What is Diastole Definition Phases and Function in Heart
A diastole or diastolic function of the heart is the process where the heart muscles go through relaxation which is followed by the filling of blood in the heart's chambers. This as a result decreases the blood pressure of an individual. Thus, diastole heart function is a phase in the cardiac cycle of a person which is responsible for ventricular relaxation along with the active and passive filling of blood in the heart chambers before pumping them out throughout the body.
This is a very important topic for understanding the cardiac cycle of humans and how an abnormal diastolic function can result in several heart diseases.
This article provides information on ventricular diastole and left ventricular diastolic dysfunction definition. Students can also refer to this article to understand diastolic dysfunction meaning.
Definition of Diastole and Systole
Before understanding the cardiac cycle and knowing the abnormalities of heart functioning, it is important to get a clear understanding of the diastole and systole.
Ventricular diastole and systole form a major part of the cardiac cycle. These can be defined as the two periods in a cardiac cycle which occurs in the form of heartbeats. They pump the blood through the blood vessels which is carried to each and every part of the body.
Diastole is the relaxation of the ventricles and pumping of blood into the heart chambers while systole can be defined as the contraction of heart muscles to pump out blood in the entire body.
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Ventricular Diastolic Dysfunction
The trouble in relaxation of heart muscles and reduction in the pumping of blood into the ventricles of the heart is known as ventricular diastolic dysfunction.
Left ventricular diastolic dysfunction (DD) is characterized as the ventricle's failure to fill to a normal end-diastolic volume, both during exercise and at rest, while left atrial pressure does not surpass 12 mm Hg.
The occurrence of mild diastolic dysfunction starts with slow heartbeats due to the limited amount of blood flow in the ventricles required for the next heartbeat.
A normal left ventricular diastole requires proper relaxation, contraction and ejaculation of blood throughout the body for normal functioning of the heart.
The two common main reasons for left ventricular diastole dysfunction are:
Due to an Overworked Heart Muscle: This is caused by the high amount of physical activity which as a result thickens the muscles of the heart creating less space inside the heart ventricles for filling in blood.
Clogged Arteries: Muscle bulking and stiffening of heart muscles can be genetic but the most common factors for these has always been a high level of cholesterol and blood pressure. Clogging of heart arteries results in narrowed heart valves which block several proteins, irons and other substances to filtrate out of the arteries making the heart stiffer.
Causes and Effects of Diastolic Heart Failure
Several factors contribute to abnormal functioning of the heart. Some of the main factors include ageing, aortic stenosis, pericardial diseases and hypertrophic cardiomyopathy.
Hypertrophic cardiomyopathy is the abnormal thickening of the left ventricular wall while aortic stenosis can be defined as the narrowing of the aortic valve opening.
These abnormalities lead to the accumulation of fluids in the pericardial space causing a sudden heart failure.
Other factors for diastolic dysfunction include diabetes, high blood pressure, obesity and coronary heart diseases.
Symptoms of Diastolic Heart Failure
Although people show no diastolic dysfunction symptoms, many may experience issues with breathing difficulty, fatigue and irregular heartbeat. They also face difficulty in doing physical activities and have a lack of appetite. Many severe symptoms include abdominal swelling, rapid weight gain and swelling of the ankle and legs (edema).
Many people also face severe chest pain and foamy, pink mucous after coughing. Therefore it is important to do a regular checkup of your heart and maintain a low cholesterol level for better functioning of the heart.
FAQs on Diastole in the Cardiac Cycle Explained Clearly
1. What is diastole in the cardiac cycle?
Diastole is the phase of the cardiac cycle in which the heart muscle relaxes and the chambers fill with blood. During diastole:
- The atria and ventricles relax.
- The atrioventricular (AV) valves open to allow blood to flow into the ventricles.
- The semilunar valves remain closed to prevent backflow from arteries.
2. What happens during ventricular diastole?
Ventricular diastole is the period when the ventricles relax and fill with blood from the atria. It includes:
- Relaxation of ventricular muscle fibers.
- Opening of the mitral and tricuspid valves.
- Passive filling of ventricles, followed by atrial contraction (late diastole).
3. What is the difference between systole and diastole?
The main difference is that systole is heart contraction, while diastole is heart relaxation and filling. Key differences include:
- Systole: Ventricles contract and pump blood into the aorta and pulmonary artery.
- Diastole: Ventricles relax and fill with blood.
- Systolic pressure is the higher blood pressure value, while diastolic pressure is the lower value.
4. Why is diastole important for the heart?
Diastole is important because it allows the heart chambers to fill with blood and ensures adequate cardiac output. During diastole:
- The ventricles receive oxygenated and deoxygenated blood.
- The coronary arteries receive blood supply to nourish the heart muscle.
- The heart muscle recovers before the next contraction.
5. What is diastolic blood pressure?
Diastolic blood pressure is the pressure in the arteries when the heart is in diastole (relaxation phase). It:
- Represents the lower number in a blood pressure reading (e.g., 80 in 120/80 mmHg).
- Reflects arterial pressure between heartbeats.
- Indicates how well blood vessels maintain pressure during relaxation.
6. How long does diastole last in a normal heartbeat?
In a normal resting heart rate (about 75 beats per minute), diastole lasts approximately 0.4 seconds. The full cardiac cycle lasts about 0.8 seconds:
- Atrial systole: ~0.1 seconds
- Ventricular systole: ~0.3 seconds
- Complete diastole: ~0.4 seconds
7. What are the phases of diastole?
Diastole consists of distinct phases that allow ventricular relaxation and filling. The main phases are:
- Isovolumetric relaxation: Ventricles relax but all valves are closed.
- Rapid ventricular filling: AV valves open and blood flows quickly into ventricles.
- Reduced filling (diastasis): Slow filling phase.
- Atrial systole: Atria contract to complete ventricular filling.
8. What is diastolic dysfunction?
Diastolic dysfunction is a condition in which the ventricles cannot relax properly during diastole, leading to impaired filling. It involves:
- Reduced ventricular compliance (stiff heart muscle).
- Increased filling pressure.
- Possible progression to heart failure with preserved ejection fraction (HFpEF).
9. How does blood flow during diastole?
During diastole, blood flows from the atria into the ventricles due to pressure differences. The sequence is:
- Ventricles relax, lowering internal pressure.
- Atrioventricular valves open.
- Blood flows passively from atria to ventricles.
- Atrial contraction pushes remaining blood into ventricles.
10. What valves are open and closed during diastole?
During diastole, the atrioventricular (mitral and tricuspid) valves are open, and the semilunar (aortic and pulmonary) valves are closed. Specifically:
- AV valves open to allow ventricular filling.
- Semilunar valves close to prevent backflow from arteries.
