Pathology Of Endocarditis, Myocarditis, Pericarditis Flashcards
3 major layers/walls of the myocardium
Internal endocardium
Middle myocardium
External epicardium
What layers are in endocardium?
Thin inner layer of endothelium and supporting CT
Middle myoelastic layer of smooth muscle fibers
Deep layer of CT called subendocardial layers that merges with the myocardium
What is the thickest layer of the heart
Myocardium
Epicardium layer details
Simple squamous mesothelioma layer supported by CT
Contains blood vessels and nerves
Corresponds to the visceral layer of the pericardium and contains lubricant fluid which prevents friction
Infective endocarditis
Microbial infection of the heart valves or the mural endocardium that leads to the formation of vegetations
Vegetations =. Thrombotic debris and organisms combined
Classifications off infective endocarditis
Acute: refers to destreuctive infections w/ Highly virulent organisms attacking previously normal valves
- significant morbidity and mortality exists even w/ antibiotic therapy
Subacute: refers to infections by organisms of low virulence affecting previously abnormal heart tissue
- typically appears insidiously and recovers fine after antibiotic therapy
Based of the tempo and severity of the clinical course
Cardiac abnormalities that predispose to infective endocarditis
Rheumatic heart disease
Mitral valve prolapse
Bicuspid aortic valves
Calcified valvular stenosis
Prosthetic heart valves (accounts for 10-20% of all cases)
Sterile platelet fibrin deposits at sites of pace markers
Neutropenia, immunodeficiencies, cancer, diabetes and drug/alcohol abuse
What organism is most commonly found during infective endocarditis
50-60% are caused by streptococcus viridans
10-20% are caused by staph aureus
- almost all cases are seen in IV drug users with endocarditis
HÁČEK group
Group of bacterial agents that can also cause infective endocarditis
Haemophilus
Actinobacillus
Cardiobacterium
Elkenella
Kingella
Culture-negative endocarditis
Occurs in 10% of cases
No organism is isolated from the blood culture since it is difficult to isolate
- often causes by strong previous antibiotic therapies
What is the primary pathogenesis factor predisposing to Infectious endocarditis?
Seeding of the blood with microbes (bacteremia)
Causes include
- surgical procedures
- wounds
- IV drug users
- etc.
What are the most common sites of infective endocarditis?
Aortic and mitral valves are the most common site
Note: tricuspid is the most common in IV drug abusers
The vegetation are friable, bulky a vegetations containing fibrin, inflammatory cells and microorganisms
Why are septic infarcts and mycotic aneurysms common in untreated infective endocarditis
Vegetations on the valves can break off and lodge somewhere, causing an abscess and septic issues.
Does subacute or acute cause less valvular destruction?
Subacute
What is the most common clinical symptoms for infective endocarditis?
Fever and heart murmurs (typically at aortic or mitral valve places)
Can also include the following
- weight loss
- flulike symptoms
- splenomegaly
- chills
- weakness
- malaise
What are systemic symptoms that can be causes my micro-emboli formed through infective endocarditis?
Petechiae in fingers and nail beds
- splinter appearance
Hemorrhages (especially retinal)
- Roth spots
Painless palm lesions
- Janeway lesions
Painful finer tip nodules
- osler nodes
How to confirm infective endocarditis?
Positive blood cultures and TEE images
- shows large leaflets in the left valves
What are possible sequelae associated with untreated infective endocarditis?
Glomerulonephritis
Hematuria
Albuminuria
Renal failure
Septicemia
Systemic embolization
Terminal arrhythmias
What are the mortality rates of infective endocarditis when treated vs not treated
Untreated low and high virulence = 98%
Low virtual virulence treated = 2%
High virulence treated = 10-30%
Non bacterial thrombotic endocarditis (NBTE)
Deposition of sterile thrombi on cardiac valves
- often seen in Hyper-coagulability states
Are nondestructive and also called “marantic endocarditis” since they are directly associated with patients who are generally disabled or wasting
What is the most common precursor for NBTE?
Hypercoagulability state
- these include:
1) history of DIC
2) hyper estrogen is states
3) having cancer
NOTE: these do not require valvular damage to be diagnosis disease, unlike infective endocarditis
Why is NBTE dangerous?
The increased and likely chance of turning into an embolus if not treated, as well as being a safe haven for potential bacterial cultures (leading to IE)
- the valve damage is usually benign
Most common cause of myocarditis
Coxsackieviruses A and B and enteroviruses
- also Chagas’ disease
To determine direct agent requires serology
Chagas’ disease brief refresher
Caused by the protozoan trypanosomia Cruzi
- uncommon in the northern hemisphere but very common in South American
- 10% of patients die during an acute attack
- can also manifest and remain as chronic inflammation, leading to CHF or lethal arrhythmias after 10-20 yrs left untreated
Lyme disease in myocarditis
Is possible, but rare (5%)
- caused by the bacterial spirochete borrelia burgdorferi
Requires temporary pacemaker while disease runs its course if myocarditis is present
Microscopic morphology of myocarditis
Edema and interstitial inflammatory infiltrates w/ myocyte injury
Chagas myocarditis specifically shows trypanosomes within the myofibrils s occupancies with inflammatory cells
Note: if patient survives, the lesions will usually progress to fibrosis
Myocarditis clinical features and symptoms
Very broad spectrum of clinical features
- can be asymptomatic and patients can recover without Tx
- can also result in CHF, lethal arrhythmias and SCD
Symptoms include the following:
1) fatigue
2) dyspnea
3) palpitations
4) pain
5) fever
Pericarditis facts
Primary (uncommon):
- caused by viral infections (and therefore often occurs concurrent with myocarditis)
Secondary (More common)
- untreated uremia
- post acute myocardial infractions and cardiac surgery as well (Dressler syndrome)
- pneumonia
- SLE
- rheumatic heart disease
Most common systemic disorder of pericarditis
Uremia
- uremia leads to pericarditis often if untreated
Cardiac tamponade w/ pericarditis
Can cause cardiac tamponade in some cases
Acute viral vs acute bacterial pericarditis exudate
Acute viral = exudate is irregular, shaggy and fibrinous in appearance
Acute bacterial = Purulent with regular shape and fibrinous
Clinical features of pericarditis
Atypical chest pain and prominent friction rub feeling
Can also show cardiac tamponade, low CO and cardiogenic shock
ECG:
- shows diffuse ST elevation w/ PR depression
- if cardiac effusion is present, may also show electrical alternans
