Essential hypertension
Common hypertension without identifiable cause, often familial.
Essential hypertension, also known as primary or idiopathic hypertension, is a form of high blood pressure with no identifiable physiologic cause. It accounts for approximately 85% of all hypertension cases, with the remaining 15% attributed to secondary causes. This condition tends to be familial and is thought to result from an interplay of environmental and genetic factors, increasing the risk of cerebral, cardiac, and renal events.
Quick Facts
- Diagnostic threshold for adults
- Consistently at least 140 mmHg systolic or 90 mmHg diastolic
- Definition of resistant hypertension
- Failure to reduce blood pressure to normal levels after adequate trial of three antihypertensive medications
Facts from the source article.
Classification
Doctors sort blood pressure into a few categories: normal, prehypertension, stage I and stage II hypertension, and isolated systolic hypertension (which often shows up in older people). These labels come from averaging several properly taken seated readings over at least two office visits. For adults, hypertension means a consistent reading of at least 140 mmHg systolic or 90 mmHg diastolic. Anyone with blood pressure above 130/80 mmHg who also has type 1 or type 2 diabetes or kidney disease needs extra treatment. Resistant hypertension happens when blood pressure stays high despite a good trial of three different blood pressure drugs. The UK and US have published guidelines for handling this stubborn condition.
Risk factors
While essential hypertension has no identifiable cause, several risk factors have been identified. A family history of hypertension increases the likelihood of developing it. More than 50 genes have been examined in association studies, including the angiotensinogen (AGT) gene; increasing the number of AGT raises blood pressure. Single variant tests have shown that SNPs related to blood pressure are enriched for variants associated with adiposity, type 2 diabetes, coronary heart disease, and kidney function. Twin studies measuring ambulatory blood pressure suggest a large genetic influence, supported by animal and clinical studies. The inheritance is likely multifactorial, though mutations in single genes inherited on a Mendelian basis may also cause hypertension. The genetic influence is not fully understood, and linking hypertension-related phenotypes with specific genome variations may yield definitive evidence of heritability.
Pathophysiology
Arterial pressure depends on the balance between cardiac output and peripheral resistance. Cardiac output is determined by stroke volume and heart rate, while peripheral resistance is influenced by functional and anatomic changes in small arteries and arterioles. The pathophysiology of essential hypertension remains not well understood, but several theories exist. Early in the disease, cardiac output is raised while total peripheral resistance is normal; over time, cardiac output drops to normal but peripheral resistance increases. Proposed mechanisms include an overactive renin–angiotensin system causing vasoconstriction and sodium and water retention, and an overactive sympathetic nervous system leading to increased stress responses. Hypertension is highly heritable and polygenic, with a few candidate genes postulated. It can lead to impaired white matter of the brain accompanied by specific cognitive impairment.
Diagnosis
Health care providers diagnose high blood pressure when readings are consistently 140/90 mmHg or above. A blood pressure test can be performed in a clinic or office, and readings may be tracked over multiple visits at different times. Patients may also check readings at home and keep a written log. Typically, two to three readings from several appointments are used for diagnosis. For an adult, prehypertension or high blood pressure is diagnosed if systolic or diastolic readings are consistently higher than 120/80 mmHg. For children, diagnosis is based on numbers outside average for same age, gender, and height. Once severity is determined, additional tests may be ordered to rule out secondary causes or identify primary hypertension, helping to develop a treatment plan.
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