Introduction

The heart, a sac-like vessel of muscles, is arguably the most vital organ in our bodies. It keeps us alive by pumping blood to circulate all over our bodies, day and night, like a superhero. However, like all organs, the heart is susceptible to diseases that can severely impair its function. One such condition is endocarditis.

Endocarditis is an inflammatory and infectious heart disease of the inner lining of the heart chambers and valves. The disease is marked by a defence mechanism called inflammation – the body’s response to injury or infection; your immune system's way of alerting that there is a problem inside your body.¹

Endocarditis is mostly caused by an infection, however, there are cases of non-infectious or idiopathic origins. If untreated, endocarditis may progress to cause systemic disease, conditions affecting multiple organs or systems. 

A systemic disease can reduce the ability of the human immune system to defend the body against infections, and sometimes it presents as a double-edged sword; it fights off infections beyond its limit and attacks healthy organs. In certain cases, it may cause death. 

What is endocarditis?

The term endocarditis is derived from:

• "Endo"- meaning inside
• "Cardio"- meaning heart
• "Itis" meaning inflammation

Thus, endocarditis refers to inflammation of the inner lining of the heart, specifically the endocardium. It is a rare but potentially fatal condition.²

Causes of endocarditis? 

Damaged valvular endothelium 

A damaged valvular endothelium refers to injury or harm to the heart valves and chambers. The damage can be from inflammation or prior heart surgery. 

Localised infection 

This involves bacteria or fungi entering the bloodstream via several kinds of portals of entry, including:²

• Dental procedures
• Bleeding gums
• Intravenous drug use
• Infected wounds or skin lesions
• Urinary or respiratory tract procedures
• Central intravenous lines

The overall pathological process follows the following steps:

• Bacteremia – This refers to the presence of bacteria in the blood. Bacteria can enter the bloodstream through:
  • Dental procedures
  • Contaminated central line
  • Open wound in the skin
  • Infection in other organ systems 
  • Surgeries 
• Adhesion – This is the stage where the bacteria in the blood attach to the damaged valve or lining of the heart layer ²
• Colonisation – This involves the proliferation of the bacteria, forming vegetations, infected clumps on the heart lining ²

Types of endocarditis 

Infective endocarditis (IE)

IE, just as the name suggests, involves infection for the condition to manifest. The heart valves and inner lining of the heart must be infected by a causative organism. Infective endocarditis is mostly used synonymously with endocarditis itself. IE may be acute or subacute.³

• Acute infective endocarditis – This is when you acquire the condition suddenly. If not treated, it can cause death within a few days
• Subacute or chronic infective endocarditis – This develops slowly over time

Causative organisms in infective endocarditis

Causative organisms (germs) that cause infective endocarditis may be bacteria, fungi, or HACEK organisms.^1,3

• Bacteria – Single-celled organisms that cannot be seen with the naked eye. They do not need a host cell to grow. They are independent and can be found almost everywhere – water, humans and soil. These bacteria involved in endocarditis include: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus gallolyticus, and Streptococcus viridans
• Fungi – Fungi are organisms that are referred to as eukaryotes (i.e. they have a defined nucleus). They can be single-celled or multicellular organisms and can be seen with the naked eye. And unlike bacteria, fungi need a host cell to grow and replicate.³ Causative fungus involved in most cases of endocarditis is Candida albicans
• HACEK organisms – Gram-negative organisms that are part of the commensal organisms typically found in the middle part of the throat (the oropharyngeal)

Non-infective endocarditis 

This occurs when fibrous blood clots and sterile vegetation form on damaged heart valves and the lining of the heart. When the vegetation becomes larger, it breaks off and moves away from the heart to block blood vessels that lead to other organs in the body, emboli, thereby preventing other organs from receiving adequate blood supply. This causes health complications such as a heart attack and stroke.

Pathophysiology 

A healthy heart is usually resistant to infection. The high-velocity blood flow within the heart chambers helps prevent bacteria from adhering to the heart’s internal surfaces, and the bloodstream is normally a sterile environment.

However, just as the human body has an immune system to defend against infection, some microorganisms have evolved protective mechanisms of their own. One such mechanism is the formation of a biofilm, a protective layer that shields bacteria from the host's immune response. When bacteria form a biofilm, it can prevent antibiotics from penetrating and destroying them effectively within the endothelium (the inner lining of blood vessels and the heart).¹

The development of infective endocarditis typically occurs in several steps:

• Damage to the heart valves – Due to injury, inflammation, or pre-existing heart conditions
• Entry of germs into the bloodstream – Through dental procedures, surgeries, injections, or infections elsewhere in the body
• Adherence of germs to the heart valves – Particularly on the damaged endothelium
• Proliferation of the germs – Leading to bacterial replication and the formation of vegetations

These germs accumulate at the site of the infection within the endothelium and become clumps (vegetations). When the clumps become larger, they break off and travel away from the heart to block blood vessels. This blockage prevents blood supply to other organs in the body, which further causes other health complications, such as strokes in the brain (when the artery that supplies blood to the brain is blocked by infectious clumps). 

Risk factors of endocarditis

Individuals who have had or currently have the following conditions are at higher risk of developing endocarditis:^3,4

• Structural heart disease
• Prosthetic valves
• Congenital heart defect (individuals born with a heart defect)
• Hypertrophic cardiomyopathy 
• Disorders of the heart valves
• Previous episodes of endocarditis 
• Use of steroids
• Diabetes
• Implanted heart devices
• Immunocompromised patients (e.g. HIV/AIDs patients)

Signs and symptoms of endocarditis

General signs and symptoms include:

• Persistent fever
• Dyspnea
• Fatigue 
• Chest pain
• Chills
• Fast heart rates
• Weight loss
• Night sweats

Physical signs and symptoms include:

• Janeway lesions (painless skin spots) 
• Heart murmur
• Splinter haemorrhages
• Osler’s nodes (painful nodules)

Complications of endocarditis 

• Congestive heart failure
• Uncontrolled sepsis
• Embolism 

What are systemic diseases? 

Systemic diseases refer to conditions that affect multiple organs or the body as a whole. In endocarditis, systemic disease can result from:

• Embolic spread from cardiac vegetations
• Co-existing systemic conditions that predispose the heart to infection

Systemic diseases associated with endocarditis

Autoimmune diseases

Autoimmune diseases occur when the body’s immune system mistakenly attacks its own healthy cells and tissues. In endocarditis, antibodies may mistakenly attack the cells of the heart valves, damaging them and increasing their susceptibility to infection. Autoimmune diseases may also weaken the immune system, which generally makes it difficult for your immune system to protect your body from diseases. Some autoimmune diseases linked with endocarditis include: rheumatoid arthritis and systemic lupus erythematosus.⁵ 

Dental infections

Dental infections often result from poor dental hygiene, gum disease, or complications during dental procedures. Gum disease is the most common cause of dental infection in endocarditis. It is characterised by bleeding during the brushing of the teeth. The bacteria, Streptococcus viridans, is present in gum diseases. The infected blood spreads from the site of injury to the already vulnerable heart (from prior damage) and attaches to the linings of the heart valves causing dysfunction and subsequently endocarditis.

Other systemic diseases

• HIV/AIDS 
• Diabetes mellitus 
• Cancer 
• Kidney diseases 

Diagnosis 

Clinical evaluation

The diagnosis of endocarditis begins with a comprehensive clinical evaluation, which includes both a detailed medical history and a physical examination.

• Medical history – This helps identify risk factors such as pre-existing heart valve disease, recent dental or surgical procedures, intravenous drug use, or a history of rheumatic fever
• Physical assessment – A thorough examination may reveal key signs and symptoms of endocarditis, including:
  • Fever
  • Osler’s nodes (tender nodules on fingers or toes)
  • Janeway lesions (painless spots on palms or soles)

Together, these components provide critical initial evidence for suspecting and further investigating endocarditis.⁶ 

Laboratory tests 

Laboratory tests involve the analysis of body samples (such as blood, serum, or tissue) to detect abnormalities that may indicate infection or inflammation. These tests support the diagnosis, guide treatment, and monitor the condition. Key tests for diagnosing endocarditis include:

• Blood culture – Identifies the specific bacteria or fungi causing the infection
• CBC (complete blood count) – ​​Detects elevated white blood cells, indicating infection
• ESR (erythrocyte sedimentation rate) – Measures inflammation levels
• CRP (creative reactive protein) – Another marker of inflammation, elevated in active infections⁶

Imaging studies 

Imaging provides a visual assessment of the heart’s structure and function, aiding in the diagnosis of endocarditis:⁶

• Chest x-ray – Assesses heart size and detects fluid in the lungs
• Echocardiography –
  • Transthoracic echocardiography (TTE) – Non-invasive initial test
  • Transesophageal echocardiography (TEE) – Offers clearer images of heart valves and is more sensitive for detecting vegetations
• Electrocardiography (ECG) – Measures the heart's electrical activity; may reveal conduction abnormalities associated with infection
• Computed tomography (CT) scan 
• Magnetic resonance imaging (MRI) 

Treatment and management 

Effective treatment of endocarditis requires a combination of antimicrobial therapy, supportive care, and, in some cases, surgical intervention. Management strategies include:

Medical

• Intravenous antibiotics (e.g., vancomycin, gentamicin)³ 
• Empiric therapy in severely ill patients
• Anticoagulants – To prevent blood clots from growing or reduce clumps of blood from growing further

Surgical

• Valve replacement (if severe damage or heart failure develops)

Supportive

• Supplemental oxygen (if required)
• Dental hygiene evaluation and prophylaxis

Summary 

Endocarditis is an inflammatory disease of the inner lining of the heart and heart valves. It can be caused by infectious bacteria and sometimes the cause is unknown. Endocarditis, in addition, can be affiliated with serious health complications if left untreated. Systemic diseases, on the other hand, are conditions that harm the entire body. As in the case of endocarditis, if the infection spreads, it can cause systemic disease by affecting other organs such as conditions that arise from embolism. It is important to seek medical attention for accurate diagnosis and treatment to prevent these complications.