Heart is the life line for all humans and many other animals and its disruption would be detrimental to sustain life. Although there are many ways in which the heart function can be affected, the level at which it affect can vary a great deal. Even through many do not become life threatening, some of them can easily trigger a life threatening incidence in susceptible individuals within few minutes.
Heart rate is the rate at which the heart musculature contracts in order to maintain the blood circulation and the usual heart rate for a healthy adult would stand at 70 – 80 beats per minute. But, in certain instances where the body demands more oxygen and therefore more blood to a particular tissue, the heart needs to function at a higher rate and in a more intense manner. The net effect would be a rise in the heart rate to compensate for the demand. Similarly, during rest and in certain other conditions, the heart will adapt a less energetic approach in pumping blood and one aspect of this would be the lowering of heart rate. In general, a heart rate falling below 60 beats per minute or a heart rate of more than 90 beats per minute would be known as bradycardia and tachycardia respectively although this depressed or elevated heart rate does not necessarily mean a diseased heart nor any abnormality although one should be vigilant enough to find an underlying cause if an obvious reason cannot be determined.
So, what are these obvious reasons affecting the heart rate?
Age : In children, the heart rate would be relatively higher than in an adult and would gradually rise again when a person reaches the elderly age.
Exercise : When a person exercise, the demand for oxygen in active musculature would increase and therefore as mentioned before the heart wound contract at a faster rate. But, in trained athletes, the increase may not be apparent.
Digestion : In a digestive process, the intestines would require additional blood circulation and therefore a possible heart rate increase can be seen.
Fever : Febrile conditions can give rise to a fast heart rate due to the increase in basal metabolic rate with the rise of the body temperature. In general, a rise of 10 beats per minute is expected with the elevation of temperature by a single degree.
Emotions : Another factor that has shown to affect the heart rate is the emotions and these include anxiety, anger, being frightened…etc.
Conduction defects : When the signal transport mechanism of the heart become dysfunctional, the rate and the rhythm in which the heart function can get deranged and therefore can give rise to a fast or a slow heart beat.
Vagal stimulus : Vagas is a nerve that connects many internal organs with the higher centers and would be receptive to certain elements in the body. Thus, when stimulated, there would be a responsive lowering of the heart rate and this is also known as a ‘vagal inhibition’.
Medicines : Drugs such as beta-blockers and digitalis have show to reduce the heart rate whereas ephedrine and cocaine have shown to increase the rate.
Apart from the above mentioned factors, the gender, breathing, diet and certain other disease conditions can affect the heart rate as well.