Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 92

When recording a patient’s resting heart rate sometimes it may be either slower or faster than expected. The term bradycardia is used to describe a resting heart rate of 60 bpm or lower. In most cases bradycardia is not indicative of disease; indeed, the most common cause of a slow heart rate is a high level of physical fitness. Bradycardia is also associated with the use of certain medications, particularly beta blockers (β blockers) which are frequently used to treat high blood pressure by slowing the heart. However, there are some medically significant causes of bradycardia such as hypothermia (see Chapter 2) or damage to the electrical conductive tissues of the heart.

Tachycardia is the opposite of bradycardia and is defined as a resting heart rate of 100 bpm or above. Tachycardia can have many causes ranging from increased release of adrenaline when a person is frightened, to more serious causes such as a major infection or severe haemorrhage.

It is essential to recognise that the terms bradycardia and tachycardia are only applied to a patient’s resting heart rate; so a heart rate above 100 bpm during exercise would not be referred to as tachycardia.