A lot of attention is given to high blood pressure, or hypertension, in America. Our diet and lifestyle, and the connection between hypertension and heart attacks tend to make this common problem very visible.
But what about the opposite? What are the signs, symptoms, and dangers of low blood pressure, which is known as hypotension? While the symptoms of low blood pressure may not be as well known by many people, you can still have life-threatening complications if your blood pressure gets too low.
How Does Blood Pressure Work?
A blood pressure reading is a measurement of the pressure exerted by your blood on the walls of your blood vessels. Regulating blood pressure is a complex job involving many different parts of your body. Naturally, the heart and major blood vessels are a big part of this process, but smaller vessels, your muscles, and even your kidneys all help regulate your blood pressure.
Your blood pressure reading is described using two numbers, such as 110/85. These two numbers are measurements of pressure in millimeters of mercury (or mm Hg) at two different points in the cycle of your heartbeat. The first, top number, known as systolic pressure, is the pressure exerted when the left ventricle of your heart contracts, pushing blood out into your arteries. The second number, called diastolic pressure, is the measurement of pressure at the moment your heart relaxes and no new blood is being pumped into your arteries.
High or low blood pressure readings are not exact numbers but are terms used when your blood pressure falls outside of a normal, healthy range. In most healthy adults, systolic pressure is considered normal if it lands between 90 and 120. Diastolic pressure, measured when the left ventricle of the heart is relaxed between contractions, is lower, and a normal measurement will typically be in the range of 60 to 80 mm Hg. These measurements can vary considerably from person to person, and your own normal blood pressure can change over time.
High blood pressure is commonly associated with sudden, unexpected, and damaging illnesses such as heart attacks and strokes. Low blood pressure, on the other hand, can often lead to many different conditions with more obvious warning signs. For this reason, a blood pressure reading is seen as an important indicator if your blood pressure is too high, but low blood pressure is not tied so tightly to specific numbers. Instead, the symptoms of associated conditions are more often used to determine when your blood pressure may be getting too low.
Your body can regulate your blood pressure in several ways. The first is by altering the speed of your pulse, causing your heart to beat faster or slower. A higher pulse rate will generally raise your blood pressure, and a slower pulse rate will typically bring it down. Muscle tension, and the restriction of blood flow through small vessels, known as arterioles, can also be a factor. Both the size and stiffness of these arterioles, which can be a greater concern as people age, also affects how easily blood can flow through tissue.
Larger vessels can expand and contract as well. Veins can enlarge to store more blood and slow the return of blood to the heart, leaving less blood to be pumped out into the arteries and lowering your blood pressure. It is also possible for the veins to constrict, forcing enough blood into the heart and out into the arteries to raise your blood pressure.
Your kidneys can also play a role in regulating blood pressure, though the effect is felt over a longer period of time. By increasing or decreasing the amount of urine produced, your kidneys can help change the overall amount of liquid in your body, thereby raising or lowering the volume of blood available. Typically, kidney function affects blood pressure over hours or days rather than the matter of seconds it takes for changes to your heart rate or vascular system to be felt.
What Causes Low Blood Pressure?
External factors such as taking certain drugs can affect your blood pressure. Not surprisingly, some of these drugs are blood pressure medications. Beta blockers, a class of drugs taken to treat high blood pressure, can interrupt the electrical signals regulating your heart rate, potentially causing hypotension or a condition known as bradycardia. Angiotensin converting enzyme inhibitors, calcium channel blockers, and alpha blockers can also lower blood pressure, especially in older people who may have heart disease or other cardiovascular issues.
Other medications, such as amitriptyline for treating depression, several drugs used to treat erectile dysfunction such as Viagra, and medications for Parkinson’s disease like Sinemet, all have low blood pressure as a potential side effect. Diuretics can decrease your blood pressure by encouraging excess urination, therefore lowering overall blood volume.
Heart Disease and Low Blood Pressure
The causes of low blood pressure can begin with the heart itself. Heart attacks are a very serious and often sudden cause of low blood pressure. As the tissue of the heart dies, either from one massive or several small attacks, your heart’s ability to pump blood effectively is reduced. Viral infections of the heart muscle and other diseases such as aortic stenosis can also affect your heart’s ability to pump blood effectively.
Your heart rate is a major factor in your overall blood pressure, but low blood pressure is not always due to ill health. Bradycardia, or a slow heart rate, is a condition where the resting heart rate falls below the normal range of 60 to 100 beats per minute. It is common for athletes to have lower heart rates than the general population, as the heart muscles become stronger and can pump more blood with each contraction.
Ironically, allowing the heart to beat less often can make you more likely to experience a condition called orthostatic hypotension. People with this condition commonly experience lightheadedness or dizziness, report blurred vision and may even pass out from a sudden drop in blood pressure when standing up too fast from a sitting or lying position. This dizziness and fainting are rarely serious in younger people, but in the elderly, fainting or losing your balance can make orthostatic hypotension a risk factor for serious injury from falls.
More serious than merely fainting, pericarditis is a condition of the sac surrounding the heart known as the pericardium. If the pericardium becomes inflamed, fluid can begin to build up and exert pressure on the heart, making it harder to pump blood to the rest of the body.
At the severe end of the spectrum of heart problems lies the possibility of a pulmonary embolism. This condition, in which a blood clot breaks off from the wall inside a vein and travels to the heart, can be life-threatening. When the clot reaches the heart, it can pass through and become lodged in the lungs, starving the heart muscles of oxygen and potentially leading to heart failure.
Dehydration, Bleeding, and Inflammation
Perhaps the most obvious external factor affecting blood pressure comes from extreme blood loss due to trauma. This bleeding can be external such as a wound from a sharp object like a knife or a fall such as a bike accident. Bleeding can also be internal from conditions like diverticulitis or an ulcer. Bleeding slowly over time may not affect your blood pressure, but if you lose too much blood too fast, the body cannot adapt quickly enough. Extreme rapid blood loss is one of the primary concerns after a physical trauma or accident, as this rapid lowering of the blood pressure can cause shock, organ damage, and death.
Dehydration is another cause of lowered blood pressure, and just like bleeding, it can range from mild to severe. In all cases of dehydration, moisture is being lost from the body, including the blood. As your blood volume drops from water loss, not only does your blood pressure drop, but also the chemistry of your blood begins to change.
Severe inflammation is another potential cause of low blood pressure. Certain health conditions can result in inflammation in your chest or abdomen. In these cases, such as acute pancreatitis, blood pools in and around the affected tissues and organs, meaning the amount of blood available for your heart to pump is reduced.
Other Causes of Low Blood Pressure
Vasovagal reaction may not be a name many people know, but it is certainly something you are familiar with. This reaction is commonly known as fainting and arises from a reaction to fear or pain in an otherwise healthy person. Vasovagal reactions happen when the autonomic nervous system releases hormones that expand blood vessels and slow your heart rate. Since the vagus nerve, which is largely responsible for this reaction, also helps regulate your digestive tract, you can end up with a vasovagal reaction from straining during a bowel movement or even from vomiting.
Septicemia is a very severe infection in which bacteria or fungal spores enter the blood. These infections can begin as pneumonia in the lungs or may originate in the bladder. Diverticulitis and even gallstones can also trigger septicemia. Wherever they originate, these foreign materials in the blood can release toxins that result in septic shock. This severe drop in blood pressure can result in damage to vital organs if it is not treated properly.
Another common cause of a sudden drop in blood pressure is having a severe allergic reaction to certain medicines, bee stings, or food such as peanuts. This reaction, known as anaphylactic shock, results in the constriction of your airways, closing of the throat, and a severe drop in blood pressure as your blood vessels quickly enlarge.
Talk to Your Doctor
The effects of chronic low blood pressure may appear slowly over long periods of time, but some conditions like sudden blood loss from trauma or anaphylaxis can arise very suddenly. For less severe conditions like orthostatic hypotension, simple solutions like wearing compression stockings can help ease symptoms. For more serious and even life-threatening matters such as the heart conditions mentioned above, careful medical intervention may be necessary. If you or someone you know is experiencing the symptoms associated with low blood pressure, it may be time to talk to your doctor.
Request an appointment at our TrustCare Heart Clinic to take a step toward ensuring you are caring for your heart and your entire body.