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Sunday May 18, 2014 MYT 12:00:00 AM
Sunday May 18, 2014 MYT 2:16:57 PM
by dr louis ignarro
The ideal blood pressure is around 120/80. If high blood pressure is not lowered and stays high for too long, this heightened pressure can lead to other problems like stroke and heart attack.
HYPERTENSION or high blood pressure is a common condition in which the force of the blood against the artery walls is so high that it may eventually cause health problems such as heart disease and stroke.
As a leading cause of cardiovascular diseases, hypertension is a problem that affects millions of people worldwide.
Hypertension can be categorised into primary and secondary hypertension.
Primary hypertension develops from a disease of the arteries, such as endothelial dysfunction, a condition in which the endothelium (inner lining) of blood vessels does not function normally.
On the other hand, the risk of secondary hypertension is increased by other health problems, such as genetic issues in different parts of the body and kidney disease.
While the causes of hypertension are multifactorial, of late, lifestyle factors such as unhealthy dietary habits and the lack of physical exercise, are the main factors for the increase in hypertension cases.
If blood pressure is not lowered and stays high for too long, this heightened pressure can lead to other problems like stroke and heart attack.
Understanding nitric oxide
Before 1986, nitric oxide (NO) was known to exist in the air and was thought to be an air pollutant similar to nitrogen dioxide. Given the deadly effects of nitrogen dioxide, no one suspected that NO could exist in the body.
However, my team and I went against all of those principles and decided to look for NO in the body through pharmacology testing in our laboratory because we believed that NO had the potential to be a powerful protective agent against cardiovascular disease.
The results were astounding as we discovered that the endothelial cells in the arteries produce NO through amino acids known as arginine.
NO is a chemical found in the body and is produced throughout a person’s life. While NO is predominantly produced by the arteries and veins, it can also be formed in other organs.
NO has several specific functions, including lowering blood pressure, promoting erectile function and serving as a neurotransmitter to transmit signals from the nerves to the brain to do a variety of things, such as preserving memory to delay the development of dementia or Alzheimer’s disease.
In cardiovascular disease, NO works to lower blood pressure, keeping it at normal levels by relaxing vascular smooth muscle and improving blood flow.
Hence, when there is a deficiency of NO in the body, a person is more likely to develop hypertension.
By discovering what NO is and how it reduces blood pressure, many studies were conducted to demonstrate that hypertension can be prevented if normal NO production is maintained.
The studies also concluded that patients who are obese, have type 2 diabetes and/or cardiovascular-related issues produce less NO compared to their healthier counterparts.
Consequently, the risk of hypertension in these patient groups is higher.
Although lifestyle changes can go a long way towards controlling high blood pressure, healthcare professionals may recommend medication to lower blood pressure, in addition to diet and exercise routines.
Among the varied medications available for hypertension, the main aim of treatment is unequivocally the same – to lower blood pressure effectively without causing serious side effects to patients.
Ultimately, the type of medication prescribed depends on the patient’s severity of high blood pressure and whether they also have other medical problems.
Beta blockers are a common class of medications for hypertension. This class of medication works by inhibiting or blocking two of the more commonly known sub-types of beta receptors, the beta-1 and beta-2 receptors.
Consequently, there is reduction in the workload of the heart and vasodilatation or opening of the blood vessels. As a result, the heart beats at a slower pace and with less force.
Beta-1 receptors are mainly found in the heart, and blockage of these receptors leads to a decrease in heart rate and force of the heart contraction.
Meanwhile, beta-2 receptors are mainly found in the airways, and blocking them keeps the airways constricted.
For this reason, selective beta blockers that block beta-1 receptors alone are regarded as being more effective than non-selective beta blockers that block both beta-1 and beta-2 receptors.
Additionally, the non-selective or traditional beta blockers are not well tolerated by many people, particularly elderly patients, as it decreases the cardiac output of these patients.
Traditional beta blockers are also limited in its use among diabetics and chronic obstructive pulmonary disease (COPD) patients as it may cause insulin resistance and constriction of airways, respectively.
Owing to its selectivity for beta-1 receptors, modern beta blockers produce fewer side effects and offer a safer option for high blood pressure patients with co-morbidities.
Many cardiologists and hypertension experts have recognised nebivolol as one of the most selective modern beta blockers available for patients.
Nebivolol has a dual mode of action as it works as a selective beta-1 blocker, as well as a vasodilator to stimulate NO production.
The combination of beta-1-adrenoceptor antagonism and NO produces a synergetic effect in lowering blood pressure without producing a decrease in cardiac output.
Due to its unique properties and good side effects profile, nebivolol has been shown to be safe for use in both elderly patients and young patients who are active in sports.
As a selective beta blocker that stimulates NO, nebivolol is also compatible when used in high blood pressure patients who have diabetes and/or COPD, as it has been shown not to worsen glucose tolerance or airway constriction.
Furthermore, patients with high sympathetic activity, heart failure, acute myocardial infarction or coronary artery disease may also benefit from using nebivolol.
Studies have also revealed nebivolol to be the only beta blocker that is effective in preventing heart failure in elderly people who are above 70 years of age.
However, patients must adhere to the recommended dosage as prescribed by their healthcare professionals to prevent complications.
While hypertension cannot be completely cured, healthy eating, regular exercise routines and weight management can contribute to the improvement of a patient’s condition.
In situations where lifestyle changes are insufficient, more patients can now take control of their condition and maintain a good quality of life with the advent of modern beta blockers that stimulate NO and have protective properties in cardiovascular disease.
Prof Dr Louis Ignarro is a Nobel Prize recipient and distinguished professor of pharmacology at the UCLA School of Medicine, California, United States. This article was contributed by Menarini Malaysia.
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Health, hypertension, treatment
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Insight into hypertension
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