BLOOD PRESSURE AND ITS MEASUREMENT
Blood pressure (BP) is the pressure that blood flowing in our arteries exerts on the vessel wall. Arteries are blood vessels that carry blood rich in oxygen from our heart to different parts of the body.
This pressure is maximum when the heart contracts on the heartbeat and ejects the blood into the artery (this is called systolic BP). The pressure is lowest in between heartbeats (this is called diastolic BP). Therefore, blood pressure is expressed in the units of mm of mercury (Hg) as a fraction of systolic upon diastolic BP (example – 120/80 mmHg).
Blood Pressure measurement should be performed with an appropriate cuff size and a calibrated instrument.
For any BP measurement, you should be at rest for at least 5 minutes (with no exercise, smoking or coffee intake 30 min prior). Preferably pass urine before a BP measurement.
BP is best measured lying down with the BP measuring instrument level with you. If BP is measured sitting, the instrument and your arm should be rested on the same table in level with your heart. Sitting BP is usually 5-10mm more than lying BP while standing BP is the lowest. If you have a tendency for dizziness, your difference between sitting and standing BP should be measured.
DEFINING HIGH BP (HYPERTENSION) – WHEN AND HOW TO INTERVENE
The cutoffs for high BP have been lowered in 2017 by the American Heart Association/ American College of Cardiology (AHA/ACC) and many other countries have accordingly embraced the new BP target of <130/80, including India. This is in sync with increased cardiovascular events being seen in populations apparently not considered as having high BP.
The European Society of Cardiology (ESC) guidelines continues to use the earlier high BP cut off of 140/90 and recommends that the target BP in patients ≥65 years and <65 years should be below 140/80 and 130/80 respectively.
There is enough evidence showing BP levels between 130-139/80-89 mm Hg in the Indian population to be causing a substantial risk of cardiovascular disease (CVD), and premature death. Lower cutoffs aim to create greater health consciousness of lifestyle and diet, help in early intervention to prevent complications, and maintain a higher level of community health.
So, <130/80 can be considered the new BP target globally from a cardiologist perspective.
However, many general physicians today would still rather go with the <140/90 target BP which is endorsed by the American Academy of Family Physicians (AAFP) and the 8th Joint National Committee (JNC-8). Sometimes target BP may be relaxed to <150/90 in patients >65 years of age.
It is to be emphasized that a single BP reading is not diagnostic and is not used for decision making. If the first visit BP reading is high it should be rechecked again (after 1-2 weeks for BP between 160/100 to 179/109 and 2-4 weeks for BP between 130/80 to 159/99). At least 3 consecutive BP readings over 3 different visits should consistently show raised readings to diagnose anyone as having Hypertension.
If BP reading is 180/110 or higher at any visit, it is treated as an emergency and will need to be immediately managed medically.
Also, the cut-offs mentioned so far are for in-clinic BP measurement. Sometimes self-BP measurement at your home (to prevent rise in BP and heart rate due to anxiousness/nervousness) or a continuous BP measurement over 24 hours (Ambulatory BP monitoring) may be advised. In such cases, the BP cutoffs for hypertension may be even lower.
FACTORS WHICH INCREASE THE RISK OF DEVELOPING HIGH BP
Increasing age and male gender are natural risk factors (An elderly male is more likely to have hypertension as compared to a young female adult). People of South Asian and African races also have a higher risk of developing high BP compared to white races.
Other risk factors include:
- Being overweight or obese,
- Taking too much salt (sodium) or too little potassium in your diet
- Sedentary lifestyle or inadequate physical activity
- Drinking too much alcohol
- Stress or suppressed anger
- If already suffering from diabetes, kidney disease or sleep apnea
- Long term usage of medicines: painkillers (of the Ibuprofen group), some decongestant medicines for cold, some antidepressants or antipsychotics, oral contraceptives, corticosteroids, and some anti-cancer drugs.
- Family history of high BP
Many of the above are also risk factors for developing Cardiovascular disease (CVD).
CONSEQUENCES AND COMPLICATIONS OF HYPERTENSION
High Blood pressure especially when not adequately or well controlled can lead to consequent complications. Blood flowing at higher pressure has more chances of causing micro-injuries to the vessel wall. This gives rise to increased formation of ‘plaques’ which cause narrowing or obstruction of blood vessels resulting in reduction (partial obstruction) or loss (complete obstruction) of blood supply to vital organs. This leads to the development of Cardiovascular Disease.
CARDIOVASCULAR DISEASE (CVD)
CVD includes Angina, Heart attack, Stroke, and Peripheral Arterial disease.
Angina or Heart attack (also called Myocardial Infarction MI) is caused due to partial, and complete blood flow obstruction to the heart respectively which causes heart pain due to oxygen deprivation to heart muscles. Since the heart has to pump blood against higher pressure and resistance, its contracting effort increases which can slowly lead to its reduced efficiency and inability to cope, causing Heart failure.
Obstruction/reduction in blood flow to the brain leads to Stroke, (also called Cerebrovascular accident). High BP can also affect blood flow to our limbs (Peripheral arterial disease) which can cause intense pain on walking.
Hypertension can cause ongoing damage to the Kidneys and eventual Kidney failure.
Other complications like rupture or blockage of the fragile narrow vessels of the retina of the eye (Hypertensive Retinopathy) can affect vision. Hypertension can cause a reduction in blood flow and damage to many other organs like bones, reproductive organs, and others, hampering their functioning.
KNOWING THE RISK FACTORS FOR HIGH BP COMPLICATIONS AND CVD
The risk of complications due to Blood pressure increases very significantly if other coexisting CVD risk factors are also present in that individual. These risk factors include Diabetes, Kidney disease, Dyslipidemia (Increased in Cholesterol +/- Triglycerides in the blood), Lack of Physical activity (Sedentary lifestyle), Obesity or being overweight, High calorie-High fat diet, Psychosocial Stress, Smoking/tobacco use, or high alcohol consumption, and family history of Cardiovascular disease due to hypertension.
Low socioeconomic and/or educational status and sleep apnea have also been added as CVD risk factors
Male gender and increasing age represent an overall higher CVD risk as compared to women and younger age. However, women who smoke, have diabetes or psychosocial stress/depression are a higher risk group as compared to men with the same risk factors. Additional risk factors in women include Menopause and Hypertension/Diabetes seen in any of their pregnancies.
Overall more the number of coexisting risk factors present in an individual, the greater the risk of developing complications of high BP. Sometimes a 10-year risk of CVD is calculated, and if it is > 10%, BP lowering medicines are started immediately along with Lifestyle-diet measures.
People in the stage of elevated BP are managed with Lifestyle and Diet modifications. These measures can reduce systolic BP by 4-10mmHg, usually in the range of around 5mmHg over a few months.
People in stage 1 hypertension who have to coexist cardiovascular risk factors (or a 10 year CVD risk >10%), will require a BP-lowering medicine in addition to Lifestyle-Diet measures, as compared to people without additional/coexisting risk factors who can be managed with Lifestyle-Diet measures alone.
All people in stage 2 hypertension should be managed with a combination of BP-lowering drugs, and Lifestyle-Diet modifications.
The target BP of all patients in stage 1 and 2 hypertension is <130/80. However, there may be variability among physicians and cardiologists in setting target BP in different patients.
Lifestyle and Diet measures for reducing BP and CVD risk
DASH– Dietary Approaches to Stop Hypertension is aimed at lowering BP, reducing the risk of cardiovascular sequelae and also helping in BMI and weight reduction.
Further Lifestyle-diet measures for Blood sugar and Lipids (Cholesterol and Triglycerides) will also be advised if these 2 risk factors are coexisting with Hypertension.
Overview of BP lowering Medicines
BP lowering medicines are given singly or in combinations (separately or combined in a single pill). Usually, one medicine is added for every 10mm systolic BP above target. Sometimes two medicines at lower doses may be preferred to one medicine at a higher dose, to improve response and reduce side effects.
There are 4 classes of BP-lowering medicines which are considered as first-line. One of these or a combination of these is used to bring and maintain the BP at target values. The second-line drugs are used when the combination of 3 first-line agents of different classes do not manage to control high BP or in certain special situations or patients with associated cardiac, kidney or other conditions.
Important points to remember
- All medicines should be taken only by prescription and recommendation of a qualified medical practitioner in the dose, schedule and time of day prescribed along with incorporating all the lifestyle/diet measures suggested.
- Separate medicines will also be needed for coexisting risk factors (like diabetes and high lipids) if present.
- Irregularity of taking these pills can lead to uncontrolled BP.
- There are certain situations where some classes of drugs may not be appropriate or suitable, while some may cause side effects in certain patients, so one should never start or change any drug without consulting a qualified physician.
- The blood pressure, and parameters for other risk factors when present, should be measured and monitored periodically under the guidance of the treating physician.
- Usually suggested follow up visit is at 3 months after starting on lifestyle-diet measures, and at 1 month after starting a BP-lowering medicine.
Some scientific terms
Essential (or Primary) hypertension is high blood pressure that doesn’t have a known cause.
Secondary Hypertension is high BP caused by another medical condition like diseases of Heart, Kidney, arteries or hormones
Resistant Hypertension is the term used when the target blood pressure of below the cut off cannot be achieved even with lifestyle measures and concurrent use of three BP lowering medicines (of the 1st line classes with one of the medicines being a thiazide group diuretic), after ensuring full compliance and regularity of treatment.
‘Uncontrolled Hypertension’ includes resistant hypertension as well as those patients not fully compliant or regular with medicines and/or incorporation of lifestyle measures.
The reserve or 2nd line medicines are then added in resistant hypertension to achieve target BP. Sometimes certain procedures (called renal denervation- by radiofrequency or ultrasound) may also be used to manage resistant cases.
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