Author(s): Declan Doyle and Simon Herrington
- Describe the various types of hypertension
- Describe the causes of hypertension
- Describe the end-organ effects of systemic hypertension
Types of hypertension Part 1 of 31
Hypertension = high blood pressure
Blood pressure (BP) = cardiac output (CO) x peripheral resistance (PR)
2 circulatory systems in which hypertension can occur:
Systemic hypertension Part 2 of 31
25% of the UK population have hypertension.
Sustained BP above a certain cut off level. Usually ≥140/80 mm Hg but this can vary with location.
Classification by cause–
- Primary (essential) – usually caused by lifestyle factors
- Secondary – caused by an underlying disease
Primary (essential) hypertension Part 3 of 31
Primary hypertension risk factors Part 4 of 31
Causes of secondary hypertension Part 5 of 31
Renal causes of secondary hypertension Part 6 of 31
Endocrine causes of secondary hypertension Part 7 of 31
- Thyroid – hypo/hyperthyroidism
- Parathyroids – hyperparathyroidism
- Adrenal – Cushing’s syndrome, hyperaldosteronism, phaeochromocytoma
Drug induced secondary hypertension Part 8 of 31
Many drugs result in secondary hypertension, below is a list of some of the most common offenders.
- Oral contraceptive pill
Other causes of secondary hypertension Part 9 of 31
Again there are lots of other physiological and pathological states which result in secondary hypertension.
It is important to think about what the most common cause may be and then to formulate a differential diagnosis list accordingly – don’t immediately jump straight to an obscure endocrine cause without excluding the more common causes first.
Physiology of renal disease & hypertension Part 10 of 31
*this is a very brief overview of the RAAS system. For more detail please look at relevant information in Davidson’s or online. This will also be revisited in the Year 2 Renal/Urology module in more detail*
The renin-angiotensin-aldosterone system (RAAS) links the kidney, endocrine organs and cardiovascular system together.
It regulates BP & fluid balance through a variety of hormones.
It is shown briefly here in 3 simplified steps.
RAAS Step 1 - Decrease in renal perfusion Part 11 of 31
- Renal blood flow is reduced and is detected at the juxtaglomerular cells near the glomerulus
- This stimulates the kidneys to convert pre-renin into renin
RAAS Step 2 - Creation of angiotensin II Part 12 of 31
- Angiotensinogen (secreted by the liver) is converted to angiotensin I by renin
- Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme ACE secreted by lungs
RAAS Step 3 - Action of angiotensin II Part 13 of 31
- Angiotensin II has multiple sites of action across the body
- The overall effect of these changes is retention of water leading to an increase in circulating blood volume and an increase in BP
RAAS overview Part 14 of 31
Hypertension physiology 1 Part 15 of 31
MCQ - hypertension physiology 2 Part 16 of 31
End organ damage Part 17 of 31
End organ damage can be roughly classified into 2 pathological categories:
- Benign hypertension results in slow changes to vessels with chronic end-organ dysfunction
- Malignant hypertension leads to rapid changes in vessels with acute end-organ dysfunction. The patient’s BP is usually ≥ 180/110 mm Hg
MCQ – End Organ Damage Part 18 of 31
Hypertension and the heart – ventricular hypertrophy Part 19 of 31
- The left ventricle thickens in order to pump blood to the body against a high BP
- This abnormal thickening can lead to lots of problems like arrhythmias, ischaemic heart disease, heart failure & stroke
- This is shown in the picture below. Notice the thickened ventricle across the blue arrow
Hypertension – microscopic vascular effects on the vascular system Part 20 of 31
Benign hypertension can lead to –
- hyaline arteriosclerosis (hardening) of arterioles
- splitting of the elastic lamina resulting in damage to the arteriole wall
- Acceleration of underlying atherosclerosis
Malignant hypertension can lead to –
- Fibrinoid necrosis – a type of necrosis with proteinaceous material which resembles fibrin
In the next frame match the picture with the pathological process
Hypertension - microvascular effects on the vascular system Part 21 of 31
Hypertension - macroscopic effects on the vacular system - arterial dissection Part 22 of 31
Hypertension - macroscopic effects on the vacular system - arterial aneurysm Part 23 of 31
Regarding the image below answer the following questions:
Hypertension and the brain Part 24 of 31
Hypertension and the brain Part 25 of 31
Answer the questions below related to the following 2 images.
Hypertension and the brain – subarachnoid haemorrhage Part 26 of 31
- Longstanding hypertension can lead to the formation of saccular (berry) aneurysms along the Circle of Willis. These are different to the microaneurysms seen in the previous section as they are found within the subarachnoid space
- These can rupture resulting in sudden onset severe headache, nausea, photophobia & stiff neck
Hypertension and the brain – cerebral infarction & carotid artery disease Part 27 of 31
This is a middle cerebral artery cerebral infarct. Cerebral infarction is the most common cause of stroke and one of the main risk factors for it is hypertension.
It’s often preceded by narrowing (stenosis) of the internal carotid artery.
This picture outlines a severe stenosis indicated by arrow ‘A’. This narrowing can also lead to thrombus and embolus formation which can also to transient ischaemic attacks (TIAs) or cerebral infarction.
MCQ - Hypertension and the kidneys Part 28 of 31
Below are 2 kidneys. Which one do you think looks normal? Compare and contrast the two and comment on the colour & surface of both.
Hypertension and the eye Part 29 of 31
- Hypertension affects the small arterioles of the retina resulting in hypertensive retinopathy
- This is usually asymptomatic, but can eventually lead to retinal haemorrhage and visual loss
- It is graded in 1-4 stages depending on clinical finding on fundoscopy
- Malignant hypertension can present with decreased vision +/- headache
Hypertensive crisis Part 30 of 31
A hypertensive crisis is a medical emergency.
Defined by an elevated BP (systolic >210mm Hg) with rapid decompensation of vital organ function
Effects all organs previously discussed:
–Cardiac failure, pulmonary oedema, myocardial ischaemia
–Acute renal failure
It has lots of symptoms and signs due to its diffuse effect on the body. It is easier to break down signs and symptoms according to the body system
–Neuro – confusion, headache, fits, nausea & vomiting
–Ophthalmology – blurred vision
–Cardio – chest pain, SOB
–Renal – changes to urine output
Summary Part 31 of 31
Hypertension is an extremely important topic. I hope that by the end of this tutorial you get a better understanding of –
- The different classifications of hypertension
- The various causes of it
- The Renin-Angiotensin-Aldosterone-System
- End organ damage particularly in the heart, vascular system & brain