Myxomatous degeneration
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]
Overivew
Myxomatous degeneration refers to a pathological weakening of connective tissue. The term is most often used in the context of Mitral valve prolapse, which is known more technically as "Myxomatous degeneration of the mitral valve." It can also be used in reference to degeneration of the aortic valve.
Pathophysiology
The degeneration occurs in conjunction with an accumulation of dermatan sulfate, a glycosaminoglycan, within the connective tissuematrix of the valve. The exact mechanism is unknown.
In many cases, the degeneration is limited to the mitral valve and follows a benign course. When associated with systemic diseases, like Marfan syndrome, the degeneration is more extensive and involves other heart valves. The valves can become sufficiently distorted to cause insufficiency and regurgitation.
Deposition of excessive proteoglycans causes widening of the fibrosa, which extends towards basal aspects and also tends to involve the annulus and chords, which further leads to loss of collagen an elastic tissue.
Myxomatous degeneration can occur in other organs like uterus, where we can see myxomatous degeneration of uterine fibroids.
Historical Perspective
- Myxomatous Mitral Valve disease was first reported by Delabere Blaine in 1817 in dogs.[1]
- Myxomatous Degeneration of Mitral Valve is a gentic abnormality mapped to Xq28 gene.
Classification
- Myxomatous degeneration may be classified as:
- Primary
- Secondary
- Whitney in1967 classified Myxomatous Mitral Valve Disease into 4 types based on the structures involved-[1]
- Type I,II- Small nodular thickening of mitral leaflets without chordae tendinae involvement
- Type III-Severe thickening and ballooning of valve cusps
- Type IV- Chordae tendinae thickening and Occasional rupture
Pathophysiology
- The pathogenesis of Myxomatous mitral valve degeneration is characterized by Valvular or chordal degeneration with excesssive systolic movement of leaflet defined by a prolapse in Left atrium >/2mm.
- It can affect one or both leaflets and can affect one or multiple scallops.
- Degeneration of Mitral valve is divided into two phenotypes:[2]
- Fibro Elastic Deficiency:
- localised to one segment.
- involves ruptured chords.
- Histologically- Myxomatous degeneration
- Macroscopically- Leaflet redundancy and thickening predominant on the flail segment.
- Reminder of the valve is thin and translucent.
- Patients present in older ages
- Diffuse Myxomatous Degeneration:
- Generalised
- Redundancy and thickening of both leaflets involving multiple segments
- .Mitral Regurgitation typically predominates in midl-ate systole.
- Severeity varies from mild to severe.
Clinical Features:
Patients can be asymptomatic,or can have mild to severe symptoms.
Patients can have heart murmur, cough, dyspnea, signs and symptoms of Congestive Heart Failure, Arrythmias.
Differentiating Myxomatous Mitral Valve Degeneration from other Diseases
- Myxomatous degeneration of Mitral Valve must be differentiated from other diseases that cause Mitral Valve Regurgiation, such as:[3]
- Ischemic Injury to Mitral Valve
- Rheumatic Heart Disease
- Connective tissue disorder
Epidemiology and Demographics
- The prevalence of Myxomatous Mitral Valve Degeneration in Canines, increases as age increase, and the prevalence especially in old, small breed dogs is 100%.
- It affects about 5% of the Human population.[4]
Age and Gender
- It is more common in Young females.
- It is frequently symptomatic in males.
Risk Factors
- Common risk factors in the development of Myxomatous degeneration are Connective tissue disorders like Marfan's Syndrome, Ehlers-Danlos syndrome, and other conditions with collagen abnormalities.
Natural History, Complications and Prognosis
- The majority of patients with Myxomatous degeneration of Mitral Valve are asymptomatic.
- Early clinical features include presence of a heart murmur.
- If left untreated,about 10% of patients with Myxomatous degeneration of Mitral Valve may progress to develop severe Mitral regurgitation requiring surgical repair of the valve.[5]
- Common complications of Myxomatous degeneration of Mitral Valve include rupture of the chordae tendinae leading to acute mitral regurgitation, Arrythmias, Congestive Heart Failure,Endocarditis ,rarely Sudden cardiac death.
- Prognosis is generally good after Mitral Valve repair.
Diagnosis
Diagnostic Criteria
- The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:
- [criterion 1]
- [criterion 2]
- [criterion 3]
- [criterion 4]
Symptoms
- Myxomatous degeneration of mitral valve can be asymptomatic.
- Symptoms of Myxomatous degeneration of Mitral valve may include the following:
- Apical Holosystolic murmur
- Systolic click to mid late systolic murmur
- Cough - due to Heart failure
- Dyspnea- Pulmonary edema, Pulmonary Hypertension.
- Syncope- arrythmias
Physical Examination
- Patients with Myxomatous degeneration of mitral valve usually present with Mitral Valve prolapse.
- Physical examination may be remarkable for:
- Systolic click or mid-late systolic murmur.
- Apical holosystolic murmur[6]
Laboratory Findings
- There are no specific laboratory findings associated with Myxomatous degeneration of Mitral valve
Imaging Findings
- 2D Echocardiography is the imaging modality of choice.
- Transesophageal Echo- shows Mitral valve prolapse and Mitral valve thickening.[7]
Other Diagnostic Studies
- Xray Chest- can show cardiomegaly.
- Electrocardiogram (ECG)- non invasive test, Can help in detecting arrythmias, Left atrial enlargement, Left Ventricle hypertrophy.
- CT Scan-non invasive imaging test,Can measure the degree of leaflet displacement and relation between valve leaflets and annulus.
- MRI- non invasive, can provide information on the severeity of Mitral Regurgitation[8].
Treatment
Medical Therapy
- There is no medical therapy for Myxomatous degeneration of Mitral Valve, the mainstay of therapy is supportive care.
- Diuretics- if symptoms of Heart failure
- ACE inhibitors
- β blockers
- Vasodilators
Surgery[9]
- Surgery is the mainstay of therapy for Myxomatous degeneration of Mitral Valve.
- Mitral Valve repair is the preferred surgical technique.
- Mitral valve repair when compared to replacement improves survival, Left ventricular function, and decreased chance of reoperation.
- Mitral Valve replacement can also be done.
Prevention
- There are no primary preventive measures available for Myxomatous degeneration of Mitral Valve.
References
- ↑ 1.0 1.1 Borgarelli M, Buchanan JW (2012). "Historical review, epidemiology and natural history of degenerative mitral valve disease". J Vet Cardiol. 14 (1): 93–101. doi:10.1016/j.jvc.2012.01.011. PMID 22386588.
- ↑ Antoine, Clemence; Mantovani, Francesca; Benfari, Giovanni; Mankad, Sunil V.; Maalouf, Joseph F.; Michelena, Hector I.; Enriquez-Sarano, Maurice (2018). "Pathophysiology of Degenerative Mitral Regurgitation". Circulation: Cardiovascular Imaging. 11 (1). doi:10.1161/CIRCIMAGING.116.005971. ISSN 1941-9651.
- ↑ . 2007. doi:10.1016/B978-1-4160-2971-7.X1000-8. Missing or empty
|title=(help) - ↑ . 2016. doi:10.1016/C2013-0-12761-4. Missing or empty
|title=(help) - ↑ . 2019. doi:10.1016/C2017-0-02974-9. Missing or empty
|title=(help) - ↑ . 2016. doi:10.1016/C2013-0-12761-4. Missing or empty
|title=(help) - ↑ . 2010. doi:10.1016/B978-1-4160-6231-8.X0001-3. Missing or empty
|title=(help) - ↑ . 2010. doi:10.1016/B978-1-4160-6231-8.X0001-3. Missing or empty
|title=(help) - ↑ . 2019. doi:10.1016/C2017-0-02974-9. Missing or empty
|title=(help)