What Is High Blood Pressure? What Causes High Blood Pressure?

Editor's Choice
Main Category: Hypertension
Also Included In: Cardiovascular / Cardiology
Article Date: 30 Jul 2009 - 2:00 PST


High blood pressure is also known as hypertension. Blood pressure is the amount of force exerted against the walls of the arteries as blood flows through them - if a person has high blood pressure it means that the walls of the arteries are receiving too much pressure repeatedly - the pressure needs to be chronically elevated for a diagnosis of hypertension to be confirmed. In medicine chronic means for a sustained period; persistent.

In the USA approximately 72 million people have hypertension - about 1 in every 3 adults, according to the National Heart Lung and Blood Institute. The National Health Service, UK, estimates that about 40% of British adults have the condition. The National Institutes of Health (NIH) estimates that about two-thirds of people over the age of 65 in the USA have high blood pressure.

The heart is a muscle that pumps blood around the body constantly - during every second of our lives. Blood that has low oxygen levels is pumped towards the lungs, where oxygen supplies are replenished. The oxygen rich blood is then pumped by the heart around the body to supply our muscles and cells. The pumping of blood creates pressure - blood pressure.

When we measure blood pressure, we gauge two types of pressure:

• Systolic pressure - the blood pressure when the heart contracts, specifically the moment of maximum force during the contraction. This happens when the left ventricle of the heart contracts.


• Diastolic pressure - the blood pressure between heartbeats, when the heart is resting and dilating (opening up, expanding).

When a person's blood pressure is taken the doctor or nurse needs to measure both the systolic and diastolic pressures. The figures usually appear with a larger number first (systolic pressure), followed by a smaller number (diastolic pressure). The figure will be followed by the abbreviation "mmHg", which means millimeters of mercury.

If you are told that your blood pressure is 120 over 80 (120/80 mmHg), it means a systolic pressure of 120mmHg and a diastolic pressure of 80mmHg.

The definition of high blood pressure (hypertension)

Anyone whose blood pressure is 140/90mmhg or more for a sustained period is said to have high blood pressure, or hypertension.

Blood pressure is usually divided into five categories:

• Hypotension (low blood pressure)
  Systolic mmHg 90 or less, or
  Diastolic mmHg 60 or less


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• Normal
  Systolic mmHg 90-119, and
  Diastolic mmHg 60-79


• Prehypertension
  Systolic mmHg 120-139, and
  Diastolic mmHg 80-89


• Stage 1 Hypertension
  Systolic mmHg 140-159, and
  Diastolic mmHg 90-99


• Stage 2 Hypertension
  Systolic mmHg over 160, and
  Diastolic mmHg over 100

What are the symptoms of high blood pressure (hypertension)?

Most people with high blood pressure will not experience any symptoms until levels reach about 180/110 mmHg. When symptoms do appear, they typically include:

• Headache - usually, this will last for several days.
• Nausea - a sensation of unease and discomfort in the stomach with an urge to vomit.
• Vomiting - less common than just nausea.
• Dizziness - Lightheadedness, unsteadiness, and vertigo.
• Blurred or double vision (diplopia).
• Epistaxis - nosebleeds.
• Palpitations - disagreeable sensations of irregular and/or forceful beating of the heart.
• Dyspnea - breathlessness, shortness of breath.

Anybody who experiences these symptoms should see their doctor immediately.

Children with hypertension may have the following signs and symptoms:

• Headache.
• Fatigue.
• Blurred vision.
• Nosebleeds.
• Bell's palsy - inability to control facial muscles on one side of the face.

Newborns and very young babies with hypertension may have the following signs and symptoms:

• Failure to thrive.
• Seizure.
• Irritability.
• Lethargy.
• Respiratory distress.

People who are diagnosed with high blood pressure should have their blood pressure checked frequently. Even if yours is normal, you should have it checked at least once every five years, and more often if you have any contributory factors.

What are the causes of high blood pressure?

When referring to the causes of hypertension, it is divided into two categories:

• Essential high blood pressure (primary high blood pressure) - no cause has been identified.


• Secondary high blood pressure - the high blood pressure has an underlying cause, such as kidney disease, or a specific medication the patient is taking.

Even though there is no identifiable cause for essential high blood pressure, there is strong evidence linking some risk factors to the likelihood of developing the condition. Most of the causes below are essential high blood pressure risk factors; there are also a couple of secondary high blood pressure examples:

• Age - the older you are the higher the risk.


• Family history - if you have close family members with hypertension, your chances of developing it are significantly higher. An international scientific study involving over 150 scientists from 93 centers in Europe and the USA identified eight common genetic differences which may increase the risk of high blood pressure.


• Temperature - A study which monitored 8801 participants over the age of 65 in three French cities, found that systolic and diastolic blood pressure values differed significantly across the four seasons of the year and according to the distribution of outdoor temperature. Blood pressure was lower when it got warmer, and rose when it got colder.


• Ethnic background - evidence in Europe and North America indicates that people with African and/or South Asian ancestry have a higher risk of developing hypertension, compared to people with predominantly Caucasian or Amerindian (indigenous of the Americas) ancestries.


• Obesity/overweight - overweight refers to having extra body weight from muscle, bone, fat and/or water. Obesity tends to refer just to having a high amount of extra body fat. Both overweight and obese people are more likely to develop high blood pressure, compared to people of normal weight.


• Some aspects of gender - in general, high blood pressure is more common among adult men than adult women. However, after the age of 60 both men and women are equally susceptible. Women aged 18-59 are more likely to identify the signs and symptoms and subsequently to seek treatment for high blood pressure, compared to men.


• Physical inactivity - lack of exercise, as well as having a sedentary lifestyle, raises the risk of hypertension.


• Smoking - smoking causes the blood vessels to narrow, resulting in higher blood pressure. Smoking also reduces the blood's oxygen content so the heart has to pump faster in order to compensate, causing a rise in blood pressure.


• Alcohol intake - the risk may even sometimes include people who drink regularly, but not in excess. People who drink regularly have higher systolic blood pressure than people who do not, say researchers from the University of Bristol, UK. They found that systolic blood pressure levels are about 7 mmHg higher in frequent drinkers than in people who do not drink.


• High salt intake - researchers from the University of Michigan Health System reported that societies where people don't eat much salt have lower blood pressures than places where people eat a lot of salt.


• High fat diet - many health professionals say that a diet high in fat leads to a raised high blood pressure risk. However, most dietitians stress that the problem is not how much fat is consumed, but rather what type of fats. Fats sourced from plants, such as avocados, nuts, olive oil, etc., as well as omega oils which are common in some types of fish, are good for you - while, saturated fats which are common in animal sourced foods, as well as trans fats are bad for you.


• Mental stress - various studies have compelling evidence that mental stress, especially over the long term, can have a serious impact on blood pressure. An interesting study carried out by researchers at the University of Texas, suggested that how air traffic controllers handle stress can affect whether they are at risk of developing high blood pressure later in life. In view of this study, and many others that focus on stress management, it would be fair to assume that some levels of stress which are not managed properly can raise the risk of hypertension.


• Diabetes - people with diabetes are at a higher risk of developing hypertension. Among patients with diabetes type 1, hyperglycemia (high blood sugar) is a risk factor for incident hypertension in type 1 diabetes - intensive insulin therapy reduces the long-term risk of developing hypertension. People with diabetes type 2 are at risk of hypertension due to hyperglycemia, as well as other factors, such as overweight/obesity, certain medications, and some cardiovascular diseases.


• Psoriasis - An American study that followed 78,000 women for 14 years found that having psoriasis was linked to a higher risk of developing high blood pressure and diabetes. Psoriasis is an immune system condition that appears on the skin in the form of thick, red scaly patches.


• Low birth weight - the link between low birth weight and hypertension becomes stronger as individuals get older - especially among white males, as opposed to female and males and female of Afro-Americans, scientists at the Tulane Center for Cardiovascular Health, New Orleans reported.


• Pregnancy - pregnant women have a higher risk of developing hypertension than women of the same age who are not pregnant. It is the most common medical problem encountered during pregnancy, complicating 2% to 3% of all pregnancies. Most countries divide hypertensive disorders in pregnancy into four categories: 1. Chronic hypertension, 2. Preeclampsia-eclampsia, 3. Preeclampsia superimposed on chronic hypertension. 4. Gestational hypertension.

How is high blood pressure diagnosed?

• Sphygmomanometer
  
  Most lay people have seen this device. It consists of an inflatable cuff that is wrapped around the upper arm. When the cuff is inflated it restricts the blood flow. A mercury or mechanical manometer measures the pressure.
  
  A sphygmomanometer is always used together with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. For example, a manual sphygmomanometer is used together with a stethoscope.
  
  
  • The cuff is placed snugly and smoothly around the upper arm, at approximately the same altitude as the heart while the patient is sitting up with the arm supported (resting on something). It is crucial that the size of the cuff is appropriate. If it is too small the reading will be inaccurately high; if it is too large the reading will be too low.
  
  
  • The cuff is inflated until the artery is completely obstructed (occluded).
  
  
  • The nurse, doctor, or whoever is doing the examination listens with a stethoscope to the brachial artery at the elbow and slowly releases the cuff's pressure (deflates it).
  
  
  • As the cuffs pressure falls the examiner will hear a whooshing sound or a pounding sound when blood flow starts again.
  
  
  • The pressure at the point when the sound began is noted down and recorded as the systolic blood pressure.
  
  
  • The cuff is deflated further until no sound can be heard. At this point the examiner notes down and records the diastolic blood pressure.
  
  
  With a digital sphygmomanometer everything is done with electrical sensors.


• Hypertension confirmation requires several readings
  
  One blood pressure reading is not enough to diagnose hypertension in a patient. People's blood pressure can vary during the day, a visit to the doctor may spike the reading because the patient is anxious or stressed, having just eaten may also temporarily affect blood pressure readings.
  
  As the definition of hypertension is defined as "repeatedly elevated blood pressure" the GP (general practitioner, primary care physician) will have to take several readings over a set period. This may require three separate measurements one week apart - often the monitoring goes on for much longer before a diagnosis is confirmed. On some rare occasions, if the blood pressure is extremely high, or end-organ damage is present, diagnosis may be made immediately so that treatment can start promptly. End-organ damage generally refers to damage to major organs fed by the circulatory system, such as the heart, kidneys, brain or eyes.


• Kidney disorder - if the patient has a urinary tract infection, urinates frequently, or reports pain down the side of the abdomen, they could be signs/symptoms of a kidney disorder. If the doctor places the stethoscope on the side of the abdomen and hears the sound of a rush of blood (a bruit), it could be a sign of stenosis - a narrowing of an artery supplying the kidney.

The doctor may also order the following tests:

• Urine and blood tests - underlying causes might be due to cholesterol, high potassium levels, blood sugar, infection, kidney malfunction, etc. Protein or blood in urine may indicate kidney damage. High glucose in the blood may indicate diabetes.


• Exercise stress test - more commonly used for patients with borderline hypertension. This usually involves pedaling a stationary bicycle or walking on a treadmill. The stress test assesses how the body's cardiovascular system responds to increased physical activity. If the patient has hypertension this data is important to know before the exercise test starts. The test monitors the electrical activity of the heart, as well as the patient's blood pressure during exercise. An exercise stress test sometimes reveals problems that are not apparent when the body is resting. Imaging scans of the heart's blood supply might be done at the same time.


• ECG (electrocardiogram) - this tests the heart's electrical activity. This test is more commonly used for patients at high risk of heart problems, such as hypertension and elevated cholesterol levels. The initial ECG is called a baseline. Subsequent ECGs may be compared with the baseline to reveal changes which may point to coronary artery disease or thickening of the heart wall.


• Holter monitoring - the patient carries an ECG portable device for about 24 hours.


• Echocardiogram - this device uses ultrasound waves which show the heart in motion. The doctor will be able to detect problems, such as thickening of the heart wall, defective heart valves, blood clots, and excessive fluid around the heart.

What is the treatment for high blood pressure (hypertension)?

Treatment for hypertension depends on several factors, such its severity, associated risks of developing stroke or cardiovascular, disease, etc.

• Slightly elevated blood pressure
  
  The doctor may suggest some lifestyle changes if the patient's blood pressure is only slightly elevated and the risk of developing cardiovascular disease considered to be small.


• Moderately high blood pressure
  
  If the patient's blood pressure is moderately high and the doctors believes the risk of developing cardiovascular disease during the next ten years is above 20%, the patient will probably be prescribed medication and advised on lifestyle changes.


• Severe hypertension
  
  If blood pressure levels are 180/110 mmHg or higher, the doctor will refer the patient to a specialist (cardiologist).

Changes in lifestyle that can help lower high blood pressure

• Regular exercise - exercising for 30 to 60 minutes five days a week will usually lower a person's blood pressure by 4 to 9 mmHg. If you embark on an exercise program you should see the benefits fairly soon - within a matter of two to three weeks, especially if you have been leading a sedentary lifestyle for a long time.
  
  It is important to make sure you check with your doctor before embarking on any physical activity program. Exercise needs to be tailored to the needs and health of the patient.
  
  The secret of getting success out of exercise is to do it regularly. Exercising at weekends and doing nothing from Monday to Friday will be much less effective.


• Reducing alcohol consumption - alcohol consumption is a double-edged sword. Some studies indicate it helps lower blood pressure, while others report the opposite. In very small amounts it may lower blood pressure. But if you drink too much, even moderate amounts regularly in some cases, blood pressure levels may go up. People who drink more than moderate amounts of alcohol regularly virtually always experience elevated blood pressure levels.


• Eating healthily - this means eating plenty of fruits and vegetables, good quality unrefined carbohydrates, vegetable oils, and omega oils. If you eat animal products make sure all the fat is trimmed and avoid processed meats.


• Lowering salt (sodium) intake - studies have shown that even a moderate reduction in sodium intake can lower blood pressure levels by 2 to 8 mmHg.
  
  A study found that most Americans who are diagnosed with hypertension still consume more than the recommended levels of salt. Study leader, Umed Ajani, an epidemiologist with the National Center for Chronic Disease Prevention and Promotion, said "Perhaps the most striking finding is that no difference in sodium intake was observed between those who received advice and those who did not."
  
  A report published in March, 2009 by the Centers for Disease Control and Prevention (CDC), USA, suggests that 7 in every 10 adult Americans should limit their sodium intake to 1,500 mg a day (about 2/3 of a teaspoon of salt). The report estimated that 145 million Americans - 70% of the adult population - have one of three risk factors for hypertension.


• Losing weight - studies have revealed that even moderate weight loss - just ten pounds - can have a significant impact in lowering elevated blood pressure. If you are overweight, the nearer you get to your ideal weight the more your blood pressure is likely to fall. Any high blood pressure medications you are taking will become more effective when you lose weight. Reducing your waistline will have the greatest effect. Achieving your ideal body weight involves a combination of exercise, good diet, and at least 7 hours good quality sleep each night.
  
  Keeping a food diary can double weight loss as part of a managed program, scientists at Kaiser Permanente's Center for Health Research discovered.


• Lowering caffeine consumption - there are scores of studies that report on whether caffeine has an impact on blood pressure. As many of them have conflicting conclusions it is understandable that people become exasperated.
  
  Habitual coffee drinking is not linked to an increased risk of hypertension in women, although a link was found with sugared or diet colas , reported researchers from Brigham and Women's Hospital and the Harvard School of Public Health.
  
  Researchers found that healthy adults who drank two cans a day of a popular energy drink experienced an increase in their blood pressure and heart rate. The researchers, from Henry Ford Hospital believe the caffeine and taurine levels in energy drinks could be responsible for increases in blood pressure and heart rate.
  
  All researchers agree on one thing: Excessive caffeine consumption is not good for people who have hypertension. Therefore, it would be wise to keep an eye on your caffeine consumption. Remember that caffeine is present in most coffees, many teas, sodas (carbonated drinks), chocolates, and some other foods and drinks.


• Relaxation techniques - researchers at Massachusetts General Hospital found that adding the relaxation response, a stress-management approach, to other lifestyle modifications may significantly improve treatment of the type of hypertension most common in the elderly.
  
  Harvard Women's Health Watch reported that in one study, tai chi significantly boosted exercise capacity, lowered blood pressure, and improved levels of cholesterol, triglycerides, insulin, and C-reactive protein in people at high risk for heart disease.


• Sleep - not getting enough sleep can increase a person's risk of developing high blood pressure, scientists from the University of Chicago reported after monitoring over 500 middle aged people for 5 years.
  
  Adults should sleep no less than 7 hours and no more than 8 hours per day. The American Academy of Sleep Medicine warns that too much sleep can be harmful as well. "People with sleep duration above or below the recommended 7-to-8 hours per night face an increased risk of hypertension, a major predictor for heart disease.".

Medications for treating hypertension

There are several anti-hypertensive medications on the market today. Some patients may need to take a combination of different drugs to effectively control their high blood pressure.

Some patients may have to be on medication to control hypertension for the rest of their lives. Doctors may advise discontinuing treatment if the patient has managed to maintain good blood pressure levels for a given period, and is not considered to be at significant risk of stroke or cardiovascular disease.

In a study, scientists from the Robarts Research Institute at The University of Western Ontario found that patients actually have more control of their high blood pressure when treated with less medication.

Below are some details of the most common drugs:

• Angiotensin-converting enzyme (ACE) inhibitors
  
  ACE inhibitors block the actions of some hormones, such as angiotensin II, that regulate blood pressure. Angiotensin II causes the arteries to constrict, and increases blood volume, resulting in increased blood pressure. By inhibiting the actions of angiotensin II, the ACE inhibitors help reduce blood volume and also widen the arteries, both of which will cause the blood pressure drop.
  
  People with a history of heart disease, pregnant women or individuals with conditions that affect the blood supply to the kidneys should not take ACE inhibitors.
  
  Doctors may order a blood test to determine whether the patient has any pre-existing kidney problems. ACE inhibitors can reduce the blood supply to the kidneys, making them less efficient. Regular blood tests are usually carried out on patients taking ACE inhibitors.
  
  ACE inhibitors may have the following more common side effects, which usually go away after a few days:
  
  
  • Dizziness
  • Fatigue
  • Weakness
  • Headaches
  • Persistent dry cough (some people find the dry cough may continue)
  
  Some patients may find the side effects too unpleasant or long-lasting. In such cases doctors will switch to an angiotensin-2 receptor antagonist. Side effects are less common, but may include dizziness, headache and/or hyperkalemia (elevated blood level of the electrolyte potassium).
  
  Drug interaction - the effects of ACE inhibitors may be altered if taken with others medications, including some OTC (over-the-counter, non-prescription) drugs.


• Calcium channel blockers
  
  Calcium channel blockers (CCBs), among other things, decrease the calcium in blood vessels. A drop in calcium relaxes the vascular smooth muscle so that it does not contract so strongly, resulting in vasodilation (widening of arteries). If the arteries are wider blood pressure will drop.
  
  Patients with a history of heart disease, liver disease, or problems with circulation should not take calcium channel blockers.
  
  Calcium channel blockers may have the following more common side effects, which usually go away after a few days:
  
  
  • Flushing - redness of the skin, usually over the cheeks or neck
  • Headaches
  • Edema (swelling) - swollen ankles, feet, and more rarely the abdomen
  • Dizziness
  • Fatigue
  • Skin rash
  
  Drug interaction - patients taking calcium channel blockers should avoid grapefruit.


• Thiazide diuretics
  
  Thiazide diuretics act on the kidneys to help the body eliminate sodium and water, resulting in less blood volume - less blood volume results in lower blood pressure. They are often the first choice in high blood pressure medications (but not the only choice).
  
  Thiazide diuretics may cause the following side effects, some of which may persist:
  
  
  • Hypokalemia - low blood potassium which can affect kidney and heart functions.
  • Impaired glucose tolerance - raising risk of diabetes.
  • Impotence (erectile dysfunction) - the side-effect resolves once the medication is withdrawn.
  
  Patients taking thiazide diuretics should have regular blood and urine tests in order to monitor blood sugar and potassium levels.
  
  Patients aged 80 or over may be given indapamide (Lozol), a special type of thiazide diuretic which helps reduce death from stroke, heart failure and some other cardiovascular diseases.


• Beta-blockers
  
  Beta-blockers were once very widely used for the treatment of hypertension. Because they have more potential side effects than other current hypertensive drugs, they tend to be used today when other treatments have not worked. Beta blockers slow the heart rate down, as well as reducing the force of the heart, resulting in a drop in blood pressure.
  
  Beta blockers may have the following side effects:
  
  
  • Fatigue.
  • Cold hands and feet.
  • Slow heartbeat.
  • Nausea.
  • Diarrhea.
  The side effects below are also possible, but less common:
  • Disturbed sleep - beta-blockers decrease nocturnal melatonin release.
  • Nightmares.
  • Erectile dysfunction - difficulty in achieving or sustaining an erection.
  
  Drug interaction - the effects of beta-blockers may be altered if the patient takes some other medicines at the same time, causing adverse side-effects.


• Renin inhibitors
  
  Aliskiren (Tekturna, Rasilez) reduces renin production. Renin is an enzyme produced in the kidneys. Renin is involved in the production of a substance in the body called angiotensin I. Angiotensin I is converted into the hormone angiotensin II, which narrows blood vessels. Aliskiren blocks the production of angiotensin I so that levels of both angiotensin I and angiotensin II fall. This causes widening of the blood vessels, resulting in a drop in blood pressure. As it is a relatively new medication its use and dosages for patients with hypertension are still being determined.
  
  Tekturna was approved in the US in March 2007 and in the European Union in August 2007 under the trade name Rasilez. Tekturna HCT, the first single-pill combination involving Tekturna, was approved in the US in January 2008. The single-pill combination Rasilez HCT was approved by the European Commission in January 2009. Rasilez is approved in over 70 countries.
  
  Aliskiren may have the following side effects:
  
  
  • Diarrhea
  • Dizziness
  • Flu-like symptoms
  • Fatigue
  • Cough
  
  In February, 2009, the European Medicines Agency (EMEA) recommended adding a contra-indication to the Product Information for aliskiren, stating that it must not be used in patients who have experienced angioedema (swelling of the tissues beneath the skin).

Effectiveness of medications may vary according to patient's ethnicity

ACE inhibitors have been found to be more effective as a first choice medication in Caucasian patients, while calcium channel blockers or thiazide diuretics are generally more effective as a first choice medication for Afro-American and Afro-Caribbean patients, according to data from the USA and the UK.

If the above-mentioned medications, and their combinations are not effective

Some patients may still have trouble reaching desirable levels of blood pressure after being treated with the drugs mentioned so far. If this happens, the doctor may prescribe:

• Alpha blockers - they reduce the effects of natural chemicals that constrict (narrow) the blood vessels by reducing nerve impulses to the blood vessels.


• Alpha-beta blockers - they slow the heartbeat, which reduces the amount of blood pumping through the blood vessels, as well as reducing nerve impulses to the blood vessels.


• Central-acting agents - they stop the brain from telling the nervous system to raise the heart rate and constrict blood vessels.

In order to reduce the risk of cardiovascular disorder, some doctors may ask their patients to take daily aspirin.

What are the complications of high blood pressure (hypertension)?

If the hypertension is not treated or controlled the excessive pressure on the artery walls can lead to damage of the blood vessels (cardiovascular disease), as well as vital organs. The extent of damage depends on two factors; the severity of the hypertension and how long it goes on for untreated.

Below is a list of some of the possible complications:

• Stroke - blood flow to the brain is impaired by blockage or rupture of an artery to the brain, and brain cells die.


• Heart attack - heart muscle dies due to a loss of blood supply.


• Heart failure - the heart struggles to pump enough blood to meet the needs of the whole body. This happens because after pumping blood against higher pressure into the blood vessels the heart muscle thickens.


• Blood clot - some blood converts from a liquid into a solid (thrombus). Some blood clots can cause serious complications.


• Aneurysm - a bulge forms on the wall of a vein, artery or the heart. The wall is weakened and may rupture.


• Kidney disease - hypertension often damages the small blood vessels in the kidneys, resulting in kidneys that do not work properly. Eventually the kidneys can fail completely (kidney failure).


• Eyes (hypertensive retinopathy) - untreated hypertension can lead to thickened, narrowed or torn blood vessels in the eyes, which can lead to vision loss.


• Metabolic syndrome - this is a disorder of the body's metabolism, including an enlarged waistline, low blood HDL levels (the good cholesterol), hypertension, and high levels of insulin. If the patient has hypertension he/she is more likely to have other components of metabolic syndrome, significantly raising the risk of diabetes, stroke and heart disease.


• Cognitive and memory problems - if the high blood pressure continues untreated the patient's ability to remember things, learn and understand concepts may be eventually become affected.

Written by Christian Nordqvist


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