Mitral regurgitation
Encyclopedia
Mitral regurgitation mitral insufficiency or mitral incompetence is a disorder of the heart
in which the mitral valve
does not close properly when the heart pumps out blood
. It is the abnormal leaking of blood from the left ventricle
, through the mitral valve, and into the left atrium
, when the left ventricle contracts, i.e. there is regurgitation
of blood back into the left atrium. MR is the most common form of valvular heart disease
.
(i.e. shortness of breath, pulmonary edema
, orthopnea, and paroxysmal nocturnal dyspnea), as well as symptoms suggestive of a low cardiac output state (i.e. decreased exercise tolerance). Palpitations are also common. Cardiovascular collapse with shock (cardiogenic shock
) may be seen in individuals with acute mitral regurgitation due to papillary muscle rupture or rupture of a chorda tendinae.
Individuals with chronic compensated mitral regurgitation may be asymptomatic, with a normal exercise tolerance and no evidence of heart failure. These individuals may be sensitive to small shifts in their intravascular volume status, and are prone to develop volume overload (congestive heart failure
).
Findings on clinical examination depend on the severity and duration of mitral regurgitation. 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.
Commonly, atrial fibrillation
is found.
In acute cases, the murmur and tachycardia
may be only distinctive signs.
Patients with mitral valve prolapse
often have a mid-to-late systolic click and a late systolic murmur.
into the left atrium), and the chordae tendineae (which connect the valve leaflets to the papillary muscles). A dysfunction of any of these portions of the mitral valve apparatus can cause mitral regurgitation.
The most common cause of mitral regurgitation is mitral valve prolapse
(MVP), which in turn is caused by myxomatous degeneration
. The most common cause of primary mitral regurgitation in the United States
(causing about 50% of primary mitral regurgitation) is myxomatous degeneration
of the valve. Myxomatous degeneration of the mitral valve is more common in females, and is more common in advancing age. This causes a stretching out of the leaflets of the valve and the chordae tendineae
. The elongation of the valve leaflets and the chordae tendineae prevent the valve leaflets from fully coapting when the valve is closed, causing the valve leaflets to prolapse into the left atrium, thereby causing mitral regurgitation.
Ischemic heart disease causes mitral regurgitation by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the left ventricle that is present in ischemic heart disease, with the subsequent displacement of the papillary muscles and the dilatation of the mitral valve annulus.
Rheumatic fever
and Marfan's syndrome are other typical causes of mitral regurgitation. It should also be noted that mitral regurgitation, as is mitral valve prolapse is also common in Ehlers Danlos Syndrome
Secondary mitral regurgitation is due to the dilatation of the left ventricle
, causing 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
. It is also called functional mitral regurgitation, because the papillary muscles, chordae, and valve leaflets are usually normal.
Acute mitral regurgitation is most often caused by endocarditis
, mainly S. aureus
. Papillary muscle
rupture or dysfunction, including mitral valve prolapse
, are also common causes in acute cases.
(the forward cardiac output
or forward stroke volume), but also the blood that regurgitates into the left atrium (the regurgitant volume). The combination of the forward stroke volume and the regurgitant volume is known as the total stroke volume of the left ventricle.
In the acute setting, the stroke volume of the left ventricle is increased (increased ejection fraction
), this happens because of more complete emptying of heart. However, as it progresses the LV volume increases and the contractile function deteriorates and thus leading to dysfunctional LV and a decrease in ejection fraction. The increase in stroke volume is explained by the Frank–Starling mechanism, in which increased ventricular pre-load stretches the myocardium such that contractions are more forceful.
The regurgitant volume causes a volume overload and a pressure overload of the left atrium. The increased pressures in the left atrium inhibit drainage of blood from the lungs via the pulmonary veins. This causes pulmonary congestion
.
In the left atrium, the volume overload causes enlargement of the chamber of the left atrium, allowing the filling pressure in the left atrium to decrease. This improves the drainage from the pulmonary veins, and signs and symptoms of pulmonary congestion will decrease.
These changes in the left ventricle and left atrium improve the low forward cardiac output state and the pulmonary congestion that occur in the acute phase of the disease. Individuals in the chronic compensated phase may be asymptomatic and have normal exercise tolerances.
s.
In this phase, the ventricular myocardium is no longer able to contract adequately to compensate for the volume overload of mitral regurgitation, and the stroke volume of the left ventricle will decrease. The decreased stroke volume causes a decreased forward cardiac output and an increase in the end-systolic
volume. The increased end-systolic volume translates to increased filling pressures of the left ventricle and increased pulmonary venous congestion. The individual may again have symptoms of congestive heart failure.
The left ventricle begins to dilate during this phase. This causes a dilatation of the mitral valve annulus, which may worsen the degree of mitral regurgitation. The dilated left ventricle causes an increase in the wall stress of the cardiac chamber as well.
While the ejection fraction
is less in the chronic decompensated phase than in the acute phase or the chronic compensated phase of mitral regurgitation, it may still be in the normal range (i.e.: > 50 percent), and may not decrease until late in the disease course. A decreased ejection fraction in an individual with mitral regurgitation and no other cardiac abnormality should alert the physician that the disease may be in its decompensated phase.
(ECG) in long standing mitral regurgitation may show evidence of left atrial enlargement and left ventricular hypertrophy
. Atrial fibrillation
may also be noted on the ECG in individuals with chronic mitral regurgitation. The ECG may not show any of these finding in the setting of acute mitral regurgitation.
The quantification of mitral regurgitation usually employs imaging studies such as echocardiography or magnetic resonance angiography of the heart.
in individuals with chronic mitral regurgitation is characterized by enlargement of the left atrium and the left ventricle. The pulmonary vascular markings are typically normal, since pulmonary venous pressures are usually not significantly elevated.
. Also, it may detect a dilated left atrium and ventricle and decreased left ventricular function.
Because of the inability in getting accurate images of the left atrium and the pulmonary veins on the transthoracic echocardiogram, a transesophageal echocardiogram
may be necessary to determine the severity of the mitral regurgitation in some cases.
Factors that suggest severe mitral regurgitation on echocardiography include systolic reversal of flow in the pulmonary veins and filling of the entire left atrial cavity by the regurgitant jet of MR.
, and, potentially, any cause of overload of the left atrium. Thus, P-sinistrocardiale may be a more appropriate term.
, which is the percentage of the left ventricular stroke volume that regurgitates into the left atrium.
where Vmitral and Vaortic are respectively the volumes of blood that flow forward through the mitral valve and aortic valve during a cardiac cycle
.
Methods that have been used to assess the regurgitant fraction in mitral regurgitation include echocardiography, cardiac catheterization, fast CT scan, and cardiac MRI.
The echocardiographic technique to measure the regurgitant fraction is to determine the forward flow through the mitral valve (from the left atrium to the left ventricle) during ventricular diastole
, and comparing it with the flow out of the left ventricle through the aortic valve in ventricular systole
. This method assumes that the aortic valve does not suffer from aortic insufficiency
.
Another way to quantify the degree of mitral regurgitation is to determine the area of the regurgitant flow at the level of the valve. This is known as the regurgitant orifice area, and correlates with the size of the defect in the mitral valve. One particular echocardiographic technique used to measure the orifice area is measurement of the proximal isovelocity surface area (PISA). The flaw of using PISA to determine the mitral valve regurgitant orifice area is that it measures the flow at one moment in time in the cardiac cycle
, which may not reflect the average performance of the regurgitant jet.
In acute mitral regurgitation secondary to a mechanical defect in the heart (i.e.: rupture of a papillary muscle or chordae tendineae), the treatment of choice is urgent mitral valve replacement. If the patient is hypotensive prior to the surgical procedure, an intra-aortic balloon pump
may be placed in order to improve perfusion of the organs and to decrease the degree of mitral regurgitation.
If the individual with acute mitral regurgitation is normotensive, vasodilators may be of use to decrease the afterload
seen by the left ventricle and thereby decrease the regurgitant fraction. The vasodilator most commonly used is nitroprusside.
Individuals with chronic mitral regurgitation can be treated with vasodilators as well to decrease afterload. In the chronic state, the most commonly used agents are ACE inhibitor
s and hydralazine
. Studies have shown that the use of ACE inhibitors and hydralazine can delay surgical treatment of mitral regurgitation. The current guidelines for treatment of mitral regurgitation limit the use of vasodilators to individuals with hypertension
, however. Any hypertension is treated aggressively, e.g. by diuretics and a low sodium diet
. In both hypertensive and normotensive cases, digoxin
and antiarrhythmics are also indicated. Also, chronic anticoagulation is given where there is concomitant mitral valve prolapse
or atrial fibrillation
.
There are two surgical options for the treatment of mitral regurgitation: mitral valve replacement
and mitral valve repair
. In the double orifice technique for mitral valve repair, the opening of the mitral valve is sewn closed in the middle, leaving the two ends still able to open. This ensures that the mitral valve closes when the left ventricle pumps blood, yet allows the mitral valve to open at the two ends to fill the left ventricle with blood before it pumps. The same idea can be used with a minimally-invasive catheter
technique which installs a clip to hold the middle of the mitral valve closed.
There is also a non-surgical option for the treatment of mitral regurgitation. Mitral-valve repair can be accomplished with an investigational procedure that involves the percutaeneous implantation of a clip that grips and approximates the edges of the mitral leaflets at the origin of the regurgitant jet. Though it is less effective at reducing mitral regurgitation than conventional surgery, the procedure is marked by superior safety and similar improvements.
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
in which the mitral valve
Mitral valve
The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
does not close properly when the heart pumps out blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. It is the abnormal leaking of blood from the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
, through the mitral valve, and into the left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
, when the left ventricle contracts, i.e. there is regurgitation
Regurgitation (circulation)
Regurgitation is blood flow in the opposite direction from normal, as the backward flowing of blood into the heart or between heart chambers. Can be categorized by:...
of blood back into the left atrium. MR is the most common form of valvular heart disease
Valvular heart disease
Valvular heart disease is any disease process involving one or more of the valves of the heart . Valve problems may be congenital or acquired...
.
Symptoms and signs
The symptoms associated with mitral regurgitation are dependent on which phase of the disease process the individual is in. Individuals with acute mitral regurgitation will have the signs and symptoms of decompensated congestive heart failureCongestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
(i.e. shortness of breath, pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
, orthopnea, and paroxysmal nocturnal dyspnea), as well as symptoms suggestive of a low cardiac output state (i.e. decreased exercise tolerance). Palpitations are also common. Cardiovascular collapse with shock (cardiogenic shock
Cardiogenic shock
Cardiogenic shock is based upon an inadequate circulation of blood due to primary failure of the ventricles of the heart to function effectively....
) may be seen in individuals with acute mitral regurgitation due to papillary muscle rupture or rupture of a chorda tendinae.
Individuals with chronic compensated mitral regurgitation may be asymptomatic, with a normal exercise tolerance and no evidence of heart failure. These individuals may be sensitive to small shifts in their intravascular volume status, and are prone to develop volume overload (congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
).
Findings on clinical examination depend on the severity and duration of mitral regurgitation. The mitral component of the first heart sound is usually soft and with a laterally displaced apex beat, often with heave
Parasternal heave
A parasternal heave is a praecordial impulse that may be palpable in patients with cardiac or respiratory disease. A parasternal impulse may be felt when the heel of the hand is rested just to the left of the sternum with the fingers lifted slightly off the chest. Normally no impulse or a slight...
. 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
Third heart sound
The third heart sound or S3 is a rare extra heart sound that occurs soon after the normal two "lub-dub" heart sounds .-Physiology:It occurs at the beginning of diastole approximately 0.12 to 0.18 seconds after S2...
is commonly heard.
Commonly, atrial fibrillation
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
is found.
In acute cases, the murmur and tachycardia
Tachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
may be only distinctive signs.
Patients with mitral valve prolapse
Mitral valve prolapse
Mitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
often have a mid-to-late systolic click and a late systolic murmur.
Cause
The mitral valve is composed of two valve leaflets, the mitral valve annulus (which forms a ring around the valve leaflets), the papillary muscles (which tether the valve leaflets to the left ventricle, preventing them from prolapsingMitral valve prolapse
Mitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
into the left atrium), and the chordae tendineae (which connect the valve leaflets to the papillary muscles). A dysfunction of any of these portions of the mitral valve apparatus can cause mitral regurgitation.
The most common cause of mitral regurgitation is mitral valve prolapse
Mitral valve prolapse
Mitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
(MVP), which in turn is caused by myxomatous degeneration
Myxomatous degeneration
Myxomatous degeneration refers to a pathological weakening of connective tissue. The term is most often used in the context of mitral valve prolapse, which is known more technically as "primary form of myxomatous degeneration of the mitral valve."...
. The most common cause of primary mitral regurgitation in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
(causing about 50% of primary mitral regurgitation) is myxomatous degeneration
Myxomatous degeneration
Myxomatous degeneration refers to a pathological weakening of connective tissue. The term is most often used in the context of mitral valve prolapse, which is known more technically as "primary form of myxomatous degeneration of the mitral valve."...
of the valve. Myxomatous degeneration of the mitral valve is more common in females, and is more common in advancing age. This causes a stretching out of the leaflets of the valve and the chordae tendineae
Chordae tendineae
The chordae tendineae, or heart strings, are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart....
. The elongation of the valve leaflets and the chordae tendineae prevent the valve leaflets from fully coapting when the valve is closed, causing the valve leaflets to prolapse into the left atrium, thereby causing mitral regurgitation.
Ischemic heart disease causes mitral regurgitation by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the left ventricle that is present in ischemic heart disease, with the subsequent displacement of the papillary muscles and the dilatation of the mitral valve annulus.
Rheumatic fever
Rheumatic fever
Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...
and Marfan's syndrome are other typical causes of mitral regurgitation. It should also be noted that mitral regurgitation, as is mitral valve prolapse is also common in Ehlers Danlos Syndrome
Secondary mitral regurgitation is due to the dilatation of the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
, causing 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
Dilated cardiomyopathy
Dilated cardiomyopathy or DCM is a condition in which the heart becomes weakened and enlarged and cannot pump blood efficiently. The decreased heart function can affect the lungs, liver, and other body systems....
, including aortic insufficiency
Aortic insufficiency
Aortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....
, nonischemic dilated cardiomyopathy
Cardiomyopathy
Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...
and Noncompaction Cardiomyopathy
Noncompaction cardiomyopathy
Non-compaction cardiomyopathy , also called spongiform cardiomyopathy, is a rare congenital cardiomyopathy that affects both children and adults. It results from the failure of myocardial development during embryogenesis....
. It is also called functional mitral regurgitation, because the papillary muscles, chordae, and valve leaflets are usually normal.
Acute mitral regurgitation is most often caused by endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
, mainly S. aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
. Papillary muscle
Papillary muscle
In anatomy, the papillary muscles are muscles located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves via the chordae tendinae and contract to prevent inversion or prolapse of these valves.- Action :There are five total papillary muscles in the heart, three...
rupture or dysfunction, including mitral valve prolapse
Mitral valve prolapse
Mitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
, are also common causes in acute cases.
Pathophysiology
The pathophysiology of mitral regurgitation can be broken into three phases of the disease process: the acute phase, the chronic compensated phase, and the chronic decompensated phase.Acute phase
Acute mitral regurgitation (as may occur due to the sudden rupture of a chorda tendinea or papillary muscle) causes a sudden volume overload of both the left atrium and the left ventricle. The left ventricle develops volume overload because with every contraction it now has to pump out not only the volume of blood that goes into the aortaAorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
(the forward cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
or forward stroke volume), but also the blood that regurgitates into the left atrium (the regurgitant volume). The combination of the forward stroke volume and the regurgitant volume is known as the total stroke volume of the left ventricle.
In the acute setting, the stroke volume of the left ventricle is increased (increased ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
), this happens because of more complete emptying of heart. However, as it progresses the LV volume increases and the contractile function deteriorates and thus leading to dysfunctional LV and a decrease in ejection fraction. The increase in stroke volume is explained by the Frank–Starling mechanism, in which increased ventricular pre-load stretches the myocardium such that contractions are more forceful.
The regurgitant volume causes a volume overload and a pressure overload of the left atrium. The increased pressures in the left atrium inhibit drainage of blood from the lungs via the pulmonary veins. This causes pulmonary congestion
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
.
Compensated
If the mitral regurgitation develops slowly over months to years or if the acute phase cannot be managed with medical therapy, the individual will enter the chronic compensated phase of the disease. In this phase, the left ventricle develops eccentric hypertrophy in order to better manage the larger than normal stroke volume. The eccentric hypertrophy and the increased diastolic volume combine to increase the stroke volume (to levels well above normal) so that the forward stroke volume (forward cardiac output) approaches the normal levels.In the left atrium, the volume overload causes enlargement of the chamber of the left atrium, allowing the filling pressure in the left atrium to decrease. This improves the drainage from the pulmonary veins, and signs and symptoms of pulmonary congestion will decrease.
These changes in the left ventricle and left atrium improve the low forward cardiac output state and the pulmonary congestion that occur in the acute phase of the disease. Individuals in the chronic compensated phase may be asymptomatic and have normal exercise tolerances.
Decompensated
An individual may be in the compensated phase of mitral regurgitation for years, but will eventually develop left ventricular dysfunction, the hallmark for the chronic decompensated phase of mitral regurgitation. It is currently unclear what causes an individual to enter the decompensated phase of this disease. However, the decompensated phase is characterized by calcium overload within the cardiac myocyteMyocyte
A myocyte is the type of cell found in muscles. They arise from myoblasts.Each myocyte contains myofibrils, which are long, long chains of sarcomeres, the contractile units of the cell....
s.
In this phase, the ventricular myocardium is no longer able to contract adequately to compensate for the volume overload of mitral regurgitation, and the stroke volume of the left ventricle will decrease. The decreased stroke volume causes a decreased forward cardiac output and an increase in the end-systolic
Systole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
volume. The increased end-systolic volume translates to increased filling pressures of the left ventricle and increased pulmonary venous congestion. The individual may again have symptoms of congestive heart failure.
The left ventricle begins to dilate during this phase. This causes a dilatation of the mitral valve annulus, which may worsen the degree of mitral regurgitation. The dilated left ventricle causes an increase in the wall stress of the cardiac chamber as well.
While the ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
is less in the chronic decompensated phase than in the acute phase or the chronic compensated phase of mitral regurgitation, it may still be in the normal range (i.e.: > 50 percent), and may not decrease until late in the disease course. A decreased ejection fraction in an individual with mitral regurgitation and no other cardiac abnormality should alert the physician that the disease may be in its decompensated phase.
Diagnosis
There are many diagnostic tests that have abnormal results in the presence of mitral regurgitation. These tests suggest the diagnosis of mitral regurgitation and may indicate to the physician that further testing is warranted. For instance, the electrocardiogramElectrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG) in long standing mitral regurgitation may show evidence of left atrial enlargement and left ventricular hypertrophy
Left ventricular hypertrophy
Left ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
. Atrial fibrillation
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
may also be noted on the ECG in individuals with chronic mitral regurgitation. The ECG may not show any of these finding in the setting of acute mitral regurgitation.
| Acute | Chronic | |
|---|---|---|
| Electrocardiogram Electrocardiogram Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body... |
Normal | P mitrale, Atrial fibrillation Atrial fibrillation Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction... , left ventricular hypertrophy Left ventricular hypertrophy Left ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular... |
| Heart size | Normal | Cardiomegaly, left atrial enlargement |
| Systolic murmur Heart sounds Heart sounds, or heartbeats, are the noises generated by the beating heart and the resultant flow of blood through it... |
Heard at the base, radiates to the neck, spine, or top of head | Heard at the apex, radiates to the axilla |
| Apical thrill | May be absent | Present |
| Jugular venous distension Jugular venous pressure The jugular venous pressure is the indirectly observed pressure over the venous system... |
Present | Absent |
The quantification of mitral regurgitation usually employs imaging studies such as echocardiography or magnetic resonance angiography of the heart.
Chest x-ray
The chest x-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
in individuals with chronic mitral regurgitation is characterized by enlargement of the left atrium and the left ventricle. The pulmonary vascular markings are typically normal, since pulmonary venous pressures are usually not significantly elevated.
Echocardiography
The echocardiogram is commonly used to confirm the diagnosis of mitral regurgitation. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systoleSystole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
. Also, it may detect a dilated left atrium and ventricle and decreased left ventricular function.
Because of the inability in getting accurate images of the left atrium and the pulmonary veins on the transthoracic echocardiogram, a transesophageal echocardiogram
Transesophageal echocardiogram
A transesophageal echocardiogram, or TEE , is an alternative way to perform an echocardiogram. A specialized probe containing an ultrasound transducer at its tip is passed into the patient's esophagus...
may be necessary to determine the severity of the mitral regurgitation in some cases.
Factors that suggest severe mitral regurgitation on echocardiography include systolic reversal of flow in the pulmonary veins and filling of the entire left atrial cavity by the regurgitant jet of MR.
Electrocardiography
P mitrale is broad, notched P waves in several or many leads with a prominent late negative component to the P wave in lead V1, and may be seen in mitral regurgitation, but also in mitral stenosisMitral stenosis
Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
, and, potentially, any cause of overload of the left atrium. Thus, P-sinistrocardiale may be a more appropriate term.
Quantification of mitral regurgitation
The degree of severity of mitral regurgitation can be quantified by the regurgitant fractionRegurgitant fraction
Regurgitant fraction is the percentage of blood that regurgitates back through the aortic valve to the left ventricle due to aortic insufficiency, or through the mitral valve to the atrium due to mitral insufficiency...
, which is the percentage of the left ventricular stroke volume that regurgitates into the left atrium.
- regurgitant fraction =
where Vmitral and Vaortic are respectively the volumes of blood that flow forward through the mitral valve and aortic valve during a cardiac cycle
Cardiac cycle
The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next. The frequency of the cardiac cycle is described by the heart rate. Each beat of the heart involves five major stages...
.
Methods that have been used to assess the regurgitant fraction in mitral regurgitation include echocardiography, cardiac catheterization, fast CT scan, and cardiac MRI.
The echocardiographic technique to measure the regurgitant fraction is to determine the forward flow through the mitral valve (from the left atrium to the left ventricle) during ventricular diastole
Diastole
Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...
, and comparing it with the flow out of the left ventricle through the aortic valve in ventricular systole
Systole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
. This method assumes that the aortic valve does not suffer from aortic insufficiency
Aortic insufficiency
Aortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....
.
Another way to quantify the degree of mitral regurgitation is to determine the area of the regurgitant flow at the level of the valve. This is known as the regurgitant orifice area, and correlates with the size of the defect in the mitral valve. One particular echocardiographic technique used to measure the orifice area is measurement of the proximal isovelocity surface area (PISA). The flaw of using PISA to determine the mitral valve regurgitant orifice area is that it measures the flow at one moment in time in the cardiac cycle
Cardiac cycle
The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next. The frequency of the cardiac cycle is described by the heart rate. Each beat of the heart involves five major stages...
, which may not reflect the average performance of the regurgitant jet.
| Degree of mitral regurgitation | Regurgitant fraction | Regurgitant Orifice area |
|---|---|---|
| Mild mitral regurgitation | < 20 percent | |
| Moderate mitral regurgitation | 20 - 40 percent | |
| Moderate to severe mitral regurgitation | 40 - 60 percent | |
| Severe mitral regurgitation | > 60 percent | > 0.4 cm2 |
Treatment
The treatment of mitral regurgitation depends on the acuteness of the disease and whether there are associated signs of hemodynamic compromise.In acute mitral regurgitation secondary to a mechanical defect in the heart (i.e.: rupture of a papillary muscle or chordae tendineae), the treatment of choice is urgent mitral valve replacement. If the patient is hypotensive prior to the surgical procedure, an intra-aortic balloon pump
Intra-aortic balloon pump
The Intra-aortic balloon pump ' is a mechanical device that increases myocardial oxygen perfusion while at the same time increasing cardiac output. Increasing cardiac output increases coronary blood flow and therefore myocardial oxygen delivery...
may be placed in order to improve perfusion of the organs and to decrease the degree of mitral regurgitation.
If the individual with acute mitral regurgitation is normotensive, vasodilators may be of use to decrease the afterload
Afterload
Afterload is the tension or stress developed in the wall of the left ventricle during ejection. Following Laplace's law, the tension upon the muscle fibers in the heart wall is the product of the pressure within the ventricle, multiplied by the volume within the ventricle, divided by the wall...
seen by the left ventricle and thereby decrease the regurgitant fraction. The vasodilator most commonly used is nitroprusside.
Individuals with chronic mitral regurgitation can be treated with vasodilators as well to decrease afterload. In the chronic state, the most commonly used agents are ACE inhibitor
ACE inhibitor
ACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
s and hydralazine
Hydralazine
Hydralazine is a direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles...
. Studies have shown that the use of ACE inhibitors and hydralazine can delay surgical treatment of mitral regurgitation. The current guidelines for treatment of mitral regurgitation limit the use of vasodilators to individuals with hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, however. Any hypertension is treated aggressively, e.g. by diuretics and a low sodium diet
Low sodium diet
A low sodium diet is a diet that includes no more than 1,500 to 2,400 mgs of sodium per day. People who follow a vigorous or moderate exercise schedule are usually advised to limit their sodium intake to 3,000 mg per day and those with moderate to severe heart failure are usually advised to...
. In both hypertensive and normotensive cases, digoxin
Digoxin
Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
and antiarrhythmics are also indicated. Also, chronic anticoagulation is given where there is concomitant mitral valve prolapse
Mitral valve prolapse
Mitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
or atrial fibrillation
Atrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
.
There are two surgical options for the treatment of mitral regurgitation: mitral valve replacement
Mitral valve replacement
Mitral valve replacement is a cardiac surgery procedure in which a patient’s mitral valve is replaced by a different valve. Mitral valve replacement is typically performed robotically or manually, when the valve becomes too tight for blood to flow into the left ventricle, or too loose in which...
and mitral valve repair
Mitral valve repair
Mitral valve repair is a cardiac surgery procedure performed by cardiac surgeons to treat stenosis or regurgitation of the mitral valve. The mitral valve is the "inflow valve" for the left side of the heart. Blood flows from the lungs, where it picks up oxygen, through the pulmonary veins, to the...
. In the double orifice technique for mitral valve repair, the opening of the mitral valve is sewn closed in the middle, leaving the two ends still able to open. This ensures that the mitral valve closes when the left ventricle pumps blood, yet allows the mitral valve to open at the two ends to fill the left ventricle with blood before it pumps. The same idea can be used with a minimally-invasive catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
technique which installs a clip to hold the middle of the mitral valve closed.
There is also a non-surgical option for the treatment of mitral regurgitation. Mitral-valve repair can be accomplished with an investigational procedure that involves the percutaeneous implantation of a clip that grips and approximates the edges of the mitral leaflets at the origin of the regurgitant jet. Though it is less effective at reducing mitral regurgitation than conventional surgery, the procedure is marked by superior safety and similar improvements.
Surgery
Indications for surgery for chronic mitral regurgitation include signs of left ventricular dysfunction. These include an ejection fraction of less than 60 percent and a left ventricular end systolic dimension (LVESD) of more than 45 mm.| Symptoms | LV EF | LVESD |
|---|---|---|
| NYHA II - IV New York Heart Association Functional Classification The New York Heart Association Functional Classification provides a simple way of classifying the extent of heart failure. It places patients in one of four categories based on how much they are limited during physical activity; the limitations/symptoms are in regards to normal breathing and... | > 60 percent | < 45 mm |
| Asymptomatic or symptomatic | 50 - 60 percent | ≥ 45 mm |
| Asymptomatic or symptomatic | < 50 percent and ≥ 45 mm | |
| Pulmonary artery Pulmonary artery The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood.... systolic pressure ≥ 50 mmHg | ||
Epidemiology
It has a prevalence of approximately 2% of the population, affecting males and females equally. It is one of the two most common valvular heart disease in the elderly.External links
- Echocardiographic features of mitral regurgitation at Wikiecho
- Mitral Regurgitation information from Seattle Children's Hospital Heart Center