Myxomatous Valve Disease Research Articles

Invited commentary

Mitral valve repair for valvular insufficiency secondary to myxomatous valve disease has been demonstrated to be superior to mitral valve replacement in most circumstances. The functional characterization of the cause of the mitral valve insufficiency by Carpentier and the techniques he developed for its correction have proved durable. Techniques of repair such as quadrangular resection, annular plication, sliding plasty and annular remodeling using annuloplasty rings are easily learned and are in wide use. Degenerative mitral valve disease in the majority of cases involves primarily the posterior leaflet and annular dilatation. In the majority of cases where the posterior leaflet is prolapsed and the annulus is dilated, quadrangular resection alone with placement of a ring is all that is needed and can be accomplished easily in most cardiac centers. Anterior leaflet involvement is uncommon. Mild cases of anterior leaflet prolapse, associated with more pronounced posterior leaflet prolapse, generally do not need to be addressed if the primary pathology of the posterior leaflet and the dilated annulus is corrected.

Relationship between different natriuretic peptides and severity of naturally acquired mitral regurgitation in dogs with chronic myxomatous valve disease

To study the responses of atrial natriuretic peptide (ANP), N-terminal fragment of pro-atrial natriuretic peptide (NT-proANP) and brain natriuretic peptide (BNP) to varying severity of mitral regurgitation (MR) in dogs with myxomatous valve disease (MVD). Case-control. DOGS: 103 Cavalier King Charles Spaniels, 27 normal individuals and 76 with varying degree of MR. Dogs were evaluated by physical examination, collection of venous blood, thoracic radiography and echocardiography. NT-proANP, ANP and BNP were measured in plasma using radio immunoassay (RIA). The mean concentrations of NT-proANP were 37.4 and 83.5 times higher than ANP and BNP, respectively. The mean ANP to BNP molar ratio was 2.6. Plasma concentrations of NT-proANP and ANP were slightly increased in asymptomatic dogs with increased cardiac dimensions; those with signs of decompensated heart failure (HF) had mean concentrations of NT-proANP and ANP 3 to 7 times higher than normal dogs. The BNP concentrations were increased only in dogs with decompensated HF and the levels were approximately twice as high in these dogs as in normal individuals. Univariate and multiple regression analysis showed that primarily left atrial and ventricular size influenced the plasma concentrations of all 3 peptides (increased with increasing measurement). Analyses of response operating characteristic (ROC) curves indicated that NT-proANP and ANP were more discriminating than BNP for either cardiomegaly of HF. Natriuretic peptides, particularly NT-proANP and ANP, may be of benefit in the overall assessment of dogs with naturally occurring MR. Analysis of NT-proANP may be more useful than ANP owing to easier handling of the samples and less laborious assay.

Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease

OBJECTIVETo determine predictors of systolic anterior motion and left ventricular outflow tract obstruction (SAM/LVOTO) after mitral valve repair (MVRep) in patients with myxomatous mitral valve disease.BACKGROUNDMechanisms for the development of SAM/LVOTO after MVRep have been described; however, predictors of this complication have not been explored. We hypothesize that pre-MVRep transesophageal echocardiography (TEE) can predict postrepair SAM/LVOTO.METHODSUsing TEE, the lengths of the coapted anterior (AL) and posterior (PL) leaflets and the distance from the coaptation point to the septum (C-Sept) were measured before and after MVRep in 33 patients, including 11 who developed SAM/LVOTO (Group 1) and 22 who did not (Group 2).RESULTSGroup 1 patients had smaller AL/PL ratios (0.99 vs. 1.95, p < 0.0001) and C-Sept distances (2.53 vs. 3.01 cm, p = 0.012) prior to MVRep than those in Group 2. Resolution of SAM/LVOTO was associated with increases in AL/PL ratio and C-Sept distance. This reflects a more anterior position of the coaptation point in those who developed SAM/LVOTO.CONCLUSIONSThese data suggest that TEE analysis of the mitral apparatus can identify patients likely to develop SAM/LVOTO after MVRep for myxomatous valve disease. The findings are consistent with the concept that SAM of mitral leaflets is due to anterior malposition of slack mitral leaflet portions into the LVOT. The position of the coaptation point of the mitral leaflets is dynamic and a potential target and end point for surgical designs to prevent SAM/LVOTO post MVRep.

Increased endothelin-receptor density in myxomatous canine mitral valve leaflets.

In dogs and humans, myxomatous mitral valve disease results in mitral valve prolapse and mitral regurgitation. Diseased leaflets display endothelial damage, which in turn might lead to subendothelial growth through release of paracrine mediators such as endothelin-1. The aim of the study was to investigate the presence and distribution of endothelin receptors and relate these to the presence and severity of myxomatous valve disease in the dog. Valves with clear macroscopic signs of disease were taken at postmortem from five old dogs. Control valves without macroscopic signs of disease were taken from five young dogs. Endothelin receptors in the leaflets were examined by using radiolabeled endothelin-1 detected by autoradiography. The endothelin-receptor density was graded semiquantitatively. To determine disease severity, adjacent sections stained with periodic acid-Schiff (PAS)/Alcian blue were examined histologically. The leaflet thickness was measured, and the mucopolysaccharide deposition, collagen degeneration, and fibrosis were graded semiquantitatively. Diseased areas displayed high endothelin-receptor densities; normal-looking areas showed low densities. The endothelin-receptor density within as well as on the leaflets correlated positively with all four measures of disease severity in the distal most affected third of the cusps, suggesting that endothelin plays a pathogenetic role in canine myxomatous mitral valve disease.

Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease

Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease

Repair of commissural prolapse by extended leaflet sliding

Three patients had chronic mitral regurgitation due to commissural chorda rupture with commissural prolapse. Two of them had myxomatous valve disease and 1 had fibroelastic deficiency. Characteristic intraoperative epicardial and transesophageal echocardiographic findings are demonstrated. A technique is proposed that involves creating a new commissure and avoiding annular plication by extended sliding plasty and rotating the posterior mitral leaflet.

Lifetime risk for patients with mitral valve prolapse of developing severe valve regurgitation requiring surgery.

Severe mitral regurgitation requiring surgery is the most common life-threatening complication of mitral valve prolapse (MVP) and is due to progressive myxomatous change in the valve. We identified all residents of New South Wales, Australia, who had mitral valve surgery for myxomatous valve disease during 1982 and, using these data and the adult population statistics from 1982, estimated the cumulative risk of valve surgery in patients with MVP. In 1982, 50 of the 5.36 million New South Wales residents required surgery for this complication of MVP. Of the 50, 36 were men and 14 were women, which was significantly different from the population sex distribution (p less than 0.02) for mean age +/- SD of 60 +/- 11 years (range, 26-78 years). Using our previously determined 4% prevalence of adult MVP in New South Wales, we estimated the number of male and female patients with MVP at risk for each 5-year age interval and calculated age-specific event rates. The results show that the cumulative risk is minimal below the age of 50 years but then rises steeply, particularly in men. The risks in men aged 50, 60, and 70 years (with 95% confidence intervals) were 1:202 (130-448), 1:53 (37-82), and 1:28 (22-41), respectively. In women, the risk was less than half that in men (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship of mitral annular shape to the diagnosis of mitral valve prolapse.

The geometric or anatomic diagnosis of mitral valve prolapse, as opposed to the pathologic diagnosis of myxomatous valve disease, is based on the relationship of the mitral leaflets to the surrounding anulus. Current echocardiographic criteria for this diagnosis include leaflet displacement above the annular hinge points in any two-dimensional view; implicit in this equivalent use of intersecting views is the assumption that the mitral anulus is a euclidean plane. Prolapse by these criteria is found in a surprisingly large proportion of the general population. In most of these individuals, however, prolapse is present in the apical four-chamber view and absent in roughly orthogonal long-axis views of the left ventricle. This frequently observed discrepancy between leaflet-annular relationships in intersecting views suggests an underlying geometric property of the mitral apparatus that would produce the appearance of prolapse in one view without actual leaflet distortion. To address this possibility, a model of the mitral valve and anulus was constructed. When the model anulus was given a nonplanar, saddle-shaped configuration, the clinical observations were reproduced: the leaflets appeared to lie above the low points of the anulus in one plane, and below its high points in a perpendicular plane. Therefore, the appearance of mitral valve prolapse can occur without actual leaflet displacement above the most superior points of the mitral anulus if the anulus is nonplanar. To determine whether this pattern is reflected in the human mitral anulus, two-dimensional echocardiographic views of the mitral apparatus were obtained by rotation about the cardiac apex in 20 patients without evident annular or rheumatic valvular disease. In all cases the mitral anulus, as reconstructed from these views, had a nonplanar systolic configuration, with high points located anteriorly and posteriorly. This is consistent with the findings of other groups in animals, and would favor the appearance of prolapse in the four-chamber view and its absence in long-axis views that are oriented anteroposteriorly. This model can therefore explain the frequently observed discrepancy between leaflet-annular relationships in roughly orthogonal views. It challenges the assumption that the mitral anulus is planar as well as the diagnosis of prolapse in many otherwise normal individuals based on that assumption.