Infective Endocarditis: Clinical Approach

Infective Endocarditis is often found in many cardiology and intensive medicine textbooks. Often found in the first few chapters, infective endocarditis is a common yet important case for undergraduates and postgraduates to know.

Remember, if there’s a fever with a new murmur, think Infective Endocarditis!

Definition

Infective Endocarditis is an infection of the endocardium by offending agents. It most commonly occurs at sites that have had previous damage.

Causes

There are a variety of causes that result in endocarditis. It ranges from a prior dental procedure until intravenous drug use. Apart from that, patients with valve replacements are at an increased risk for Infective Endocarditis and should be started on prophylactic antibiotics.

Pathophysiology

The patho-physiology of Infective Endocarditis have several causes. Most of them are caused by bacterial organisms, such as those listed below. The offending agents are introduced to the body by intravenous drug use, dental procedures or bacteremia from a previous infections. In addition to that, a previous cardiac procedure done with valve replacements increases the risk of Infective Endocarditis.

The offending agents are introduced to the heart valves (most probably the left side of the heart) and form vegetation to the valves and their surrounding structures. Vegetations are formed by the fibrins and the offending agents, almost like a blood clot.

As this is an infection, let’s take a look at the causative organisms.

Causative Organisms

• Staph. aureus. Most commonly seen in Infective Endocarditis.
• Strep. viridans: Accounts for 50 to 60% of sub-acute disease (see below)
• Strep intermedius: May cause abscesses.
• Abiotrophia: 5% of all sub-acute Infective Endocarditis. Large vegetations seen. Leads to embolizations.
• Group D strep: Most cases of sub-acute/
• Group B strep: Most occurs in pregnant women and older patients with underlying disease.
• Pseudomonas aeruginosa: Acute cases, but involve right side of the the heart. Common in Intravenous Drug Abusers.
• HACEK (Haemophillus, Actinobacillusactinomycetemcomitans, Cardiobacteriumhominis, Eikenmllacorrodens, Kengellakingae) cause sub-acute disease.
• Fungal: Causes sub-acute dieases.
• Multiple pathogens: Pseudomonas and enteroccocci and the most common combination. Observed in IVDA Infective Endocarditis.

Types

There are 7 types of Bacterial Endocarditis named as follows :

1. Acute Infective Endocarditis
2. Sub-acute native valve endocarditis
3. Intra-venous drug abuse (IVDA) infective endocarditis
4. Prosthetic infective endocarditis
5. Pacemaker infective carditis
6. Bacteria Free Infective Endocarditis
7. Nosocomial infective endocarditis

Clinical Features

Signs and Symptoms

1. Septic signs: Fever ( > 1 week), rigors, chills, night sweats, malaise, weight loss, anaemia, splenomegaly, and clubbing
2. Cardiac lesions: Any new murmur and changing of pre-existing murmur
3. Immune complex deposition: Vasculitis, microsopic haematuria, glomerulonephritis and acute renal failure, Roth spots, splinter haemorrhages, Osler nodes. (painful pulp infarct on finger or toes)
4. Embolic phenomena: abscesses, Janeway lesions (painless macules on palm of hand)

Diagnosis

Investigations for infective endocarditis require following to be done :-

Common laboratory test such as FBC, BUSE, LFT’s and etc are done initially along with ECG and the Chest X-ray modality. However 2 diagnostic investigations are pointed out here, as they are required for Duke’s Criteria :

1. Blood Culture (look for organisms listed above)
2. Echocardiography (Oscillating intracardia mass on valve or supporting structures; or new valvular regurgitation)

After such investigations are done, Duke’s Criteria is followed.

What is Duke’s Criteria?

If ever you come across a patient with a fever and murmur happening concurrently, think Infective Endocarditis until proven otherwise.

To diagnose infective endocarditis, Duke’s Criteria was formulated; two sets of criteria are used

Major Criteria:

• Positive blood culture for Infective Endocarditis. 2 positive results, taken 12 hours apart
• Evidence of endocardial involvement. This includes positive ECHOCARDIOGRAM, oscillating intracardia mass on valve or supporting structures; or new valvular regurgitation.

Minor Criteria:

• Predisposing heart condition or IV drug use
• Fever more than 38 degree Celsius
• Vascular phenomena: arterial emobili, mycotic aneurysm, conjunctival haemorrahge, Janeway Lesions and etc.
• Immunologic Phenomena: Roth spots, glomerulonephritis, Osler’s nodes
• Serological evidence of active infection
• Unusual Echo findings: does not meet the major criteria

To diagnose as Infective Endocarditis using Duke’s Criteria, you need:

• 2 Major
• 1 Major and 3 minor
• 5 minor

Treatment

Treatment of Infective endocarditis involve:

• Long course of antibiotic use, administered parentally.
• Penicillin G is used for IE caused by S. viridans or S. bovis
• Vancomycin is used for those with penicillin allergy, or those infected with MRSA.
• Gentamycin an aminoglycoside with bactericidal activity
• Steptomycin, also an aminoglycoside. Used for streptoccocal or entorococcal organisms
• Ampicillin and Sulbactam combination, this drug interferes with bacterial cell wall synthesis during active replication while still having bactericidal effects
• Ceftazidime is a third generation cephalosprin with broad spectrum, gram-negative activity
• Ceftriaxone, another third generation cephalosporin, used for HACEK organisms
• Cefepime is a fourth generation cephalosporin

Remember to begin with empirical antibiotic treatment while waiting for blood culture results.

Note: Ensure that intravenous drug abusers, are screened for HIV.

References

Excellence in Clinical Case Presentation
Oxford Handbook of Clinical Medicine