Endocarditis

Infective endocarditis is a serious infection of the endocardium (the smooth interior lining of the heart ) and/or the heart valves.  Although several different types of organisms can cause endocarditis, it is usually caused by a bacterial infection.  Endocarditis occurs when bacteria in the bloodstream "take up residence" and begin to grow and multiply on the heart valve.  Contrary to what the name might suggest, "infective" endocarditis is not in fact contagious.

There are four one-way heart valves that allow blood to be pumped forward from one chamber to another and throughout the body.  At the same time these valves prevent blood from backing up into other chambers and the lungs.

Infective endocarditis may be acute or sub-acute.  It can come on suddenly and become life-threatening within a matter of days, in which case it is called acute infective endocarditis.  Subacute endocarditis usually develops gradually and subtly over a period of weeks to several months.

Causes and Development; Contributing Risk Factors

The vast majority of cases of endocarditis are caused by a bacterial infection.  Heart valves that have previously been damaged in some way or are dysfunctional are believed to be more prone to develop infections, though infection can also occur on a perfectly normal heart valve.

There are numerous ways that bacteria can get into the bloodstream to cause infection of the heart valve.  Something as minor as a small cut can enable bacteria that normally live on the skin to get into the bloodstream.  In some cases, this can occur during a dental procedure.  In hospitalized patients, the IVs and catheters that are often inserted into the veins may be the portal through which bacteria get into the blood.  For many endocarditis patients, however, no clear explanation is ever found regarding how the bacteria first got into the bloodstream.

Fungal infection is a rare cause of endocarditis.  This occurs most commonly in patients with compromised immune systems, such as those with AIDS or those who have undergone chemotherapy.

The most common cause – a bacterial infection – may present in two ways:

• Acute bacterial endocarditis (ABE), mainly caused by staphylococci, streptococci, pneumococci or gonococci.
• The Subacute (SBE) illness, mostly caused by other streptococci or haemophilus bacteria.

Risk of endocarditis increases with:

• Rheumatic fever or rheumatic heart disease
• Congenital heart disease
• Injections of contaminated materials into the bloodstream, such as with self-administered intravenous drugs
• Invasive procedures such as cardiac catheterizations, intravenous lines and catheters etc.
• Pregnancy
• Excess alcohol consumption
• Artificial heart valves
• Use of immunosuppressive drugs
• Mitral valve prolapse
• Minor surgical procedures, such as dental work, in susceptible individuals

Signs and Symptoms

Endocarditis can cause a wide variety of symptoms, particularly in the earlier stages of infection.  Patients may experience such general symptoms as fevers, chills, fatigue, weight loss, muscle aches, and sweating.  These general, nonspecific, symptoms can make it hard both for the patient and the doctor to recognize endocarditis.

As infection progresses, other symptoms may develop.  If the infection begins to damage the heart valve, the valve may become "leaky."  A leaky heart valve can eventually lead to blood backing up into the lungs.  This accumulation of fluid in the lungs can cause shortness of breath.  If the infection spreads to the kidneys, patients may notice blood in the urine.  If the infection spreads to the brain, it can cause headaches, confusion, or even stroke.

Subacute bacterial endocarditis (SBE) has an insidious onset and may have some or all of all of the following symptoms:

• Intermittent low-grade fever, chills and excessive sweating, especially at night
• Fatigue and weakness
• Vague aches and joint pains.  Back pain, may be severe
• Heart murmur
• Weight loss

• Late stages:

  • Severe chills and high fever
  • Shortness of breath on exertion
  • Swelling of the feet, legs and abdomen
  • Rapid or irregular heartbeat

Acute bacterial endocarditis (ABE) has similar symptoms, but the course is much more rapid.

Diagnosis and Tests

A physician may suspect endocarditis based on symptoms alone, especially in a patient with a predisposing condition.  Patients suspected of having acute bacterial endocarditis are usually hospitalized promptly for diagnosis and treatment.  Diagnostic tests may include laboratory blood counts and blood cultures, electrocardiogram, X-rays of the heart and lungs, including echocardiogram.

In some 5 to 10% of cases, fungal infection or some rare bacteria may be the cause of endocarditis and in this group the blood cultures are negative.

Treatment and Prevention

The goal of treatment is to eradicate the infecting organism with medications and supportive care for relieving symptoms, with hospital care during the acute phase.  Once stable, some patients can continue with treatment at home.  Surgery may be used to replace infected valve in patients in whom antibiotics have not been effective or in patients with artificial heart valves, or in patients with dramatically worsening symptoms.

Prognosis; Complications

The disease is usually curable with early diagnosis and treatment, but recovery may take weeks.  If treatment is delayed, heart function deteriorates, resulting in congestive heart failure and possible death.

Left untreated, this bacterial infection can gradually "eat away" at and damage the heart valve, causing it to malfunction.  It is always fatal if untreated.

Possible complications include: Infected blood clots that may travel to the brain, kidneys, or abdominal organs causing infections, abscesses or stroke; heart-rhythm disturbances (atrial fibrillation is most common); destruction of heart valves; lung clots; arthritis; myositis (inflammation of muscles); acute renal failure.