Primary myxomatous degeneration of cardiac valves. Clinical, pathological, haemodynamic, and echocardiographic profile

Comparative pathology of human and canine myxomatous mitral valve degeneration: 5HT and TGF-β mechanisms

Myxomatous mitral valve degeneration (MMVD) is a leading cause of valve repair or replacement secondary to the production of mitral regurgitation, cardiac enlargement, systolic dysfunction, and heart failure. The pathophysiology of myxomatous mitral valve degeneration is complex and incompletely understood, but key features include activation and transformation of mitral valve (MV) valvular interstitial cells (VICs) into an active phenotype leading to remodeling of the extracellular matrix and compromise of the structural components of the mitral valve leaflets. Uncovering the mechanisms behind these events offers the potential for therapies to prevent, delay, or reverse myxomatous mitral valve degeneration. One such mechanism involves the neurotransmitter serotonin (5HT), which has been linked to development of valvulopathy in a variety of settings, including valvulopathy induced by serotonergic drugs, Serotonin-producing carcinoid tumors, and development of valvulopathy in laboratory animals exposed to high levels of serotonin. Similar to humans, the domestic dog also experiences naturally occurring myxomatous mitral valve degeneration, and in some breeds of dogs, the lifetime prevalence of myxomatous mitral valve degeneration reaches 100%. In dogs, myxomatous mitral valve degeneration has been associated with high serum serotonin, increased expression of serotonin-receptors, autocrine production of serotonin within the mitral valve leaflets, and downregulation of serotonin clearance mechanisms. One pathway closely associated with serotonin involves transforming growth factor beta (TGF-β) and the two pathways share a common ability to activate mitral valve valvular interstitial cells in both humans and dogs. Understanding the role of serotonin and transforming growth factor beta in myxomatous mitral valve degeneration gives rise to potential therapies, such as 5HT receptor (5HT-R) antagonists. The main purposes of this review are to highlight the commonalities between myxomatous mitral valve degeneration in humans and dogs, with specific regards to serotonin and transforming growth factor beta, and to champion the dog as a relevant and particularly valuable model of human disease that can accelerate development of novel therapies.

Gross and histological features of excised portions of posterior mitral leaflet in patients having operative repair of mitral valve prolapse and comments on the concept of missing (= ruptured) chordae tendineae

OBJECTIVES

The aim of the study is to describe gross and histological features of operatively excised portions of mitral valves in patients with mitral valve prolapse (MVP).

BACKGROUND

Although numerous articles on MVP (myxomatous or myxoid degeneration, billowing or floppy mitral valve) have appeared, 2 virtually constant histological features have been underemphasized or overlooked: 1) the presence of superimposed fibrous tissue on both surfaces of the leaflets and surrounding many chordae tendineae; and 2) the absence of many chordae tendineae on the ventricular surfaces of the leaflets as the result of their being hidden (i.e., covered up) by the superimposed fibrous tissue.

METHODS

We examined operatively excised portions of prolapsed posterior mitral leaflets in 37 patients having operative repair.

RESULTS

Histological study of elastic-tissue stained sections disclosed that the leaflet thickening was primarily due to the superimposed fibrous tissue. All leaflets had variable increases in the spongiosa element within the leaflet itself with some disruption and/or loss of the fibrosa element and occasionally complete separation of it from the spongiosa element. Both the leaflet and chordae were separated from the superimposed fibrous tissue by their black-staining elastic membranes.

CONCLUSIONS

These findings demonstrate that the posterior leaflet thickening in MVP is mainly due to the superimposed fibrous tissue rather than to an increased volume of the spongiosa element of the leaflet itself. The superimposed fibrous tissue on both leaflet and chordae is likely the result of subsequent abnormal contact of the leaflets and chordae with one another. Chordal rupture (i.e., missing chordae) occurred in all 37 patients, but finding individual ruptured chords was rare.

Relation of mitral valve prolapse to basal left ventricular hypertrophy as determined by cardiac magnetic resonance imaging

We aimed to characterize the extent and distribution of focal basal left ventricular (LV) hypertrophy in patients with mitral valve prolapse (MVP). Sixty-three patients (mean age: 58 ± 14 years) with MVP and 20 age-matched normal volunteers (mean age: 53 ± 11 years) were assessed using cardiac magnetic resonance imaging. We compared the ratio of basal to mid end-diastolic wall thickness in both groups and correlated it with clinical and imaging parameters. Of the 63 patients, 44 (70%) had posterior leaflet prolapse, 2 (3%) had anterior leaflet prolapse, and 17 (27%) had bileaflet prolapse. There was a significantly increased ratio of basal to mid-ventricular end-diastolic wall thickness in all segments of the left ventricle in those with MVP compared to the controls. The inferolateral (2.1 vs 1.0, p <0.01) and anterolateral (2.1 vs 1.1) ratios (p <0.01) were the greatest compared to the other myocardial segments. The degree of mitral annular excursion had a strong positive correlation with the degree of hypertrophy (r(2) = 0.81, p <0.01) and was an independent predictor in adjusted multivariate analysis (p <0.0001). Age, body mass index, LV end-diastolic volume index, LV end -systolic volume index, LV stroke volume index, degree of prolapse, and mitral regurgitation volume did not have any significant correlation with the degree of hypertrophy. In conclusion, MVP is associated with concentric basal LV hypertrophy and good correlation between the excursion of the mitral valve annulus and the degree of relative LV hypertrophy suggests that locally increased myocardial function could be responsible for this remodeling.

Echocardiographic determination of the prevalence of primary myxomatous degeneration of the cardiac valves

BACKGROUND

There is a paucity of data on the prevalence of primary myxomatous degeneration (PMD) of the cardiac valves. Because the gold standard for the diagnosis is pathology, its preoperative detection rate is relatively low. The purposes of this study were to determine the capability of echocardiography to identify PMD compared with surgical pathological findings and to determine the echocardiographic features of PMD.

METHODS

Echocardiograms were retrospectively compared with pathologic findings in 1,080 patients undergoing surgery for moderate or severe cardiac valve regurgitation. PMD of the mitral, aortic, and tricuspid valves was retrospectively identified, with a comparison of the echocardiographic and pathologic findings, to estimate the prevalence of PMD and to summarize its echocardiographic features.

RESULTS

Of 1,080 patients, 104 were diagnosed with PMD (prevalence, 9.62%). Echocardiography identified valvular prolapse and thickening in 85% of patients. The echocardiographic characteristics of PMD included valvular regurgitation, valvular thickening, valvular prolapse, and rupture of chordae tendineae. Combinations of these characteristics were seen on multiple valves. Among patients with PMD, 59 had only mitral valve involvement, 25 had only aortic valve involvement, two had only tricuspid valve involvement, 10 had both mitral and aortic valve involvement, and three had both mitral and tricuspid valve involvement.

CONCLUSIONS

In patients undergoing surgery for valvular regurgitation, a high prevalence of PMD was found. PMD has distinctive echocardiographic features, suggesting its preoperative diagnosis.

Cardiac Valvular Pathology: Comparative Pathology and Animal Models of Acquired Cardiac Valvular Diseases

Recent voluntary withdrawal of the ergoline-derivative Alzheimers’ drug Pergolide (Permax) resulting from demonstrated risk of cardiac valve injury illustrates the increased importance of valve injury in pharmaceutical toxicology. Following the 2001 landmark discovery of cardiac valve injury associated with the widely prescribed anti-obesity drug combination fenfluramine-phentermine, and subsequent withdrawal, the need to understand and assess cardiac valve biology and pathology both preclinically and clinically has been accentuated. Unique aspects of the developmental biology, anatomy, and physiology of cardiac valves compared to main cardiac tissue have been discovered, and key elements of the pathophysiology of various valvular injury mechanisms have been described. Although general clinical cardiac valvular disease in humans has been well characterized, animal modeling of valvular injury has proved to be difficult and undersubscribed. Additionally, both the preclinical, pharmaceutical, toxicologic assessment of valvular injury and the understanding of species-comparative valvular pathology have been limited. As discoveries and awareness grows, the purpose of this paper is to review the structure and function of cardiac valves, mechanisms, and outcomes of the common acquired human cardiac valve diseases, including those that are drug-related; to summarize comparative laboratory animal valvular pathology; and to review the literature of contemporary animal models of valvular injury.

Uncontrolled acromegaly is associated with progressive mitral valvular regurgitation

INTRODUCTION

Recent cross-sectional studies have documented an association between acromegaly and regurgitant valvular heart disease. The aim of this study was to evaluate the change in prevalence of valvular heart disease in relation to the clinical activity, because the natural history of valvular changes in acromegaly is unknown.

PATIENTS AND METHODS

Valvular regurgitation was assessed in 37 acromegalic patients (18 patients with active disease, and 19 with controlled disease) by conventional two-dimensional and Doppler echocardiography before and after an interval of 1.9 years (range 1.5-3.0 years).

RESULTS

At baseline, valvular regurgitation (mitral and aortic sites combined) was present in 46% of the patients and increased to 67% at follow-up (P=0.008). Mitral regurgitation increased significantly from 32% to 60% (P=0.002), but no change was noted for the aortic valve (27% vs. 31%, NS). In patients with active disease, valvular regurgitation increased significantly from 56% at baseline to 88% at follow-up (P=0.031) due to a significant increase of mitral regurgitation from 39% to 78% at follow-up (P=0.016). In contrast, no increase in valvular regurgitation was found in patients with controlled disease.

CONCLUSION

The prevalence of mitral, but not aortic, valvular regurgitation increased in patients with active acromegaly during follow-up. Patients with acromegaly require adequate cardiac evaluation and follow-up to establish the extent and progression of valvular involvement.

Mechanical properties of myxomatous mitral valves

OBJECTIVE

We sought to characterize the mechanical properties of normal and myxomatous mitral valve tissues.

METHODS

We tested 113 mitral valve sections from patients undergoing mitral valve repair or replacement for myxomatous mitral valve prolapse and sections from 33 normal valves obtained at autopsy.

RESULTS

Myxomatous mitral valve leaflets were more extensible than normal leaflets when tested parallel to the free edge (41.2% +/- 18.5% vs 17.3% +/- 6.7% circumferential strain [mean +/- SD]; P <.001), as well as perpendicular to the free edge (43.2% +/- 19.4% vs 17.3% +/- 6.7% radial strain; P <.001). Myxoid leaflets were less stiff circumferentially (4.0 +/- 1.6 vs 6.1 +/- 1.4 kN/m; P <.001) and radially (4.5 +/- 1.1 vs 6.1 +/- 1.4 kN/m; P <.001) than normal leaflets. Leaflet strength, however, was similar in both groups.

CONCLUSIONS

Myxomatous mitral valve leaflets are physically and mechanically different from normal mitral valve leaflets. They are more extensible and less stiff. Compared with chordae examined previously, however, they are affected much less. Myxomatous mitral valve disease may therefore affect the collagen in the chordae more severely than that in the leaflets.

Causes of isolated aortic insufficiency in an urban population in the 1990s a review of 56 surgical pathology cases

Until recently, the cause of isolated aortic insufficiency (AI) was usually thought to be inflammatory or rheumatic in most cases. However, at our institution we have noted a high prevalence of myxomatous degeneration (MD) in aortic valves removed for AI. In this study we report anatomic observations on valves from 56 consecutive patients with isolated AI undergoing aortic valve replacement surgery. Fifty-six consecutive aortic valves removed at our institution from 1994 to 1996 for isolated AI and/or aortic aneurysm were reviewed. Anatomic features were compared with clinical history and echocardiographic data. The anatomic results were also compared to 22 age-matched control aortic valves obtained at autopsy. In 13/56 cases (23%), a specific valvular cause of AI was determined (infectious endocarditis, seven cases; chronic rheumatic disease, four cases; congenital bicuspid valve, two cases). Of the remaining (idiopathic) 43 cases, 18 (42%) had severe isolated MD defined as >50% expansion of the spongiosa and disruption of the fibrosa by the deposition of acid mucopolysaccharides in the absence of severe calcification, fibrosis, or other pathologic findings. Only 1/22 aortic valves from the autopsy controls had severe MD. Eighteen of the 56 patients also had a clinical history of aortic dilatation/aneurysm of which 12 were confirmed to be dilated by echocardiographic criteria. Of these 12, five (42%) had MD of the aortic valve only, three (25%) had both MD and cystic medial degeneration (CMD) of the aorta, two (17%) had CMD of the aorta only, and two (17%) had no specific diagnosis. Isolated MD of the aortic valve is the most common cause of isolated AI in our patient population. Furthermore, in a subset of non-Marfan's patients with both AI and dilatation of the aortic root/aortic aneurysm the incidence of MD is even higher (67%). These results suggest that there is overlap between MD and CMD in non-Marfan's patients and that both entities may be part of a spectrum of a generalized connective tissue disorder.

Mucoid dysplasia of tricuspid and congenital bicuspid aortic valves in Syrian hamsters (Mesocricetus auratus)

A histological study was made of the aortic valves of 141 Syrian hamsters aged between 35 and 657 days, belonging to an inbred laboratory colony with a high incidence of congenital bicuspid aortic valves. A tricuspid aortic valve was found in 81 specimens, whereas the remaining 60 possessed a bicuspid aortic valve. In all bicuspid valves there were two aortic sinuses, a ventral and a dorsal, each supporting one cusp. Thirty-three (23.4%) of the 141 specimens showed mucoid dysplasia of the aortic valve. The defect was characterized by thickening of the valve cusps and disruption of the fibrosa layer accompanied by an increased amount of glycosaminoglycans. Ten (12.3%) of the 81 tricuspid aortic valves and 23 (38.3%) of the 60 bicuspid aortic valves were dysplastic. This difference was statistically significant (P < 0.001). The findings indicate that, in the Syrian hamster, the simultaneous occurrence of bicuspid aortic valve and aortic valve dysplasia is not a random event. However, the fact that these valve defects also occur independently suggests that there is no primary morphogenetic dependence between them, but that some other cause predisposes to their concurrence.

Surgical pathology of the mitral valve: gross and histological study of 1288 surgically excised valves

A consecutive series of 1288 mitral valves surgically excised from 1981 through 1989 were studied macroscopically and histologically. The explanted valves were affected by: chronic rheumatic disease (1179, 91.5%), floppy mitral valve (84, 6.5%), bacterial endocarditis (19, 1.5%), and post-ischemic mitral incompetence (6, 0.5%). Among 1179 post-rheumatic cases, mixed mitral stenosis and incompetence was the most frequent malfunction (747, 58%). Isolated mitral incompetence was diagnosed in 72 (6.11%) cases only, and isolated stenosis in 360 cases. In 52 valves, excised because of chronic rheumatic disease, the histology showed unexpected signs of acute rheumatism of the leaflets and the papillary muscles. In these patients clinical symptoms and blood tests were negative for rheumatic disease. Mitral incompetence, possibly due to papillary muscle dysfunction, was the prevalent lesion (61.5%). A total of 181 patients (14.05%) with pure mitral incompetence underwent surgery. In 84 patients (46.4%), the floppy mitral valve was the most frequent cause of valve dysfunction, 72 (39.8%) had rheumatic disease, 19 (10.5%) infective endocarditis, and 6 (3.4%) ischemic heart disease. In the group with floppy mitral valve, males were more prevalent than females (51:33). The mean age of the 4 patients with Marfan's syndrome and non-Marfan patients was noticeably different (17 vs 49 yr). Moreover leaflet deformation, tendinous cord elongation and annulus dilatation were the most common causes of valve incompetence. Floppy mitral valve and infective endocarditis were the cause of cordal rupture in 43.5% of the cases. This was a severe complication which always required emergency surgery.

Myxoid heart disease: an assessment of extravalvular cardiac pathology in severe mitral valve prolapse

Because of the microscopic features of the affected leaflets in mitral valve prolapse (MVP), myxoid degeneration of the valve is a common pathologic designation applied to this condition. We undertook this study as a means of gaining an insight into the occurrence and prevalence of extravalvular cardiac alterations in hearts with severe MVP. Tissues of 24 hearts with severe myxomatous transformation of the mitral valve as the sole cardiac abnormality were examined. Eighteen of the 24 subjects with severe MVP died suddenly. Only two of these had pathologic evidence of severe mitral insufficiency. Twenty-four normal hearts served as controls. The two groups of hearts came from victims of homicide, suicide, accident, or natural death. Sections of the mitral valve, working myocardium, conduction system, and cardiac nerves and ganglia were studied by routine and special connective tissue and proteoglycan stains. Similar to the findings in severely affected mitral valves, prominent deposits of proteoglycans in neural and conduction tissue readily distinguished hearts with myxomatous valve changes from the control hearts. We conclude that the commonly recognized local derangement of valvular tissue in MVP is but one specific reflection of a more general myxomatous alteration in cardiac connective tissue.

Cystic medionecrosis of the coronary arteries and fatal coronary vasospasm

The histopathological basis of coronary vasospasm is not well defined. We report a patient with directly observed coronary artery spasm in whom cystic medionecrosis of the coronary arteries and great vessels and myxomatous degeneration of the mitral valve were evident. We suggest that myxoid connective tissue lesions of the heart may be linked to coronary vasospasm.

Hydrocephalus, tall stature, joint laxity, and kyphoscoliosis: a new inherited disorder of connective tissue?

We describe two sisters with hydrocephalus, tall stature, joint laxity, and thoracolumbar kyphosis.

Biochemical characterization of individual normal, floppy and rheumatic human mitral valves

Human mitral valves (32 floppy and 17 rheumatic) obtained at surgery were analysed and compared with 35 normal (autopsy) valves. Total amounts of collagen, proteoglycan and elastin were increased approx. 3-fold in floppy and rheumatic valves. The water content of rheumatic cusps was lower than normal. The most significant changes in floppy valves were the 59% increase in mean value of the proteoglycan content, a large increase in the ease of extractability of proteoglycans from 26.7 to 57.2% of the total and a 62% increase in mean value of the elastin content in the anterior cusps. Normal human mitral valve cusps contained a mean proportion of 29.3 (and chordae 26.6) type III collagen (as % of total types III + I collagen), the values increasing significantly to 33.2 and 36.3% respectively in chronic rheumatic disease. The ratio observed in floppy valves depended on the extent of secondary surface fibrosis, which could be demonstrated histologically; in valve cusps with considerable secondary fibrosis, the percentage of type III increased significantly (to 34.4%), whereas it decreased significantly (to 25.2%) when fibrosis was negligible. It is concluded that the ratio of collagen types in floppy valves reflects the extent of secondary fibrosis rather than the pathogenesis of the disrupted collagen in the central core of the valve.

Abnormal chordal insertion: a cause of mitral valve prolapse

Although the morphology of mitral valve prolapse (MVP) has been described, abnormalities of chordal arrangement and insertion have not been emphasized. We retrospectively reviewed 23 surgically-excised MVP and 10 control mitral valves removed at necropsy. Two-dimensional echocardiograms (2DE) were available in 10 MVP and in six additional controls. 2DE accurately assessed the length of anterior leaflet (AL) and posterior leaflet (PL) of the mitral valve (3.2 +/- 0.7 cm and 2.2 +/- 0.6 cm, respectively) as compared to morphologic measurements (3.0 +/- 0.4 cm and 2.1 +/- 0.4 cm, respectively). However, annular diameter as assessed by echocardiography was significantly less (4.6 +/- 0.7 cm) than that derived by morphologic measurements of annular circumference (AC) (5.3 +/- 0.7 cm). The AL and PL lengths and the mitral anuli were significantly larger in patients with MVP as compared to controls (p less than 0.01) when assessed both by 2DE and by morphology. The ratio of the maximum distance of chordal separation/AC was 0.11 +/- 0.04 in MVP and 0.13 +/- 0.02 in controls (p less than 0.05). Chordal divisions were increased in MVP (4.2) compared to controls (3.1, p less than 0.01). The most striking morphologic feature of MVP was abnormal chordal insertion and a random, unpredictable pattern of chordal distribution. We postulate that abnormal chordal architecture may be responsible for unequal stress on the valve leaflets and may thus lead to MVP.

Myxoid degeneration of the aortic valve and isolated severe aortic regurgitation

Clinical and pathologic data were reviewed in 55 patients who had valve replacement for pure aortic regurgitation (AR) during a 6-year period. The clinical histories established the cause for AR in 34 cases: 11 rheumatic, 13 infective endocarditis, 4 congenital, 4 associated with aortic aneurysms and 2 the Marfan syndrome. In the valves from the other 21 patients, 13 had myxoid degeneration, defined as significant disruption of the valve fibrosa and its replacement by acid mucopolysaccharides and cystic change. Myxoid degeneration was also the primary pathologic abnormality in the 2 patients with the Marfan's syndrome, in 3 patients with a history of rheumatic disease and in 1 patient with a history of infective endocarditis. The patients with myxoid degeneration of uncertain origin were predominantly elderly (average age 63 years), had a long-standing history of systemic hypertension (77%) and had coronary artery disease (46%); 85% were male. In these patients the replacement valves were not larger than those of the other groups studied, indicating that dilatation of the aortic anulus was not a significant factor in the pathogenesis of the valve disease. These findings indicate that myxoid degeneration of the aortic valve is common (36% of all valves examined) and, in many cases, may be secondary to long-standing systemic hypertension.

Floppy aortic valve presenting as sudden death

A previously healthy 34-year-old Dutch immigrant to Australia died unexpectedly in his sleep. At autopsy the only significant finding was a floppy aortic valve (FAV). Histologic, histochemical and electron microscopic studies corroborated the macroscopic diagnosis. Previously described associations of the FAV include the floppy mitral valve, Marfan's syndrome, aortic root dilatation and aortic cystic medial necrosis. None of these features were found in the present case which is the first recorded example of isolated FAV presenting as sudden death. The mechanism of death is obscure, and while it is presumed to be dysrhythmic, a detailed histological examination of the cardiac conducting system revealed no anatomic abnormality.

Mitral valve prolapse and spasm of normal coronary arteries: report of four cases and review of the literature

The association between mitral valve prolapse (MVP) and atypical chest pain has been well-described. Numerous theories have been proposed to explain this association. A number of lines of evidence suggest that underlying ischemia may cause chest pain in some patients with MVP. We have recently evaluated 4 patients with chest pain syndromes who had angiographic evidence of MVP and spasm of angiographically normal coronary arteries. The possibility that coronary spasm is the underlying etiology of chest pain in some patients with mitral valve prolapse raises a theoretical argument against beta-blockade in these patients. Three of our patients were successfully treated with calcium channel blockers.

Mitral valve prolapse and joint hypermobility: evidence for a systemic connective tissue abnormality?

Clinical evidence for an abnormally of extracardiac connective tissue was sought in 21 patients with idiopathic mitral valve prolapse and was compared to that in 21 matched controls. The incidence of rheumatic and orthopaedic complaints and the prevalence of hypermobile joints, Marfanoid habitus, and skeletal deformity were compared in the 2 groups. Skin thickness and elasticity were measured, and the mean values in the 2 groups were compared. hypermobile joints were significantly commoner in patients with mitral valve prolapse. Easy bruising was reported significantly more commonly by patients with mitral prolapse; the incidence of other rheumatic complaints was similar in the 2 groups. There was no significant difference in skin thickness, skin elasticity, and the prevalence of either skeletal deformity or Marfanoid habitus between patients with mitral valve prolapse and controls. The results support previous evidence of an association between mitral valve prolapse and benign hypermobility of the joints, but emphasise that many patients with mitral valve prolapse have no clinically apparent connective tissue abnormality outside the heart. It remains uncertain whether the valve lesion in these patients represents a tissue-specific abnormality of mitral valve collagen or the only clinical expression of a minor systemic connective tissue abnormality.

Abnormal aortic valve echoes in mitral prolapse. Echocardiographic features of floppy aortic valve

The following distinctive combination of M-mode and two dimensional echocardiographic abnormalities of the aortic valve was observed in a group of 12 patients, of whom 11 had mitral valve prolapse. On two dimensional scans, the aortic cusps were freely mobile but appeared thickened or folded. On M-mode records, cusp excursion was normal: there was well defined systolic oscillation, and cusp echoes were multiple and centrally positioned within the aortic root during diastole. The aortic valve was inspected at operation in two patients: a typically myxomatous valve was replaced in one and findings were in keeping with this diagnosis in the other. It is suggested that the echocardiographic features described are characteristic of the floppy aortic valve. Despite the echocardiographic abnormalities, only three patients had clinical evidence of an aortic valve lesion. It is, therefore, further suggested that the investigation of patients with mitral prolapse should include echocardiographic assessment of the aortic valve, even when associated myxomatous degeneration of that valve is not suspected clinically.