Infective endocarditis is an infection of the inner surface of the heart (endocardium), usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications may include backward blood flow in the heart, heart failure – the heart struggling to pump a sufficient amount of blood to meet the body's needs, abnormal electrical conduction in the heart, stroke, and kidney failure.
The cause is typically a bacterial infection and less commonly a fungal infection. Risk factors include valvular heart disease, including rheumatic disease, congenital heart disease, artificial valves, hemodialysis, intravenous drug use, and electronic pacemakers. The bacteria most commonly involved are streptococci or staphylococci. Diagnosis is suspected based on symptoms and supported by blood cultures or ultrasound of the heart. There is also a noninfective form of endocarditis.
The usefulness of antibiotics following dental procedures for prevention is unclear. Some recommend them for people at high risk. Treatment is generally with intravenous antibiotics. The choice of antibiotics is based on the results of blood cultures. Occasionally heart surgery is required.
The number of people affected is about 5 per 100,000 per year. Rates, however, vary between regions of the world. Infective endocarditis occurs in males more often than in females. The risk of death among those infected is about 25%. Without treatment, it is almost universally fatal. Improved diagnosis and treatment options have significantly enhanced the life expectancy of patients with infective endocarditis, particularly with congenital heart disease.
Classification Infective endocarditis is divided into three categories of acute, subacute, and chronic based on the duration of symptoms. Acute infective endocarditis refers to the presence of signs and symptoms of infective endocarditis that are present for days up to six weeks. If these signs and symptoms persist for more than six weeks but less than three months, this is subacute infective endocarditis. Chronic infective endocarditis refers to the presence of such signs and symptoms when they persist for more than three months. Subacute bacterial endocarditis (SBE) is often due to streptococci of low virulence (mainly viridans streptococci) and mild to moderate illness which progresses slowly over weeks and months (>2 weeks) and has low propensity to hematogenously seed extracardiac sites. Acute bacterial endocarditis (ABE) is a fulminant illness over days to weeks (<2 weeks), and is more likely due to Staphylococcus aureus, which has much greater virulence or disease-producing capacity and frequently causes metastatic infection.
This classification is now discouraged because the ascribed associations (in terms of organism and prognosis) were not strong enough to be relied upon clinically. The terms short incubation (meaning less than about six weeks) and long incubation (greater than about six weeks) are preferred.
Culture results Infective endocarditis may also be classified as culture-positive or culture-negative. By far the most common cause of "culture-negative" endocarditis is prior administration of antibiotics and can occur in up to 31% of cases.
Sometimes microorganisms can take a longer period to grow in the culture media, for example Cutibacterium spp. and the HACEK bacteria group. Some organisms are said to be fastidious because they have demanding growth requirements. Some examples include pathogens like Aspergillus species, Brucella species, Coxiella burnetii, Chlamydia species. Due to delay in growth and identification in these cases, patients may be erroneously classified as "culture-negative" endocarditis.
Heart side Endocarditis can also be classified by the side of the heart affected: People who intravenously inject drugs such as heroin or methamphetamine may introduce infection which can travel to the right side of the heart, classically affecting the tricuspid valve, and most often caused by S. aureus. Regardless of cause, left-sided endocarditis is the most common, while right-sided endocarditis accounts for 5-10% of cases and is more common in people who inject IV drugs and in patients with congenital heart disease.
Infection setting Another form of endocarditis is healthcare-associated endocarditis when the infecting organism is believed to be transmitted in a health care setting like a hospital, dialysis unit, or a residential nursing home. Nosocomial endocarditis is a form of healthcare associated endocarditis in which the infective organism is acquired during a stay in a hospital and it is usually secondary to presence of intravenous catheters, total parenteral nutrition lines, pacemakers, etc.
Valve type Finally, the distinction between native-valve endocarditis and prosthetic-valve endocarditis is clinically important. Prosthetic valve endocarditis can be early (within 1 year of surgery) or late (> 1 year following valvular surgery). Early prosthetic valve endocarditis is usually due to intraoperative contamination or postoperative bacterial contamination, which is usually nosocomial in nature. Late prosthetic valve endocarditis is usually due to community-acquired microorganisms.
Prosthetic valve endocarditis is commonly caused by Staphylococcus epidermidis as it is capable of growing as a biofilm on plastic surfaces. Cutibacterium acnes almost exclusively causes endocarditis on prosthetic heart valves.
Signs and symptoms Fever occurs in 97% of people; malaise and endurance fatigue in 90% of people. A new or changing heart murmur, weight loss, and coughing occurs in 35% of people. Vascular phenomena: septic embolism (a piece of infected debris or tissue breaking off and traveling through the bloodstream to a distant site) (causing thromboembolic problems such as a stroke or gangrene of the fingers), Janeway lesions (painless hemorrhagic cutaneous lesions on the palms and soles), bleeding in the brain, conjunctival hemorrhage, splinter hemorrhages, kidney infarcts, and splenic infarcts. Infective endocarditis can also lead to the formation of mycotic aneurysms. Immunologic phenomena: glomerulonephritis which allows for blood and albumin to enter the urine, Osler's nodes ("ephemeral spots of a painful nodular erythema, chiefly in the skin of the hands and feet"), Roth's spots on the retina, positive serum rheumatoid factor Other signs may include night sweats, rigors, anemia, spleen enlargement
Cause Many microorganisms can cause infective endocarditis. These are generally isolated by blood culture, where the patient's blood is drawn and any growth is noted and identified. The term bacterial endocarditis (BE) is commonly used, reflecting the fact that most cases of IE are due to bacteria; however, infective endocarditis (IE) has become the preferred term.
Bacterial Staphylococcus aureus is the leading cause of infective endocarditis in most parts of the world and is responsible for about 31% of cases. Staphylococcus aureus is the most common cause of endocarditis in people who use intravenous drugs. Viridans streptococci and Enterococci are the second and third most common organisms responsible for infective endocarditis. Viridans streptococci are a common cause of infective endocarditis in South America. Other Streptococci are also a frequent cause. Infective endocarditis due to Streptococcus bovis occurs more commonly in Europe than in North America. Infection with the HACEK group of bacteria is also a rare cause of infective endocarditis in North America.
The viridans group includes S. oralis, S. mitis, S. sanguis, S. gordonii, and S. parasanguis. The primary habitats for these organisms are the oral cavity and the upper respiratory tract. These bacteria are present in the normal oral flora and enter the bloodstream due to disruption of tissues in the mouth when dental surgical procedures are performed (tooth extractions) or genitourinary manipulation. Similarly, HACEK organisms are a group of bacteria that live on the dental gums and can be seen in people who inject drugs who contaminate their needles with saliva. Patients may also have a history of poor dental hygiene or pre-existing valvular disease.
Viridans alpha-hemolytic streptococci, which are present in the mouth, are the most frequently isolated microorganisms when the infection is acquired in a community setting. In contrast, Staphylococcus bloodstream infections are frequently acquired in a health care setting where they can enter the bloodstream through procedures that cause breaks in the integrity of skin, such as surgery, catheterization, or during access of long term indwelling catheters or secondary to intravenous injection of recreational drugs.
Enterococcus can enter the bloodstream as a consequence of abnormalities in the gastrointestinal or genitourinary tracts.
Some organisms, when isolated, give valuable clues to the cause, as they tend to be specific. Pseudomonas species, which are very resilient organisms that thrive in water, may contaminate street drugs that have been contaminated with drinking water. P. aeruginosa can infect a child through foot punctures, and can cause both endocarditis and septic arthritis. S. bovis and Clostridium septicum, which are part of the natural flora of the bowel, are associated with colon cancers. When they present as the causative agent in endocarditis, it usually prompts a colonoscopy to be done immediately due to concerns regarding spread of bacteria from the colon through the bloodstream due to the cancer breaking down the barrier between the inside of the colon (lumen) and the blood vessels which drain the bowel. Less commonly reported bacteria responsible for so called "culture negative endocarditis" include Bartonella, Chlamydia psittaci, and Coxiella. Such bacteria can be identified by serology, culture of the excised valve tissue, sputum, pleural fluid, and emboli, and by polymerase chain reaction or sequencing of bacterial 16S ribosomal RNA.
Multiple case reports of infective endocarditis caused by unusual organisms have been published. Cutibacterium spp., which are normal skin flora, have been responsible for infective endocarditis, preferably in patients with prosthetic heart valves, in rare cases leading to death.Tropheryma whipplei has caused endocarditis without gastrointestinal involvement. Citrobacter koseri was found in an immunocompetent adult. Neisseria bacilliformis was found in a person with a bicuspid aortic valve.
Dental operations One in eight cases of infective endocarditis is thought to be caused by viridans streptococci infection associated with dental procedures such as cleaning or tooth extraction. This was thought to be more clinically significant than it is. However, it is important that a dentist or a dental hygienist be told of any heart problems before commencing treatment. Prophylactic antibiotics were regularly administered to patients with certain heart conditions as a precaution, although this practice has changed in the US, with new American Heart Association guidelines released in 2007, and in the UK as of March 2008 due to new NICE guidelines.
Fungal Fungal endocarditis (FE) is often fatal and one of the most serious forms of infective endocarditis. The types of fungi most seen associated with this disease are:
Candida albicans is found as a spherical or oval budding yeast. It is associated with endocarditis in people who inject drugs, patients with prosthetic valves, and immunocompromised patients. It forms biofilms around thick-walled resting structures like prosthetic heart valves and additionally colonizes and penetrates endothelial walls. C. albicans is responsible for 24-46% of all the cases of FE, and its mortality rate is 46.6–50%.