Mitral regurgitation (MR), also known as mitral insufficiency or mitral incompetence, is a form of valvular heart disease in which the mitral valve is insufficient and does not close properly when the heart pumps out blood. It is the abnormal leaking of blood backwards – regurgitation from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Mitral regurgitation is the most common form of valvular heart disease.
Definition Mitral regurgitation, also known as mitral insufficiency or mitral incompetence, is the backward flow of blood from the left ventricle, through the mitral valve, and into the left atrium, when the left ventricle contracts, resulting in a systolic murmur radiating to the left armpit.
Signs and symptoms
Mitral regurgitation may be present for many years before any symptoms appear. The symptoms associated with MR are dependent on which phase of the disease process the individual is in. Individuals with acute MR are typically severely symptomatic and will have the signs and symptoms of acute decompensated congestive heart failure (i.e. shortness of breath, pulmonary edema, orthopnea, and paroxysmal nocturnal dyspnea). In acute cases, a murmur and tachycardia may be the only distinctive signs. Individuals with chronic compensated MR may be asymptomatic for long periods of time, with a normal exercise tolerance and no evidence of heart failure. Over time, however, there may be decompensation and patients can develop volume overload (congestive heart failure). Symptoms of entry into a decompensated phase may include fatigue, shortness of breath particularly on exertion, and leg swelling. Also, there may be development of an irregular heart rhythm known as atrial fibrillation. Findings on clinical examination depend on the severity and duration of MR. The mitral component of the first heart sound is usually soft and with a laterally displaced apex beat, often with heave. The first heart sound is followed by a high-pitched holosystolic murmur at the apex, radiating to the back or clavicular area. Its duration is, as the name suggests, the whole of systole. The loudness of the murmur does not correlate well with the severity of regurgitation. It may be followed by a loud, palpable P2, heard best when lying on the left side. A third heart sound is commonly heard. Patients with mitral valve prolapse may have a holosystolic murmur or often a mid-to-late systolic click and a late systolic murmur. Cases with a late systolic regurgitant murmur may still be associated with significant hemodynamic consequences. Mitral regurgitation as a result of papillary muscle damage or rupture may be a complication of a heart attack and lead to cardiogenic shock.
Cause
The mitral valve apparatus comprises two valve leaflets, the mitral annulus, which forms a ring around the valve leaflets, and the papillary muscles, which tether the valve leaflets to the left ventricle and prevent them from prolapsing into the left atrium. The chordae tendineae are also present and connect the valve leaflets to the papillary muscles. Dysfunction of any of these portions of the mitral valve apparatus can cause regurgitation. The most common cause of MR in developed countries is mitral valve prolapse. It is the most common cause of primary mitral regurgitation in the United States, causing about 50% of cases. Myxomatous degeneration of the mitral valve is more common in women as well as with advancing age, which causes a stretching of the leaflets of the valve and the chordae tendineae. Such elongation prevents the valve leaflets from fully coming together when the valve closes, causing the valve leaflets to prolapse into the left atrium, thereby causing MR. Ischemic heart disease causes MR by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the left ventricle. This can lead to the subsequent displacement of the papillary muscles and the dilatation of the mitral valve annulus. Rheumatic fever (RF), Marfan's syndrome and the Ehlers–Danlos syndromes are other typical causes. Mitral valve stenosis (MVS) can sometimes be a cause of MR in the sense that a stenotic valve (calcified and with restricted range of movement) allows backflow (regurgitation) if it is too stiff and misshapen to close completely. Most MVS is caused by RF, so one can say that MVS is sometimes the proximal cause of MI/MR (that is, stenotic MI/MR) and that RF is often the distal cause of MVS, MI/MR, or both. MR and mitral valve prolapse are also common in Ehlers–Danlos syndromes. Secondary mitral regurgitation is due to the dilatation of the left ventricle that causes stretching of the mitral valve annulus and displacement of the papillary muscles. This dilatation of the left ventricle can be due to any cause of dilated cardiomyopathy including aortic insufficiency, nonischemic dilated cardiomyopathy, and noncompaction cardiomyopathy. Because the papillary muscles, chordae, and valve leaflets are usually normal in such conditions, it is also called functional mitral regurgitation.Acute MR is most often caused by endocarditis, mainly S. aureus. Rupture or dysfunction of the papillary muscle are also common causes in acute cases, dysfunction, which can include mitral valve prolapse.
Pathophysiology The pathophysiology of MR can be broken into three phases of the disease process: the acute phase, the chronic compensated phase, and the chronic decompensated phase.
… excerpt ends here. Continue reading the full article.
