Valve diseases (AS/ AR/ MS/ MR)

Question 1

Valve diseases (AS/ AR/ MS/ MR): Definition

Answer 1

Four main diseases:

• Aortic stenosis - obstruction of blood flow across the aortic valve due to pathological narrowing
• Mitral regurgitation - backflow of blood from LV to LA during systole
• Aortic regurgitation - leakage of blood into LV during diastole due to ineffective coaptation of the aortic cusps
• Mitral stenosis - obstruction of LV inflow that prevents proper filling during diastole. Very uncommon in the western world (bc most cases are caused by rheumatic fever which is rare in the developed world)

Question 2

Valve diseases (AS/ AR/ MS/ MR): Aetiology

Answer 2

• Aortic stenosis (3 types)
  
  • valvular (maj), supravalvular, subvalvular
  • Calcification of normal trileaflet valves is the most common cause (80% US)
  • Congenitally bicuspid valves account for the majority of the remainder of cases
• Aortic regurgitation
  
  • can be caused by primary disease of the aortic valve leaflets or dilation of the aortic root
    
    • congenital bicuspid aortic valve (less effective than tricuspid) and aortic root dilation account for most of the cases in developed countries
    • rheumatic heart disease (dev countries)
    • infective endocarditis
      
      • can lead to rupture of leaflets or even paravalvular leaks
    • Vegetations on the valvular cusps can also cause inadequate closure of leaflets, resulting in leakage of blood
    • Aortic root dissection is a cause of acute AR.
• Mitral stenosis
  
  • Usually occurs as a consequence of rheumatic fever
    
    • caused by an infection of Group A streptococcus bacteria
  • infective endocarditis
  • mitral annular calcification
    
    • a chronic degenerative process of the mitral valve ring
• Mitral regurgitation
  
  • Mitral valve dysfunction may result from aberrations of any portion of the mitral valve apparatus, due to
    • mechanical
    • traumatic
    • infectious
    • degenerative
    • congenital
    • metabolic causes
  • MR can be either acute or chronic.
  • typical causes include
    
    • infective endocarditis
    • ischaemic papillary muscle dysfunction or rupture
    • acute rheumatic fever
    • acute dilation of the left ventricle due to myocarditis or ischaemia

Question 3

Valve diseases (AS/ AR/ MS/ MR): Risk factors

Answer 3

AR

• congenitally bicuspid aortic valve
• rheumatic fever
• endocarditis
• Marfan’s syndrome and related connective tissue disease

AS

• age >60 years
• congenitally bicuspid aortic valve
• rheumatic heart disease
• chronic kidney disease

MR

• mitral valve prolapse
• hx of rheumatic heart disease
• infective endocarditis
• hx of cardiac trauma

MS

• streptococcal infection
• female sex
• ergot medications
• serotogenic medications

Question 4

Valve diseases (AS/ AR/ MS/ MR): Pathophysiology

Answer 4

Aortic regurgitation:

• acute AR is a medical emergency
  
  • ​with high mortality and results in an acute rise in left atrial pressure, pulmonary oedema, and cardiogenic shock
    
    • End-diastolic pressure in the left ventricle rises sharply
    • The heart tries to compensate by increasing the heart rate and increasing the contractility (Starling’s law) to keep up with the increased preload, but this is insufficient to maintain the normal stroke volume and fails.
• Chronic results in
  • Both left ventricular volume AND pressure overload, causing inc wall tension
  • wall tension inc causes wall to undergo hypertrophy
  • i.e. compensatory mechanisms: LV dilation
  • Progressive dilation leads to heart failure.
    
    • In chronic AR, most patients remain asymptomatic for decades, as the left ventricle maintains forwards stroke volume with compensatory chamber enlargement and hypertrophy.
    • Eventually, the left ventricular systolic dysfunction supervenes and left ventricular end-diastolic pressure rises resulting in symptomatic congestive heart failure.

Aortic stenosis:

• pressure gradient between LV and aorta increasing the afterload (increased afterload).
• LV function initially maintained by compensatory pressure hypertrophy.
• When compensatory mechanisms exhausted, LV function declines
• Aortic stenosis (AS) represents obstruction of blood flow across the aortic valve due to pathological narrowing.
  
  • ​Often via calcification
  • ​Endocardial injury initiates an inflammatory process similar to atherosclerosis and ultimately leads to deposition of calcium on the valve
  • Progressive calcium deposition limits aortic leaflet mobility and eventually produces stenosis.
  • Or can be due to congenital valve abnormalities (unicuspid and bicuspid)

Mitral regurgitation:

• pure volume overload.
• Compensatory mechanism: LA enlargement, LVH and increased contractility.
• Progressive LA dilatation and RV dysfunction due to pulmonary hypertension.
• Progressive LV volume overload leads to dilation and progressive heart failure
• Mitral valve dysfunction may result from aberrations of any portion of the mitral valve apparatus, due to mechanical, traumatic, infectious, degenerative, congenital, or metabolic causes. MR can be either acute or chronic.

Mitral stenosis:

• As the valve progressively narrows, the resting diastolic mitral valve gradient, and hence left atrial pressure, increases.
  
  • This leads to transudation of fluid into the lung interstitium and dyspnea at rest or with minimal exertion. (ie. Increased left atrial pressure is referred to the lungs, where it leads to congestion and the symptoms associated with it) - pul HTN can occur
  • also, The restricted orifice limits filling of the left ventricle, thereby limiting cardiac output.
    
    • Thus, although left ventricular contractility is usually normal, the pathophysiological effects of mitral stenosis produce a syndrome mimicking left heart failure.
• Mitral stenosis is a narrowing of the mitral valve orifice, usually caused by rheumatic valvulitis producing fusion of the valve commissures and thickening of the valve leaflets.

Question 5

Valve diseases (AS/ AR/ MS/ MR): Cinical manifestations: key presentations, other symptoms and signs

Answer 5

AR

• The patient can present with sudden onset of pulmonary oedema and hypotension or in cardiogenic shock
• AR is usually detected on clinical examination with a diastolic murmur, or incidentally during echocardiographical evaluation for other causes.

AS

• Many cases of AS are diagnosed during the subclinical phase while a murmur, noted on physical examination, is being investigated
  
  • Even patients with severe AS may be truly asymptomatic.
• Complaints of decreased exercise tolerance, shortness of breath on exertion, exertional chest pain (angina), syncope, or near syncope, and heart failure symptoms should prompt consideration of AS

MR

• There are no pathognomonic features to diagnose MR by history; however, dyspnoea on exertion, orthopnoea, paroxysmal nocturnal dyspnoea, lower extremity oedema, palpitations, fatigue, and diaphoresis are common presenting symptoms.

MS

• A history of dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea, or peripheral oedema is suggestive of mitral stenosis.
• Occasionally, a documented history of rheumatic fever may prompt the provider to seek a history probing for the typical symptoms.
• usually diagnosed when the characteristic diastolic murmur is heard on physical examination.

Question 6

Valve diseases (AS/ AR/ MS/ MR): Investigations (diagnosis): 1st line, gold standard & other

Answer 6

AR

• ECG
• CXR
• echocardiogram

AS

• transthoracic echocardiogram (including Doppler)
• ECG

MR

• transthoracic echo
• ECG

MS

• ECG
• CXR
• trans-thoracic echocardiography

Question 7

Valve diseases (AS/ AR/ MS/ MR): DDX

Answer 7

AR

• Mitral regurgitation (MR)
• Mitral stenosis
• Aortic stenosis

AS

• Aortic sclerosis
• Ischaemic heart disease
• Hypertrophic cardiomyopathy (HCM)

MR

• Acute coronary syndrome (ACS)
• Infective endocarditis
• Mitral stenosis

MS

• Unexplained atrial fibrillation
• Mitral stenosis

Question 8

Valve diseases (AS/ AR/ MS/ MR): Management

Answer 8

AR

• Acute AR is an emergency requiring urgent surgical intervention.
• All symptomatic patients require surgery, regardless of their LV function and dilation
  
  • valve replacement
  • valve repair
• AS
• The primary treatment of symptomatic AS is aortic valve replacement.
• Valve replacement is recommended in symptomatic patients with severe AS and asymptomatic patients with severe AS who have a reduced left ventricular ejection fraction (LVEF) or who are undergoing other cardiac surgery

MR

• Acute MR
  
  • presents as a medical emergency and immediate surgery is indicated.
  • Prior to surgery, afterload reduction using diuretics may be required to stabilise the patient
• Chronic asymptomatic
  
  • ​patients with impaired left ventricular function are usually treated with angiotensin-converting enzyme (ACE) inhibitors and beta-blockers.
• Chronic symptomatic
  
  • All patients should be treated with ACE inhibitors, beta-blockers, and diuretics.

Once the patient is stabilised, the treatment of choice is surgery,

MS

• A diuretic may reduce left atrial pressure and relieve mild symptoms.
• However, patients with severe disease are unlikely to benefit from medical therapy alone, and mechanical relief from valve obstruction is often the only effective remedy for symptoms and for pulmonary hypertension.
• therefore condier surgery