Our heart consists of three layers.
Endocardium: The inner layer of the heart.
Myocardium: The muscular middle layer of heart.
Epicardium: The outer layer of the heart wall.
The heart is situated within the chest cavity and surrounded by a fluid filled sac known as the pericardium.
What is infective endocarditis?
Endocarditis is an infection of the inner lining of the heart (endocardium). It usually occurs when bacteria or other infectious organisms (like fungus) spread through your blood stream and attach to the inner layer of the heart. Later on, they cause damage to that area and ultimately destroy adjacent heart valves leading to life threatening complications. Any site of infection of the body can be a source of endocarditis. But it is not usually common in people with healthy hearts. Endocarditis tends to occur if there is damaged heart valves due to previous rheumatic valve disease, artificial (prosthetic) valves or other heart defects.
What are the symptoms of infective endocarditis?
Symptoms of endocarditis are really variable. It may develop suddenly or over prolong period. Symptoms usually depend on the organism causing it and preexisting heart disease. That is why, high level of clinical suspicion is necessary to diagnose endocarditis.
Common symptoms include:
Fever with or without chills
A new onset or recently changed heart murmur (abnormal heart sounds produced by fast flowing blood rushing through the heart valves)
Pain in joints and muscles
Shortness of breath
Swelling in your feet, legs or abdomen
Unexplained weight loss
Blood in your urine (microscopic or macroscopic)
Osler's nodes (tender, reddish spots under the skin of your fingers)
Janeway lesion (non-tender, often haemorrhagic (bleeding into the skin), and occur mostly on the palms and soles)
Petechiae. These are tiny purple or red spots on the skin, whites of your eyes or inside your mouth
What are the organisms responsible for infective endocarditis?
Commonly encountered organisms of infective endocarditis are:
At present, this organism is the most common cause of IE. Mortality associated with Staphylococcus aureus induced endocarditis is very high. It is mostly associated with prosthetic valves and intravenous drug abuse.
S. viridans. Usually associated with subacute (50-60% of subacute cases) form of endocarditis.
Group D streptococci:
Group A, C and G streptococci: Causes acute endocarditis. Associated with high mortality.
Group B streptococci
HACEK organisms (Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium spp., Eikenella corrodens, Kingella kingae):
Usually causes acute endocarditis and requires surgery for cure.
Cause subacute disease.
What causes infective endocarditis?
When infectious organisms enter your bloodstream by any means, they travel to your heart and attach to abnormal heart valves. Gradually they multiply and damage heart valve and surrounding tissues.
The sources of microorganisms are many. They may be common bacteria that live in your mouth, throat, gastrointestinal tract etc.
How organisms enter into your bloodstream?
Brushing your teeth or even chewing foods allow bacteria to enter your bloodstream. This is especially true if there is very poor oral hygiene.
Intravenous needles or catheters:
Catheters are used to inject or remove body fluids from the body. There is every possibility of contamination if adequate precaution is not taken before inserting these. Needles used for tattooing or body piercing are also responsible. Lastly, people who abuse intravenous drugs often are at greater risk of endocarditis.
Bacteria anywhere in the body may spread into bloodstream. Infections like skin disease, sexually transmitted disease, inflammatory bowel disease or gum disease give bacteria the chance to cause endocarditis.
If there is any cut or injury to your gums during dental procedure bacteria may spread to your bloodstream.
Fortunately, you immune system is strong enough to kill organisms before they cause any harm to your heart and prevent endocarditis. But if your immune system is weak or you have a damaged heart valve organisms get a chance to survive and cause damage.
Who are at risk?
In normal heart valves, organisms do not have a chance to stick to the valves and cause infection. In damaged valve, the roughened surface allows organisms to get attached to the surface and multiply. That is why, if your heart is healthy, you're unlikely to develop endocarditis. Even most types of heart disease don't increase the risk of endocarditis.
People are at higher risks if they have :
Artificial heart valves: Risk of infection is highest in the first year after insertion of prosthetic heart valve.
Congenital heart disease: Certain congenital heart diseases may be associated with increased risk of infections.
Damaged heart valve:
Previous rheumatic fever or infection can cause damage to your heart valves, making them susceptible to endocarditis.
Previous history of endocarditis
Intravenous drug abuse:
People who use intravenous needles are at greater risk of developing right sided endocarditis. The needles used to inject drugs are often contaminated with bacteria (staphylococcus aureus).
If you have a congenital heart defect or valvular disease, consult your doctor about your risk of developing endocarditis.
What are the diagnostic tests for infective endocarditis?
Your doctor will suspect an endocarditis based on your medical history and physical signs and symptoms, such as fever, anorexia and weight loss. Your doctor may also find a new heart murmur or a change in a previous heart murmur. Until proved otherwise, fever and a murmur (new onset or recently changed) favor the diagnosis of endocarditis.
Further tests will help to decide upon accurate diagnosis as symptoms are often vague.
Important investigations to look for endocarditis are:
Blood cultures (usually multiple) are done to identify causative organisms. Complete blood count also helps to reveal anemia-a sign of endocarditis. A negative blood culture never rules out endocarditis as there are some culture negative endocarditis.
Echocardiogram uses sound waves to produce images of different parts of the heart. By that means doctors can visualize any vegetation or infective tissues in heart. Transesophageal echocardiogram is often used in clinical practice. In conditions where ultrasound device can not be passed through the mouth, transthoracic echo is used instead.
Endocarditis may be associated with irregular heart beats (arrhythmia) . An ECG will help to demonstrate these disorders.
If endocarditis has caused your heart to enlarged in size or if the infection has spread to your lungs, a chest X-ray is useful.