Cardiology - Endocardial disease Flashcards
What is valvular stenosis?
Stenosis is the failure of the valve to open completely, which impedes forward flow of blood.
What is valvular insufficiency or regurgitation?
Insufficiency results from failure of a valve to close completely, thereby allowing reversed flow of blood.
What is functional regurgitation?
This is used to describe the incompetence if a valve stemming from an abnormality in one of its support structures, as opposed to a primary valve defect. For example, dilation of the right or left ventricle can pull the ventricular papillary muscles down and outward, thereby preventing proper closure of otherwise normal mitral or tricuspid leaflets. Functional mitral valve regurgitation is particularly common and clinically important in IHD, as well as dilated cardiomyopathy.
What is the most common cause of mitral stenosis?
Mitral stenosis is almost always rheumatic in origin. The valve orifice is slowly diminished by progressive fibrosis, leaflet calcification and fusion of the cusps and subvalvular apparatus.
How is blood flow affected in mitral stenosis?
Restricted blood flow from the left atrium to the left ventricle causes a rise in left atrial pressure which is reflected back across the pulmonary system causing pulmonary venous congestion and breathlessness, while a low cardiac output may cause fatigue.
Outline the clinical course of mitral stenosis
Patients usually remain symptomatic until the mitral valve area is approximately 1 cm2 (or >70% stenosed). At first, symptoms occur only on exercise; however, in severe stenosis left atrial pressure is permanently elevated and symptoms may occur at rest. AF due to progressive dilatation of the left atrium is very common. The onset of AF causes a rapid rise in left atrial pressure because ventricular filling depends on left atrial contraction and adequate diastolic filling time.
Pulmonary hypertension may lead to RV hypertrophy and dilatation, tricuspid regurgitation and right heart failure. All patients with mitral stenosis and particularly those with AF, are at risk from left atrial thrombosis and systemic VTE.
What are the clinical features of mitral stenosis?
Effort related dyspnoea is usually the dominant symptom and produces a gradual reduction in exercise tolerance over many years.
Onset of AF may precipitate acute pulmonary oedema.
Haemoptysis and systemic embolism may occur.
On examination:
- patient is usually in AF
- mitral facies/ malar flush may be apparent
- tapping apex beat
- loud first heart sound, an opening snap and a low pitched mid-diastolic murmur
- elevated JVP, RV heave, loud pulmonary component of the second heart sound and features of triscupid regurgitation all signify the presence of pulmonary hypertension
How should mitral stenosis be investigated?
ECG may show bifid P waves (P mitrale) due to left atrial hypertrophy or AF.
CXR may show enlarged left atrium and features of pulmonary congestion.
Echo provides the definitive diagnosis, allowing estimation of valve area, pressure gradient across the valve and pulmonary artery pressure.
How should mitral stenosis be managed?
Medical management consists of diuretics for pulmonary congestion, and anticoagulants and rate limiting agents in the presence of AF.
Valve replacement (or where possible, balloon valvuloplasty or valvotomy) should be considered if symptoms persist or if pulmonary hypertension develops.
Name some causes of mitral regurgitation
- mitral valve prolapse
- dilatation of the left ventricle and mitral valve ring (e.g. coronary artery disease, cardiomyopathy, myocarditis)
- damage to papillary muscles
- damage to valve cusps and chordae (e.g. rheumatic heart disease, endocarditis, valvotomy or valvuloplasty)
- MI
How is blood flow affected in mitral regurgitation?
Chronic mitral regurgitation causes gradual dilatation of the left atrium with little increase in pressure; progressive LV dilatation occurs due to chronic volume overload. Acute mitral regurgitation causes a rapid rise in left atrial pressure resulting in pulmonary oedema.
What are the clinical features of mitral regurgitation?
Chronic mitral regurgitation typically causes progressive exertional dyspnoea and fatigue, while sudden onsent mitral regurgitation usually presents with acute pulmonary oedema.
The regurgitant jet causes an apical systolic (pan) murmur that radiates to the axilla. The first heart sound is quiet and there may a third heart sound.
The apex beat feels hyperdynamic and is usually displaced to the left, indicating LV dilatation. Signs of AF, pulmonary venous congestion and pulmonary hypertension may be present.
How should mitral regurgitation be investigated?
CXR may show left atrial or ventricular enlargement or features of pulmonary venous congestion (pulmonary oedema if acute).
Echocardiography allows assessment of chamber dimensions, LV function and severity of regurgitation as well as detection of structural abnormalities of the valve.
How should mitral regurgitation be managed?
Medical treatment includes diuretics and afterload reduction with vasodilators (e.g. ACE inhibitors). Regular review is important to detect worsening symptoms, progressive cardiac enlargement and LV impairment as all of these are indicators for surgical intervention (mitral valve replacement or repair). Acute severe mitral regurigtation necessitates emergency valve repair or replacement.
What is myxomatous mitral valve? Is this the same as mitral valve prolapse?
In myxomatous degeneration of the mitral valve, one or both mitral leaflets are “floppy” and prolapse - they balloon back into the left atrium during systole. Mitral valve prolapse is a primary form of myxomatous mitral degeneration and is sometimes a feature of connective tissue disorders such as Marfan’s syndrome. Men and women are equally affected.
Secondary myxomatous mitral degeneration can occur in any one of a number of settings where mitral regurgitation is caused by some other entity (e.g. IHD).
What is the pathogenesis of myxomatous mitral degeneration?
The basis of primary myxomatous degeneration is unknown. But an underlying (possibly systemic) intrinsic defect of connective tissue synthesis or remodelling is likely. Thus myxomatous degeneration of the mitral valve is a common feature of Marfan’s syndrome (due to fibrillin-I mutations) and occasionally occurs in other connective tissue disorders. In some patients with primary disease, additional features such as scoliosis and a high arched palate may indicate structural abnormalities in systemic connective tissue.
Secondary myxomatous change results from injury to the valve myofibroblasts, probably due to chronically aberrant haemodynamic forces.
What are the clinical features of mitral valve prolapse?
Most patients are asymptomatic. In mild mitral polapse, the valve remains competent but bulges back into the atrium during systole, causing a mid systolic click but not murmur. In the presence of a regurgitant valve, the click is followed by a late systolic murmur. The condition is associated with a variety of benign arrhythmias and atypical chest pain but the overall long term prognosis is good. If regurgitation becomes severe, mitral valve repair can be used to treat most forms of mitral valve prolapse, and is preferred to mitral valve replacement.
Patients with primary myxomatous degeneration are also at an increased risk for the development of infective endocarditis as well as sudden cardiac death.
What are the morphological features of myxomatous degeneration of the mitral valve?
Myxomatous degeneration of the mitral valve is characterised by ballooning of the mitral leaflets. The affected leaflets are enlarged, redundant, thick and rubbery, and the tendinous cords tend to be elongated, thinned and occassional rupture. In those with primary disease, concomitant tricuspid valve involvement is frequent (20-40%); less commonly aortic and pulmonic valves can also be affected.
The essential change is thinning of the valve layer known as the fibrosa layer, on which the structural integrity of the valve depends, accompanied by expansion of the middle spongiosa layer because of increased depoisition of myxomatous (mucoid) material.
The SAME changes occur whether the myxomatous degeneration is due to an intrinsic ECM defect, or is caused by regurgitation secondary to another process.
What are the 3 most common causes of aortic stenosis?
1) Rheumatic fever (usually associated with mitral valve disease)
2) Calcification of a congenitally bicuspid valve
3) In the elderly, calcification of a structurally normal valve
How is cardiac function affected by aortic stenosis?
Cardiac output is initially maintained but the left ventricle becomes increasingly hypertrophied. Eventually, it can no longer overcome the outflow tract obstruction and heart failure supervenes. Patients with aortic stenosis typically remain asymptomatic for many years but deteriorate rapidly when symptoms develop.
How common is a congenital bicuspid aortic valve? What causes it and what are its features?
Biscuspid aortic valve occurs with a frequency of 1-2% in all live births and has been associated with a number of mutations including those affecting proteins of the Notch signally pathway. The two cusps are of unequal size, with the larger cusp exhibiting a midline raphe resulting from incomplete cuspal separation.
What are the clinical features of aortic stenosis?
Mild to moderate aortic stenosis is usually asymptomatic but may be detected incidentally on routine examination. The three cardinal symptoms are angina, syncope and breathlessness:
- angina arises because of the increased oxygen demands of the hypertrophied left ventricle working against the high pressure outflow tract obstruction (or co-existing coronary artery disease)
- syncope usually occurs on exertion, when cardiac output fails to rise to meet demand because of severe outflow obstruction, causing a fall in BP. Exertional breathlessness suggests cardiac decompensation as a consequence of chronic excessive pressure overload
What are the characteristic clinical signs of aortic stenosis?
Slow rising carotid pulse Narrow pulse pressure Heaving but undisplaced apex beat Harsh ejection systolic murmur radiating to the neck (often with a thrill) Soft second heart sound
How should aortic stenosis be investigated?
The ECG usually shows features of LVH, often with down-sloping ST segments and T inversion (“strain pattern”), but can be normal despite severe stenosis.
Doppler echo may show calcified valves with restricted opening and permits calculation of the gradient across the valve.
Cardiac catheterisation is usually necessary to assess coronary arteries before aortic valve replacement.
How is aortic stenosis managed?
All patients with asymptomatic aortic stenosis should be kept under review, as the development of symptoms is an indication for prompt aortic valve replacement.
Surgery in the absence of symptoms is controversial.
Old age is NOT a contraindication to valve replacement.
What is the pathogenesis of calcific aortic stenosis in the elderly?
Progressive age asociated “wear and tear” has been the pathologic mechanism most often proposed, but cuspal fibrosis and calcification are increasingly seen as valvular counterparts of age related arteriosclerosis. Thus, chronic injury due to hyperlipidaemic, hypertension, inflammation and other factors implicated in atherosclerosis probably play a significant role in the pathogenesis.
