What are the macrovascular and microvascular complications of diabetes in a high-yield summary?

High-Yield Summary of Diabetic Vascular Complications

Diabetes causes two distinct categories of vascular damage: microvascular complications affecting small vessels (retinopathy, nephropathy, neuropathy) and macrovascular complications affecting large vessels (coronary artery disease, cerebrovascular disease, peripheral vascular disease), with up to 80% of patients with type 2 diabetes developing or dying from macrovascular disease. 1

Microvascular Complications

Diabetic Retinopathy

• Pathophysiology: Hyperglycemia-induced damage to retinal capillaries leading to vision-threatening changes
• Clinical manifestations: Ranges from non-proliferative to proliferative retinopathy and diabetic macular edema
• Key point: Tight glycemic control reduces retinopathy risk by 60% in type 1 diabetes and 25% in type 2 diabetes 2
• Management: Anti-VEGF therapy (bevacizumab, ranibizumab, aflibercept) has replaced laser photocoagulation as first-line treatment for central-involved diabetic macular edema 3

Diabetic Nephropathy

• Pathophysiology: Progressive glomerular damage from chronic hyperglycemia
• Clinical progression: Begins with microalbuminuria, advances to proteinuria, ultimately leading to end-stage renal disease
• Prevention strategy: Meticulous glycemic control combined with aggressive blood pressure management using RAAS blockers 1
• Critical threshold: Blood pressure control is essential; however, systolic targets <120 mmHg provide no additional retinopathy benefit 3

Diabetic Neuropathy

• Assessment timing: Screen at type 2 diabetes diagnosis; 5 years after type 1 diabetes diagnosis, then annually 3
• Clinical presentations:
  • Distal symmetric polyneuropathy: Small fiber involvement (pain, burning, dysesthesia) and large fiber involvement (numbness, loss of protective sensation)
  • Autonomic neuropathy: Gastroparesis, erectile dysfunction, bladder dysfunction, cardiovascular autonomic neuropathy
• Screening method: Annual 10-g monofilament testing plus assessment of temperature/pinprick sensation and 128-Hz tuning fork vibration testing 3
• Note: Neuropathy may not be entirely microvascular in origin 1

Macrovascular Complications

Coronary Artery Disease

• Epidemiology: Adults with diabetes have 2-4 times increased cardiovascular risk compared to non-diabetics 4
• Mortality impact: Cardiovascular disease is the principal cause of death in diabetes, accounting for 75% excess mortality 4
• Critical distinction: Tight glycemic control effectively reduces microvascular complications but has minimal effect on macrovascular outcomes 1, 5

Cerebrovascular Disease

• Risk elevation: Substantially increased stroke risk in diabetic patients
• Prevention focus: Requires comprehensive cardiovascular risk factor management beyond glycemic control alone 6

Peripheral Vascular Disease

• Clinical significance: Leads to increased amputation risk, particularly when combined with neuropathy
• Management approach: Early detection through careful examination, specially fitted shoes, trauma minimization, aggressive wound management 7

Pathophysiological Mechanisms

Four interconnected biochemical pathways drive vascular damage 8, 9:

1. Polyol pathway flux: Increased sorbitol accumulation
2. Advanced glycation end-products (AGEs): Protein glycation and RAGE activation
3. Protein kinase C (PKC) activation: Altered vascular signaling
4. Hexosamine pathway flux: Metabolic dysregulation

Unifying mechanism: All pathways stem from mitochondrial overproduction of reactive oxygen species (ROS) due to chronic hyperglycemia, creating oxidative stress that damages both small and large vessels 8, 9

Management Priorities

Glycemic Control

• Target A1C: <7% for most adults reduces microvascular complications 2
• Evidence base: DCCT showed 60% microvascular reduction in type 1 diabetes; UKPDS demonstrated 25% reduction in type 2 diabetes 2
• Macrovascular caveat: Three major trials (ACCORD, ADVANCE, VA Diabetes) failed to show significant macrovascular benefit with very intensive control (A1C ~6.5%), with ACCORD showing increased cardiovascular mortality 10

Blood Pressure Management

• Definition: Hypertension is systolic ≥130 mmHg or diastolic ≥80 mmHg 6
• Screening: Measure at every clinical visit; confirm with multiple readings on separate days 6
• Impact: Antihypertensive therapy reduces both ASCVD events and microvascular complications 5

Lipid Management

• Secondary prevention: All patients with known coronary artery disease and type 2 diabetes require lipid-lowering therapy 1
• Primary prevention: Statins for patients with type 2 diabetes and other cardiovascular risk factors 1
• Dosing: Minimum moderate-dose statin once initiated 1
• Monitoring: Routine liver function or muscle enzyme testing not recommended except in specific circumstances 1

Emerging Therapies

• SGLT2 inhibitors (e.g., dapagliflozin): Reduce heart failure hospitalization, cardiovascular mortality, and all-cause mortality in both primary and secondary prevention 6, 11
• GLP-1 receptor agonists: Cardiovascular outcomes benefit 11
• Fenofibrate: May slow retinopathy progression in patients with dyslipidemia, particularly with mild baseline retinopathy 3

Clinical Pitfalls

1. The glycemic paradox: While tight glycemic control prevents microvascular disease, it does not reliably prevent macrovascular disease and may cause harm if targets are too aggressive 10
2. Delayed diagnosis: Type 2 diabetes frequently remains undiagnosed for years despite ongoing vascular damage, emphasizing the importance of screening 12
3. Comprehensive risk factor management: Focusing solely on glucose control is insufficient; blood pressure, lipids, and lifestyle modifications are equally critical 6
4. Neuropathy screening gaps: Loss of protective sensation is often asymptomatic but dramatically increases ulceration and amputation risk 3