Valvular Heart Disease

Yet another pathology lecture because, once again, that's the part I've been struggling with most. Do comment below if there's anything else you want me to cover though!

This post is all about valvular heart disease, which is about diseases that affect the heart valves (!). The heart valves have three main layers. The fibrosa, made up of a dense layer of collagen, is located close to the outflow surface. Below that is the spongiosa, which is made up of loose connective tissue. Finally, close to the inflow surface is an elastic layer called the atrialis (in the case of the mitral/tricuspid valves) or the ventricularis (in the case of the aortic/pulmonary valves).

Classification

Valvular heart disease can be classified as stenosis (in which the heart valves can't open properly) or stenosis (in which the heart valves can't close properly). It is possible to get stenosis and incompetence simultaneously- sometimes the changes that prevent a valve from closing fully also prevent the valve from opening fully. Sometimes valves can be affected by surrounding structures- for instance, abnormalities in supporting structures may lead to functional regurgitation (regurgitation due to an abnormality in a supporting structure rather than due to abnormality in the valve itself). Valvular heart disease can also be classified according to which valve is affected.

Aetiology and predisposing factors

Major aetiologies are slightly different between the types of valvular heart disease, but the common ones include post-inflammatory scarring from rheumatic heart disease, infectious endocarditis, and damage to supporting structures (e.g. rupture of papillary muscles can lead to mitral regurgitation). Rheumatic heart disease is common to pretty much all types of valvular heart disease and occurs as a result of previous damage to heart valves from rheumatic fever (see here for more information on rheumatic fever, as well as more information on infective endocarditis). I will discuss other common causes of particular types of valvular heart disease later.

Different causes of valvular heart disease may lead to growth of different kinds of vegetations on the cusps. Rheumatic fever may lead to small, warty vegetations. Infective endocarditis may lead to large, irregular masses that may extend onto the chordae tendinae. Nonbacterial thrombotic endocarditis may lead to small, bland vegetations. Libman-Sacks endocarditis, which is sometimes seen in systemic lupus erythematosus (see here), may lead to small- or medium-sized vegetations on either or both sides of the leaflets.

Pathogenesis and pathophysiology
Morphological changes, complications, clinical features and clinical sequelae of valvular heart disease

I'm going to break this up into types of valvular heart disease, because that might be easier.

Mitral stenosis

Mitral stenosis, which is more common in females and is usually caused by rheumatic fever, is where the mitral valve fails to open properly. It is associated with a rumbling diastolic murmur. Since blood fails to get through to the left ventricle, blood can back up into the pulmonary system, leading to haemoptysis (coughing up blood), pulmonary congestion, pulmonary hypertension, and right ventricular hypertrophy.

Mitral incompetence

Mitral incompetence, which is more common in males, is where the mitral valve fails to close properly. The main causes are myxoid degeneration ("floppy valve"), rheumatic fever, dilation of the valve ring, and damage to papillary muscles. It is associated with a mid-systolic click.

Another common cause of mitral incompetence is mitral valve prolapse, where the valves bulge back into the left atrium. The valves tend to be thickened with elongated, thinned, or ruptured chordae tendinae. Mitral valve prolapse is associated with a mid- or late systolic click.

Aortic stenosis

Aortic stenosis is where the aortic valve fails to open properly. It is usually caused by degenerative calcification of the valve, which in turn is more common in patients with a congenital bicuspid valve (an aortic valve in which two of the leaflets remain fused together so that the aortic valve has two cusps). It may also be a result of rheumatic heart disease. Aortic stenosis is associated with an ejection systolic murmur.

Aortic incompetence

Aortic incompetence is where the aortic valve fails to close properly. It is often caused by severe hypertension, rheumatic heart disease, dilation of the aortic root, or rheumatoid arthritis. Patients with aortic incompetence may have a wide pulse pressure. Aortic incompetence is associated with a mid-diastolic murmur with an opening snap as well as a third heart sound.

Clinical sequelae

Valvular heart disease might be treated using a prosthetic valve. Valves may be mechanical or tissue-based, and they can be implemented via TAVI (transcatheter aortic valve implantation- essentially where a catheter is used to insert the new valve). Unfortunately, serious complications are very common, with around 60% of recipients suffering from a serious complication within 10 years of implementation.