Overview of high blood pressure
High blood pressure (BP) or hypertension is a medical condition in which the blood pressure is chronically elevated. Hypertension is the most important modifiable risk factor for coronary heart disease (CHD), stroke, congestive heart failure (CHF), end-stage renal disease and peripheral vascular disease.
High blood pressure affects about 65 million adult Americans.1 Worldwide, hypertension is seen in about 1 billion people and the prevalence has been estimated to increase by more than 29% by the year 2025.2 This condition is associated with increased obesity and aging population. Due to the associated morbidity, mortality and economical burden to the society, hypertension remains as a significant public health challenge.
As hypertension or high blood pressure rarely causes specific symptoms, it is undetected until an individual’s blood pressure is measured by a physician or until it had caused complications such as stroke or heart attack. The primary goal of treatment is to lower the blood pressure to a normal level through appropriate combination of drugs that achieves this goal. Recommendations for pharmacologic treatment are based on the presence of symptomatic hypertension, evidence of end-organ damage and unresponsiveness to lifestyle modifications. Drug selection is largely determined by individual’s needs including the presence of any coexisting illness.
Classification of high blood pressure
Hypertension is classified as primary hypertension and secondary hypertension. Primary or essential hypertension which accounts for more than 90% of cases of hypertension is diagnosed in the absence of an identifiable secondary cause.3 Primary hypertension is more common in adolescents and adults, and has multiple risk factors. Secondary hypertension indicates that the high blood pressure is a consequence of another condition such as a kidney disease or adrenal disease.
The Seventh Report of the Joint National Committee of Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC VII) recommends the following classification of blood pressure for adults above 18 years:4
- Normal: Systolic BP (SBP) <120 mmHg, diastolic BP (DBP) <80 mmHg
- Prehypertension: SBP 120–139 mmHg, DBP 80–89 mmHg
- Stage 1: SBP 140–159 mmHg, DBP 90–99 mmHg
- Stage 2: SBP ≥160 mmHg, DBP ≥100 mmHg
Pathophysiology and Risk Factors of high blood pressure
Essentially, blood pressure is the outcome of cardiac output and peripheral vascular resistance (BP=cardiac output×peripheral vascular resistance). Therefore, maintenance of a normal blood pressure is dependent on the balance between the cardiac output and peripheral vascular resistance.
The pathogenesis of essential hypertension is multifactorial and highly complex. Many factors (and risk factors) have been implicated in the genesis of essential hypertension, which include the following:
- Increased sympathetic nervous system activity.
- Increased production of sodium-retaining hormones and vasoconstrictors.
- Deficiencies of vasodilators such as prostacyclin and nitric oxide.
- Inappropriate or increased renin secretion, resulting in increased production of angiotensin II and aldosterone.
- Genetic predisposition.
The risk factors associated with increase in the blood pressure include the following:
- Long-term increased sodium intake
- Reduced dietary potassium, calcium and magnesium
- Diabetes mellitus and insulin resistance
- Excessive alcohol consumption
- Lack of physical activity
- High stress levels
The common identifiable causes of hypertension are the following:
- Chronic kidney disease
- Renovascular disease
- Cushing’s syndrome (hypersecretion of the hormone cortisol)
- Pheochromocytoma (adrenal tumor)
- Drugs such as nonsteroidal antiinflammatory drugs (NSAIDs) and oral contraceptives
Clinical Features ( Symptoms of high blood pressure)
Although patients with isolated hypertension are usually asymptomatic, occasionally they have symptoms such as dizziness, headache (especially pulsating headaches behind the eyes that occur early in the morning), blurred vision, facial flushing or tinnitus (ringing sound in the ears).
Hypertension which is very severe with a SBP >240 mmHg or DBP >120 mmHg is called accelerated hypertension. Accelerated hypertension is associated with confusion, visual disturbances, nausea and vomiting. When hypertension causes increased intracranial pressure (pressure exerted by the cranium on the brain tissue and brain fluid), it is called malignant hypertension or hypertensive crisis and is a medical emergency that requires immediate reduction of the blood pressure. This condition may present with end-organ damage.
Over time, untreated high blood pressure can damage organs such as the heart, kidneys or eyes leading to complications such as:
- Angina, heart attack or heart failure
- Kidney failure
- Peripheral arterial disease
- Retinopathy (eye damage)
Diagnosis of high blood pressure
A complete history, physical examination and certain diagnostic tests are recommended, once the presence of hypertension has been confirmed. An accurate blood pressure measurement is the key to diagnosis of hypertension. An average of three blood pressure readings, each taken 2 min apart is preferable to ascertain the diagnosis. Blood pressure should be measured in both the supine and sitting positions. Patients should be encouraged to abstain from smoking and caffeine intake for at least 30 min before the measurement.
Once the diagnosis of hypertension has been established, it is necessary to identify the presence of any risk factors, secondary causes of hypertension and any evidence of end-organ damage.
Initial, screening tests should be simple. Detailed history, physical examination, measurement of body mass index, assessment of routine blood chemistry, blood sugar, lipid profile and urinalysis are required. Further investigations are carried out in order to outline other cardiovascular risk factors and to detect target organ damage with only limited screening for secondary hypertension.
The cardiovascular risk of hypertension can be determined from the evidence of the following:5
- Target organ damage to the eyes, heart and kidneys.
- Coexisting illness such as diabetes or hypercholesterolemia.
- Lifestyle risk factors such as obesity and smoking.
Treatment of high blood pressure
The goal of treatment for most hypertensive patients is to lower the SBP below 140 mmHg and the DBP below 90 mmHg. In some patients, as those with diabetes, it is recommended that SBP maintained below 130 mmHg and a DBP less than 85 mmHg.
Management of high blood pressure is focused on lifestyle modification and pharmacological therapy. Management of secondary hypertension may require surgical correction of the underlying problem such as removal of a pheochromocytoma.
Follow-up visits should focus on identification of new risk factors, evidence of end-organ damage and adequacy of blood pressure control. However, regardless of the therapy, hypertension will be controlled only if patients are motivated to stay on their treatment plan. Resistance to antihypertensive treatment is more often due to patients’ noncompliance to medications or use of NSAIDs or alcohol abuse than to underlying secondary causes.
Lifestyle Modifications for high blood pressure
Sufficient evidence supports the beneficial effects of healthy lifestyle modifications in the prevention and management of hypertension. The following modifications are recommended as the first steps in treating mild-to-moderate hypertension:6
- Regular aerobic exercise
- Weight reduction
- Salt-restricted diet
- Low cholesterol diet
- Limit alcohol intake
- Stop smoking
- Stress management
- Include enough calcium, potassium and magnesium in the diet
Individuals in the prehypertensive category also require health-promoting lifestyle modifications in order to prevent further progress to full-fledged hypertension.
Pharmacological Management of high blood pressure
The choice of antihypertensive drugs depends on numerous factors including the presence of coexisting medical conditions, adverse effects and drug interactions.
Commonly used groups of antihypertensives (and the examples of each) are:
- Diuretics: chlortalidone and hydrochlorothiazide.
- Angiotensin-converting enzyme (ACE) inhibitors: captopril, enalapril and lisinopril.
- Angiotensin II Receptor Blockers (ARBs): telmisartan, irbesartan and losartan.
- Beta-blockers: atenolol, metoprolol and propranolol.
- Calcium channel blockers (CCBs): nifedipine, amlodipine and diltiazem.
- Alpha-blockers: doxazosin and prazosin.
In general, clinicians follow the following recommended guidelines while starting pharmacotherapy:4
- Patients should be started on a low-dose of the initial medication and the dose should be gradually titrated upward every 1–2 months, depending upon the response to therapy.
- Most patients will require two or more antihypertensives at lower doses to achieve the target blood pressure and to lower the adverse effects of the individual drugs in high doses.
- Thiazide-type diuretics should be used for most patients with uncomplicated hypertension, either alone or combined with drugs from other classes.
- A diuretic or a long-acting CCB may be more effective in elderly patients with isolated systolic hypertension.
- An ACE inhibitor should be the initial treatment for hypertension associated with CHF, diabetes mellitus and post-myocardial infarction.
- An ARB may be substituted in patients who develop persistent cough subsequent to ACE inhibitor therapy.
- A beta-blocker (if not contraindicated) should be prescribed following an acute myocardial infarction.
Alternative Therapies for high blood pressure
Alternate therapies in the management of high blood pressure include acupuncture, biofeedback, herbal medicine, meditation and yoga. These approaches are focused only on the reduction in blood pressure but not in the overall morbidity and mortality. Therefore, alternative therapies should be considered as adjuncts to lifestyle modification and drug therapy in the management of high blood pressure.
- Fields LE, Burt VL, Cutler JA, Hughes J, Roccella EJ, Sorlie P. The burden of adult hypertension in the United States 1999 to 2000: a rising tide. 2004; 44: 398–404.
- Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton PK, He J. Global burden of hypertension: analysis of worldwide data. 2005; 365: 217–223.
- Oparil S, Zaman MA, Calhoun DA. Pathogenesis of hypertension. Ann Intern Med. 2003; 139(9): 761–776.
- Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA. 2003; 289(19): 2560–2572.
- Brown MJ, Haydock S. Pathoetiology, epidemiology and diagnosis of hypertension. 2000; 59(Suppl 2): 1–12; discussion 39–40.
- Touyz RM, Campbell N, Logan A, Gledhill N, Petrella R, Padwal R. Canadian Hypertension Education Program. The 2004 Canadian recommendations for the management of hypertension: Part III–Lifestyle modifications to prevent and control hypertension. Can J Cardiol. 2004; 20(1): 55–59.
- American heart association