Hypertension Overview

Overview of Hypertension

• Hypertension is a risk factor, not a disease, and is modifiable.
• Lowering blood pressure (BP) decreases the risk of stroke, coronary events, cardiac failure, and renal impairment.

Prevalence and Incidence

• More than 25% of the world's adult population is already hypertensive.
• 29% of the adult US population is hypertensive.
• By 2025, 1.56 billion people will be hypertensive.
• Prevalence is related to body mass index (BMI) and is higher in African Americans.
• 5% of the pediatric population has hypertension, and prevalence increases with age.
• There is a strong positive relationship between blood pressure and the risk of cardiovascular disease (CVD) events.

Prevalence in Sri Lanka

• The prevalence of hypertension in Sri Lanka is 18.8% in males and 19.3% in females.
• Only 22% of diagnosed hypertensive patients are adequately controlled.
• Only 6-15% of diagnosed hypertensive patients are adequately evaluated for risk factors for CVD and target organ damage.

Pathophysiology

• Blood pressure is a function of cardiac output multiplied by peripheral resistance.
• Atherosclerosis decreases the diameter of blood vessels, increasing blood pressure.

Determinants of Blood Pressure

• Blood volume
• Vascular resistance to pressure
• Heart stroke volume

Vascular Resistance

• Viscosity of blood
• Width of vessels (constriction or dilation) controlled by muscle tone in vessel walls

Regulation of Blood Pressure

• Sympathetic nervous system (SNS)
• Renin-angiotensin system
• Kidneys

Homeostatic Control of Blood Pressure

• Short-term: sympathetic nervous system, vasoconstriction, and vasodilation
• Long-term: fluid volume and renin-angiotensin system

Renin-Angiotensin Cascade

• Redrawn from Guyton AC: Textbook of Medical Physiology, 8th edition, Philadelphia, 1991, WB Saunders.

Hypertension Aetiology

• 90% of hypertension is essential (cause unknown), and 10% is secondary to other diseases.

Causes of Secondary Hypertension

• Renal parenchymal disease
• Renovascular disease
• Primary aldosteronism
• Obstructive sleep apnea
• Drug or alcohol-induced
• Less common causes:
  • Pheochromocytoma/paraganglioma
  • Cushing's syndrome
  • Hypothyroidism
  • Hyperthyroidism
  • Aortic coarctation (undiagnosed or repaired)
  • Primary hyperparathyroidism
  • Congenital adrenal hyperplasia
  • Mineralocorticoid excess syndromes other than primary aldosteronism
  • Acromegaly

Risk Factors for Hypertension

• Algorithm content developed by John Anderson, PhD, and Sanford C. Garner, PhD, 2000.

Presentation of Hypertension to Primary Care

• Usually asymptomatic
• May be found on routine screening/incidental
• Headache/visual disturbance
• Symptoms of end-organ damage: LVH, TIAs, CVA, MI, angina, renal impairment, PVD, and retinopathy

Measurement of Blood Pressure

• Screening: all adults should have BP measured every 5 years (British Hypertension Society)
• If BP is 'high normal' (SBP 130-139 mmHg, DBP 85-89), BP should be checked annually
• Screen any patient with known renal disease, atherosclerotic disease, diabetes as part of routine follow-up
• Accurate BP measurement is important to confer substantial risk of cardiovascular disease and to detect and treat high BP before target organ damage develops

Home Self-Measurement (HSM) and Ambulatory BP Monitoring (ABPM)

• HSM: consider for pts with white coat effect, avoiding overdiagnosis due to white coat effect
• ABPM: consider for evaluating pts with suspected white coat hypertension, apparent drug resistance, episodic hypertension, and hypotensive symptoms on antihypertensive Rx