Dominic Stone
The papillary muscles are a group of five muscles originating from the ventricular walls of the heart. They play a crucial role in maintaining mitral valve function and preventing ventricular blood regurgitation. Papillary muscle fibrosis is a condition where one or both of the papillary muscles become fibrotic, often due to an overgrowth of class A vessels or an interruption of all channels. This can lead to mitral regurgitation, which is a form of papillary muscle dysfunction. The condition is typically acquired and can result in severe consequences such as cardiogenic shock and pulmonary edema.
| Characteristics | Values |
|---|---|
| Definition | Papillary muscle dysfunction with a morphologically normal muscle is an acquired condition that results in mitral regurgitation. |
| Common Causes | Transient ischemia, LV dilation, fibrosis in the adjacent LV free wall, or a small LV cavity. |
| Most Common Cause | Transient ischemia, which produces mitral regurgitation during an anginal attack. |
| Effect of LV Dilation | Causes migration of the LV wall caudolaterally from the mitral annulus, resulting in the oblique orientation of the papillary muscles with secondary dysfunction and regurgitation. |
| Effect of Scarring/Aneurysm of LV | Causes dysfunction due to abnormal papillary muscle anchoring, which is caused by abnormal LV motion. |
| Effect on Patients with HCM | The AL papillary muscle may be distorted by thickening of the mid-septum, preventing proper contraction in systole. |
| Foci of Fibrosis or Necrosis | Commonly seen in the left ventricular papillary muscles, particularly the posteromedial papillary muscle, which has a poorer blood supply than the anterolateral muscle. |
| Most Common Cause of Necrosis or Fibrosis | Coronary arterial luminal narrowing. |
| Other Causes of Necrosis or Fibrosis | Left ventricular outflow tract obstruction, acute valvular regurgitation, various cardiomyopathies, and primary endocardial fibroelastosis with or without anomalous origin of one or both coronary arteries from the pulmonary trunk. |
| Types of Papillary Muscle Fibrosis | Focal type (13% of autopsies), diffuse type (almost 50% of autopsies). |
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What You'll Learn
Papillary muscle rupture
The heart contains five papillary muscles originating from the ventricular walls. Three of these—anterior, posterior, and septal—attach to the tricuspid valve, while the remaining two—anterolateral and posteromedial—connect to the mitral valve. The anterolateral muscle receives a dual blood supply, while the posteromedial muscle is supplied only by the posterior descending coronary artery. Due to this single blood supply, the posteromedial papillary muscle is more likely to rupture following a myocardial infarction.
Other documented causes of papillary muscle rupture include trauma, syphilis, periarteritis nodosa, vegetative valvulitis, myocardial abscess, iatrogenic injury, and cocaine use. Rupture of the tricuspid papillary muscles can occur due to myocardial ischemia, trauma, or infective endocarditis.
Acute rupture often results in severe mitral valve regurgitation, leading to acute life-threatening cardiogenic shock and pulmonary edema. Papillary muscle dysfunction causes blood to regurgitate through the valves, leading to backflow that can result in left- or right-sided heart failure.
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Papillary muscle dysfunction
The heart contains five papillary muscles originating from the ventricular walls. These muscles attach to the tricuspid and mitral valve leaflets through the chordae tendineae, preventing ventricular blood regurgitation by stabilising the valves during systole. Papillary muscle dysfunction can cause blood to regurgitate through the valves, leading to a backflow of blood that can result in left- or right-sided heart failure.
The function of the papillary muscles is to restrain the mitral valves. Failure of one or both papillary muscles to shorten during the ejection phase of ventricular systole, fibrosis, and atrophy of a papillary muscle or centrifugal migration of the papillary muscles due to left ventricular dilatation result in mitral incompetence. Depending on the cause of the papillary muscle dysfunction, apical systolic murmurs of varying characteristics may be heard. In general, a non-contracting papillary muscle in a normal-sized heart is associated with a murmur that is late in onset and crescendo-decrescendo in quality, whereas in the dilated heart, the murmur is early, beginning with the first heart sound, and may be decrescendo, plateau, or crescendo-decrescendo in quality.
Mitral insufficiency due to acquired or congenital valvular disease has been extensively studied, but mitral insufficiency secondary to disease of the papillary muscles has been relatively neglected. However, since the description of the papillary muscle syndrome in 1963, numerous papers have appeared, dealing directly or indirectly with this syndrome. The syndrome of papillary muscle dysfunction includes a number of diseases that have been implicated in the production of papillary muscle dysfunction. These include circulatory insufficiency, coronary atherosclerosis, shock, infective endocarditis, acute valvar regurgitation, anaemia, LVOT obstruction, systemic hypertension, cardiomyopathies, endocardial fibroelastosis, endomyocardial fibrosis, myocardial disorders, and anomalous origin of the coronary arteries from the pulmonary arteries.
In patients with hypertrophic cardiomyopathy (HCM), the papillary muscles are frequently hypertrophied, with a mass roughly twice that of papillary muscles in healthy controls. The hypertrophy of the papillary muscles correlates with LV wall thickness and myocardial mass. Papillary muscle dysfunction with a morphologically normal muscle is usually an acquired condition that results in mitral regurgitation. Common causes include transient ischemia, LV dilation, fibrosis in the adjacent LV free wall, or a small LV cavity. Transient ischemia is the most common cause, producing mitral regurgitation during an anginal attack.
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Mitral regurgitation
This condition can lead to an increase in blood volume and pressure in the left atrium, which, in turn, can increase pressure in the pulmonary veins. If left untreated, severe regurgitation may result in congestion or fluid buildup in the lungs. Mitral regurgitation often presents with mild or no symptoms. However, as the condition progresses, symptoms such as coughing, exhaustion, lightheadedness, increased urination at night, rapid breathing, or palpitations may occur.
The treatment approach for mitral regurgitation depends on its severity and the patient's individual needs. Mild cases may be managed with anticoagulation medication, while severe or symptomatic cases often require surgery to repair or replace the valve. A multidisciplinary team of cardiologists, cardiac surgeons, nurses, and imaging specialists collaborate to optimise patient outcomes and improve overall cardiac health.
Papillary muscle fibrosis is a condition where the papillary muscles, specifically the left ventricular papillary muscles, undergo fibrosis or scarring. These muscles play a crucial role in restraining the mitral valves. Fibrosis can affect one or both papillary muscles but is more commonly observed in the posteromedial papillary muscle due to its poorer blood supply. Coronary arterial luminal narrowing is the most common cause of fibrosis in these muscles. Mitral regurgitation can occur in patients with papillary muscle fibrosis, particularly when the fibrosis involves the free wall beneath the papillary muscle, impairing left ventricular contraction.
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Causes of fibrosis
Papillary muscle fibrosis is associated with the left ventricular papillary muscles, which are the last portions of the heart to be perfused by coronary arterial blood. This makes them sensitive markers of myocardial ischemia, with necrosis or fibrosis being commonly observed. The most common cause of fibrosis in the left ventricular papillary muscles is coronary arterial luminal narrowing.
Other conditions that can lead to fibrosis in these structures include:
- Left ventricular outflow tract obstruction, particularly due to congenitally malformed aortic valves.
- Acute valvular regurgitation, which can be caused by infective endocarditis.
- Various cardiomyopathies, including hypertrophic cardiomyopathy, which can result in hypertrophy of the papillary muscles.
- Primary endocardial fibroelastosis, which can occur with or without anomalous origin of one or both coronary arteries from the pulmonary trunk.
- Infiltrative diseases, such as inflammation, amyloid, iron, and neoplasms, can also affect the papillary muscles.
- Transient ischemia, which is a common cause of mitral regurgitation.
- LV dilation, which can lead to papillary muscle dysfunction due to abnormal anchoring caused by LV wall migration.
- Scarring or aneurysm of the LV adjacent to the papillary muscle, resulting in abnormal anchoring and LV motion.
- Fibrosis in the adjacent LV free wall, which can simulate papillary muscle dysfunction.
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Treatment options
Papillary muscle rupture is a rare but potentially fatal complication, usually occurring after a myocardial infarction or due to infective endocarditis. The condition has a high mortality rate without surgical intervention, with an estimated 50% mortality within 24 hours in cases of complete rupture. Therefore, prompt surgical intervention is required, typically in the form of mitral valve repair or replacement.
The prognosis is generally poor without immediate treatment due to the high risk of cardiogenic shock and other complications. Early detection and rapid intervention improve survival outcomes, but long-term prognosis depends on the extent of left ventricular damage and overall patient health. Risk factors for papillary muscle rupture include advanced age, female sex, a history of heart failure, delayed treatment after myocardial infarction, and chronic kidney disease.
In cases of papillary muscle dysfunction, fibrosis of the papillary muscle or left ventricular wall may be observed. Mitral annuloplasty and papillary muscle relocation are the surgical options available to treat this condition.
There are two types of papillary muscle fibrosis: focal and diffuse. Focal fibrosis is evidently a healed infarct of the papillary muscle, present in 13% of autopsies, and is a histologically characteristic lesion associated with coronary artery disease and healed myocardial infarction. Diffuse fibrosis, on the other hand, is probably an aging change present in almost half of the autopsies and is associated with sclerosis of the arteries in the papillary muscle.
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Frequently asked questions
Papillary muscle fibrosis is a condition that affects the heart's ventricular walls and can lead to mitral regurgitation, or blood backflow, through the valves. It is caused by an overgrowth of class A vessels or an interruption of all channels.
The symptoms of papillary muscle fibrosis can include mitral regurgitation, or blood backflow, through the valves, which can lead to left- or right-sided heart failure.
Papillary muscle fibrosis is typically diagnosed through magnetic resonance imaging (MRI) or magnetic resonance (MR) scanning.
The treatment for papillary muscle fibrosis typically involves surgical options such as mitral annuloplasty and papillary muscle relocation.
