Definition and Overview
Bacterial endocarditis is a condition in which the inner lining of the heart becomes inflamed due to bacterial infection. Known as endocardium, this lining is made up of heart valves. It is a serious condition that, if left untreated, can lead to severe complications such as stroke or even death, especially since the heart valves in the endocardium do not have a dedicated blood supply and therefore does not directly receive white blood cells. When bacteria attach to the endocardium, a lesion surrounded by a platelet layer (vegetation) forms. Bacteria that are enclosed by the vegetation become inaccessible to the body’s bacterial-specific host antibodies. Thus, treatment becomes necessary.
Bacterial endocarditis presents in two forms, namely:
Subacute bacterial endocarditis (SBE) - Caused by streptococci bacteria, specifically viridans streptococci. Patients with SBE experience mild to moderate symptoms that progress slowly over a period of weeks or even months.
Acute bacterial endocarditis (ABE) - Progresses faster, usually over a period of days to weeks. It is often due to Staphylococcus aureus bacteria and can cause metastatic infection.
These terms are no longer always used nowadays with cases generally classified as either short or long incubation depending on whether they progress within a period of six weeks or longer.
Causes of Condition
The most common organisms that are known causes of bacterial endocarditis are:
Streptococci of the viridians group, or viridians Alpha-hemolytic streptococci
Coagulase negative Staphylococci
Less common causes are:
In a healthy individual, when these bacteria enter the bloodstream, the body is able to clear them out without any consequences to the person’s health. However, some individuals are unable to fend off the bacteria, which may eventually reach their endocardium. The risk of this happening is greater in patients who have pre-existing heart problems, such as damaged or artificial heart valves, congenital heart defects, chronic rheumatic heart disease, and degenerative valvular lesions. This is also true for those with an implantable cardioverter-defibrillator and whose immune system is weak or compromised. Patients who suffer from kidney failure that requires haemodialysis, diabetes mellitus, and HIV/AIDS, as well as unrelated medical conditions, such as colorectal cancer and chronic urinary tract infection also face a greater risk of developing infective endocarditis.
Common bacterial endocarditis symptoms include:
Low-grade but intermittent fevers
Petechiae or round spots caused by bleeding into the skin
Subungual haemorrhages or dark red linear lesions of the nail bed
Tender subcutaneous nodules on the finger pads
Lesions on the palms and soles
Retinal haemorrhages with clear centres
Splenomegaly or enlargement of the spleen
More severe symptoms of bacterial endocarditis include embolic stroke and intracerebral haemorrhage.
On the other hand, subacute bacterial endocarditis symptoms include:
Rheumatic fever syndrome
Abdominal pain, usually in the right upper quadrant
Who to See and Types of Treatments Available
Patients who experience at least some of the symptoms above should go to a doctor right away for bacterial endocarditis treatment. A general practitioner or family doctor can diagnose the condition, prescribe the appropriate medication, or refer the patient to a specialist, if needed.
The primary treatment for bacterial endocarditis is antibiotic therapy. Doctors prescribe the appropriate type of antibiotic based on the organisms that caused the condition as well as the patient’s medical history. To minimise bacterial resistance, doctors also usually prescribe combination therapy, in which they use two types of medications, such as penicillin and aminoglycoside.
The goal of treatment is to destroy the infectious agent to relieve and stop all of the patient’s symptoms. This typically requires a high dose of antibiotics delivered intravenously, which helps maximise the delivery of antibiotic molecules into the vegetation that has formed in the heart valves. Antibiotic therapy is usually continued for two to six weeks depending on the specific bacteria involved. The treatment period can be shortened to two weeks if the infection in the bloodstream has cleared earlier than expected or if there are complications, such as heart failure, arrhythmia, or pulmonary embolism.
Patients who are suffering from certain complications due to the infection are provided with additional treatment. In around 15 to 25% of cases, this may require surgical procedures, such as debridement of the infected material. This is usually necessary when the patient has:
Congestive heart failure that does not respond to standard medical therapy
Fungal endocarditis, which does not respond to antibiotics
Sepsis that persists 72 hours after correct antibiotic therapy
Septic emboli that recur two weeks after antibiotic therapy
Valve stenosis or regurgitation
Infective endocarditis that is not treated promptly and correctly can lead to fatal results. Even with treatment, the prognosis can be quite poor, especially if the patient is old, the infection is caused by resistant strains of bacteria, treatment is delayed, the vegetation is too large, and if there is valve ring abscess or prosthetic valve infection.
Bacterial endocarditis prognosis is also generally better for right-sided endocarditis than left-sided endocarditis as the former tends to respond better to antimicrobial therapy.
Brusch JL. “Infective endocarditis treatment and management.” Medscape. http://emedicine.medscape.com/article/216650-treatment#d11
Huckell VF. “Infective endocarditis.” Merck Manuals. http://www.merckmanuals.com/professional/cardiovascular-disorders/endocarditis/infective-endocarditis
Windle ML. “Antibiotic prophylactic regimens for endocarditis.” 2016. Medscape. http://emedicine.medscape.com/article/1672902-overview
Cabell CH, Abrutyn E, Karchmer AW. “Bacterial endocarditis: The disease, treatment, and prevention.” AHA Journals. 2003;107:e185-e187. http://circ.ahajournals.org/content/107/20/e185
Hoen B. “Infective endocarditis.” N Engl J Med 2013; 368:1425-1433. http://www.nejm.org/doi/full/10.1056/NEJMcp1206782
Macdonald JR. “Acute infective endocarditis.” Infect Dis Clin North Am. 2009 Sep; 23(3): 643-644. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2726828/