Hypertension


Hypertension or high blood pressure, sometimes called arterial hypertension, is a chronic medical condition in which the blood pressure in the arteries is elevated (1). This requires the heart to work harder than normal to circulate blood through the blood vessels. Blood pressure is summarised by two measurements, systolic and diastolic, which depend on whether the heart muscle is contracting (systole) or relaxed between beats (diastole). Normal blood pressure at rest is within the range of 100-140 mmHg systolic (top reading) and 60-90 mmHg diastolic (bottom reading). High blood pressure is said to be present if it is persistently at or above 140/90 mmHg.

Hypertension is classified as either primary (essential) hypertension or secondary hypertension; about 90–95% of cases are categorized as “primary hypertension” which means high blood pressure with no obvious underlying medical cause (2). However, recent, landmark studies have shown that increased serum uric acid can cause increased blood pressure in adolescents (3, 4, 5, 6, 7) suggesting a new avenue for treatment of early onset hypertension. The remaining 5–10% of cases (secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart or endocrine system.

Hypertension is a major risk factor for stroke, myocardial infarction (heart attacks), heart failure, aneurysms of the arteries (e.g. aortic aneurysm), peripheral arterial disease and is a cause of chronic kidney disease. Even moderate elevation of arterial blood pressure is associated with a shortened life expectancy. It is estimated that 1 in 3 adults in the US (~76 million people) has hypertension and less than half have their blood pressure under control (8). In 3-18 year olds in the US, the prevalence of hypertension is estimated at 3 to 4% (2-3 million people) (9, 10, 11) and growing. Both hypertension and pre-hypertension have become a significant health issue in the young due to the strong association between blood pressure and weight in combination with the increase in the prevalence of overweight children. In the United States, childhood obesity affects approximately 12.5 million children and teens (17% of that population) (8).

Hypertension Treatments:

Hypertension treatment focuses on the use of one or more approaches that include prevention/lifestyle changes, stress reduction and/or medicinal treatments.

Much of the disease burden of high blood pressure is experienced by people who are not labelled as hypertensive (12). Consequently, population strategies are required to reduce the consequences of high blood pressure and reduce the need for antihypertensive drug therapy. Lifestyle changes are recommended to lower blood pressure, before starting drug therapy.

Effective lifestyle modification may lower blood pressure as much as an individual antihypertensive drug. Combinations of two or more lifestyle modifications can achieve even better results (12).

The first line of treatment for hypertension is identical to the recommended preventative lifestyle changes (13) and includes: dietary changes (14), physical exercise, and weight loss. These have all been shown to significantly reduce blood pressure in people with hypertension (15). If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication. Dietary change such as a low sodium diet is beneficial. A long term (more than 4 weeks) low sodium diet in Caucasians is effective in reducing blood pressure, both in people with hypertension and in people with normal blood pressure (16). Also, the DASH diet, a diet rich in nuts, whole grains, fish, poultry, fruits and vegetables promoted in the USA by the National Heart, Lung, and Blood Institute lowers blood pressure. A major feature of the plan is limiting intake of sodium, although the diet is also rich in potassium, magnesium, calcium, as well as protein (17).

Medications

When lifestyle changes are insufficient to reduce concerns regarding hypertension and drug treatment is initiated, the Joint National Committee on High Blood Pressure (JNC-7) recommends that the physician not only monitor for response to treatment but should also assess for any adverse reactions resulting from the medication (1). Reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischaemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from cardiovascular disease (18). The aim of treatment should be to reduce blood pressure to <140/90 mmHg for most individuals, and lower for those with diabetes or kidney disease (some medical professionals recommend keeping levels below 120/80 mmHg) (19, 20). If the blood pressure goal is not met, the addition of a second medication is made (1,21). JNC7(1) and ESH-ESC guidelines (21) advocate starting treatment with two drugs when blood pressure is >20 mmHg above systolic or >10 mmHg above diastolic targets. Acceptable drug classes include: thiazide-type diuretics, ACE inhibitors, angiotensin receptor blockers, beta-blockers, and calcium channel blockers. However, despite these current therapies, hypertension still remains a poorly treated disease, suggesting that hypertension has multi-factorial causes. Treatment of increased serum uric acid as a root cause of hypertension is anticipated to become another important therapeutic option.

References

Key References

  1. Fieg DL. The Role of Uric Acid in the Pathogenesis of Hypertension in the Young. The Journal of Clinical Hypertension 2012; 14:346-352.
  2. Feig DI, Johnson RJ. Hyperuricemia in childhood primary hypertension. Hypertension 2003; 42:247-52.
  3. Grayson PC, et al. Hyperuricemia and incident hypertension: a systematic review and meta-analysis. Arthritis Care Res. 2011; 63:102–110.