Cardiovascular Flashcards
What is blood pressure normally controlled by?
Renin-angiotensin system
Describe how the renin-angiotensin system works
1) If renal perfusion is low, kidney juxtaglomerular cells convert pro-renin (present in blood) into renin
2) Renin converts angiotensinogen (secreted by liver) into angiotensin I
3) Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE), released from lungs
4) Angiotensin II is potent vasoconstrictor + promotes adrenal glands to produce aldosterone
5) Aldosterone makes kidneys reabsorb sodium and water into blood (and excrete potassium to maintain electrolyte balance)
What are the stages of hypertension?
Stage 1: clinic blood pressure at least 140/90 and subsequent ABPM daytime average of at least 135/85
Stage 2: clinic BP >160/100; ABPM >150/95
Severe hypertension: >180 systolic; >110 diastolic
Accelerated hypertension: >180/110 with signs of papilloedema +/or retinal haemorrhage
What are some secondary causes of hypertension?
Renal disease
Endocrine diseases - Cushing’s, Conn’s, phaeochromocytoma, adrenal hyperplasia
Congenital disease - coarctation of the aorta
Pregnancy - pre-eclampsia
Drugs - oestrogen-containing contraceptives, steroids, NSAIDs, EPO
If the blood pressure is raised on a one-off reading, what is required to confirm the diagnosis?
ABPM or HBPM
Hypertension is confirmed if:
- Clinic BP of 140/90 PLUS
- ABPM/HBPM of >135/85
How do you do home BP monitoring?
Twice a day for 7 days
Each of BP recording must be done twice at least 1 minutes apart with patient seated
Discard readings for day 1
Take an average of the rest
What conditions can HTN cause?
Heart failure Coronary artery disease Stroke CKD Peripheral arterial disease Vascular dementia
It is the single biggest risk factor for cardiovascular disease and related disability - half of all MIs and CVA are associated with hypertension
What score is relevant to HTN?
QRISK3
Estimates 10-year risk of developing CVD
If over 20%, consider high risk and encourage patient to take statin
Between 10-20% is moderate risk; NICE recommends discussing with patient about starting a statin
What is the drug treatment of hypertension?
Step 1: <55 years - ACE inhibitor
> 55 years or black of any age - calcium channel blocker (if CCB not tolerated, use a thiazide diuretic instead)
Step 2: ACE inhibitor + calcium channel blocker
Step 3: ACEi + Ca channel blocker + thiazide diuretic
Step 4 (resistant hypertension): step 3 + further diuretic (e.g. spironolactone) or beta blocker
What is the mechanism of action of thiazides?
Inhibit sodium resorption at distal convoluted tubule by binding to Na/Cl co-transporter
This causes increased Na + K excretion
When are thiazides contraindicated?
Hyponatraemia - in the elderly, thiazides are a common cause of hyponatraemia
Hypokalaemia
Hypercalcaemia
Renal impairment
What is the mechanism of action of loop diuretics?
How do they compare to thiazides?
They inhibit resorption of sodium in ascending loop of Henlé
This causes increased Na+ and K+ excretion
Compared to thiazides:
- more potent
- shorter half-life
- better tolerated in patients with CKD
What is the mechanism of action of potassium-sparing diuretics?
Competitively inhibit aldosterone-dependant sodium-potassium exchange channels in the distal convoluted tubule
This action leads to increased sodium and water excretion, but more potassium retention
When are ACE inhibitors contraindicated?
Renal artery stenosis
What the side effects of ACE inhibitors?
Dry cough
Impotence
Hypotension - take the first one in bed at night
What is decubitus angina?
Occurs when lying down
Impaired left ventricular function due to severe coronary artery disease
What is the drug management of coronary artery disease?
20mg artovastatin to those with >10% risk of CV disease (calculated with QRisk3)
80mg artovastatin if previous MI, Hx of type 2 diabetes, current ACS symptoms (e.g. angina, total cholesterol >4, LDL>2)
What is the mechanism of action of statins?
Inhibit HMG Co-A reductase which limits the rate of cholesterol synthesis
How can you describe heart failure?
When the cardiac output is inadequate for the body’s metabolic requirements leading to peripheral hypoperfusion
What is high output cardiac failure?
What are some causes of high output heart failure?
This is when the heart is working at normal/increased rate but needs of the body are beyond that which heart can supply
AAPPTT
- Anaemia
- Arteriovenous malformation
- Paget’s disease
- Pregnancy
- Thyrotoxicosis
- Thiamine deficiency (wet Beri-Beri)
What is the difference between systolic and diastolic low output heart failure?
Systolic
- Inability of the ventricle to contract normally resulting in reduced cardiac output
- Ejection fraction <40%
Diastolic
- Inability of the ventricle to relax and fill normally causing increased filling pressures
- Ejection fraction >50%
What are some causes of systolic heart failure?
- Ischaemic heart disease
- Dilated cardiomyopathy
- Myocarditis
- Infiltration (e.g. in haemochromatosis or sarcoidosis)
How does left sided heart failure present?
Symptoms caused by pulmonary congestion…
- Shortness of breath on exertion
- Orthopnoea
- Paroxysmal nocturnal dyspnoea
- Nocturnal cough (± pink frothy sputum)
Failure of the left side of the heart causes blood to back up into the lungs, causing respiratory symptoms as well as fatigue due to insufficient supply of oxygenated blood
What are the signs and symptoms of right side heart failure?
Symptoms of venous congestion… • Ankle swelling • Weight gain • Abdominal distension and discomfort, • Anorexia/nausea.
Signs of venous congestion… • Raised JVP • Pitting ankle/sacral oedema • Tender smooth hepatomegaly • Ascites • Transudative pleural effusions (typically bilateral)
failure of the right ventricle leads to congestion of systemic capillaries, which generates excess fluid accumulation in the body