Salim Flashcards
Relate laplace law to chamber pressures in the left atrium as a result of mitral stenosis
In mitral stenosis, the pressure in the left atrium rises because it must work harder to push blood through the narrowed valve.
According to Laplace’s law, this increased pressure leads to increased tension on the atrial wall.
In response, the left atrium may undergo hypertrophy to handle the higher tension, which increases its oxygen demand.
Over time, chronic pressure overload causes atrial remodeling, resulting in dilation and weakening of the atrium, which can impair its ability to pump blood effectively and contribute to complications like arrhythmias
Why does angina occur is aortic stenosis
(1) Perfusion of the coronary arteries depends on the pressure difference between Diastolic blood pressure (e.g. 80mmhg) and LVEDP (e.g. 10mmHg). In aortic stenosis, the LVEDP increases which reduces the pressure difference which reduces perfusion of the coronaries.
(2) In severe stenosis, reduced stroke volume caused by the stenotic valve can lead to less blood passing back through the openings of the coronary arteries adjacent to the valve leaflets.
Describe the morphological features of acute and chronic rheumatic heart disease
Acute RHD
(1) Pancarditis with Aschoff body scattering in all layers of the heart
-Pericardial exudate (bread and butter exudate)
-Myocardial connective tissue with scattered aschoff bodies
-Endocardium (valves): fibrin deposition along the closure lines of the valves.
(2) Areas of fibrinoid necrosis can be seen.
Aschoff bodies are aggregates of: plasma cells, lymphocytes and Anitschow cells (large activated macrophages)
Chronic RHD
(1) Aschoff bodies are replaced with fibrous scar tissue
(2) valve cusps are thickened, calcified and have fibrous bridges across the opening - Button hole appearance.
(3) Chordae tendinae are thickened, fused and retracted.
List the 5 major criteria to make a diagnosis of ARF
Evidence of recent GAS infection plus
(1) Carditis
(2) Chorea
(3) Polyarthritis
(4) Erythema marginatum
(5) Sub cut nodules
List 5 minor criteria for ARF diagnosis
(1) Arthralgia
(2) elevated CRP
(3) elevated ESR
(4) Hyperpyrexia (>41.5)
(5) Prolonged PR interval
How is a diagnosis of ARF made
Evidence of recent GAS infection plus
2 major criteria
1 major and 2 minor criteria
list 3 ways to confirm a recent GAS infection
(1) Positive throat culture
(2) Antibody tests
-Antistreptolysin O Titre (ASO)
-Antistreptococcal DNAse B Titre (ADB)
(3) Rapid GAS carbohydrate antigen test.
Describe the pathogenesis of Post-streptococcal glomerulonephritis and how it presents
PSGN manifests approx 1-4 weeks after recovery from GAS infection.
-Antibodies against strep A form immune complexes with Strep antigens (commonly GADPH and Strep endotoxin B).
-These complexes can then lodge in the glomeruli and cause inflammation via complement activation and leukocyte infiltration.
Results in:
-> glomerular hypercellularity due to swelling and proliferation of the mesangial and endothelial cells.
-> IgG deposition in vessel wall
-> Vessel wall necrosis and crescent formation can be seen in more severe cases.
The result is impaired glomerular filtration barrier which presents as nephritic syndrome:
- Oliguria
- Haematuria
- mild proteinuria
- HTN
- Oedema.
Describe the mechanism of action of heparin
Heparin in general binds to Anti-thrombin III, thereby increasing AT III’s affinity for the active sites of Thrombin (IIa) and Xa.
Unfractionated heparin is larger molecule and so can inhibit both Thrombin and Xa. This is because, in order to inactive Thrombin, it requires heparin to bind to both it and AT-III.
LMWH mostly only inhibits Xa, because Xa inhibition only requires binding of heparin to AT-III.
Explain why unfractionated heparin is less predictable than LMWH
Unfractionated heparin (UFH) is less predictable because its elimination follows zero-order kinetics at therapeutic doses. In zero-order kinetics, a constant amount of UFH is eliminated per unit time, regardless of its concentration in the blood. This occurs when the body’s usual elimination pathways become saturated, meaning they cannot handle higher concentrations of the drug. As a result, excess heparin can accumulate in the blood if too high a dose is given, leading to prolonged effects. This accumulation increases UFH’s half-life, further extending its anticoagulant action and making its effects harder to predict.
In contrast, low molecular weight heparin (LMWH) follows first-order kinetics, where a constant percentage of the drug is eliminated per unit time. This means that its half-life remains constant, regardless of the dose, leading to more predictable drug levels and anticoagulant effects in the body.
Opening snap and diastolic rumble is what?
Mitral stenosis.
The snap is caused by forced opening of the mitral valve leaflets caused by increased pressures within the left atrium. The valves are stiff and calcified causing an opening snap sound to be heard. The opening of mitral valve occurs at the beginning of diastole after the 2nd heart sound. Under normal conditions the opening is silent.
The rumble is caused by turbulent blood flow through the stenotic/narrowed valve which creates reverberations/vibrations off the left ventricle wall, heard as a rumble.
Systolic click is what?
Mitral valve prolapse causing mitral regurgitation.
During systole, on ventricular contraction, the mitral valves can billow upwards into the left atrium, pulling on the chordae tendinea/papillary muscles and causing a click sound. It is typically heard in the middle of systole but it depends when during systole the prolapse occurs. To generalise it, it occurs between S1 and S2.
name 2 organisms that commonly cause infective endocarditis and where on the body each can be found
Staph aureus: nostrils, mucous membranes, skin, oropharynx
Strep viridians: oral cavity, nasopharynx, GI tract, female genital tract.
explain what is meant by immunological cross-reactivity
Immunological cross-reactivity refers to when immune components (like antibodies or T-cells) that are designed to recognize one specific antigen also bind to a different antigen because of structural similarity. This can happen between two different pathogens or between a pathogen and unrelated environmental antigens. When this reaction involves the body’s own tissues, it can contribute to autoimmune reactions, which is where molecular mimicry comes into play
List 3 indications for valvular surgery in infective endocarditis
Name 3 surgical options for infective endocarditis
Indications
(1) Heart failure or cardiogenic shock
(2) Embolic complications or high risk of
- Vegetations >10mm
- Highly mobile vegetations
- Afib
- Multi valve involvement
(3) Uncontrolled infection
-persistent positive blood culture
-Enlarging vegetations
-Abscess formation
Surgical options
(1) Valve replacement
(2) Patch repair
(3) Aortic root replacement.
