Monday, September 30, 2013

What Is Resistant Hypertension?

A person is said to have resistant hypertension if this person’s hypertension does not respond to a 3-drug combination therapy that includes a diuretic. A diuretic is any substance that promotes the production of urine. It is used to treat heart failure, liver cirrhosis, hypertension and certain kidney diseases.

In Singapore, about 25 percent of adults have high blood pressure, based on the 2010’s National Health Survey. Many of them take 2 to 3 types of hypertensive medications to control their blood pressure. About 3 to 5 percent of these patients, usually elderly, have resistant hypertension.

The 3 most common causes of resistant hypertension are: patients’ noncompliance to medications, secondary hypertension (usually from overactive adrenal glands) and fluid retention (usually expansion from kidney failure). More importantly, doctors have to ensure that what appears to be resistant hypertension is not actually pseudo hypertension or white coat hypertension.

Pseudohypertension is when blood pressure measurements are high but the blood pressure is actually normal. It is not very common, and is usually found in older patients. White coat hypertension is a scenario in which a person has high blood pressure readings only when he or she is in medical setting. The blood pressure can be normal when measuring at home.

Persistent uncontrolled hypertension is a significant risk factor for stroke and heart disease. Studies have shown that each incremental increase of 20 mmHg in systolic blood pressure and 10 mmHg in diastolic (minimum) blood pressure above normal levels directly correlates to a doubling of the risk of death from cardiovascular disease over a 10-year period.

It was also found that a lowering of 5 mmHg in blood pressure results in a decline of 14 percent in the risk of stroke, a 9 percent in the risk of heart disease and a 7 percent in the risk of death.

Sometimes, targeting the kidneys can treat high blood pressure. A minimally invasive procedure is used to remove the renal sympathetic nerves so that kidney would stop reacting excessively and the blood pressure would drop.

Such procedure, however, might not be suitable for all patients. It can only be employed for patients with normal kidney function. The kidney arteries need to be relatively disease-free and more than 4mm in diameter. Its main complications are damage to the kidney arteries or side effects from using contrast agents.

The National Heart Centre Singapore carried out the first such procedure in September 2011. Studies in Europe and Australia have shown that patients who have been followed up for 2 years without unfavorable effects.

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