Infective Endocarditis

Infective Endocarditis

·        Due to microbial infection of

o   Heart valve (native or prosthetic)

o   Lining of a cardiac chamber or blood vessel

o   Congenital anomaly (e.g. septal defect)

·        Underlying condition

o   RHD

o   Congenital heart disease

o   Calcified aortic valve

o   Floppy mitral valve

 

Pathophysiology

·        Sites

o   Heart with pre-existing endocardial damage – attract deposition of platelets and fibrin – vulnerable to colonization by blood-borne organisms, protected from host defence mechanisms by fibrin and platelet aggregates à vegetations grow à

§  Obstruction

§  Embolism

§  Damage to adjacent tissue à abscess formation

§  Valve regurgitation d/t valve damaged by tissue distortion, cusp perforation, distortion of chordae

o   Previously normal heart – infection with a virulent/ aggressive organism (eg S aureus – endocarditis of tricuspid valve in IVDU)

·        Risk of endocarditis

o   High - areas of endocardial damage caused by a high-pressure jet of blood, such as ventricular septal defect, mitral regurgitation and aortic regurgitation

o   Low - sites of haemodynamically important low-pressure lesions, such as a large atrial septal defect

·        Extracardiac manifestations eg vasculitis, skin lesions d/t emboli/ immune complex deposition

·        Mycotic aneurysms in arteries at site of infected emboli

·        Infarction of spleen, kidneys

 

Etiology

·        Staphylococci

o   S aureus  - commonest cause (including PVE, acute IE, IVDU IE); high virulence; classically leads to cerebral embolization and haemorrhage within first 48 hours

o   Coagulase negative

§  S epidermidis – commonest organism causing post-operative endocarditis

§  S lugdenensis – rapidly destructive acute endocarditis

·        Streptococci

o   Oral – Strep pneumonia, Strep pyogenes; viridans group (S mitis, S sanguis – commensals; cause SABE)

o   Others (non-enterococcal)

o   GBS – acute IE in pregnant and older patients with underlying diseases eg cancer, diabetes, alcoholism

o   GDS (3rd commonest) – subacute IE

·        Enterococcus – E faecalis, E faecium, S bovis

·        HACEK - Haemophilus spp., Actinobacillus actinomycetem-comitans, Cardiobacterium hominis, Eikenella spp. and Kingella kingae

·        Brucella

·        Coxiella

·        Fungi – normal/ prosthetic valves esp in immunocompromised/ those with indwelling iv lines; SABE

o   Candida

o   Aspergillus

Types

·        Acute IE

·        Subacute IE

·        IVD abuse IE

·        Prosthetic valve endocarditis

·        Pacemaker IE

·        Bacteria-free IE

·        Nosocomial IE

 

Clinical Features

Subacute endocarditis

In a patient with congenital/ valvular heart disease

·        Fever – persistent

·        Tiredness

·        Night sweats

·        Weight loss

·        New signs of valve dysfunction/ heart disease

·        Embolic stroke

·        Peripheral arterial embolism

·        Purpura and petechial haemorrhages in the skin and mucous membranes

·        Splinter haemorrhages - fingernails or toe nails

·        Osler's nodes - painful tender swellings at the fingertips d/t vasculitis

·        Digital clubbing - late sign

·        Splenomegaly (in Coxiella infections - spleen and the liver may be considerably enlarged)

·        Microscopic haematuria

 

Acute endocarditis

·        Severe febrile illness

·        Prominent and changing heart murmurs

·        Petechiae

·        Stigmata of chronic endocarditis – absent

·        Embolic events +++

·        Cardiac/ renal failure

 

Post-operative endocarditis

·        Unexplained fever in a patient who has had heart valve surgery

·        May resemble subacute or acute endocarditis, depending on the virulence of the organism.

·        Usually due to coagulase-negative staphylococcus

 

Diagnosis – Duke’s criteria

·        Major criteria

o   Positive blood culture

§  Typical organism from two cultures

§  Persistent positive blood cultures taken > 12 hrs apart

§  Three or more positive cultures taken over > 1 hr

o   Endocardial involvement

§  Positive echocardiographic findings of vegetations

§  New valvular regurgitation

·        Minor criteria

o   Predisposing valvular or cardiac abnormality// Intravenous drug misuse

o   Pyrexia ≥ 38 °C

o   Embolic phenomenon

o   Vasculitic phenomenon

o   Blood cultures suggestive: organism grown but not achieving major criteria

o   Suggestive echocardiographic findings

 

Definite endocarditis = two major, or one major and three minor, or five minor (vs 2 major/ 1 major + 2 minor in RHD)

Possible endocarditis = one major and one minor, or three minor

 

Investigations

·        Blood culture

o   Identify infection, guide antibiotic treatment

o   3-6 sets taken

o   Aseptic technique observed

o   Sample from different venepuncture sites; avoid sampling from in-dwelling line

o   Aerobic, anaerobic cultures

·        Echocardiography

o   Detect and follow the progress of vegetations, for assessing valve damage and for detecting abscess formation

·        FBC

o   Normocytic normochromic anemia

o   Leucocytosis

·        ESR, CRP – raised (CRP more reliable in monitoring progress)

·        Urinalysis

o   Proteinuria

o   Hematuria – microscopic

·        RFT – elevated BUN, creatinine

·        ECG

o   AV block

o   Infarction d/t emboli

·        CXR

o   Cardiac failure

o   Cardiomegaly

 

Treatment

·        Medical treatment – for 2 weeks

o   Acute presentation

§  Flucloxacillin

§  Gentamicin

o   Subacute/ indolent

§  Benzyl penicillin

§  Gentamicin

o   Penicillin allergy, prosthetic valve, suspected MRSA

§  Triple therapy – vancomycin, gentamicin, oral rifampicin

o   Empirical treatment

§  Penicillin

§  Gentamicin

o   Staphylococcal infection

§  Vancomycin

§  Gentamicin

·        Cardiac surgery - débridement of infected material and valve replacement (start antimicrobial therapy before surgery)

o   Indications

§  Heart failure d/t valve damage

§  Failure of antibiotic therapy (persistent sepsis 72 hours after starting antibiotics)

§  Large vegetations on left-sided heart valves with evidence/ high r/o systemic emboli

§  Abscess formation (eg septal abscess à conduction disturbance)

§  Fungal IE (except Histoplasmacapsulatum)

§  Recurrent septic emboli especially after 2 weeks of antibiotic treatment

§  Rupture of aneurysm of sinus of Valsalva

§  Kissing infection of anterior mitral valve leaflet in patients with IE of aortic valve

 

Prevention

·        Antibiotic prophylaxis to people at risk of infective endocarditis undergoing interventional procedures – Amoxicillin 2g PO 30-60 minutes before procedure

o   High risk – prosthetic heart valves, previous endocarditis, complex cyanotic congenital heart disease, surgically constructed systemic pulmonary shunts or conduits

o   Moderate risk – acquired valvular dysfunction (eg RHD), hypertrophic cardiomyopathy, MVP with valvular regurgitation and thickened valve leaflets

 

Complications

·        CNS

o   Stroke – embolic

o   Intracranial haemorrhage

o   Infectious mycotic aneurysm (mushroom shaped) à leak à meningeal irritation à secondary aseptic meningitis

o   Seizures

§  Focal – embolic sitology

§  Generalized – meningitis

o   Immune complex vasculitis – streptococcal endocarditis

·        CVS

o   MI

o   Pericarditis

o   Cardiac arrhythmia

o   Valvular insufficiency

o   CCF

o   Aortic root/ myocardial abscess

o   Arterial emboli, infarcts, mycotic aneurysm

·        Musculoskeletal

o   Arthritis

o   Myositis

·        Renal

o   GN

o   Acute renal failure

·        Mesenteric, splenic abscess, infarct