Myocardial Abscess (Pus in Heart Wall Muscle)

An abscess is a common problem that is most noticeable when it affects the skin, or lies just underneath it. Most of us refer to this as a boil and it is usually not serious. Often it resolves on its own or may require a combination of antibiotics and drainage. Sometimes abscesses can occur in vital organs, like the heart, and the outlook in these cases is usually poor.

What is a myocardial abscess?

A myocardial abscess is a collection of pus in the heart. Although the myocardium is the middle muscular layer of the heart wall, which accounts for the thickest section, a myocardial abscess may also refer to an abscess involving the endocardium (inner layer), the valves and its structures, or the conduction structures of the heart. A myocardial abscess is a very serious condition which is life-threatening if prompt medical and/or surgical treatment is not forthcoming.

Overall a myocardial abscess is not a common condition in the United States. Prior to modern diagnostic techniques this condition was mainly diagnosed after death, upon autopsy. A myocardial abscess often occurs as a complication of infective endocarditis. In turn complications can arise when a myocardial abscess is not diagnosed and treated in the early stages.

Causes of a Myocardial Abscess

A myocardial abscess usually occurs as a complication of infective endocarditis – a condition where the inner layer of the heart becomes infected, especially when the heart valves are involved. When the infection extends deeper into the heart wall then an abscess is more likely to occur. Most cases arise when the aortic valve is infected. A number of different bacteria may cause a myocardial abscess but Staphylococcous aureus is by far the most common. Other bacteria that may cause a myocardial abscess includes:

  • Bacteroides species
  • Beta-hemolytic streptococci
  • Escherichia coli
  • Enterococci
  • Haemophilus species
  • Streptococcus pneumoniae

Certain parasites may also cause a myocardial abscess but this is uncommon. In most cases only one microorganisms causes the infection and abscess. However, there are rare cases where multiple microorganisms may be responsible simultaneously. Sometimes a myocardial abscess may develop as a complication of a heart attack (myocardial infarction), with angioplasty and stenting and HIV infection.

Spread to the Heart

Penetrating trauma to the chest, like surgery, can introduce these microorganisms into the chest cavity which may then result in infective endocarditis and a myocardial abscess. However, this is an uncommon route of transmission. Instead in most cases the microbes travel from distant sites via the bloodstream (hematogenous spread) to the heart where it causes an infection.

Therefore infective endocarditis may arise secondary to infections elsewhere in the body, such with orodental infections, sexually transmitted infections and when the microbes enter the bloodstream via needles and catheters. With regards to the latter, IV drugs users are naturally at a higher risk of contracting infective endocarditis and developing a myocardial abscess.

People with congenital heart defects and heart valve disorders are also at a greater risk. This includes people with artificial heart valves (prosthetic valves). It is also possible for a myocardial abscess to arise with septicemia, where bacteria enter the bloodstream and travel to various sites throughout the body. This can occur secondary to pneumonia (lung infection) or a kidney and bladder infection.

Signs and Symptoms

Infective endocarditis can develop gradually or arise suddenly. The signs and symptoms seen in a myocardial abscess are largely due to the underlying infective endocarditis. The main signs and symptoms includes:

  • Fever and chills
  • Murmur – an abnormal heart sound
  • Tachycardia – a rapid heart rate
  • Hand lesions – Osler nodes and Janeway lesions

These three main symptoms are also accompanied by other less specific symptoms, including:

  • Night sweats
  • Joint pains
  • Muscle aches
  • Difficulty breathing
  • Paleness
  • Coughing
  • Swelling – hands, legs and/or abdomen
  • Enlarged and tender spleen

It is not uncommon for many of these symptoms to be associated with acute viral infections like the seasonal flu. Therefore people who are at risk with worsening symptoms should seek medical attention to exclude infective endocarditis. The hand lesions are considered to be characteristic of infective endocarditis and therefore a myocardial abscess.

Tests for Diagnosis

It is important to note that a myocardial abscess does not resolve spontaneously. Early diagnosis and prompt treatment is these necessary. Blood tests are conducted to confirm the presence of an infection, although these tests may not be specific for a cardiac infection. It is done in conjunction with imaging studies of the heart such as:

  • Transesophageal echocardiogram
  • Transthoracic echocardiography
  • Magnetic resonance imaging (MRI)

Initially simple imaging studies like a chest x-ray may be done. An electrocardiogram (ECG) may also be done to monitor heart activity but this test will not specifically identify infective endocarditis or a myocardial abscess.

Treatment of Myocardial Abscess

A myocardial abscess requires prompt medical attention as it is a serious and life-threatening condition. Treatment involves medication like antibiotics, anti-clotting agents and medication to stabilize the circulatory disturbances that arise. If necessary, surgery may be required to remove the abscess and repair or replace damaged heart valves. Bed rest and rehydration are important supportive measures.

The prognosis for a myocardial abscess is good if it is detected early and treated promptly. Without prompt medical and surgical treatment, a host of complications can arise such as tears in the heart wall, heart failure, heart valve disorders and even blocks in the conduction system which can impair normal heart rate and rhythm. Delaying treatment can also lead to a poor response to antibiotics once it is commenced.

Prevention of a Myocardial Abscess

Early diagnosis and prompt treatment of infective endocarditis may prevent a myocardial abscess from occurring. The focus should therefore be on preventing infective endocarditis. Practicing good dental hygiene, attending to common skin infections quickly and avoiding tattoos and bod piercings which can lead to infections are some of the main ways to prevent infective endocarditis and therefore a myocardial abscess.

When necessary, preventative antibiotics should be used. This is only a consideration before certain dental procedures or procedures involving the throat.  Preventative medication should only be used when prescribed by a health care professional. It may not always be necessary and a doctor or dentist will determine if it is advisable to administer antibiotics prior to the procedure.

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