The simplest way to get a picture of how a heart is functioning is through a blood pressure reading. Blood pressure is a measurement of force that the blood exerts against a vessel wall. It is recorded as systolic pressure over diastolic pressure. Systolic pressure is peak pressure during which the heart is working or pumping. Diastolic pressure is the minimum pressure the heart faces. It is recorded while the heart is resting and filling between beats. Controlling diastolic blood pressure is important to avoid hypertension, which can lead to a myriad of other diseases.
Influences
The most influential factor determining diastolic blood pressure is the total peripheral resistance the heart faces. According to Saladin's "Anatomy and Physiology," resistance is made up of blood viscosity, vessel length and vessel radius. Viscosity and vessel length are the least changeable. The most influential factor on peripheral resistance is blood vessel radius. Blood vessels can become narrower or vasoconstrict and wider or vasodialate. Increased vasodialation leads to faster blood flow and lower peripheral resistance. The same is true for the opposite; narrowing vessels slow the blood flow and create higher peripheral resistance. Diastolic blood pressure is directly related to peripheral resistance. The more resistance there is, the higher the diastolic pressure.
Function
The rate of blood flow through the vessels is determined by blood pressure. Brooks, Fahey and Baldwin's "Exercise Physiology" reasons that blood flow between two points is directly proportional to the driving force between them. In this case, the heart. During diastole, the heart's chambers fill with blood. Low resistance or low diastolic pressure allows more blood to fill the heart. The Frank-Starling mechanism states that the heart's ventricles are stretched when they receive more blood, which causes the heart to more forcefully contract leading to a higher blood flow. A higher blood flow assures that muscles in need of blood will receive it.
Identification
Arterial blood pressure is written as systolic pressure over diastolic pressure. The National Heart Lung and Blood Institute suggests that a normal healthy blood pressure is less than 120mm of mercury or mmHG over 70mmHg. Prehypertension begins when the pressure rises to 120 to 139mmHG over 80 to 89mmHg. Stage one hypertension is classified as 140 to 159mmHG over 90 to 99mmHg. Stage two hypertension is a reading greater than or equal to 160mmHg over 100mmHg.
Significance of Hypertension
The American Heart Association states that a high blood pressure can cause several health risks. Vascular weakness and scarring can occur. Overstretching of vessels caused by increased force causes weakness and scarring that can lead to plaque buildup and an increased risk of rupture. Hypertension can increase the risk of blood clots and plaque buildup, both of which can lead to heart attacks or strokes. Narrowed or blocked arteries caused by plaque buildup can cause undue stress on organs that can't get enough oxygenated blood and on the cardiovascular system, which must work harder to move blood.
Controlling Diastolic Blood Pressure
The main goal to keep diastolic blood pressure in a healthy range is to maintain the elasticity of the vessels. If a vessel is elastic and pliable, the body has greater control over its vasoconstriction and vasodilation. The American Heart Association suggests there are steps that a person can take to prevent hypertension. These steps include eating a healthy diet low in sodium, regular physical activity, maintaining a healthy weight, managing stress, avoiding smoking, limiting alcohol intake and complying with doctor prescribed medications.
References
- "Anatomy and Physiology"; Kenneth S. Saladin; 2004
- "Exercise Physiology"; George A. Brooks et al.; 2005
- National Heart Lung and Blood Institute: Categories for Blood Pressure Levels in Adults
- The American Heart Association: Prevention & Treatment of High Blood Pressure
