Mitral Valve Replacement - Albert Starr (1926- ) & Lowell Edwards (1898-1982)

In the early 1950's, the development of cardiopulmonary bypass became a reality after 20 years of research led by John Gibbons and his wife, Mary.John Gibbons performed the first successful cardiac operation on a human using heart-lung machine on May 6, 1953. The procedure was an atrial septal defect closure in an eighteen year old girl. The availability of extracorporeal circulation opened the era of open heart surgery with direct access to intracardiac structures including the mitral valve.

Lillehei performed the first mitral valve repair under direct vision for mitral regurgitation in 1956. Subsequently other repair techniques were described; Most these techniques, however, were palliative leading to over-narrowing of the mitral orifice and were associated with high failure rate. In addition, in many instances, valvular lesions were too advanced to be repairable and valve replacement would have been the only therapeutic option. In the late 1950's, intense research efforts were undertaken to develop a reliable prosthetic substitute to replace the damaged mitral valves. As the history showed only the efforts of very few, including those of Starr's, proved to be fruitful.

Albert Starr started his career as a young cardiothoracic surgeon at the University of Oregon Medical School in 1958. During the same period, he initiated his collaboration with Lowell Edwards who was a retired mechanical engineer on the design of a prosthetic valve in the mitral position.

The first implanted valves in the animal model were made of Silastic leaflets mounted in a rigid Teflon ring and surrounded by a Dacron cloth sewing margin. The results were disappointing because of a high rate of early thrombotic events and this design was abandoned. After designing and implanting several types of valves using various materials in laboratory, they decided to use a moving, free-floating poppet as in a ball valve.

As Starr recognized himself, ball valves were already available but their design was suboptimal leading to an extremely high early failure rate. Their first effort was to develop a mitral ball-valve prosthesis which would have the advantage of being independent of subvalvular attachment. After several months of intense research, Starr and Edwards made their own ball valve with new and improved materials. The case of the caged-ball valve was cast in one piece stainless steel or Stellite 21. The surface was then silicone coated. The knitted Teflon cloth fixation ring was attached by Teflon spreader rings and braided Teflon thread. The ball was made of Silastic. The first procedure was performed on August 25, 1960.

In their landmark article, Starr and Edwards reported eight cases of mitral valve replacement with their first generation of mechanical valve. Two patients died postoperatively and two had serious postoperative complications. At the time of the publication of their work,in 1961, most patients were doing well and were free of cardiac symptoms. For the first time, long-term survival could be obtained following mitral valve replacement.

In the discussion of their landmark paper, Starr and Edwards wrote:

"..the results presented in this report, in terms of extracorporeal accelerated fatigue testing and animal and human implantation, suggest that under certain circumstances the use of the ball-valve mitral prosthesis is justified. The indications for mitral replacement with this prosthesis are related to the operative findings and the comparative risks and advantages of replacement versus more conservative surgical management.However, the advantages of the prosthesis over plastic procedures on the mitral in terms of predictability of hemodynamic result must be balanced by the unknown long-term hazards involved in total dependence upon an intracardiac appliance. For this reason the only indication for mitral valve replacement in this series has been the operative findings of a hopelessly diseased valve not amendable to any reasonable plastic procedure in a patient with severe symptomatology (functional class III or IV)for whom prior permission for the use of the prosthesis has been obtained."

The pioneering work of Starr and Edwards opened the era of valve replacement surgery. Following this early experience, results improved steadily with a significant decrease in hospital mortality and mitral valve replacement became a routine procedure.Starr and Edwards continued their research and Starr-Edwards ball valve went through several design and material modifications until the final product became available in 1964.

The design of the valve was also adapted to function as an aortic prosthesis. The cage was only constituted with three struts to align the aortic commissures. The sewing ring was extended downstream to be more suitable for the aortic annulus. The first clinical experience with the aortic valve prosthesis took place on September 1961.
Forty years after Cutler's initial work, surgeons had at their disposal a relatively simple, reproducible and reliable procedure to treat effectively their patients with valvular heart disease.

Chronologic Approach | Galenic Teaching

In a Chronologic Approach the development of knowledge of the structure and function of the heart, circulatory system and subsequently the diseases of the heart with a particular emphasis on the mitral valve.

For more than 1400 years, Galen's concept of cardiovascular anatomy, blood motion and humoral theory of disease had prevailed in Europe. Claudius Galen (AD 130-200) is considered the last great Greek physician and philosopher of the antiquity. He believed in the concept of "pneuma" or "spirit" and described three distinct types: pneuma physicon or natural spirit that was created in the liver, pneuma zoticon or vital spirit that was generated in the left ventricle, and pneuma psychicon or animal spirit which was the true substance of the soul and created in the brain.

According to Galen, after the ingestion of food, the latter was transformed into chyle and transported from the intestine to the liver via the portal vein. Then the blood was formed in the liver, mixed with the natural spirit and transported to the whole body for nutrition through the veins. The liver was regarded by Galen as the center of the venous system. The nutritive blood was thought to ebb and flow, up and down in the veins. During this movement, the impurities were also extracted from various organs of the body and brought into the venous system. Part of the venous blood was transported from the liver via the vena cava to the right ventricle. A major function of the lungs and the heart was to clean the blood from its impurity. That function was accomplished by the transport of the blood through the pulmonary artery during the expiratory phase of respiration.This purified blood ebbed to and fro within the venous system for nutritional purposes.

A small portion of the right ventricular blood was passed to the left ventricle through small and invisibles pores in the interventricular septum. During the same time, the air was transported from the lungs via the pulmonary veins to the left ventricle.In the left ventricle, the blood and air were mixed forming "vital spirit" which was then conveyed to the entire body via the arterial system. In his description, Galen adhered to the ebb and flow motion of the blood and did not visualize its circulatory movement. Galen believed that the vital spirits were responsible for all types of muscular activity and movements.He considered the heart as primarily an organ of respiration and the production of animal heat and the lungs as a cooling bath to the heart.

From anatomic point of view, he considered the heart as a two-chamber structure. The right and left atria were described as reservoir chambers and were not an integral component of the heart. According to Galen's theory of blood motion, cardiac valves and the mitral valve to a greater extent were incompetent. As described above, the air was transported from the lungs to the left ventricle through the pulmonary veins and the mitral valve. Once the blood and air were mixed to form the vital spirit, the latter was transported either through the aorta and arterial system to the body or from the heart to the lungs via the mitral valve to expel the "sooty vapours" which the natural heat had produced in that organ.According to Galen, the greater incompetency of the mitral valve was due to the fact it was composed of two membranes (leaflets) whereas the tricuspid and semilunar valves were composed of three membranes.As we will see Harvey who discovered the blood circulation in 1628 rejected strongly this theory.

Galen's humoral theory of disease was based on the concept that disease resulted from an imbalance between the four humors which were blood, phlegm, yellow bile and black bile. They were directly linked to four elements of fire, water, air, and earth respectively. This aberrant concept therefore ignored the anatomic structural changes that could affect negatively an organ function as well as abnormal physiologic conditions that could lead to an end organ dysfunction.

Cardiac valve surgery-Alain Carpentier

Prior to the invention of cardiopulmonary bypass, a few attempts were made to correct mitral regurgitation by pericardial approaches. They were almost always unsuccessful and abandoned. After the advent of cardiopulmonary bypass, several repair techniques were described to correct pure mitral regurgitation. Walton Lillehei performed the first mitral valve repair under direct vision by suture plication of both commissural areas in 1956. The principle concept behind these repair procedures was the over-narrowing of the mitral orifice to reduce the size of the annulus and to correct valvular regurgitation. These palliative techniques were progressively abandoned for three main reasons: first, they failed to produce a reliable and predict able result, second they were associated with a high rate of early recurrent mitral regurgitation or induced mitral stenosis, and third, suitable valvular prostheses became available.

In the late 1960's, several clinical studies demonstrated that prosthetic Mitral valve replacement in the mitral position was associated with serious drawbacks. Structural valve degeneration was the most common complication of the biological valves requiring a second operation whereasanticoagulation-related events were a major source of morbi-mortality in patients with mechanical valves. Carpentier was convinced that in the mitral position, surgical techniques preserving the native valve were superior to Mitral valve replacement. He was also aware of the conceptual limitations of repair techniques available at that time. As previously mentioned, these palliative procedures were commonly complicated with recurrent mitral regurgitation or stenosis as a result of dysfunctions of the leaflets, the persistent process of annular dilatation, and the fibrous transformation of the plicated commissure. In 1968, Carpentier introduced the concept of remodeling annuloplasty using a prosthetic ring and opened a new era in mitral valve reconstructive surgery.
The principle goals of the remodeling annuloplasty were to restore the normal shape and size of the annulus while respecting the normal motion of the leaflets and the commissures. The prosthetic ring would also stabilize the mitral annulus in the systolic position and prevent its further dilatation.

The introduction of remodeling annuloplasty allowed the development of complementary reconstructive techniques. In the early 1970's, Carpentier and his team performed extensive anatomic studies of the mitral valve in both normal and pathologic conditions to identify precisely all valvular lesions enabling them to design appropriate reconstructive techniques.

In the late 1970's the anatomic approach, "too complex to be practical", was abandoned and more attention was placed on the valve dysfunction resulting from these anatomic lesions.
The functional approach, first described in 1978, was based on the analysis of the motion of the leaflets during diastole and systole. Three functional types were distinguished depending upon whether the leaflet motion is normal (type I) increased (type II) or decreased (type III).

In his landmark paper, The "French correction," published in 1983, Carpentier wrote:

"Surgeons are not basically concerned with lesions. We care more about function. Therefore one may define the aim of a valve reconstruction as restoring normal valve function rather than normal valve anatomy. This functional approach has led to a significant simplification. There are only two functional anomalies: The opening and closing motions of each leaflet are either increased as with leaflet prolapse or diminished as with restricted leaflet motion".

Nowadays, the functional classification has become the foundation of valve analysis and reconstruction. Preoperatively, the functional classification allows the echocardiographer to assess and localize valvular dysfunctions. It provides valuable information to the surgeon, who can then proceed intraoperatively to a complete inventory of the lesions in the areas where a dysfunction has been identified. The exact determination of the valvular dysfunctions and lesions allows the surgeon to design the appropriate reconstructive procedure(s) based on the "one-lesion-one-technique" principle. Following the pioneering work of Alain Carpentier, several groups in Europe, North America and Asia implemented successfully his reconstructive techniques into their practices. Today, Carpentier's reconstructive valve surgery is the gold standard in the management of patients with mitral valve disease. The procedure is extremely safe, reliable, and reproducible with excellent early and late results. As Carpentier has remarked: "For the first time in the history of valvular disease, patients can be cured for the rest of their lives."

Mitral Valve Regurgitation

For mild cases, treatment may not be necessary.Mitral valve regurgitation happens when your heart's mitral valve doesn't close tightly, which allows blood to flow backward in your heart.Treatment of mitral valve regurgitation depends on how severe your condition is, whether it's getting worse, and signs and symptoms.Mitral valve regurgitation is also called mitral insufficiency or mitral incompetence.

You may need heart surgery to repair or replace the valve for more-severe cases.Left untreated, severe mitral valve regurgitation can cause heart failure or serious heart rhythm problems (arrhythmias).When the mitral valve doesn't work properly, blood can't move through your heart or to the rest of your body as efficiently, making you feel tired or out of breath.

What is the treatment for mitral valve prolapse?

Beta-blockers, such as atenolol (Tenormin), metoprolol (Lopressor), and propranolol (Inderal), are the drugs of choice.Examples of antibiotics used include oral amoxicillin and erythromycin as well as intramuscular or intravenous ampicillin, gentamycin, and vancomycin.Since valve infection, endocarditis, is a rare, but potentially serious complication of mitral valve prolapse, patients with mitral valve prolapse are usually given antibiotics prior to any procedure which can introduce bacteria into the bloodstream.Patients with severe prolapse, abnormal heart rhythms, spells, significant palpitations, chest pain, and anxiety attacks may need treatment.These act by increasing the size of the left ventricle, thereby reducing the degree of prolapse.These procedures include routine dental work, minor surgery, and procedures that can traumatize body tissues such as , gynecologic, or urologic examinations.

For these individuals, routine examinations including echocardiograms every few years may suffice.The calcium blockers verapamil (Calan) and diltiazem (Cardizem) are useful in patients who cannot tolerate beta-blockers.Therefore, mitral valve prolapse patients with mitral regurgitation are often evaluated annually.The vast majority of patients with mitral valve prolapse have an excellent prognosis and need no treatment.

Mitral regurgitation in patients with mitral valve prolapse can lead to heart failure, heart enlargement, and abnormal rhythms.

What are the signs and symptoms of mitral valve prolapse?

Such imbalances may cause inadequate blood oxygen delivery to the working muscles during exercise, thereby causing fatigue.Mitral valve prolapse may be rarely associated with strokes occurring in young patients.In very rare cases, potentially serious heart rhythm abnormalities may underlie palpitations which require further evaluation and treatment.Like fatigue, these symptoms are believed to be related to imbalances of the autonomic nervous system.Palpitations are sensations of fast or irregular heart beats.In most patients with mitral valve prolapse, palpitations are harmless.These patients appear to have increased blood clotting tendencies due to abnormally sticky blood clotting elements, called platelets.Most people with mitral valve prolapse have no symptoms, however, those who do commonly complain of symptoms such as fatigue, palpitations,chest pain, and migraine headaches is a very rare complication of mitral valve prolapse.Sharp chest pains are reported in some patients with mitral valve prolapse, which can be prolonged.Anxiety, and may be associated with mitral valve prolapse.

Fatigue is the most common complaint, although the reason for fatigue is not understood.They are probably related to abnormal nervous system control of the tension in the blood vessels in the brain.

Unlike , chest pain with mitral valve prolapse rarely occurs during or after exercise, and may not respond to nitroglycerin.Migraine headaches have been occasionally linked to mitral valve prolapse.Patients with mitral valve prolapse may have imbalances in their autonomic nervous system, which regulates heart rate and breathing.

Mitral Valve Repair

In patients with rheumatic valve disease, it is critical to evaluate the aortic and tricuspid valves as associated lesions are very common.The marginal chordae are fenestrated with a small triangular wedge resection or split.Post bypass TEE is critical in patients with rheumatic disease.Patch extension can be applied to both the anterior or posterior leaflet depending upon the localization and extent of the lesions.Care should be taken to leave one chordae on each side of the commissural opening.In this scenario, it is necessary to implant a remodeling prosthetic ring to prevent post-commissurotomy regurgitation.Commissurotomy is started along this groove while leaving a 5mm tissue ridge from the annulus and is directed toward the center of the orifice.Locating the site of the commissure can be difficult in the presence of advanced rheumatic lesions.Most patients present with type IIIa dysfunction.The presence and the severity of valvular calcification should be assessed.Residual mean transvalvular gradient less than 5 mmHg is acceptable, but gradients greater than 8 mmHg indicates the need for a second exploration and valve replacement.It is not advisable to increase the height to more than 2 cm as that may create a curtain effect with a risk of mitral stenosis.In patients with commissural fusion, mitral commissurotomy is performed to increase the opening of the mitral valve.When fused chordae beneath the commissure are identified, they should be fenestrated using a triangular wedge resection.Typically a ring 30 or 32 mm is selected in female whereas a ring 32 or 34 mm is selected in male.In patients with mitral stenosis and annular dilatation, an isolated commissurotomy may result in mitral regurgitation.It is also important to assess the mobility of the anterior leaflet and the extent of subvalvular lesions as they both predict the feasibility of valve reconstruction.The latter procedure further enhances the commissural opening.Finally, mitral valve area and transvalvular gradient should be calculated.Marginal chordae can also be resected provided that the free margin is supported every 4mm along its entire length.

Occasionally the marginal chordae can be thickened and elongated.Subvalvular lesions are addressed by the resection of thickened secondary chordae.Leaflet thickening/retraction is best treated with patch extension using Glutaraldehyde-treated autologous pericardium.The insertion of smaller rings is associated with the risk of mitral stenosis and early repair failure.Commissural fusion is usually more intense at the postero-medial commissure than the antero-lateral commissure.In patients with anterior leaflet prolapse, the responsible lesion is either a posterior or a lateral displacement of the paramedial chordae.The principle objectives of the patch extension are to increase leaflet mobility, to enhance the surface of coaptation and to allow the implantation of a larger prosthetic ring.Calcified nodules in the commissural area should be excised.The height of the reconstructed posterior leaflet should be between 15 to 20 mm.A mild degree of mitral regurgitation does not require a second look provided that a large surface of coaptation has been created.In patients with mitral regurgitation and type II dysfunction, minor prolapse of the anterior leaflet should be identified and corrected with chordae repositioning.A careful valve analysis should be performed to determine the mechanism of mitral regurgitation.The corresponding papillary muscle should also be split.The association of a restricted posterior leaflet motion (type IIIa dysfunction) with a prolapse of the anterior leaflet (type II-A2 dysfunction) is very characteristic.After the exposure of the mitral valve, the surgeon should perform a detailed valvular analysis and make a full inventory of the lesions: commissural fusion, leaflet thickening/retraction, chordae fusion and shortening, and annular dilatation.

Following the patch extension, a ring is selected which is one or two size bigger than the size of the measured anterior leaflet.Following valvular analysis, the appropriate reconstructive techniques are selected according to Carpentier's one-lesion- one-technique principle.Prior to cardiopulmonary bypass, an intraoperative transesophageal echocardiography is performed in all patients.Following the detachment of the posterior leaflet and the resection of secondary chordae, a diamond-shaped patch of appropriate size is tailored and implanted using a running suture technique.Traction on the main chordae of the anterior leaflet opposite to the commissure is key to identify the commissural groove.

Post-cardiopulmonary bypass, transesophageal echocardiography is used to assess: 1) the deairing of the cardiac chambers, 2) the quality of repair, 3) the transvalvular gradient and the orifice area, and 4) the right and left ventricular functions.

These complex and multiple lesions raise the question of the feasibility of valve reconstruction which ultimately depends upon two factors: 1) the surface area and pliability of the anterior leaflet and   2) the extent of subvalvular lesions.The incision should be extended to the papillary muscle leaving a greater thickness on the anterior leaflet side than on the posterior leaflet side.In practice, patch extension of the posterior leaflet is performed more commonly.