Cardiovascular Risk Factors Flashcards
Which is more common, primary or secondary hypertension?
Primary (~90% of cases)
How is hypertension diagnosed?
Clinic BP is 140/90 or higher
- Take a second measurement
Ambulatory BP is 135/85 or higher
- Hypertension confirmed
What are some secondary causes of hypertension?
Renal/Endocrine/Aortic disease
Renal artery stenosis
Drug therapy
How does renal artery stenosis cause hypertension?
Decreased renal blood flow
Excess renin secretion
Huge sodium and water retention - plasma volume increases
What is Conn’s syndrome?
Excess aldosterone
What is Cushing’s syndrome and how does it present?
Excess corticosteroid
Weight gain, rounded face etc
What can hypertension lead to?
LVH
CCF
Atheroma
Aneurysm rupture (Berry aneurysm - subarachnoid haemorrhage - thunderclap headache)
What is pre-eclampsia?
Hypertension and proteinuria in pregnancy
Resolves after birth
What can result due to cardiac Ischaemia?
Angina
Infarct
Cardiac failure
How is the heart affected when fibrosis occurs?
Loses elasticity
Decreased EDV and hence decreased SV
What can occur if the carotid arteries become stenosed?
TIAs
CVAs
Vascular dementia
What can cause an aneurysm can form?
Congenital causes Syphilis Mycotic - bacterial infection of artery wall Iatrogenic Copper deficiency
What is the difference between a true aneurysm and a pseudoaneurysm?
True aneurysm
- Involves all three layers of arterial wall
Pseudo
- Blood leaking completely out of artery into surrounding tissues
What is an arterial dissection?
Tunica media split by blood
What colour is an arterial thrombus?
White - mainly platelets in fibrin mesh
What colour is a venous thrombus?
Red
What happens in the coagulation cascade?
Factor X — Factor Xa
Factor Xa stimulates Prothrombin (II) — Thrombin (IIa)
Thrombin stimulates Fibrinogen (soluble) — Fibrin (insoluble)
Fibrinogen and Thrombin cause platelet aggregation
Why is and what form is vitamin K required for coagulation?
Used in production of carboxylase enzyme Reduced form (Hydroquinone)
What reaction does carboxylase enzyme mediate?
Activation of precursors (II, VII, IX and X) to gamma-carboxyglutamic acid residues (serine proteases)
How does warfarin work?
Prevents reduction of Vitamin K back to hydroquinone by competing for vitamin k reductase
What does Antithrombin III do?
Neutralises serine proteases
How does heparin work?
Binds to ATIII
Increases its affinity for serine proteases (esp IIa and Xa)
How do low molecular weight heparins work?
Inhibit factor Xa
Heparin or LMWH; when is each preferred?
Heparin
- Renal failure since LMWH is excreted by the kidneys
LMWH
- In outpatient treatment as it can be given subcutaneously
- Huge PE due to more predictable pharmacokinetics
What chemicals cause platelet aggregation and how?
ADP 5-hydroxytryptamine (5-HT) Thromboxane A2 (TXA2)
Cause expression of GPIIb/IIIa receptors - cross link platelets via fibrinogen
How does aspirin work?
Blocks COX-1 irreversibly
Prevents TXA2 synthesis
Less GPIIb/IIIa expression
Less cross linking
How does tirofiban work?
Blocks the GPIIb/IIIa receptors
Prevents fibrinogen cross-linking of platelets
How does clopidogrel work?
Blocks P2Y12 receptor irreversibly
ADP cannot bind to and activate receptor
Decreased GPIIb/IIIa expression
Less cross linking
How does plasminogen work?
Converted to plasmin
Promotes conversion of fibrin to fibrin fragments
Clot lysis
What does streptokinase act as and how?
A fibrinolytic extracted from streptococci
Stimulates conversion of plasminogen to plasmin
What patients is streptokinase not suitable in?
Patients with strep infection
Patients who have received it for longer than 4 days - antibodies produced
Give examples of tPAs and explain how they work?
Alteplase and Duteplase
Convert fibrin-bound plasminogen to plasmin
- Selective for clots
How can fibrinolytic drug overdose be treated?
Tranexamic acid
Inhibits plasmin production
What are some special adaptations of the coronary circulation?
High capillary density
High basal blood flow
High oxygen extraction into tissues
What effect does decreased PaO2 have on coronary arteries?
Vasodilation
What effect does adenosine have on coronary arteries?
Vasodilation
The coronary arteries are supplied by sympathetic nerves, why don’t they vasoconstrict?
Over-ridden by metabolic hyperaemia - functional sympatholysis
Adrenaline activates Beta2 receptors - vasodilation
What happens to coronary flow if diastole is shortened?
Decreased coronary flow
What do the internal carotids and vertebral arteries combine to form?
Basilar artery
What is the circle of Willis?
An anastomosis of the basilar artery and internal carotid arteries
- Maintains perfusion if one carotid occluded
Between what BPs can autoregulation protect the brain against MAP changes?
60-160
What happens if intracranial pressure increases?
Decreased cerebral perfusion pressure
Decreased blood flow
Why, in hypoxia, do pulmonary arteries vasoconstrict instead of dilate like everywhere else in the body?
To divert blood away from poorly oxygenated alveoli
- Blood taken to areas rich in oxygen to maintain gas exchange
Why does skeletal muscle blood flow increase during exercise?
Local hyperaemia overcomes SNS vasoconstrictor tone
Adrenaline - Beta2 receptors - Vasodilation
Increased cardiac output - increased blood flow
