more than 10 % of the leaflet surface area. Large resection of the anterior leaflet reduces the coaptation area, compromises leaflet mobility and is incriminated as a risk factor for repair failure.

Another option is leaflet fixation on secondary chordae. This technique is indicated whenever a strong, non elongated secondary chordae is less than 5mm from the free edge of the prolapsed area. If this distance is greater than 5mm, secondary chordae transposition is recommended.

Chordae transposition

One or two strong and non-elongated secondary chordae adjacent to the prolapsing area are identified. They are cut at 2 mm from their attachment to the body of the anterior leaflet. If these chordae are detached at their base, this will likely cause leaflet perforation. Then, they are attached to the free margin of the anterior leaflet in the prolapsed area with a figure of eight suture. In case of a large prolapsed area, additional secondary chordae should be transferred to the free margin with a maximum 5mm interval between two adjacent chordae. Another alternative is to use a composite technique combining limited leaflet resection and secondary chordae transposition.

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010
Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010

If normal secondary chordae are not available, chordae transposition from the posterior leaflet to the anterior leaflet is a viable alternative option. Marginal chordae of the posterior segment opposite to the prolapsed area of the anterior leaflet, if normal, are used for chordae transposition. A small segment of the posterior leaflet is detached and then reattached to the free margin of the anterior leaflet at the site of prolapse. Interrupted sutures are used to close the defect in the posterior leaflet.

Finally artificial chordae can be used to correct anterior leaflet prolapse if the two previous techniques cannot be applied.

Papillary muscle sliding plasty

This technique is convenient for anterior leaflet prolapse due to elongation (< 5 mm) of multiple chordae arising from a papillary muscle. The portion of the papillary muscle supporting the elongated chordae is split longitudinally and re-sutured to the other portion at a lower level. This downward displacement of papillary muscle corrects leaflet prolapse.

Papillary muscle shortening

Papillary muscle elongation or chordae elongation involving a group of chordae can also be treated by papillary muscle shortening. A triangular wedge at the base of the papillary muscle is resected. This defect is then closed by direct suture resulting in a reduced height of the papillary muscle and correction of chordae length.

Stephen Hales
From Carpentier A, Adams DH, Filsoufi F. Carpentier's Reconstructive Valve Surgery. Saunders (Elsevier), 2010

 

These techniques of papillary muscle shortening and sliding plasty are extremely useful in patients with Barlow's disease and bileaflet prolapse. The ultimate goal of these procedures is leaflet edge repositioning. The latter corrects not only leaflet prolapse but also leaflet billowing in a harmonious manner by repositioning the free margin of all leaflet segments at the same level low in the ventricle. The correction of both leaflet prolapse and billowing is necessary in patients with Barlow's disease to ensure excellent long-term results.

Commissural prolapse

Commissural prolapse due to chordae rupture is best treated by resection of the prolapsed area followed by annular plication (limited prolapse) or sliding plasty of the paracommissural area (extensive prolapse) (e.g. A3 and P3 sliding plasty for postero-medial commissural prolapse). Additional inverting sutures should be placed in the newly created commissure in order to avoid residual minimal regurgitation. Alternative techniques such as chordae transposition or artificial chordae implantation can be employed to correct prolapse.

Commissural prolapse due to chordae elongation is commonly seen in Barlow's disease. Papillary muscle shortening or sliding plasty is indicated taking into consideration the anatomy of the papillary muscles.

Remodeling ring annuloplasty

In patients with a normal mitral valve, the ratio between antero-posterior (septo-lateral) and transverse diameter of the mitral annulus is 3:4 during systole. This ratio is inverted in patients with degenerative disease and annular dilatation.

The remodeling annuloplasty using a prosthetic ring restores this physiologic ratio while preserving maximal orifice area during systole. It reduces the tension on the reconstructed valve and subvalvular apparatus. The prosthetic ring increases leaflet coaptation area without producing any valvular stenosis and prevents late annular dilatation.  Thus, the implantation of a remodeling ring guarantees the long-term durability of the repair.

Appropriate ring sizing is based on: 1) the intercommissural distance and 2) the surface area of the anterior leaflet measured with an obturator. If the surgeon hesitates between two sizes, in patients with degenerative valve disease, the greater size should be selected. In Barlow's disease, the size of the prosthetic ring is usually equal or greater than 36 mm. In fibroelastic deficiency the size of the ring varies between 30 to 34 mm with an average of 32 mm. It is important to stress that in Barlow's disease, the implantation of a small (undersized) ring increases considerably the risk of postoperative systolic anterior motion.

Saline test and post bypass transesophageal echocardiography

The quality of the repair must be evaluated at the completion of the reconstruction and before tying the ring to the annulus with a saline test. Saline is injected into the ventricular cavity through the mitral valve with a syringe while the aortic root is vented to prevent air emboli into the coronary arteries. A symmetric line of coaptation, parallel to the posterior aspect of the annulus, and at distance from the left ventricular outflow tract (3/4 to 1/4 ratio of anterior to posterior leaflet) indicates a satisfactory result. An asymmetrical line of coaptation indicates residual leaflet prolapse or restricted leaflet motion, which must be addressed. If the posterior leaflet occupies half or more of the orifice area, its height should be reduced (less than 15 mm) to minimize the risk of systolic anterior motion. Two hooks should also be used to determine the length of the coaptation which is ideally greater than 10 mm. At the completion of cardiopulmonary bypass, the quality of reconstruction is assessed by TEE. This examination should evaluate leaflets motion, the competency of the valve and rule out the diagnosis of systolic anterior motion in patients with excess leaflet tissue. In the presence of residual leak, TEE is critical to determine the mechanism and the severity of regurgitation which may justify a second look. No patient should leave the operating room with residual mitral regurgitation greater than 1+. In patients with ≥ 2+ mitral regurgitation, a second bypass run is mandatory to analyze the valve and to correct a residual valvular dysfunction.

 

Results

Patients with degenerative mitral valve disease are the most suitable for reconstructive surgery. Operative mortality in this group of patients is less than 0.5% in experienced centers. Risk factors incriminated in early mortality include advanced age, functional class (New York Heart Association class III and IV), and concomitant coronary artery disease. Postoperative complications occurs rarely following valve reconstruction. The rate of major neurologic events is estimated at about 1%. The risk of respiratory failure is directly correlated with preoperative left ventricular function.

Long-term survival is excellent particularly in patients with minimal preoperative symptoms (NYHA class I and II) and preserved left ventricular function. It is important to stress that in patients with degenerative disease and normal preoperative left ventricular systolic function and minimum symptoms (NYHA I-II) the observed life expectancy following repair is similar to that of the general population at the same age. In our experience, 20-year survival following reconstructive surgery for degenerative mitral valve disease was 47%. Freedom from cardiac events was estimated at 75% at 20 years.   Congestive heart failure is the most common cause of late death. This complication is often due to preoperative left ventricular dysfunction, best reflected by depressed ejection fraction. Thus, the current recommendation for early surgical referral before left ventricular dysfunction occurs.


Several clinical studies have shown the excellent durability of valve reconstruction in patients with degenerative valve disease. In our report, freedom from reoperation after valve reconstruction was 97%, 86% and 83% for posterior, anterior, and bileaflet prolapse respectively at 20 years. The linearized rate of reoperation was 0.4% per patient-year.  In this very early series, the increased rate of reoperation in the anterior leaflet prolapse group was attributed to technical failure. The widespread use of intraoperative transesophageal echocardiography and improved surgical techniques (chordae transposition) has most likely contributed in reducing the incidence of early failure in the last two decades. The freedom from reoperation, however, was unchanged at 10, 20 and 25 years of follow-up in this series. These excellent and stable results confirm the predictability and durability of mitral valve reconstruction in degenerative disease. Similarly the rate of thrombo-embolic events and endocarditis was extremely low after valve reconstruction. Several studies have reported a linearized rate of thrombo-embolic events and bleeding of about 0.1 to 0.2% per patient-year. In currect series, the freedom from endocarditis is about 99% at 10 years confirming our own experience. Today reconstructive valve surgery allows patients to enjoy a normal life and to be cured for the rest of their lives.




REFERENCES

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