Cardiac cycle, BP and hypertension Flashcards
(15 cards)
What is hypertrophic cardiomyopathy and how does it present histologically and clinically?
Hypertrophic cardiomyopathy is a disorder where the heart becomes massively hypertrophied, often with a disproportionate thickening of the septum as compared to the rest of the heart. The chamber size of the left ventricle is reduced, leading to impaired ventricular filling during diastole, decreased SV, and decreased CO.
Histologically, cardiac myocytes, look very big and the cells show extreme hypertrophy with branching and disarray. There’s also a lot of interstitial fibrosis between the myocytes.
Clinically, patients may exhibit atrial fibrillation, intractable cardiac failure, and ventricular arrhythmias. Presenting symptoms may be things like shortness of breath or fainting.
Where are the baroreceptors located?
- Carotid sinus: thin walled, highly innnervated, internal carotid artery
- Aortic arch
- more strech = more firing
- responds quickly (within 1 cardiac cycle)
Where is the brainstem CV control centre and how does it regulate BP?
- In the medulla
- pressor and depressor centres
- operates via sympathetic and parasympathetic nerves
Where are the chemoreceptors and what do they respond to?
Central Chemoreceptors:
- located on ventrolateral surface of medulla oblongata
- sensitive to changes in pH and CO2
Peripheral chemoreceptors(stimulated when BP drops <60mmHg and baroreceptors go silent)
- In carotid and aortic bodies outside the arteries
- respond to low pO2
- stimulated by low MAP
How do sex, age and weight affect BP
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SEX: Men have higher BP than women
AGE: BP rises with age - systolic BP increases with age, but hardening of the arteries increased pulse pressure which means diastolic BP rises up to 60 but less compliance means diastolic BP flattens out but systolic keeps on increasing.
Steepest rise in BP from birth and anther smaller spike during puberty
WEIGHT: Bigger body relates to larger BP
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What environmental factors affect BP?
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Diurnal variation: lower night BP (20mmHg), less variability at night, less sympathetic activity at night
Seasonal variation: BP about 3 mmHg lower in summer (vasodilation, sweat decreasing BV, body weight during summer)
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What is the population paradox in relation to CVD?
In a population people with average BP have a moderate risk, but make up largest proportion of the population and so have the most deaths in absolute terms
What are the known risk factors for hypertension and how can they be reduced?
Smoking - quit
Diet - reduce alcohol, salt, total and saturated fats
Weight – reduce BMI
Stress - exercise, relaxation
What are the 4 major classes of anti-hypertensive drugs?
Angiotensin System Inhibitors: “perils” and “sartans”
β-Adrenoceptor Antagonists: “olols”
Ca2+ Channel Blockers
Diuretics
How do ACE inhibitors (“perils”) work and what are their side effects?
Block conversion of Ang I to Ang II
–Reduce vascular tone
– Reduce aldosterone production
– Reduce cardiac hypertrophy
- Prevent Bradykinin breakdown
- Adverse effects – First-dose hypotension – Dry cough – Loss of taste – Hyperkalaemia – Acute renal failure – Itching, rash, angio-oedema – Foetal malformations
Contraindicated in: pregnancy, bilateral renal stenosis, angioneurotic oedema
How do Angiotensin receptor antagonists (“sartans”) work and what are their side effects?
block AT1 receptors
- Reduce vasoconstriction
- Reduce aldosterone
- Reduce cardiac hypertrophy
- Reduce sympathetic activity
Adverse effects – Hyperkalaemia (+ thiazide diuretic) – Headache, dizziness
How do ß-adrenoceptor antagonists (“olols”) work and what are their side effects?
Mechanism:
– Reduce CO: Rate, contractility
– Reduce renin release: Blood volume, TPR
Adverse effects
– Cold extremities
– Fatigue: Contraindicated in diabetes
– Dreams, Insomnia
– Bronchoconstriction: Contraindicated in asthma
How do Ca2+ channel blockers work and what are their side effects?
Inhibit voltage-gated L-type Ca2+ channels in myocardium and vasculature
– Reduce cardiac/vascular contractility
Adverse effects:
– Verapamil, Diltiazem • Oedema, flushing • Headache • Bradycardia • Care if heart failure present
– Dihydropyridines • Oedema, flushing • Headache • Reflex tachycardia • Care if tachyarrhythmias present
How do Thiazide diuretics work and what are their side effects?
Inhibit Na+/Cl- cotransporter in DCT
decrease Na+ and Cl reabsorption in renal tubules, increase [Na+] and water excretion
Also K+ loss from collecting duct lowers BV and reduce BP
Adverse effects: K+ loss, gout, hyperglycaemia, allergic reaction
Why is there a potential need for combination therapy and what limits the usefulness of some antihypertensive drugs?
Hypertension is a multfactorial disease with both nervous and hormonal control of BP, so there are many organ, signalling chemicals and proteins which may be targeted.
Need for:
– adequate reduction in BP: Dose-response, drug combinations
– patient safety and compliance: concomitant disease, initial choice / contraindication
