Cardio Week 6 Flashcards
What is contained in the posterior mediastinum?
Oesophagus descending thoracic aorta Thoracic duct sympathetic trunks
In which type of valvular disease is it possible to wait until the appearance of symptoms to intervene?
Aortic stenosis
What are some common causes of haemorrhagic necrosis?
- Venous occlusion
- Reperfusion of necrotic tissue
- Dual circulation or natural collateral circulation
What are aminoglycosides?
Antibiotics they target protein synthesis by binding to and distorting the codon reading frame on the ribosome.
Usually the appearance of symptoms in valvular disease indicates the progression of irreversible, pathological changes to the heart. In which type is this not the case?
Aortic stenosis - and LVH can regress.
What are some side effects of ACE inhibitor and angiotensin receptor blockers?
Dry cough
First use hypotension
Loss of appetite
Hyperkalaemia
Acute renal failure
Foetal malformations
Why is warfarin described as a “moody” drug?
- Short half-life
- Binds to plasma protein
- Highly dependent on dietary vitamin K
What is an example of antimicrobial resistance via drug inactivation due to convalent modification
Gentamicin (an aminoglycoside) acetyltransferase - acetylates the gentamicin
What are examples of antimicrobial resistance mediated by altering of target?
- Alternate PBP (mecA) - methicillin doesn’t recognise
- Switch terminal D-ala with monosaccaride to prevent vancomycin blocking cell wall synthesis (VRE)
- VISA - vancomycin intermediate resistant Staphlococcus aureus. Over produces peptidoglycan to soak up vancomycin
Why can’t you treat Pseudomonas aeruginosa with co-amoxyclav?
Because P. aeruginosa has a chromosomally encoded beta-lactamase that clavulanic acid can’t inhibit and therefore it goes on to hydrolyse the amoxycillin. However you can use Ticarcillin + clavulanic acid as Ticarcillin is resistant to P. aeruginosa’s chromosomal beta-lactamase (you also need clavulanic acid because Ticarcillin is susceptible to plasmid encoded beta-lactamases which clavulanic acid will inhibit).
What does damage to blood vessels lead to in the clotting cascade?
- Vasocontriction
- Platelet adhesion and activation
- Fibrin formation
What is the end result of the coagulation cascade
Activation of thrombin from prothrombin which cleaves fibrinogen into fibrin
What is the function of clavulanic acid?
It is a suicide inhibitor of plasmid encoded beta-lactamases
How is vitamin K relevant to coagulation?
Vitamin K is a substrate for Vitamin K reductase that is essential for the formation of coagulation factors II, VII, IX and X.
What is an example of a platelet inhibitor?
Aspirin - inhibits cyclo-oxygenase to prevent thromboxane production (thromboxane is a potent activator of platelets)
What are some drug actions that will decrease preload?
Diuretics
Venodilators - nitrates
Aldosterone receptor antagonists
Aquaretics
What are some fibrinolytic drugs?
Streptokinase, alteplase
Rheumatic fever almost always causes this type of valvular disease…
Mitral stenosis
What are some drug actions that will decrease afterload?
Angiotensin receptor antagonists
Beta-adrenoceptor antagonist
Arterial vasodilator
ACE inhibitor
How does valve stenosis cause a pressure difference across valves?
Narrower space for blood to travel through therefore it requires greater pressure to get the blood through
Bowel infarcts are usually haemorrhage T/F? Why?
True, commonly due to venous occlusion
What is an examples of antimicrobial resistance via drug inactivation via hydrolysis
Chromosomal encoded beta-lactamase in P. aeruginosa hydrolyases beta-lactams
What is the mecA protein?
An altered penicillin binding protein that isn’t recognised by beta-lactams therefore affording resistance to penicillin/methicillin to the pathogens that have it. This is the mechanism in methicillin resistance and the protein is called mecA.
Define Thrombosis
Pathological haemostatic plug formation in the absence of blood loss
At what level does the superior vena cava enter the right atrium?
Posterior to the 3rd costal cartilage
What causes the 4th heart sound?
Forceful atrial contraction to overcome stiff ventricle, occurs during diastole due
Describe the action of heparin
- Anti-coagulant
- Enhances activity of antithrombin III which inactivates Factor Xa and thrombin
- Injectable
What are some stimuli for platelet activation?
- Collagen 2. Thrombin 3. Thromboxane 4. ADP
Why is Amrinone useful when beta1-adrenoceptors are desensitised due to over activation?
Amrinone mechanism to increase intracellular Ca is not mediated via those receptors. Rather it inhibits phosphodiesterases > less cAMP to AMP > more active PKA > more phosphorylation of Ca channels > more intracellular Ca.
What is the ligamentum arteriosum?
Connects the aorta to the pulmonary trunk - remanence of shunt that allowed blood to bypass the pulmonary circulation in utero.
At what level to the left and right brachiocephalic veins meet?
Posterior to the 1st costal cartilage
Which vitamin is important in coagulation?
K
Who is the co-ordinator of secondary haemostasis
Thrombin - cleaves fibrinogen to fibrin
What is the course of the vagus nerve in the mediastinum?
-Descending in the carotid sheath, posterorlateral to common carotid artery -R: Along trachea L: Lateral aortic arch -Posterior to lung root -Along ant. of oesophagus where L & R join to form the oesophageal plexus
What does the descending aorta supply in the thoracic cavity?
Intercostal space (posterior intercostal arteries)
Bronchial arteries
Pericardium
Volume overload is caused by what?
Valve regurgitation
What is the course of the phrenic nerve in the mediastinum?
Descending on the scalenus anterior Passes between the subclavian artery and vein Passes anterior to the lung root Pierces the diaphragm
What are some examples of emboli?
- Thrombus 2. Atherosclerotic rupture 3. Gas 4. Vegetative mass from bacteria aka septic emboli 5. Tumour emboli 6. Fat emboli
What are examples of antimicrobial resistance mediated by prevent drug getting to its target?
Reduced entry into cell - eg modification of outer membrane in gram -ve to prevent entry of aminoglycosides
Increase efflux of drug from cell
How long can neurones survive without blood supply?
3-4 minutes
How does valve stenosis cause a pressure difference across valves?
Narrower space for blood to travel through therefore it requires greater pressure to get the blood through
In which type of valvular disease do you hear no second heart sound but murmur instead?
Aortic regurgitation
What are some side effects of heparin?
Haemorrhage, thrombocytopaenia and osteoporosis
How long can cardiac muscle survive without blood supply?
20 minutes
An inhibitor of vitamin K reductase is?
Warfarin
What are the goals of treatment for cardiac failure?
- Decrease cardiac work and improve cardiac function 2. Decrease signs and symptoms 3. Increase survival
What is the mechanism of vasoconstriction in response to blood vessel damage?
Platelets adhere to the damaged wall and are activated and release ADP and 5-HT - potent vasoconstrictors
What is the mechanism of glycosides on the heart?
Increase contractility by increase intracellular Ca by inhibiting ATPase which reduces the amount of Ca pumped out of the cell.
What does Amrinone do?
Inhibits phosphodiesterases that break down cAMP therefore Ca channels are more activated = increased intracellular Ca = Increased contractility
What can you use to reduce preload?
Diuretics
Venodilators
Aldosterone inhibitors
Angiotensin Receptor Antagonists
ACE inhitiors
What are the 3 essential features of accurate clinical trials?
- Randomisation (reduce compounding error)
- Blinding (reduce observational bias/error)
- Intention to treat (reduce selection error) - treat people like they’re still in their original group (control or treatment) regardles of whether they stick with it.
What are they four functions of the kidneys?
- Regulate electrolyte and water volume
- Endocrine production
- Exogenous waste excretion
- Endogenous waste excretion
What are the structural components of the kidney?
- Glomerulus
- Proximal tubule
- 60-70% of water and NaCl reabsorbed - Loop of Henle
- water, K+ and 20-30% of NaCl reabsorbed - Distal tubule
- 5-10% of NaCl reabsorbed and K+ secreted - Collecting ducts
- K+ secreted and rest of NaCl is reabsorbed
What is the significance of probenecid?
It is a drug that prevents to secretion of banned substances used by unethical athletes.
What are diuretics?
Drugs that decrease NaCl reabsorbion thereby increase its secretion and water’s secretion.
What are the 4 classes of diuretics?
Loop diuretics
Thiazide diuretics
Potassium-sparing diuretics
Osmotic diuretics
What is the mechanism of action of loop diuretics?
They inhibit Na/Cl/K carriers into the cell in the loop of Henle. Leads to reduced water reabsorption due to reduction of hypertonicity in interstitum and greater [Na] in the distal tubule.
What is the duration of action of loop diuretics? What are some side effects?
3-6 hours.
Hypokalaemia (due to increased Na+ in distal tubule = more Na reabsorbed and more K+ secreted via Na/K ATPase)
Hypovolaemia
Why are thiazide diuretics less potent than loop diuretics when they both act on Na/Cl co-transport?
Because thiazide diuretics act in the distal tubule where less Na/Cl is reabsorbed.
Thiazide diuretics have a slower, less urgeny effect compared to loop diuretics T/F?
True
The duration is 8-12 hours
When are K sparing diuretics mainly used?
With loop or thiazide diuretics to prevent hypokalaemia
What is spironolactone? What is its mechanism of action?
It is a K-sparing diuretic and a aldosterone receptor antagonist - stops stimulation of Na reabsorption thereby preventing K secretion.
Why is the kidney susceptible to toxins?
- Toxins can be at a high concentration
- The kidney filters 25% of blood
- The kidney can metabolise
- Contribution from extrarenal events.
