Bacteria are harmful organisms that can enter your body in several ways. When they penetrate the heart they can cause serious infections, impacting the various cardiac functions. Understanding how to identify an infection in the layers of the heart, the symptoms to expect and how it is managed can lead to early identification and diagnosis. Multiple treatment options can lead to greater recovery rates from endocarditis when initiated effectively.

Understanding endocarditis

The heart is split into four chambers with valves between the atria (upper) and ventricle (lower) chambers, separating the flow of blood between these. The heart has three layers of protective tissue to encompass it. These are the inner layer (endocardium), middle layer (myocardium), and outer layer (pericardium).

The endocardium is the innermost layer of the heart and is made up of thin, smooth tissue. This layer, as well as the valves within the heart, are made of endocardium cells. They serve as a protective barrier between the circulating blood within the atria and ventricles and the cardiac muscle layer.¹ As part of this protective lining, the endocardium also protects the heart's conduction pathway, which is responsible for regulating the contraction of the heart muscle.

Due to the vital role of this layer in both the flow of blood through the heart valves and the protection of the conduction system to regulate heartbeat, any disruption to this layer can cause detrimental effects on an individual’s health.

Pathophysiology of endocarditis

Endocarditis is the name given when a bacterial infection penetrates the endocardium layer. The endocardium has a built-in resistance to bacterial penetration, so generally, some form of endocardial injury takes place before bacterial entry into the cell. Injury can arise from surgical procedures where surgical instruments come into contact with the endocardium or valves. In individuals with disease of the heart valves, disrupted flow surrounding the valves can cause injury.²

Tissue factor, a protein, is released when the cells are damaged and leads to the formation of a platelet-fibrin nidus. Platelets and fibrin are cells responsible for blood clotting in the wound healing process. The collection of these cells is sterile and is released in an attempt to repair where the damaged cells have been released from. However, when there are bacteria present, this collection becomes a “vegetation” and becomes infected itself.² The bacteria infiltrate this vegetation from the circulating blood. Bacteria could enter the bloodstream in several ways, through other surgical procedures or biopsies and even dental work, where bacteria has penetrated the mucosa of the mouth.

Types of endocarditis

There are two types of endocarditis. Both can be potentially life-threatening if appropriate identification and treatment are not initiated.

Acute endocarditis - this form develops very suddenly and can quickly become life-threatening. This form often develops in healthy hearts.

Subacute endocarditis - this form develops gradually over weeks to months and is more common in individuals with existing heart disease.³

Recognising symptoms of endocarditis

Common symptoms of endocarditis include:

• Heart murmur – an abnormal heart sound
• Fever – symptoms related include rigours
• Fatigue
• Muscle and joint aches
• Shortness of breath
• Headaches
• Night sweats
• Cough
• Small red, brown or purple spots on the skin (petechiae)
• Painless red spots on the soles of feet and palms of hands
• Painful lumps on the pads of fingers and toes
• Confusion
• Unexplained weight loss

These symptoms may progress slowly and may not all be present in subacute endocarditis. However, in acute endocarditis, individuals may present with extremes of some of the symptoms above including high fevers, shortness of breath and symptoms of sepsis.

Diagnostic procedures for endocarditis

Blood tests

To diagnose endocarditis, several tests will be performed. Blood tests can be taken to identify abnormalities in tests such as inflammatory markers. An increase in inflammatory markers such as white blood cells and c-reactive protein (CRP) can indicate the body is fighting an infection. A test for blood cultures can reveal any bacteria present in the blood’s circulation, so can provide important diagnostic information.

Imaging

An ultrasound scan of the heart called an echocardiogram can produce imaging of the heart's structure including the chambers of the heart and the valves. This procedure can be performed in two ways:

• Transthoracic – this is performed by placing gel and a probe across an individual’s chest to obtain images through the chest walls.
• Transoesophageal – the probe progresses through the mouth down the oesophagus to obtain internal imaging of the structures. Individuals are usually given some sedation to make the examination more comfortable.

Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI) scans may also be performed in the presence of potential complications to obtain more detailed images.

Confirmation of diagnosis

The Duke Criteria can be used to assist clinicians in confirming a diagnosis of endocarditis.⁴ A positive diagnosis is suggested from the presence of:

• Direct evidence from a sample taken from a surgery or autopsy
• The presence of 2 major clinical criteria, 1 major and 3 minor criteria or 5 minor criteria (as defined below).
• Major clinical criteria – includes positive blood cultures from 2 samples in 24 hours, persistent positive blood cultures or one positive blood culture for the microorganism Coxiella burnetii and evidence of endocardial involvement (e.g. from positive echocardiogram result).
• Minor clinical criteria – predisposition- risk factors such as valve disease, fever > 38°C, vascular or immunologic diseases, microorganisms detected that do not meet the major criteria but are suggestive of infection.

Difficulties in diagnosis

There are a few potential differential diagnoses to be aware of including intra-abdominal infections, connective tissue disease, Lyme’s disease and cardiac tumours.⁵ The use of the Duke Criteria and the clinician’s clinical experience can lead to a successful diagnosis. However, not all individuals will present with the standard symptoms expected. A multidisciplinary approach to diagnosis may be required which may include the involvement of a number of healthcare professionals including cardiologists and infectious disease specialists. This can ensure an appropriate, prompt diagnosis is made.

Treatment approaches

Antibiotics

The first line of treatment once a diagnosis of endocarditis has been made is for antibiotic therapy. Antibiotics are a group of medications used to kill harmful bacteria that have entered the body. They can be administered in the form of tablets, creams and liquids that can be injected directly into the bloodstream.

There are specific antibiotics known to directly affect the bacteria that can cause endocarditis, this type of therapy is called empirical antibiotic therapy. Through the blood tests that are performed, it is possible to identify the type of bacteria that is causing the infection. Once identified in the lab setting, it is possible to then test different antibiotics and see which are most effective at destroying the bacteria. 

Surgical intervention

In severe cases where the infection does not respond sufficiently to antibiotics, surgical intervention may be required. Procedures to remove or debride the infected tissues can be performed. In individuals where valve disease is present, it may be recommended to perform a valve repair or replacement.

Prognosis and follow-up

Factors that may influence the success rate of recovery from the condition include underlying health conditions such as heart failure, diabetes and conditions affecting the immune system. Poorly managed conditions may lead to complications in the responsiveness of the body to the antibiotic therapy and overall recovery.

Other factors include compliance with the antibiotic therapy, as courses are usually administered over a period of weeks. Full compliance and completion of the full course of antibiotics are required to completely eradicate the bacteria. Engaging in activities such as smoking and drinking excessive alcohol may lead to the development of complications when being treated for endocarditis. Therefore, adherence to healthcare professionals’ advice and treatment plans is imperative for successful recovery.

Ongoing monitoring and reviews with the clinician are important to prevent recurrent infections in the future through  blood check-ups and echocardiogram follow-ups.

Education and support

It is important to have an awareness of preventative strategies to prevent infection in the future to minimise the potential for recurrence. Practices such as adequate hand washing, dental hygiene and regular check-ups can identify any vulnerable areas  and will be treated as necessary.
Receiving a diagnosis of endocarditis whether it is in the subacute or acute category can be a frightening experience and leave individuals with anxiety surrounding their heart health and future. Engaging with your medical professional is important to obtain support and counselling for the psychological impacts this condition may have. There may be local support groups local to you that may be suitable for engaging with others and sharing experiences. Always reach out to your healthcare professional if you require any further information or support in understanding and coping with any medical diagnosis.

Summary

Endocarditis is a serious condition, where bacteria has infiltrated an important layer in the heart's system. If left untreated it can become life-threatening and require emergency treatment. Early identification of symptoms is vital to treatment success. Diagnosis is best made through consideration of Duke’s Criteria and between multiple medical professionals consideration. Treatment can be successful when tailored to the individual and adhered to in its entirety. Outcomes are generally positive for patients presenting with endocarditis, however, ongoing prevention and monitoring is required through patient education and support.