Blood pressure basics

People often ask me “What is a normal blood pressure?” or “Is my blood pressure too high?” A lot of medical questions are pretty hard – these ones are actually pretty easy. Published guidelines give us pretty solid recommendations on a definition of hypertension and treatment goals. Before we get into that, though, let’s start by discussing what blood pressure is. This will give you some deeper insight into the reasons why it is so important to keep blood pressure under control.

“What is blood pressure?”

Think of your arteries (the vessels, or tubes, that carry blood from your heart to the rest of your body) as pipes, kind of like the ones that carry water in your home. If your water pressure is really, really high, it hurts a little when you stand under the showerhead. Similarly, high blood pressure can damage the organs blood is going to, like the kidneys and the brain. Physicians call these end-organs (because they are at the end of the pipes).

Additionally, your blood vessels aren’t exactly like the pipes in your house. They aren’t made out of metal or plastic, so they are much more fragile. The pressure in the arteries doesn’t just push out against the end-organs – it also pushes out against the walls of the arteries. Over time, these arteries can develop blockages that cause heart attacks and strokes, or can even rupture.

You need to know that blood pressure is reported as a top number and a bottom number. The top number, called the systolic (remember “s” for “sky”) is the pressure generated when the heart squeezes, while the bottom number, called the diastolic (remember “d” for “down”), is the pressure when the heart is relaxed. For example, if your blood pressure is 120/80 (read “120 over 80”), the systolic is 120 and the diastolic is 80.

“What causes high blood pressure?”

On rare occasions, there are specific reversible causes of high blood pressure that are lumped into a category called “secondary hypertension.” However, the vast majority of the time, hypertension is due to a combination of factors – it used to be called “essential hypertension” and now is called “primary hypertension.” Unfortunately, neither of these actually answers the question, and that is why I often call this disease “lifestyle hypertension,” because it is usually caused by an unhealthy lifestyle. Sedentary behavior, unhealthy and excessive food intake, obesity, and smoking and alcohol can all contribute to this problem. Genetic factors can certainly contribute, and some patients will have hypertension despite a healthy lifestyle.

Perhaps what is even more important is that high blood pressure causes high blood pressure. The arteries pictured above are damaged by the high pressure, causing them to stiffen, resulting in a vicious cycle of increased pressures.

Because high blood pressure is so common, many people have unfortunately started to view it as a normal part of aging – but it is not! A recent study of tribes living in the South American rain forest showed steady increase in blood pressure with age in a tribe exposed to Western food, but no increase in a tribe that had no exposure to Western food.

“Is my blood pressure too high?”

The most recent guidelines published by the American College of Cardiology and the American Heart Association identify a blood pressure of less than 120/80 as normal, with a blood pressure of greater than or equal to 130/80 as hypertension. Either number being elevated will meet the definition of hypertension. The intermediate range with systolic 120-129 and diastolic < 80 is defined as “elevated blood pressure”. Technically, a blood pressure of 120/80 (which many people think of as “perfect”) is hypertension.

A blood pressure of 120/80 (which many people think of as “perfect”) is hypertension.

– Doctor T

This classification is much stricter than it has been in the past. It is based on evidence that higher blood pressures are associated with a higher risk of cardiovascular disease. More importantly, a number of trials have shown that treatment of high blood pressure results in substantial benefits.

So, to answer the question, a systolic blood pressure of 120 or higher, or a diastolic blood pressure of 80 or higher, is abnormal and should be acted upon. Ideally, this can be done through lifestyle modifications (stay tuned to the blog for frequent updates on nutrition, exercise, and weight loss!), but often will benefit from medications.

Appropriate lifestyle modifications include:

• Increased exercise
• Healthy diet, specifically one that is high in potassium such as the DASH diet
• Weight loss if overweight or obese
• Restriction of salt intake
• Quitting smoking
• Restricting alcohol to 2 drinks a day for men and 1 drink a day for women

“Should I be on medication for blood pressure?”

This is a topic that should be discussed with your physician. The guidelines mentioned above answer this question based on how high your blood pressure is and also your risk of having a heart attack or stroke over the next 10 years. See our blog post about calculating your own 10-year risk so that you can have an informed discussion with your physician.

Provided your blood pressure has been documented to be elevated on separate occasions, the guidelines recommend medication for a blood pressure greater than or equal to 140/90 for all patients. However, if you are at increased risk (10-year risk of a cardiovascular event > 10%), you should be treated with medications more aggressively, for a BP > 130/80. If you are treated with medications, the goal blood pressure should be less than 130/80.

You may eventually be able to improve your blood pressure with lifestyle modifications and your physician may be able to wean you off of your medication. However, treating initially with medications is important to avoid end-organ damage and prevent a vicious cycle of arterial stiffening that results in even higher blood pressures.

“What else should be done?”

Basic testing in patients with hypertension should include blood chemistries, blood thyroid testing, a complete blood count, fasting blood glucose and lipid panel, a urinalysis, and an electrocardiogram. This panel of tests assesses for other cardiovascular risk factors such as high cholesterol and diabetes, and can detect any damage that may have already occurred to the kidneys and heart. It can also help diagnose a secondary cause of hypertension, which is uncommon. In selected individuals, your physician can determine if you need further testing to determine a cause of hypertension, possibly through referral to a hypertension specialist.

Most importantly, hypertension is a a serious diagnosis in and of itself and also serves as a marker of poor health overall. We can all do more to live healthier lives, and having high blood pressure is a reminder of that. Follow up with your physician closely, make your health a priority, and stay tuned to Paging Doctor T for tips and strategies to get healthy!