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.

What To Do If Your Blood Pressure Refuses To Decline?

If a person’s blood pressure is too high, his or her heart has to work harder to pump. This can cause organ damage and lead to diseases including heart disease, stroke, aneurysm and renal failure. Hence, keeping one’s blood pressure below the normal range, which is 120/80 mmHg, is important.

Patients with high blood pressure (hypertension or sometimes called arterial hypertension) are usually prescribed with hypertensive medication. However, there are patients who are not responding to the medical treatments. These patients are said to have resistant hypertension, which is defined as hypertension that remains above target blood pressure in spite of concurrent use of at least 3 antihypertensive agents belonging to different antihypertensive drug classes.

In Germany, only 5 to 17 percent of patients treated for hypertension can achieve lasting control of their blood pressure. On the other hand, about 5 to 15 percent of all hypertensive patients have resistant hypertension.

A group of German researchers presented a set of treatment strategies for resistant hypertension in the July 25, 2011’s issue of ‘Deutsches Arzteblatt International’. They stressed that a multimodal interdisciplinary strategy involving systematic identification of secondary causes of hypertension and exclusion of pseudoresistance (inadequate treatment) is needed to successfully treat resistant hypertension.

Drug treatment must be tailored to individual patient and reversible or secondary causes of hypertension must be systematically sought and treated. This should be complemented by non-pharmacological conservative treatment measures including optimization of weight, a low-salt diet, physical exercise, and abstinence from alcohol.

Out of the 2 new partially still experimental therapy options, namely renal denervation and baroreceptor stimulation, researchers reviewed and suggested that renal sympathetic denervation can be used as an added treatment option for patients whose high blood pressure is inadequately controlled with medication.

Renal denervation, which is an interventional procedure with a low rate of complication, can help patients achieve significant and enduring reduction in blood pressure. The nerves in the vascular wall (adventitia layer) can be denervated by applying radiofrequency pulses to the renal arteries. This will reduce renal sympathetic afferent and efferent activity and blood pressure can hence be decreased.

Patients in German have to be enrolled in clinical registries and monitored at regular intervals following treatment for conclusive evaluation of the long-term effects and safety of this new approach. The German Renal Denervation (GREAT) Registry has been set up for this purpose.