The pressure that is exerted by blood, in the phase when the heart pumps blood is called systolic BP and the pressure which is exerted between the heartbeats is called diastolic blood pressure.
By Dr Praveen Gupta
Low blood pressure is a condition in which blood in the arteries exerts less pressure on its walls. The pressure that is exerted by blood, in the phase when the heart pumps blood is called systolic BP and the pressure which is exerted between the heartbeats is called diastolic blood pressure. The optimal BP is around 120/80 or lower. Some people, especially women routinely have blood pressure around 100/60 or 90 / 60 and yet they do not experience any symptoms. Clearly, systolic BP below 90 is low and is usually associated with symptoms. However, it is difficult to define a clear number for diastolic BP.
In general, high blood pressure is more common and requires treatment to prevent long term vascular risk. Low diastolic BP usually does not require treatment as it is asymptomatic. However, as it alters the mean blood pressure, a low diastolic BP may reduce the amount of blood flowing to organs, especially the brain, which can cause symptoms. The mechanism of symptomatic low blood pressure is the inefficiency of the heart to generate enough pressure while pumping. This dilates the arteries and restricts the blood flow in the arteries.
What causes low diastolic BP?
The causes of low diastolic BP are:
- Prolonged bed rest as it causes reduction in tone of arteries
- Loss of blood due to cleaning
- Trauma dehydration due excess sweating
- Reduced water intake
- Loss of water in stools medications such as diuretics, prostate medications, antihypertensive medications, medications for Parkinson’s disease, and narcotics tricyclic antidepressants
- Alcohol can cause dilation of blood vessels, which may lead to lower diastolic BP; lower heart rate; malfunctioning of heart valves; and heart attack. These are serious disorders which require care and treatment
- Hormonal deficiencies and other endocrine dysfunctions like hypothyroid or excess blood loss in menstruation
- Allergic reactions due to drugs, food or insect bites
- Nutritional deficiency of vitamin B and iron leading to anemia
- Prolonged standing that may lead to pooling of blood in the legs
What are the symptoms of low diastolic BP?
The common symptoms of low diastolic BP are:
- Dizziness as you stand up and walk
- Unusual thirst
What kind of treatment is required for low diastolic BP?
Usually, asymptomatic hypotension that is only detected by machines does not require treatment. However, for symptomatic patients, careful examination including anemia screening and cardiovascular assessment is required. If certain medications are causing low BP, change in medicine or dosage is necessary. Alcohol and other addictions need to be controlled. Regular exercise is compulsory. If you get up from prolonged rest, do some leg exercises. Increase the intake of salt and water. If the problem still persists, a detailed cardiovascular check with neuroendocrine assessment is required. There are certain medications like fludrocortisone that may be prescribed in certain cases, if nothing is found and the patient is symptomatic despite general measures as outlined above. To conclude, blood pressure readings on machines shouldn’t scare you but due care needs to be taken if symptoms persists.
The columnist is Director & Head, Neurology, Fortis Memorial Research Institute, Gurugram. Views expressed are the author’s own.