Infective endocarditis

Published on 23/06/2015 by admin

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Last modified 23/06/2015

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5.7 Infective endocarditis

1 Infective endocarditis is the microbial infection of cardiac endothelium.

2 Risk factors include congenital heart disease, central venous access, intravenous drug use and immunodeficiency.

3 Diagnosis is based on the presence of positive blood cultures with evidence of carditis, peripheral embolisation and immunological phenomena.

4 Acute management includes elimination of causative organisms and treatment of associated complications such as congestive heart failure.

5 Long-term chemoprophylaxis is recommended for procedures likely to result in bacteraemia in at-risk patients.

Introduction

Infective endocarditis (IE) is the microbial infection of the endothelial lining of the heart. Infection may be bacterial or fungal, and may arise in both structurally normal and abnormal hearts. Presentation can be acute or subacute and the long-term morbidity and mortality is high.

Epidemiology

Over the last decade the incidence of IE has increased owing to the improved survival of children with congenital heart disease and an increase in patients with central venous catheters. Up to 75% of children with bacterial endocarditis are known to have pre-existing cardiac abnormalities, most commonly ventricular septal defect and tetralogy of Fallot. Other risk factors include acquired valve disease, intravenous drug use, immunodeficiency and previous bacterial endocarditis.

Pathophysiology

Turbulent cardiac blood flow through a structurally abnormal heart can damage endothelium and lead to overlying thrombus formation. Transient bacteraemia may infect the thrombus and a vegetation is formed. The local effects of vegetations include valvular insufficiency, valvular obstruction, and perivalvular extension leading to intracardiac fistulae and conduction system abnormalities. Extracardiac manifestations result from peripheral embolisation of thrombus material with subsequent infarction or infection of involved tissue. Mycotic aneurysms are secondary to bacterial embolisation causing infection and distension of the arterial wall and are most common in intracranial arteries.

Microbiology

Streptococcus viridans and Staphylococcus aureus are the most frequently encountered organisms in children with IE. Less common aetiological agents include enterococci, Staphylococcus epidermidis and Gram-negative HACEK bacilli – Haemophilus, Actinobacillus, Cardiobacterium, Eikenella and Kingella species. Fungal species such as Candida and Aspergillus may cause IE in neonates, immunocompromised patients and those with long-term central venous lines. Other agents such as Coxiella, Pneumococcus and Listeria are rare causes of endocarditis.

History

Patients with acute IE are often readily identified by systemic toxicity and high fever of short duration. The presentation of subacute endocarditis is more non-specific and usually includes fever, anorexia, malaise, cough, headache and arthralgia. A high degree of suspicion is required to identify these patients. Any presentation of unexplained prolonged fever, new neurological deficit or other embolic phenomena should be evaluated for endocarditis. Systemic embolisation occurs in up to 50% of patients with IE, and is most frequently seen in the first month post-diagnosis. Embolic events may cause infarction or abscess formation in the brain, lungs, kidneys, spleen, bone and extremities. Peripheral embolisation is often absent in acute endocarditis and right-sided heart disease, making their diagnosis more difficult. Endocarditis may also present with cardiac failure secondary to acute valvular dysfunction, fistulous tract formation or prosthetic dehiscence.

Examination

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