Blood pressure is a fundamental measure of the force exerted by circulating blood against the walls of the body’s arteries. This measurement is always presented as two numbers. The first, or top, number is the systolic pressure, which reflects the pressure when the heart contracts and pumps blood out. The second, or bottom, number is the diastolic pressure, representing the pressure in the arteries when the heart relaxes and refills with blood between beats.
Understanding Diastolic Blood Pressure
Diastolic blood pressure indicates the pressure within the arteries during the heart’s resting phase, between beats. This period is crucial because the heart muscle receives oxygenated blood through the coronary arteries. For most adults, a healthy blood pressure reading is generally considered to be below 120/80 millimeters of mercury (mm Hg). A diastolic blood pressure reading is typically considered low when it falls below 60 mm Hg. While a low blood pressure (hypotension) is defined as anything below 90/60 mm Hg, isolated diastolic hypotension occurs when diastolic pressure is less than 60 mm Hg but systolic pressure remains above 100 mm Hg.
Common Causes of Low Diastolic Pressure
Various factors can contribute to low diastolic blood pressure. Medications are a significant cause, particularly those prescribed to lower high blood pressure, such as diuretics, alpha-blockers, and certain types of antidepressants. These drugs can sometimes reduce blood pressure more than intended. Other medications, including those for Parkinson’s disease, erectile dysfunction drugs, and opioids, can also cause this effect. Aging is another common factor, as arteries can stiffen over time, which may raise systolic pressure while lowering diastolic pressure. Dehydration, resulting from insufficient fluid intake or excessive fluid loss (e.g., severe sweating or diarrhea), reduces blood volume and can lead to lower blood pressure. Certain heart conditions, such as a very slow heart rate (bradycardia), heart valve problems, or advanced heart failure, can also contribute to low diastolic pressure by affecting the heart’s ability to fill or pump blood. Additionally, severe infections like sepsis, allergic reactions (anaphylaxis), blood loss, and prolonged bed rest can cause a drop in blood pressure.
Recognizing Symptoms and When to Act
Low diastolic blood pressure can manifest through several symptoms. Common indicators include dizziness, lightheadedness, and fatigue. Individuals might also experience blurred vision, nausea, confusion, or even fainting. These symptoms arise because insufficient blood flow reaches vital organs, including the brain. Seek medical attention if these symptoms are severe, persistent, or if low readings are discovered during routine checks without an obvious cause. Immediate emergency medical attention is necessary if low blood pressure is accompanied by signs of shock, such as a very weak but rapid pulse, rapid shallow breathing, cold clammy skin, or loss of consciousness. Consulting a healthcare provider for repeated dizziness or fainting episodes is advisable, as these can indicate underlying health issues.
Potential Health Implications and Management
Persistently low diastolic blood pressure can have health implications, particularly because the coronary arteries, which supply blood to the heart muscle, receive blood primarily during the diastolic phase. If the diastolic pressure is too low, the heart may not receive enough oxygenated blood, potentially leading to a weakening of the heart over time. This chronic, low-level lack of oxygen, known as ischemia, can increase the risk of heart failure and other cardiovascular events. Management of low diastolic blood pressure involves addressing the underlying cause. If medications are the cause, a doctor may adjust dosages or switch prescriptions. Lifestyle adjustments can also be beneficial, such as increasing fluid intake and making dietary changes to include adequate salt, if advised by a physician. Avoiding sudden changes in position, like standing up too quickly, can help mitigate symptoms like dizziness. While lifestyle measures can help, a medical diagnosis and specific treatment plan from a healthcare professional are essential for effective management.