- Risk Factors
- Signs and Symptoms
- Textbook signs of infective endocarditis
- Diagnosing infective endocarditis
- Related Articles
Infective Endocarditis (IE) is a condition caused by infection of the endocardium by bacteria, or very rarely, fungus. It most commonly affects the heart valves (natural or prosthetic), but can occur anywhere along the lining of the heart or blood vessels.
50% of all cases of infective endocarditis will occur on normal valves. This type of infection tends to follow and acute course.
50% of infections occur on abnormal tissue, and these infections will tend to follow a sub-acute course.
The incidence in the UK is 4-7 per 100 000, although this is higher in the developing world
- The disease is rare before the age of 55 in the UK
- 4-7 per 100 000 in general population
- 15 per 100 000 in the over 55’s
Without treatment, the mortality is close to 100%!
- Previous Rheumatic heart disease (rare in the western world)
- Age related valvular degeneration
- Prosthetic valve (both mechanical and bioprostheses)
IV drug use
- More chance of multiple organisms with IV drugs users. IV drug users are usually affected at the tri-cuspid valve, and the right side of the heart. Often the endocarditis is less clinically severe in IV drug users
- The presence of organisms in the blood – Many things can cause this. Common mechanisms include poor dental hygiene, IV drug use, soft tissue infection, and iatrogenic causes (including dental treatment, cannulae, cardiac surgery, and pacemakers).
- Abnormal / unusual endocardial tissue (most often the valve cusps themselves)
- Aortic and mitral valves are more commonly affected – because these exist in a higher pressure system than the tricuspid and pulmonary valves.
- Right sided infection is more common in drug users – although the mechanism for this is poorly understood.
Signs and Symptoms
Fever + new heart murmur (90%)
- These are red/purple spots of 1-2mm diameter. They often form at sites of trauma, and in this instance they will usually disappear within a couple of days. Extreme bouts of vomiting, coughing or crying can also produce them around the eyes. They may also be a sign of a low platelet count (thrombocytopaenia).
- In children they also may occur as a result of viral infection
- They can be a sign of malignancy
- Basically – lots of things can cause them!
- They are non-blanching and essentially caused by bleeding under the skin.
Cardiac / renal failure can develop rapidly (50-70%)
- Haematuria secondary to renal failure present in about 70% of patients
Splinter haemorrhages (10-20%)
- Red lines that run vertically along the nails. A non-specific sign, often associated with rheumatologic conditions as well as infective endocarditis. In the case of infective endocarditis, they are caused by small emboli.
Nail fold infarcts (5-10%)
Roth spots (5%)
- Cerebral emboli (TIA/stroke) – 15%
- Unknown murmurs
- Splenomegaly (40%)
- Coxiella infection – this particular bacterium will often caused a considerably enlarged liver and spleen
- Clubbing (10%)
- General fatigue
- These are basically the same as petechiae, except they are 3-10mm in diameter.
- Osler’s nodes (rare) – these are painful swellings at the fingertips; commonly due to vasculitis.
- Palpable spleen
Textbook signs of infective endocarditis
- These are non-tender, small erythematous or haemorrhagic or nodular lesions on the palm or the sole, and generally about 2-4mm in diameter. They are specific for endocarditis.
- Pathologically, the lesion is in the dermis, and made up of necrotic tissue with inflammatory infiltrate. The epidermis is not affected. They are caused by septic emboli.
- Remember these are non-tender!
- They occur most commonly in endocarditis that is staphylococcal in origin
- These are painful red lesions on the palms and sole. They are caused by immune complex deposition. This causes a localised immune response, resulting in a tender red swelling. They are usually indicative of IE, but can also be caused by SLE, gonococcal infection, infected arterial catheter.
- Vasculitis – this is probably the cause in IE. In IE petechiae are most commonly seen in the conjunctiva
- Thrombocytopaeina – low platelet count
- Malignancy –
- Viral infection – particularly in children
- Leukaemia –
- Q fever – this is disease caused by coxiella burnetti and is most commonly found in people who have been working with farm animals; it is also found in cats and dogs. It is highly infectious. It most commonly affects the aortic valve, and there may be liver complications and purpura. Life-long antibiotic therapy may be required.
- Gram-negative bacteria from the ‘HACEK’ group (haemophilus, Kingella, eikenella) are slow growing, and generally resistant to penicillin.
- Brucella is associated with contact with goats, and will often affect the aortic valve.
- Yeasts are most common on immuno-compromised individuals, IV drug users, or those with IV lines. There may be abscesses and emboli, and often co-existing bacterial infection. The prognosis is extremely poor, and surgery will often be required.
Diagnosing infective endocarditis
- Positive blood culture for infective organisms (on 2 separate tests if >12 hours apart, or on 3/3 or 3/4 tests >1 hour apart)
- Evidence of IR from other tests:
- Echocardiogram shows:
- strictures, unusual blood flow, implanted /unusual material
- Echocardiogram shows:
- New valve regurgitation
- Fever >38’C
- Predisposition to IE; e.g. IV drug user, congenital heart condition, prosthetic valve
- Unusual echo, but not with findings stated above
- Immunological factors present; Roth spots, Osler’s nodes, glomerulonephritis, rheumatoid factor
- Blood cultures positive, but major criteria not satisfied
- Vascular abnormalities; embolism, aneurysm, infarcts, conjunctival haemorrhage, intracranial haemorrhage etc
- IE definitely present:
- 2 major criteria present OR
- 1 major criteria, 3 minor criteria OR
- 5 minor criteria
- IE possibly present:
- 1-4 minor criteria AND
- No other more likely diagnosis
- Note that in some cases the causatory organism will not grow in blood cultures. So in cases where you have negative blood cultures, you need to send serology tests to check for organisms. These organisms include; coxiella, bartonella, legionella and chlamydia.
- Giving antibiotics before taking samples can result in negative samples, despite the presence of a causatory organism
- Always check the CRP and WCC if you suspect infection. If CRP and WCC are normal, yet you have a positive blood culture, the positive culture is likely due to contamination.
Other lab tests
- Full blood count- A normocytic, normochromic anaemia (anaemia of chronic disease) may be present, as are polymorphonuclear leucocytes. Thrombocytopaenia (low platelet count) and thrombocytosis (high platelet count) are also common.
- U+E- Renal dysfunction is common
- LFT’s- ALP is likely to be raised, other values may be slightly abnormal
- Inflammatory markers – CRP and ESR are likely to be raised. CRP is a more acute phase protein than ESR, and thus is more accurate and useful in monitoring progress.
- Immunoglobulins and complement – Ig’s will be increased, but complement decreased, because there is increased immune complex formation. This test is not routinely performed, but results will be abnormal in 70% of cases.
- Urine – proteinurea may occur, and microscopic haematuria is nearly always present
- PCR – rare – polymerase chain reaction – this is used in cases where a blood culture has not produced any growth, but infective endocarditis is still highly suspected. It is a technique that can extract DNA and RNA from any tissue or blood sample.
- Acute presentation – flucloxacillin, gentamycin
- Subacute presentation – benzylpenicillin, gentamycin
- Prosethetic valve / resistant organism – triple therapy of vancomycin, gentamycin and rifampicin
- IE resistant to antibiotic treatment
- Often Gram-negative disease
- Fungal disease resistant to treatment
- IE causing embolic events
- IE with CHF
- Severe structural damage on echo
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy