3.19 - Microvascular and macrovascular complications of diabetes mellitus Flashcards
What does microvascular mean?
Small vessel complications
What are the microvascular complications of DM? (3)
- retinopathy - damage to retina
- nephropathy - damage to kidneys
- neuropathy - damage to nerves
What does macrovascular mean?
Large vessel complications
What are the macrovascular complications of DM? (3)
- cerebrovascular disease - stroke
- ischaemic heart disease
- peripheral vascular disease - usually foot
What is the risk of developing microvascular complications strongly associated with?
The extent of hyperglycaemia (judged by HbA1c)
What is the target HbA1c to reduce the risk of microvascular complications?
53 mmol/mol (<7%) or below
What other big risk factor (other than HbA1c) increases the risk of microvascular complications?
- hypertension
- clear relationship between rising systolic BP and risk of MI and microvascular complications in people with T1DM and T2DM
- therefore, prevention of complications requires reduction in HbA1c and BP control
What other risk factors (other than HbA1c and hypertension) are related to the development of microvascular complications? (5)
- duration of diabetes
- smoking - endothelial dysfunction and inflammation of vessels
- genetic factors - some people develop complications despite reasonable glycaemic control
- hyperlipidaemia
- hyperglycaemic memory - inadequate glucose control early on can result in higher risk of complications later, even if HbA1c improved
What is the mechanism of damage to the microvascular system by DM?
- increased formation of mitochondrial superoxide free radicals in the endothelium (oxidative stress)
- generation of glycated plasma proteins to form advanced glycation end products (AGEs) - high lipids and high glucose
- hypoxia
- these three mechanisms cause activation of inflammatory pathways
- damaged endothelium
What does damaged endothelium as a result of the inflammatory pathway activation result in?
DM mechanism of damage
- ‘leaky’ capillaries - blood and blood products leak out of capillaries
- ischaemia - endothelium cannot transport blood properly to tissues
What is diabetic retinopathy the main cause of?
- visual loss in people with diabetes
- blindness in people of working age
What are the symptoms of the early stages of retinopathy?
Asymptomatic (therefore screening is needed)
Why is yearly retinal screening of DM patients needed?
- early stages of retinopathy are asymptomatic
- the aim of screening is to detect retinopathy early when it can be treated before it causes visual disturbance/loss
What does a normal retina look like?
Macula (central, high resolution, colour vision) in middle (darker), optic disc on side (bright)
What is the progression of diabetic retinopathy/maculopathy?
- background retinopathy
- pre-proliferative retinopathy
- proliferative retinopathy
- diabetic maculopathy
What are the features of background retinopathy?
- hard exudates (cheese colour dots, lipid) - lipids leaked out due to dysfunctional endothelium
- microaneurysms (red dots)
- blot haemorrhages - vessels more leaky
What are the features of pre-proliferative retinopathy?
- cotton wool spots (larger yellow spots) AKA soft exudates - represent retinal ischaemia
- haemorrhages
What are the features of proliferative retinopathy?
- visible new vessels on disc or elsewhere in retina
- these have developed due to ischaemia and hypoxia to increase blood/oxygen to ischaemic retina
- vessels are very friable and easy to damage/bleed
What are the features of diabetic maculopathy?
- hard exudates/oedema near macula
- same disease as background retinopathy but happens to be near macula
- this can threaten vision
Can also have cotton wool spots
How do we treat background retinopathy?
Continued annual surveillance
How do we treat pre-proliferative retinopathy?
- if left alone will progress to new vessel growth
- so, early panretinal photocoagulation
How do we treat proliferative retinopathy?
Panretinal photocoagulation