Case 1.1 – Hypertension

When a patient's Systolic and Diastolic blood pressures fall into different categories, the higher category should apply.

Most likely: Essential hypertension (affects about 95% of diagnosed patients)

Causes of Secondary Hypertension:

• Alcohol
• Obesity
• Pregnancy (pre-eclampsia)
• Renal disease (most common cause of secondary hypertension): Renal vascular disease, Parenchymal renal disease (glomerulonephritis), Polycystic kidney disease
• Endocrine disease: Phaeochromocytoma, Cushing's syndrome, Primary hyperaldosteronism (Conn's syndrome), Hyperparathyroidism, Acromegaly, Primary hypothyroidism, Thyrotoxicosis, Congenital adrenal hyperplasia, Liddle's syndrome
• Drugs: Oral contraceptives containing oestrogens, anabolic steroids, corticosteroids, NSAIDs, carbenoxolone, sympathomimetic agents
• Coarctation of the aorta

The pathogenesis of essential hypertension is not clearly understood. Investigators have proposed that the primary abnormality may involve the kidney, the peripheral resistance vessels, or the sympathetic nervous system. In reality, the problem is probably multifactorial.

• More common in some ethnic groups (particularly African Americans and Japanese)
• Genetic factors play a role in approximately 40-60% cases
• Environmental factors: High salt intake, heavy alcohol consumption, obesity, lack of exercise, impaired intrauterine growth
• Very little evidence that 'stress' causes hypertension

In about 5% of unselected cases, hypertension is a consequence of a specific disease leading to sodium retention and/or peripheral vasoconstriction (secondary hypertension).

Normal aortic structure: Large elastic artery comprised of three concentric layers:

• Intima: Single layer of endothelial cells, separated from media by internal elastic lamina
• Media: Connective and muscle tissue
• Adventitia: Connective tissue with nerve fibres and vasa vasorum (network of small arterioles supplying oxygen and nutrients)

Changes in hypertension:

• Larger arteries (\>1mm): Internal elastic lamina becomes thickened, smooth muscle hypertrophied, fibrous tissue deposited. Vessels dilate and become tortuous, walls become less compliant
• Smaller arteries (\<1mm): Hyaline arteriosclerosis occurs in wall, lumen narrows, aneurysms may develop

Generally, high blood pressure is asymptomatic.

However, patients may complain of:

• Headache
• Symptoms secondary to vascular disease: visual disturbance, chest pain (angina), breathlessness, calf pain
• Symptoms related to possible secondary causes of hypertension

History:

• Known duration of elevated BP and previous BP levels
• Previous therapy, adverse effects
• Past history or current symptoms of ischaemic heart disease, heart failure, cerebrovascular disease, peripheral vascular disease
• Past history or current symptoms of kidney disease
• Symptoms suggestive of secondary hypertension (e.g. paroxysmal headache, sweating, palpitations for phaeochromocytoma; sleep apnoea)
• Asthma, COPD, diabetes, dyslipidaemia, gout, other significant illnesses
• Family history of hypertension, diabetes, dyslipidaemia, stroke, CAD, kidney disease
• Modifiable risk factors: obesity, alcohol intake, salt use, physical activity, smoking, saturated fat intake
• Medications that may cause hypertension (OCP, NSAIDs, nasal decongestants, corticosteroids)

Examination:

• Presence of other cardiovascular risk factors
• Body mass index, Waist circumference
• CVS: heart size, evidence of heart failure, arterial disease (carotid, peripheral, renal)
• Lungs: basal crackles, wheeze
• Abdomen: renal size, other masses, bruits
• Optic Fundi
• Nervous system: evidence of previous neurological disease
• Endocrine system: evidence of Cushing's, hypothyroidism, hyperthyroidism, acromegaly
• Blood pressure in sitting and standing position (postural hypotension)

Initial investigations should determine:

• Possible causes of hypertension
• Presence of end organ disease
• Cardiovascular risk factors
• Baseline values for judging biochemical effects of therapy

Hypertension Investigation of All Patients:

• Urinalysis for blood, protein and glucose
• Blood urea, electrolytes (including Calcium) and creatinine
• Fasting blood glucose
• Fasting serum total and HDL cholesterol, LDL, Triglyceride
• 12-lead ECG (left ventricular hypertrophy, coronary artery disease)

Main means of lowering blood pressure:

• Reduce cardiac output (beta-blockers, Ca Channel blockers)
• Reduce plasma volume (diuretics)
• Reduce peripheral vascular resistance (vasodilators)

MAP = CO x TPR

NICE Guideline 2011:

• Age \<55: offer ACE inhibitor or ARB
• Age \>55: offer Calcium channel blockers, or Thiazide-like if calcium channel blockers not suitable

SNAP (Smoking, Nutrition, Alcohol & Physical activity):

• Weight reduction (waist circumference <94cm males, <80cm females, BMI <25kg/m²)
• Regular physical activity (30 mins moderate activity, 5 times a week)
• Reduce & limit intake of alcohol
• Reduce intake of salt (below 90mmol per day)
• Diet: increase plant based foods, reduce saturated fats
• Smoking cessation

Common causes of treatment failure in hypertension:

1. Non-adherence with drug therapy
2. Inadequate therapy
3. Failure to recognise an underlying cause such as renal artery stenosis or phaeochromocytoma
4. Chronic use of medication such as NSAID, corticosteroid and OCP