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An average normal resting heart rate in an adult is between 70 and 75 beats per minute (bpm). Women tend to have a slightly higher heart rate than men. Heart rate is most rapid in newborn babies and gradually decreases with age until a person reaches adulthood. It is very easy to find out a persons heart rate. The pulse rate, which is in most cases the same as the heart rate can be determined by compressing a peripheral artery. As you do, you will feel pulses; these correspond to the pumping of blood out of the heart and thus the heart beat. If you count the number of pulses you detect over a set period of time, you can calculate your heart rate in bpm.
Variations to Heart Rate
There are a number of variations that can occur to the heart rate.
An abnormally slow heart rate, typically below 60bpm (in resting adults). There is a vast array of conditions, drugs and medications or abnormalities in the transmission of the electrical signals stimulating heart muscle contractions, which can cause bradycardia. In addition people with above average cardiovascular fitness will have resting heart rates lower than normal adults, and in such people 60bpm may be normal. People with bradycardia will feel weak or faint, may be dizzy and can lose consciousness.
An abnormally fast heart rate, typically above 100 bpm (in resting adults). When undertaking strenuous activities or exercise you will naturally experience tachycardia. This is a necessary change in heart rate required to ensure proper oxygenation and nutrient supply to organs and muscle tissue. However, it can also be abnormal and dangerous. Rapid beating means the heart muscle itself requires more oxygen and nutrients and it can also cause imbalances in blood gases resulting in alteration in the blood chemistry and pH. Abnormally decreases in blood pressure (hypotension) can result in tachycardia as the body compensates and tries to increase blood flow by pumping blood out of the heart faster.
Depending on the heart chambers affected fibrillation can be classified as atrial or ventricular. Fibrillation is an abnormal twitching of the heart instead of the usual synchronised, regular contractions. Ventricular fibrillation is the more serious of the two classes of fibrillation, as the twitching ventricles are not able to properly pump blood to the lungs or periphery. A defibrillator is used to shock the heart back into its normal rhythm. If this is not successful the tissues of the body will die from oxygen starvation very rapidly.
A broad term that encompasses any type of abnormal heart rate rhythm caused by problems with the electrical signalling in the heart.
Other Conditions Affecting the Heart
· Myocardial infarction
Myocardial infarction is the correct medical term for a heart attack. They occur when the supply of blood and therefore oxygen and nutrients are cut off from the cells that make up the cardiac muscle tissue. This causes the heart tissue to die due to oxygen starvation. Regions of cardiac muscle tissue that have died are ischemias and they cannot be regenerated.
· Cardiac Tamponade
The heart is enclosed by a protective, lubricating membrane known as the pericardium. It enables the heart to contract and relax constantly without rubbing against other adjacent organs and structure and being damaged or causing damage to them. When the pericardium is damaged mechanically, by infection or inflammatory reactions fluid or blood can accumulate between the pericardium and the heart. The fluid puts pressure on the outside of the heart making it hard for the contracted ventricles to relax. This relaxation is needed to allow blood to flow into the ventricles from the atria. Inadequate ventricular filling leads to poor cardiac output and ineffective supply of blood to the body. This is a life-threatening emergency that requires immediate medical aid.
Article by Staff of ACS Distance Education
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