What Are the Differences Between Systolic and Diastolic Blood Pressure?
When people say "taking your blood pressure," they mean measuring the force of the blood that your heart pumps through your body. These two figures are referred to as systolic and diastolic blood pressure, both figures are significant, but for different reasons.
Blood Pressure Overviews
When the heart beats, blood moves through the arteries to get to different parts of the body. is different from what you see from a garden hose or water faucet.
The pulse of the blood flow and the pressure it puts on the body change from time to time. You can tell because it's at its highest point during a heartbeat and at its lowest point between beats (diastolic).
If the readings are too high, it could mean that a person has high blood pressure, which can be dangerous. If the readings are too low, there may not be enough blood moving to the brain and other important parts of the body. It's a sign that there might be a heart condition or other problem
Systolic
By looking at your pulse, you can tell when your heart is beating. This is called a heartbeat, and this is why it is called systole. It's the pressure in your heart during a heartbeat and the highest pressure you can measure.
Systolic Blood Pressure is too High:
When a person is exercising, stressed, or has a high heart rate, the heart muscle pushes out blood with more force. Because of it, the pressure in your heart goes up as well. When there is more pressure, that's normal. In other words, when the pressure is high while a person is at rest, that's called high blood pressure.
Systolic Blood Pressure is too Low:
The term "hypotension" is used when the systolic blood pressure is lower than it should be. If this low blood pressure is bad enough, it can make you lightheaded, dizzy, or faint. If it goes on for a long time and isn't treated, your kidneys may start to shut down, which can be very bad.
Systolic hypotension may happen if there is not enough blood in your body, which can make you feel weak. If you are very thirsty or have a lot of bleeding, this can happen. There isn't enough blood to move through the body.
Diastolic
The heart takes a break between beats so it can get more blood. This pause between beats is called "diastole." During this pause before the next heartbeat, your diastolic blood pressure is the number that is read out.
The diastolic reading, or bottom number, is the pressure in the arteries when the heart is at rest between beats. This is the period during which the heart receives blood and oxygen.
Your diastolic blood pressure reading indicates the following
Less than 80 is considered normal.
For stage 1 hypertension, the range is 80-89.
The diastolic reading, or bottom number, is the pressure in the arteries when the heart is at rest between beats. This is the period during which the heart receives blood and oxygen, having high blood pressure can make your diastolic number go up even when you're just lying down and not moving.
FAQs on Systolic and Diastolic Blood Pressure Explained
1. What are systolic and diastolic blood pressure?
Systolic blood pressure (the top number) measures the maximum pressure your blood exerts against your artery walls when the heart's ventricles contract to pump blood out. Diastolic blood pressure (the bottom number) measures the pressure in your arteries when the heart is in a state of relaxation between beats, allowing its chambers to refill with blood. A typical reading is written as systolic over diastolic, for example, 120/80 mmHg.
2. What is the fundamental difference between systole and diastole in the cardiac cycle?
The key difference lies in the action of the heart muscle. Systole is the contraction phase, where the heart's ventricles squeeze to forcefully eject blood into the aorta and pulmonary artery. This phase is shorter and generates higher pressure. In contrast, diastole is the relaxation phase, where the ventricles relax and fill with blood from the atria. This phase is longer and is associated with lower pressure in the arteries.
3. What are the different categories of blood pressure readings for adults?
Blood pressure readings are categorised to help assess cardiovascular risk. According to the standard guidelines, the categories are:
Normal: Systolic less than 120 mmHg and diastolic less than 80 mmHg.
Elevated: Systolic between 120–129 mmHg and diastolic less than 80 mmHg.
Hypertension Stage 1: Systolic between 130–139 mmHg or diastolic between 80–89 mmHg.
Hypertension Stage 2: Systolic 140 mmHg or higher or diastolic 90 mmHg or higher.
Hypertensive Crisis: Systolic higher than 180 mmHg and/or diastolic higher than 120 mmHg. This requires immediate medical attention.
4. What is the importance of distinguishing between hypertension and hypotension?
It is important to distinguish between them as they represent opposite health conditions. Hypertension, or high blood pressure, is a condition where the force of blood against the artery walls is consistently too high (e.g., above 130/80 mmHg). It is a major risk factor for heart disease and stroke. Hypotension, or low blood pressure, occurs when blood pressure is significantly lower than normal (e.g., below 90/60 mmHg). While often harmless, it can cause dizziness and fainting and may indicate an underlying medical issue.
5. Which blood pressure number is more important for assessing health risks: systolic or diastolic?
Both numbers are important, but their significance can vary with age. For individuals over 50, systolic blood pressure is generally considered a more significant predictor of cardiovascular disease. This is because arteries tend to stiffen with age, leading to a rise in systolic pressure. However, in younger individuals (under 50), an elevated diastolic pressure can also be a strong indicator of future health risks. Therefore, doctors evaluate both readings together to get a complete picture of heart health.
6. How is blood pressure measured and what do the units 'mmHg' mean?
Blood pressure is measured using an instrument called a sphygmomanometer, which consists of an inflatable cuff placed around the upper arm. The units mmHg stand for 'millimetres of mercury'. This unit originates from the earliest pressure gauges, which measured how high the force of the blood pressure could raise a column of mercury. Even with modern digital devices, this standard unit of measurement is still used worldwide.
7. How do factors like exercise, stress, and age affect blood pressure readings?
Blood pressure is not static and is affected by various factors. During exercise, systolic pressure rises to deliver more oxygen-rich blood to muscles, while diastolic pressure may stay the same or slightly decrease. Emotional stress can cause a temporary spike in both systolic and diastolic pressure due to the release of stress hormones. With age, arteries can become less flexible, often leading to a gradual increase in the baseline systolic pressure, a condition known as arteriosclerosis.
8. What is pulse pressure, and why is it considered an important indicator?
Pulse pressure is the numerical difference between your systolic and diastolic blood pressure (Systolic - Diastolic = Pulse Pressure). For a reading of 120/80 mmHg, the pulse pressure is 40 mmHg. It represents the force the heart generates each time it contracts. A consistently high pulse pressure (e.g., over 60 mmHg) can be a strong predictor of heart problems, particularly in older adults, as it may indicate stiffer, less elastic arteries.
9. Is it possible to have high systolic but normal diastolic pressure, and what does it mean?
Yes, it is possible. This condition is known as Isolated Systolic Hypertension (ISH). It is defined by a systolic pressure of 130 mmHg or higher while the diastolic pressure remains below 80 mmHg. ISH is the most common form of high blood pressure in older adults and is primarily caused by age-related stiffening of the major arteries. It is a significant risk factor for stroke and heart disease and is managed similarly to other forms of hypertension.
