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infective endocarditis

Written by Nimesh Jayasuriya

Last Reviewed: August 2019

Review Due: August 2020

 

DEFINITION1

'an infection involving the endocardial surface of the heart, including the valvular structures, the chordae tendineae, sites of septal defects, or the mural endocardium'

 

AETIOLOGY2

The most common causative organisms in IE are Viridans Group Streptococci and Staphylococcus Aureus.

Other organisms include Enterococci, Coagulase-Negative Staphylococci, Haemophilus Parainfluenzae, Actinobacillus, Streptococcus Bovis, Coxiella Burnetii, Brucella species, Culture-Negative Haemophilus Species or fungi.

risk factors2

Previous history of IE

Presence of prosthetic heart valves 

Intravenous drug use

Congenital heart disease 

Post heart transplant

Mitral valve disease

Previous rheumatic heart disease

SIGNS AND SYMPTOMS1

Signs

Pyrexia

New cardiac murmur 

Janeway lesions 

Osler nodes 

Roth spots 

Splinter haemorrhages

Symptoms

Fever with chills/rigor

Night sweats

Malaise

Anorexia

Fatigue

Weight loss

Weakness

Arthralgia

Headache

Shortness of breath

 

PATHOPHYSIOLOGY1

IE usually develops on the valvular surfaces of the heart. Endothelial damage secondary to turbulent blood flow leads to the creation of prothrombotic state and thrombus formation. Bacteria would then colonize the thrombus and results in further fibrin deposits which then forms a mature infected vegetation.  The bacteraemia would present with the flu like symptoms (fever/ night sweats/ malaise etc.) while the vegetation on the endocardium/ valves would result in new cardiac murmurs. These vegetations can also break off and embolise to other parts of the body resulting in pulmonary infarcts, strokes and signs such as splinter haemorrhages. 

 

Investigations1

As a general rule, a diagnosis of IE should be considered in all patients presenting with fever and a new heart murmur.

Blood Tests

FBC - Increased WCC

CRP - Increased

ECG

May show a prolonged PR interval or non-specific ST-segment or T-wave abnormalities.

Blood Cultures

Ideally, three different sets of cultures should be taken at three different times and from three different sites. Identification of the causative organism will help to guide future antimicrobial therapy.

Echocardiography

An echocardiogram can show evidence of valvular vegetations or other structural abnormalities of the heart and is important in the diagnosis of IE or monitoring its response to treatment.

diagnostic criteria3

A diagnosis of IE is made using the Modified Dukes Criteria. A diagnosis is made in the presence of 2 Major Criteria, 1 Major and 3 Minor Criteria or 5 Minor Criteria.

 

TREATMENT2,4

Early input from cardiology, cardiothoracic surgery and microbiology/infectious diseases may be of benefit.

Note that the below antibiotics guidelines are based on the NHS GGC antimicrobial handbook. Always consult local guidelines for the correct dosing and antibiotic information.

Native Valve

IV Amoxicillin, Flucloxacillin and Gentamicin

or IV Vancomycin and Gentamicin

Prosthetic Valve

IV Vancomycin and Gentamicin

Surgery may be indicated if there is evidence of uncontrolled infection or if valve dysfunction leads to heart failure.

 
 

EPIDEMIOLOGY1

The incidence of IE ranges from 1.7 to 6.2 cases per 100,000 person-years. Changing patient demographics mean the average age of patients with IE has been increasing. However, in IE associated with IV drug use, the median age tends to be lower. Prosthetic valve endocarditis accounts for approximately 7-25% of all cases.

The mortailty rate for IE ranges from 20-25% and is influenced by man factors. The main cause of death is typically CNS embolic events.

REFERENCES

  1. Mylonakis E, Calderwood SB. Medical progress: infective endocarditis in adults. N Engl J Med. 2001 Nov 1;345(18):1318-30.

  2. Wilkinson I, Raine T, Wiles K, Goodhart A, Hall C, O'Neill H. Oxford handbook of clinical medicine. 10th ed. 2017.

  3. Li JS, Sexton DJ, Mick N, et al. Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clin Infect Dis. 2000 Apr;30(4):633-8.

  4. GGC Medicines - Adult Therapeutics Handbook 2019