What is Infectious Endocarditis?
Infectious endocarditis is a condition where the inside lining of the heart and the doors that divide the heart’s four chambers get inflamed. It’s mainly caused by a type of germ called bacteria. This disease can show up in many different ways and have a range of effects.
Without early detection and treatment, it can cause several complications, both within the heart and elsewhere in the body. That’s why it’s really important for doctors to pay close attention and use all their skills, including a detailed look at your medical history and a physical exam, to identify and manage the disease. Doing this promptly can reduce the risk of death and other harmful effects.
What Causes Infectious Endocarditis?
Most of the cases of infections of the inner layer of the heart, known as infectious endocarditis, are caused by a type of bacteria known as gram-positive streptococci, staphylococci, and enterococci. These bacteria cause around 80% to 90% of all cases, with a particular type called Staphylococcus aureus responsible for about 30% of cases in developed countries. Other bacteria from the mouth, such as Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella, can also cause this condition but less frequently. There are other types of bacteria also involved but they only account for about 6% of cases. Endocarditis caused by fungi accounts for only about 1% of cases and usually results from systemic Candida and Aspergillus infections in people with weakened immune systems.
Many factors can influence which bacteria cause the infection, including where the bacteria were acquired, whether in a healthcare setting or in the community. Healthcare-related endocarditis often occurs after heart valve surgery, procedures involving blood vessels, hemodialysis (a treatment for kidney failure), hospitalization, or other surgeries. Staphylococcus aureus is the most common cause of these healthcare-related cases, accounting for around 50% of them. Other, less potent bacteria such as Staphylococcus epidermidis are typically associated with medical devices inserted into blood vessels or recently implanted heart valves. Enterococcal infection is equally common in both healthcare-associated and non-healthcare-associated endocarditis, responsible for about 15% and 18% of cases, respectively.
Infections that people acquire in community settings tend to occur in people with weakened immune systems, people who use intravenous drugs, people with poor dental health, and people with valve disease or rheumatic heart disease. Intravenous drug use accounts for nearly 10% of infectious endocarditis cases, typically introducing bacteria from the skin, such as Staphylococcus aureus or Staphylococcus epidermidis. Staphylococcus aureus preferentially affects the healthy tricuspid valves (a type of heart valve). Infections with Streptococcus gallolyticus bacteria, which are not that common in healthcare-associated endocarditis, account for about 20% of community-acquired infections and should alert physicians to check for colon cancer.
Risk Factors and Frequency for Infectious Endocarditis
Infectious endocarditis is a relatively rare disease, with only 3 to 10 cases annually occurring in every 100,000 people. It’s more prevalent in men than women, with a ratio of almost 2 to 1. Most patients diagnosed with this condition are now typically older than 65. The likelihood of getting this disease increases with age due to common conditions in this age group like artificial heart valves, long-term heart devices, heart valve diseases, dialysis, and diabetes. Historically, rheumatic heart disease used to be a major risk factor for infectious endocarditis, but these days it only underlies less than 5% of all cases due to modern antibiotics. However, intravenous drug use has become a significant concern, accounting for an estimated 10% of all infectious endocarditis cases.
- Infectious endocarditis is quite rare, with 3 to 10 cases per 100,000 people each year.
- Men are more affected by this condition than women.
- The average age of diagnosis is above 65 years.
- Risk factors include artificial heart valves, having long-term heart devices, heart valve diseases, undergoing dialysis, and having diabetes.
- Rheumatic heart disease, a former major risk factor, is now less common due to modern antibiotics.
- Recreational intravenous drug use now accounts for nearly 10% of all cases.
Signs and Symptoms of Infectious Endocarditis
Infective endocarditis is a disease that can show a wide range of symptoms. Doctors should think about this condition when patients at risk display symptoms like fever or sepsis that cannot be traced to a specific cause. Often, patients describe slowly emerging symptoms like fevers, chills, a feeling of discomfort, and extreme tiredness. These generally lead to them seeking medical help within the first month.
A fever, defined as a temperature over 38.0 degrees C (100.4 degrees F), is a common symptom, observed in over 95% of all patients in a large study. In some cases, factors like immunosuppression, old age, usage of fever-reducing medicines, or previous antibiotic courses could prevent the occurrence of a fever. Other indicators of a wide-ranging infection could also likely be symptoms like loss of appetite, headaches, and general weakness.
Certain symptoms might point to the heart and lungs as the cause. These include chest pain, difficulty breathing, reduced ability to exercise, difficulties sleeping due to discomfort while lying flat (orthopnea), and sudden awakenings due to difficulties breathing (paroxysmal nocturnal dyspnea). But these are infrequent and might suggest problems with the aortic or mitral valve. At times, when the valves become extremely compromised, the patients might suddenly experience severe heart failure symptoms.
The patient’s medical history may reveal conditions or risk factors that make the diagnosis easier. The presence of, or history of, cardiovascular devices or treatments such as catheters, IV drug use, recent pacemaker surgery, or prosthetic heart valves could suggest a likelihood of damage to the heart’s inner lining. A history of certain types of heart valve diseases like calcific aortic stenosis or mitral valve prolapse can also provide clues, as they underlie about 30% of all cases. However, less than 5% of infective endocarditis cases in the developed world today are preceded by rheumatic heart disease, once a major risk factor for infectious endocarditis. In North America, diabetes is a common underlying condition.
- Fevers
- Chills
- Feeling of discomfort
- Extreme tiredness
- Loss of appetite
- Headaches
- General weakness
- Chest pain
- Difficulty breathing
- Reduced ability to exercise
- Orthopnea
- Paroxysmal nocturnal dyspnea
The physical examination could reveal signs that strengthen the diagnosis and point to possible complications due to peripheral embolization. Fever is often present, and rapid breathing and heart rate could indicate underlying valvular problems or systemic infection. Low blood pressure can be due to septic or cardiogenic shock in the event of sudden valve perforation. A new or worsening murmur can point to the exact valve that is affected and can be found in less than 50% of all cases. If severe regurgitation (backward flow of blood) occurs in the mitral or aortic valve, the doctor may identify crackling sounds in the lungs. The dermatologic exam could show characteristic skin changes linked to infectious endocarditis, but these are rare. Finally, abdominal examination could reveal an enlarged spleen, which indicates the spread of the infection to the bloodstream, or localized peritonitis, which suggests possible bowel perforation due to blocked blood supply. If embolization to the brain has occurred, there may be signs of specific motor or sensory loss related to the area of the brain that is affected.
Testing for Infectious Endocarditis
If you have endocarditis, which is an infection of your heart valves, you might experience general symptoms like fatigue, fever, or chest pain. These symptoms can be a sign of many serious conditions, so your doctor needs to check for a variety of problems to find out what’s causing them. If you’re having chest pain or difficulty breathing, it’s important to check for other serious heart and lung conditions like heart disease, blood clots in the lungs, and pneumonia right away. If you seem seriously ill with infection, your doctor will follow the best practice steps for quick evaluation.
To begin, if you’re experiencing chest pain or difficulty breathing, a 12-lead electrocardiogram, or EKG, can quickly and cheaply check for any underlying heart rhythm problems, blockages, or damage that might be causing these symptoms. When it comes to endocarditis, the EKG normally looks normal. Any ST-elevation, a certain pattern on the EKG, can be seen in endocarditis, but this should be treated as a sign of a heart attack, even if you’ve been diagnosed with endocarditis before. A chest X-ray can help identify infections in the lungs, fluid buildup around the lungs, or blood vessels that are more visible in the upper part of the lung which is common in heart failure. If there are findings that suggest a possible lung infection, pus collection around the lungs, or blocked arteries in the lungs, it might be necessary for a more detailed scan such as a CT scan or CT angiogram. If there’s concern about a heart attack or inflammation of the heart, tests that measure certain proteins in the blood (cardiac biomarkers) are critical to pinpoint a heart muscle damage.
Given that the symptoms can be vague, a broad range of laboratory tests is usually needed. A complete blood count can often point out a high white blood cell count indicating infection. In cases where the symptoms have been present for a while, the blood count might show a normal red cell size along with low red cell count which is seen in chronic diseases. Inflammatory markers such as the erythrocyte sedimentation rate (ESR) and c-reactive protein (CRP) are high in about 60% of cases, these tests measure body’s response to inflammation or infection. A chemistry panel should be carried out to identify any electrolyte imbalances which need to be corrected while initially stabilizing the patient.
Once more urgent causes have been ruled out, the diagnosis for infectious endocarditis is typically focused on finding evidence of infection through blood tests and heart imaging. The Modified Duke Criteria has long been used for diagnosis. Depending on the specific results, diagnosis may need either two major criteria, one major and three minor criteria, or five minor criteria to be met. The first major criterion involves confirmation of bacteria in the bloodstream. This requires two separate blood cultures showing common causes of endocarditis. The second major criterion needs sonographic (soundwave) evidence of infection on the heart structures. An echocardiogram, which is an image of your heart created from sound waves, should show swinging mass attached to a heart valve or implanted device. If the suspicion of endocarditis is high despite a negative result, a more specific and sensitive type of echocardiogram called transesophageal echocardiogram (TEE), is recommended. This type of imaging might be necessary due to conditions such as chronic obstructive pulmonary disease, previous chest surgery, obesity, and artificial heart valves which might make it difficult to visualize using the standard, transthoracic approach.
The minor criteria include: existing conditions such as underlying heart valve issues, heart defect, or intravenous drug use; fever over 38 degrees celsius; signs of blood vessel problems such as an infected aneurysm, stroke, skin lesions, arterial clots, or lung infarcts; signs of immune response such as skin nodules, retinal hemorrhages, kidney inflammation, or a positive rheumatoid factor test; and positive blood cultures that do not fulfill the major criterion or a test showing an immune response to an infection consistent with endocarditis.
Treatment Options for Infectious Endocarditis
In order to get better quickly and avoid other issues, people with severe symptoms of endocardial vegetation (a condition where clusters of bacteria or fungi mix with platelets and blood cells in your heart) need immediate medical care. This includes stabilizing conditions like severe heart failure, septic shock (a life-threatening reaction to infection), or stroke through maintaining stable airway, breathing, and blood circulation processes.
Once the patient is stable, doctors focus on treatments such as prolonged use of antibiotics that kill bacteria and, if necessary, heart surgery.
Choosing and deciding on the duration of antibiotic treatment depends on the type of valve infection and the resistance pattern of the infecting organism. Different types of antibiotic regimen are proposed depending on these factors.
For those at risk of staphylococcal infection (a type of bacterial infection), a longer course of antibiotics is usually necessary. Patients with infections caused by certain types of bacteria known as MSSA (methicillin-sensitive S. aureus) and MRSA (methicillin-resistant S. aureus) can be provided with specific antibiotic regimens.
On the other hand, enterococcal infections (infections caused by a genus of bacteria known as Enterococcus) in both native and prosthetic valves would require combination of different antibiotics, as a single course may not be effective enough against these bacteria. It’s important to note that these infections might need different treatments if there’s resistance to penicillin.
It’s crucial to highlight that understanding of the best antibiotics use in treatment is always changing, and needs to be frequently updated. To guide this, infectious disease specialists are often consulted. To ensure infection has been cleared from the bloodstream and to guide ongoing treatment, blood cultures are taken every 24 to 48 hours.
In general, early surgery to repair or replace the valve might be required if there is severe heart failure, extensive infection with localized complications, and frequent arterial embolization (blockage of an artery). Early surgery might also be recommended in cases of atrioventricular block (a type of heart block), paravalvular abscess (an abscess near the valve), or destructive infiltrative lesions. Surgery is also recommended if there are recurring embolic events or large, mobile vegetations (abnormal growths in the heart) under some specific conditions.
It has been found that starting antibiotic treatment can decrease the risk of stroke. However, early surgery within 48 hours significantly reduces the risk of death while in hospital and the risk of embolic events in six weeks. Almost half of the people with infectious endocarditis (inflammation of the inner layer of the heart) undergo some type of surgery because of these benefits.
What else can Infectious Endocarditis be?
When trying to identify if someone has infectious endocarditis, which is an infection of the heart valves, many factors need to be considered. Depending on the symptoms presented, a wide variety of potential causes involving infection, inflammation, abnormal growths (neoplasms), and mechanical issues should be looked into.
For individuals showing chest pain, some possibilities include:
- Acute coronary syndrome (sudden reduced blood flow to the heart)
- Acute heart failure (rapid onset of heart’s inability to pump blood)
- Aortic dissection (tear in the large blood vessel branching off the heart)
- Myopericarditis (inflammation of the heart muscle and outer lining)
- Pulmonary embolism (blockage in the lungs)
- Pneumonia (lung infection)
- Empyema (pus in the space between the lung and the inner surface of the chest wall)
If a person has had a prosthetic valve replacement, it’s vital for doctors to consider problems like blood clot formation around the valve, especially if the patient hasn’t been properly following any recommended blood-thinning medication plans. Doctors should also check for suture dehiscence, which is the surgical wound reopening.
If a patient with a recent history of heart attack experiences recurring arterial blood clots, this could indicate a heart wall clot, called ventricular mural thrombus.
A new heart murmur in a young and otherwise healthy individual may suggest a growth in the heart chamber, called an atrial myxoma.
Finally, it’s worth noting that some rare forms of non-infectious endocarditis exist. This includes sterile valvular thrombi, associated with either advanced cancer (marantic endocarditis) or the autoimmune disease systemic lupus erythematosus (Libman-Sacks endocarditis).
What to expect with Infectious Endocarditis
The outlook for a patient can greatly differ based on several factors such as the strength of the causing infection, any additional complications that may arise, any pre-existing health conditions, and whether the heart valve is natural or artificial. The mortality rate during hospital stays averages at around 18%, and the mortality rate within a year can go up to 40%.
Generally, the situation is most grave in cases where an artificial heart valve gets infected within the first 60 days of surgery. These cases have the highest hospital mortality rates, about 30%. A detailed study carried out in Japan found that infection by the bacterium staphylococcus, and heart failure were the highest predictors of death during hospital stay.
It’s worth mentioning that even though almost 50% of cases of infectious heart valve infection (endocarditis) undergo a surgical procedure, the procedure itself doesn’t seem to increase the chance of death during the hospital stay.
Possible Complications When Diagnosed with Infectious Endocarditis
Infective endocarditis can lead to a range of complications within the heart. It can cause acute valvular incompetence, which can cause symptoms like heart failure. This happens in about one-third of patients and can be due to damage to the valves, chordae tendineae (heart strings), and papillary muscles. Regurgitation of mitral or tricuspid valves may therefore lead to bigger atrium and this may result in atrial fibrillation and other types of irregular heart rhythms. However, it’s less common to see heart abscesses (14%) and atrioventricular blocks (8%).
Infective endocarditis can also lead to a series of complications outside the heart. For example, right-sided vegetation can lead to blood clots causing widespread lung abscesses, pneumonia, empyema (pus in the lung cavity), or specific parts of lung cell death. The most severe and common complications outside the heart are neurological ones, affecting 15% to 30% of all cases. These problems can include ischemic stroke, bleeding in the brain, meningitis, brain abscess, and brain aneurysms due to infection. Ischemic strokes—caused by blockages in the cerebral arteries—are the most common neurological complications. These usually happen when infected growths from the mitral/aortic valves travel to the brain.
Less common complications include acute kidney failure. This can be triggered by immune-mediated glomerulonephritis (a type of kidney disease) or localized cell death due to blocked blood vessels. Infected emboli can also cause spleen cell death and abscesses, especially in the setting of S. aureus infection. One of the most serious complications is acute mesenteric ischemia, which is when the small intestine does not get enough blood, leading to cell death and perforation. This is a scarily common result of arterial blockages.
Common Complications:
- Acute valvular incompetence
- Atrial fibrillation and other supraventricular dysrhythmias
- Heart abscesses and atrioventricular blocks
- Pulmonary abscesses, pneumonia, empyema, or pulmonary infarctions
- Neurological complications including ischemic stroke
- Acute kidney failure
- Spleen cell death and abscesses
- Acute mesenteric ischemia
The use of antibiotics to prevent infection during certain high-risk procedures remains a debated topic. Despite this, the American Heart Association (AHA) and the American College of Cardiology (ACC) continue to advise that some individuals receive preventative treatment with medication. This applies especially to patients with artificial heart valves, materials used to repair heart valves, prior cases of heart infection, complex heart defects present from birth that haven’t been repaired, repaired heart defects with ongoing valve problems, or a heart transplant with faulty valves. These patients should consider taking preventative antibiotics before dental procedures that involve piercing the soft tissues in the mouth or manipulating the gums or tissues around the root of a tooth.
An example of a preventative medication plan could include 2 grams of amoxicillin or 600 milligrams of clindamycin (for those who can’t take a type of antibiotics called beta-lactams) taken less than 60 minutes before the procedure starts. It’s important to note that current guidelines no longer suggest taking preventative antibiotics for skin, urinary, and digestive procedures.