Diastolic pressure, or minimum pressure, is the value of arterial pressure when the heart is relaxing; in other words, it is the blood pressure between two heartbeats.
Brief review of what blood pressure is
Arterial pressure is the force that blood exerts against the walls of blood vessels, following the pump action carried out by the heart.
Measured in millimeters of mercury ( mmHg ) and in a state of rest, blood pressure is usually defined by the values of systolic pressure and diastolic pressure .
In humans, blood pressure depends on factors, such as:
- Force of contraction of the heart;
- Systolic range (ie the amount of blood leaving the heart at each ventricular contraction);
- Heart rate (ie the number of heartbeats per minute);
- Peripheral resistances (ie resistances opposed to blood circulation from the state of constriction of small arterial vessels);
- Elasticity of the aorta and large arteries (vascular compliance);
- Volemia (ie the total volume of blood circulating in the body).
What is diastolic pressure?
Diastolic pressure - also called minimal or simply " minimal " pressure - is the value of arterial pressure when an individual's heart relaxes. In other words, it is the value assumed by arterial pressure when the heart rests between a beat and the next beat (to understand the mechanism by which the heart works, see the article on cardiac mechanics).
The diastolic pressure is in contrast to the systolic pressure, which is, instead, the value of arterial pressure when an individual's heart contracts, hence the pressure value at each heartbeat.
Where does the term "diastolic" come from?
The term "diastolic" comes from the word " diastole ".
In the medical field, the word "diastole" indicates the relaxation phase of the heart, due to the accuracy of the myocardium (the heart muscle).
During diastole, there is an enlargement of the cardiac cavities (the result of the aforementioned relaxation), which has the purpose of accommodating the return blood.
How is arterial blood pressure reported?
Already mentioned in the unit of measurement used, in reporting the arterial pressure of a person, doctors compare the systolic pressure with the diastolic pressure. From this it follows that, in the report, the upper value is the maximum pressure, while the lower value is the minimum pressure.
Now, if in an individual the systolic pressure is 120 mmHg and the diastolic pressure is 80 mmHg, the pressure ratio (so the total arterial pressure) of the subject in question will be written 120/80 mmHg and read "120 out of 80 millimeters of mercury ".
Normal diastolic pressure
Measurement of blood pressure in an individual in excellent health may present
- systolic pressure values between 90 and 120 mmHg,
- diastolic pressure values between 60 and 80 mmHg.
Therefore the so-called normal diastolic pressure falls within a range of values not lower than 60 mmHg and not higher than 80 mmHg.
Almost always, in association with systolic pressure, diastolic pressure can be permanently subjected to dips or increases that exceed the limits of normality. These alterations generally represent something that does not work perfectly in the human body.
Going into more detail:
- When the diastolic pressure is constantly lower than 60 mmHg and the systolic pressure is constantly lower than 90 mmHg (so the ratio is <90/60 mmHg), the doctors speak of a hypotension or low pressure .
- When the diastolic pressure is constantly higher than 80 mmHg, but less than 90 mmHg and when the systolic pressure is constantly higher than 120 mmHg but less than 140 mmHg (so the maximum / minimum ratio is between 120/80 and 139/89 mmHg ), doctors talk about pre-hypertension .
- Finally, when the diastolic pressure is constantly higher than 90 mmHg and the systolic pressure is constantly higher than 140 mmHg (so the maximum / minimum ratio is> 140/90 mmHg), the doctors talk about hypertension or high blood pressure .
As readers can see, in order to assess the arterial pressure of an individual and any anomalies, it is necessary to consider, to obtain a complete picture of the situation, both the maximum pressure and the minimum pressure.
Hypotension or low blood pressure
The state of hypotension can have a different origin; in fact, it can be:
- A physiological condition due to genetic factors or to the regular practice of physical activity ( constitutional hypotension ). In these circumstances, the drop in blood pressure is slight both in the systolic values and in the diastolic values and lacks real symptomatology.
Generally, constitutional hypotension is not a dangerous condition; indeed, according to some experts, it would seem to protect against cardiovascular risk.
- A condition due to a particular disease ( pathological hypotension ). In such situations, the degree of maximum low pressure and low minimum pressure can be extremely marked and, therefore, cause symptoms and complications.
Pathological hypotension requires ad hoc treatment.
Among the diseases that can cause a substantial reduction in blood pressure, include: Addison's disease, anemia due to folate deficiency or vitamin B12, anaphylactic shock, dehydration, myocardial infarction, congestive heart failure, some forms of arrhythmia, bradycardia, valvulopathies, pulmonary embolism, septic shock, acidosis, severe traumatic brain injury and spinal cord injuries.
- A condition due to taking certain drugs ( drug hypotension or iatrogenic hypotension ). In these situations, the drop in systolic pressure and diastolic pressure is variable, in the sense that it can be more or less marked.
Among the drugs that can potentially cause hypotension, include: antihypertensive drugs (diuretics, calcium channel blockers, angiotensin II receptor antagonists, alpha-blockers, beta-blockers, etc.), trinitrina (or nitroglycerin), the anesthetics used for spinal anesthesia, narcotics, tricyclic antidepressants, levodopa combined with carbidopa and some drugs for erectile dysfunction (eg: Viagra, Levitra or Cialis) in association with nitroglierin.
- A condition due to pregnancy, to be precise to the hormonal changes that gestation involves for the woman ( gestational hypotension ).
Normally, in the first 24 weeks of pregnancy, pregnant women are subject to an average drop in systolic blood pressure of around 5-10 mmHg and an average decrease in diastolic blood pressure greater than 10 mmHg.
To learn more, readers can consult the article: Low Pressure in Pregnancy.
Pre-hypertension is not exactly a pathological state - as it is hypertension or intermediate / severe degree hypotension - but it is rather a condition to be monitored, as if it were a sort of alarm bell that warns of the presence of something abnormal.
Those suffering from hypertension do not need a pharmacological cure, but must change their lifestyle (which is often wrong) and pay attention to:
- Physical activity.
If timely, the adoption of a healthy lifestyle allows the control of pre-hypertension and the normal values of systolic and diastolic pressure.
Hypertension or high blood pressure
Hypertension is a clinically relevant condition that, if not treated properly and timely, can lead to serious complications, sometimes even with a fatal outcome.
In fact, high levels of systolic pressure and diastolic pressure cause the arterial blood to flow in such a way as to produce microlesions in the arteries in which it circulates, which, precisely for this reason, slowly undergo a process of atherosclerosis ( that is, they undergo hardening and are the site of atheromas).
Atherosclerosis increases the risk of thromboembolism and affects the circulation of important organs, such as the brain, heart, kidneys and eyes.
While in adults under the age of 60 hypertension manifests itself with high levels of systolic pressure and diastolic pressure, in elderly people hypertension tends to be particularly high in systolic blood pressure values and to be only slightly increased in diastolic blood pressure .