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Mitral stenosis

Mitral stenosis ( MS ) refers to a reduction in in mitral valve area and associated reduction in left ventricular inflow

 

Most common cause worldwide is rheumatic fever Rheumatic heart valve disease ( RHVD ) is the leading cause of cardiovascular death in children and young adults – mainly women in middle and low income countries Two thirds of the world population lives in developing countries with a high prevalence of rheumatic fever or RHVD Rheumatic heart disease causes 250 ,000 deaths in young people worldwide Rheumatic mitral valve stenosis is more common in females Incidence of RHVD has declined in the developed world with an estimated incidence of 1 in 10 000 ( on the contrary for e.g in Africa it is 35 cases per 100 000 ) It is estimated that up to 30 million schoolchildren and young adults have chronic rheumatic heart disease worldwide & nearly a third also have MS
 Degenerative calcification – DMS is the leading cause in the developed worldseen in the elderly
○ they often have other CV risk factors ( hypertension , atherosclerotic disease and often aortic stenosis )
○ may also be seen in those with CKD or more rarely in congenital metabolic disorders or Marfan’s syndrome
 Other uncommon/ rare causes of mitral stenosis include
○ calcification
○ congenital heart disease
○ infective endocarditis
○ mitral annular calcification
○ endomyocardial fibroelastosis
○ malignant carcinoid syndrome
○ systemic lupus erythematosus
○ Whipple disease
○ Fabry disease
○ rheumatoid arthritis.

 

Rheumatic heart disease or rheumatic heart valve disease ( RHVD ) – happens due to the systemic immune response against beta-hemolytic streptococci infection of the pharynx rheumatic fever attacks may be single or repeated RHVD is an indolent progressive lifelong condition acute rheumatic fever happens around 3 week after group A streptococcal pharyngitis and can affect joints , skin , brain and the heart it is thought that recurrent Streptococcus pyogen infection leads to RHVD the abnormal immune response cause damage to the mitral valve antibodies to streptococcal antigens cross react with valve tissue – damage to the valve accumlating over decades

 mitral valve is a complex , dynamic structure which incorporates the two main leaflets and also an annulus , tendinous chords and papillary muscles connecting the valve leaflets to the LV In RHVD the anatomical lesions combine to varying degrees ; fusion of one or both commissures ( main mechanism of RHVD is commissural fusion ) ; thickening fibrosis and calcification of valves and shortening , thickening and fusion of the subvalvular structure the valve narrows to the shape of a fish mouth the normal area of the mitral valve in 4 to 6 cm symptoms only manifest once the stenosis is moderate to severe 
( for e.g valve area < 1.5 cm ) RHVD can also affect the aortic valve leading to calcific degeneration.

 

Mitral valve is narrowed -It is more difficult for the blood to flow from the left atrium ( LA ) in to the left ventricle ( LV ) during the ventricular diastole -Blood flows back to LA and the LA pressure increases-LA enlarges over time as it has to generate higher than normal pressure when it contracts against the high resistance of a stenosed MV.

 

LA dilatation pulmonary venous hypertension reflex pulmonary arterioralol constriction obliterative changes in pul vascular bed pulmonary arterial hypertension rt ventricular hypertrophy tricuspid valve dysfunction systemic venous congestion compromised LV filling reduced / subnormal cardiac output.

 

long latent period ( often up to 20 yrs ) often asymptomatic in the early disease – LA dilates & keeps the pulmonary venous pressure stable
 often the symptoms would manifest in 3rd or 4th decade of life dyspnoea ( often during exercise or in combination with disorders that increase heart rate or flow across the mitral valve ) paroxysmal nocturnal dyspnoea fatigue ( reduced cardiac output )
 patients tend to adapt to their level of functional capacity and deny any symptoms of dyspnoea despite objective evidence
 triggers for marked dyspnoea or pulmonary oedema may include
○ pregnancy ( symptoms may manifest in the 2nd trimester due to increase i n blood volume and cardiac output )
○ emotional stress
○ sexual intercourse
○ infection
○ onset of AFib

ie factors that change the heart rate , volume status or the cardiac output would act as triggers for acute deterioration 
 atrial fibrillation ( left atrial dilatation and hypertrophy , rheumatic insult to the atria , internodal tracts and SA node )
○ presentation with AF is not related to severity of MS
○ AFib happens in 30% to 40 % of patients with MS
○ can be paroxysmal or chronic
○ thrombosis
 rare symptoms include
○ haemoptysis
○ chest pain ( often due to pulmonary hypertension )
○ dilated LA exerting pressure on adjacent structures for e,g hoarseness due to compression of the left recurrent laryngeal nerve against the pulmonary artery or cough due to compression of the bronchi
 Death happens due to heart failure or systemic embolism.

 

Physical -palpable S1 over apex advanced case may present with symptoms of rt sided heart failure left parasternal heave (rt ventricular hypertrophy 2ary to pul 
hypertension ) tapping apex beat irregular pulse ( AFib ) severe -Mitral facies or malar flush-non specific sign due to chronic low cardiac output state combined with systemic vasoconstriction

 

Auscultation -1st HS is loud 2nd HS split -pulmonic component P2 can be loud if severe pul hypertension present diastolic murmur -rumble ( due to turbulence as the blood flows across a stenosed valve ) best heard at apex with patient in left lateral position murmur is often preceded by an opening snap due to sudden opening of a stiffened valve from higher LAP.

 

ECG -LA enlargement ( P wave changes ) Atrial fibrillation Rt axis deviation and rt ventricular hypertrophy suggests severe pulmonary hypertension.

 

CXR -signs of LA enlargement Rt ventricular enlargement as the disease progresses symptoms of elevated pulmonary pressure prominent pulmonary arteries redistribution of pulmonary vasculature to the upper lobes interstitial edema ( Karley A and B lines )

 

Echocardiography-specific and sensitive method diagnostic test of choice -provides two vital parameters ie pressure gradient between the left ventricle and left atrium and the mitral valve area 2-D echo , colour flow Doppler shows morphology which includes leaflet mobility & flexibility , leaflet thickness , leaflet calcification and impairment of the subvalvular apparatus Transthoracic echo ( TEE ) delivers better quality images and the presence of left atrial appendage thrombus

 

States of mitral stenosis At risk of MS progressive MS asymptomatic severe MS symptomatic severe MS

 

Medical management -management of atrial fibrillation prophylaxis for infective endocarditisPlease refer to NICE guideline 64 or look at the documentAntibiotic prophylaxis against infective endocarditis 2018 by NHS Education for Scotland relieve symptoms of pulmonary congestion prevent thromboembolic complications

 

Percutaneous MV balloon valvuloplasty -invasive procedure increases the mitral valve area and reduce mitral valve gradient therapy of choice in uncomplicated MS balloon is passed percutaneously from using femoral vein through to the atrial septum to the mitral valve where it is inflated highly successful with low rate of restenosis.

 

Surgical -closed valvotomy open valvotomy mitral valve replacement.

References

  1. Diagnosis and Management of Mitral Stenosis – The Cardiology Advisor
  2. Mitral valve stenosis | Radiology Reference Article | Radiopaedia.org
  3. Dass C, Kanmanthareddy A. Rheumatic Heart Disease. [Updated 2021 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538286/
  4. Frontiers | Rheumatic Heart Valve Disease Pathophysiology and Underlying Mechanisms | Cardiovascular Medicine (frontiersin.org)
  5. Shah SN, Sharma S. Mitral Stenosis. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430742/
  6. Mitral stenosis – Oxford Medicine
  7. Mitral Stenosis – Cardiovascular Disorders – MSD Manual Professional Edition (msdmanuals.com)
  8. *Mitral stenosis (jvsmedicscorner.com)
  9. Mitral valve and mitral valve disease | BJA Education | Oxford Academic (oup.com)
  10. Mitral Valve Stenosis – an overview | ScienceDirect Topics
  11. *Mitral valve and mitral valve disease (bjaed.org)

 

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