Nov 11 2002

HYPERTENSION AND STROKE PREVENTION

by Dr Joseph Chu, Neurologist,Trillium Health Centre, Toronto.

INTRODUCTION 

High blood pressure, which is also known as hypertension, is one of the most common reasons for an adult patient to visits a physician and is estimated to be the 3^rd leading risk associated with death worldwide. It is a key risk factor for cardiovascular diseases such as stroke and heart attack. 

Stroke is the leading cause of death worldwide and contributes to significant disability in developed countries. In North America, there are approximately 5 million people have had a stroke and 550,000 new cases occur each year. For those who survive a stroke or a threatened stroke (also known as Transient Ischemic Attack or TIA), about 20 % will suffer another stroke within 5 years.

Hence, it is important to look carefully the relationship between hypertension and stroke prevention. The following article will review some of the recent data published in the literature. 

WHAT IS HYPERTENSION?

Blood pressure is a measurement of the pressure within our blood vessels when the heart contracts and relaxes. It is this pressure that maintains circulation of blood which carries essential

nutrients and oxygen to various vital organs of our body such as the brain, heart, lung and kidneys. Systolic blood pressure is the pressure within the blood vessels when the heart contracts while diastolic blood pressure is the measurement when the heart relaxes. Blood pressure could be expressed as xxx/yyy where xxx stands for the systolic BP value and yyy stands for the diastolic value. The current Canadian Hypertension guideline recommends blood pressure to be less than or equal to 140/90. In patients with Diabetes

or non-diabetic nephropathy, it is recommended that blood pressure be further reduced to less than 130/<80. 

RELATIONSHIP OF BLOOD PRESSURE AND STROKE 

Epidemiological studies in the past have shown that patients with hypertension have three times the risk of having a stroke. This includes both ischemic and hemorrhagic strokes. Studies from Asia, particular China and Hong Kong have indicated that Chinese patients have a higher incidence of hemorrhagic strokes and it was hypothesized to be due to unrecognized or uncontrolled hypertension. Many hypertensive patients have no symptoms of hypertension until they presented with either a heart attack or stroke. By then, vital organs of the body had already sustained irreparable damage which may result in serious disability. One common example is relatively young patients who developed a catastrophic intracerebral hemorrhage due to uncontrolled hypertension with resultant permanent disability and unable to return back to work. It is therefore of paramount importance to have regular visits with your family doctor if you have hypertension so that it can be monitored carefully. If you have a family history of hypertension, you should also visit your family doctor to have your blood pressure checked. Ambulatory blood pressure monitor, blood and urine tests, cardiac and kidney tests may be required as ordered by your physicians. 

Other risk factors which are important in the primary prevention of strokes are:

(1)Smoking
(2)Diabetes
(3)Hyperlipidemia
(4)Heart Disease, particular Valvular Heart Disease and Atrial Fibrillation
(5)Obesity
(6)Sedentary life-style
(7)Family history of strokes 

RECENT DATA ON SECONDARY PREVENTION OF SROKE 

There is a recent published study from Australia known as PROGRESS study looking at 6105 patients who had experienced a prior stroke or TIA and given blood pressure medication perindopril (an Angiotensin Converting Enzyme Inhibitor) and indapamide (a Diuretic). After 4 years of follow up, systolic BP/diastolic BP reduction of 12/5 mm of Mercury reduces stroke risk by 43%. It appears that a higher relative risk reduction of 62% is achieved if the diastolic BP > 95 mm Hg. Besides, there is also a significant reduction of risk of dementia by 34% for the treatment group. In addition, there are also beneficial effects of reduction in heart attacks and death due to vascular diseases.

Based on this large scale study, it is recommended that any patient who has suffered a stroke or TIA should be treated aggressively for blood pressure control to maintain its reading to be < 140/<85. Even in patients who do not have hypertension, the fact that they have suffered a stroke or TIA warrants blood pressure reduction with medications. 

SUMMARY
In conclusion, hypertension is an important and treatable risk factor for stroke and heart disease. Although many hypertensive patients remain entirely asymptomatic, optimal control of their systolic and diastolic blood pressure is vital in the prevention of recurrent heart attack and stroke. This is particular important in the secondary prevention of future stroke in those patients who have already suffered a stroke or warning stroke.