Knowing your heart rate

By Dr Harold Gunatillake - Health Writer

A baby in the womb (intrauterine) develops its heart surprisingly quit early. Foetal heart rate varies from about 50bpm and by the 12th week in the womb raises approximately to 140-150bpm (beats per minute). Grown-ups have an average persistent heart rate between 70- 90 bpm depending on the physical fitness of the individual. If you are in the athletic range your heart rate can further drop depending on the extent of training. An Olympic athlete would bring down the heart rate even to as low as 40bpm depending on the extent of training.

The heart muscles are so strong in a trained individual that it could pump more blood, so beating less number of times per minute. If you are sedentary and not active, the heart rate can go even up to 100bpm. In the latter situation, the heart is weaker and less blood is pumped per beat, and need to pump a number of times per minute. Men seem to have a lower normal pulse rate than the women.

Your target heart rate

When you exercise on a treadmill you need to know your target heart rate. It is important to keep your level of exercise to between 50% and 85% of your maximum heart rate to be on the safe side.

This is estimated by subtracting your age from 220 and limiting your exercise to about 85% of the upper limit.

Anyhow, whilst exercising vigorously if you feel breathless, dizzy, ache in the heart, you should stop immediately before you strain your heart unnecessarily.

If you are on beta blockers which slow down the heart rate, you should be very careful not to strain your heart by overdoing.

Wear an electronic heart monitor with built in heart sensors whilst you exercise to be on the safe side. That can tell you how hard you are exercising

The heart rate of an individual varies and influenced by exercise, age, emotions, medications, glandular activities, body positions, and the health condition of the heart muscle conducting system (Bundle of His).

Resting heart rate is an indicator of general health and cardiovascular fitness. It is measured by feeling the pulse, in your wrist, neck or groin. It is more convenient to feel the radial pulse at the wrist level. To check on your neck place your index and mid-finger over the side of the lower neck wind-pipe and you may feel the thuds of the carotid arteries. It is more practical to feel the pulse in the wrist by placing the index and mid-fingers across just above the crease line at the wrist, more towards the outside (base of your thumb).
Once in a while it is important to check your pulse when you are lying down on your “hansi putuwe”-(resting chair) or the modern type of reclining chair. Count the pulse for 15 seconds without moving and multiply that by four to get the rate per minute (rpm).

Changes in heart (pulse) rate-Arrhythmias
All is well and done as long as the pulse has a regular beat and within the normal range of the rate. It is also advisable to roll the radial artery at the wrist with your index and middle fingers. This vaguely gives you an idea how thickened (arteriosclerotic) your blood vessels are: gives an indication of the integrity of the coronary arteries. If on rolling the artery is collapsible and the walls are thin, it is unlikely that your arteries in the body are thickened to give intra-artery problems like narrowing and forming clots, etc. Taking fish oil daily seems to keep your arteries thin and flexible. Also, remember thickened arteries affect more stress on the left ventricle of your heart to cause an increase in blood pressure.

If you feel that the pulse is very slow, very rapid, or any irregularity such as a drop beat, then you need to consult your doctor soon. If there are breathless, tiredness and fainting bouts you need to visit the casualty in the closest well-equipped hospital. The doctors at the casualty will perform a quick EKG examination and check on your chemical troponins normally released when the heart is stressed or damaged.

Your pulse can be running a marathon whilst resting, and its origin could be sudden. In such a situation hold your breath for a short while may give relief. The EKG tracing may diagnose the condition as “Supra-ventricular Tachycardia” The doctors will give you a shot of chemical called ‘adenosine’ to bring your heart rate to normal.

You could try the Valsalva manoeuvre holding the breath does help to reduce the heart rate. You hold the breath whilst mouth closed and bearing down may help as a home remedy. It works by increasing the pressure in the chest cavity which stimulates the vagus nerve (longest nerve in the body) that slows the heart rate.

The ultimate permanent solution for supra-ventricular tachycardia is a procedure known as cardiac ablation.

Ventricular tachycardia
Supraventricular tachycardia starts in the upper chambers (atria) of the heart whilst ventricular tachycardia starts in the main pumping lower chambers of the heart called the ‘ventricles’. This is a dangerous situation as the heart can suddenly stop (cardiac arrest). You need to be rushing to the hospital by well-equipped ambulance with intensive care facilities to handle such as eventualities.

Other causes of irregular heart beat

Atrial fibrillation and flutter
This seems to be the commonest heart irregularity rhythm. It is important to control this irregular rhythm of the upper chambers of the heart as this condition puts you at risk for blood clots and stroke. You may be put on blood thinners to prevent such events.

Premature ventricular contractions
These are very common. They are the skipped heart beats you feel at the wrist. It can be caused by too much-consuming beverages containing caffeine, smoking, and electrolyte imbalance in the body or early heart disease. If you experience more frequent dropped (skipped) beats you need to see your doctor, soon.

Hyperthyroid state
Quite an early symptom of an overactive thyroid gland in the lower part of your neck sitting on the windpipe could be an increased pulse rate. You may experience, sweating, wasting of muscles, and a sweaty skin. See you doctor and he will do a thyroid function test on a sample of blood.

All bacterial infections cause an increase in heart rate, due to the toxaemia it causes, whilst viral conditions the pulse get slower with high temperature.
This is a very important clinical finding, because people panic when they get fever and headache in Sri Lanka, presently due to the Dengue epidemic, rush to the hospitals to get the dengue antigen blood test.

If people are educated through the mass media and TV channels not to panic if you are subjected to headaches, high fever and a rapid pulse. That is not Dengue- positive about that.

Bradycardia-lowering of heart rate
If you feel fatigue, dizziness, light-heartedness, breathless with a slower pulse rate (less than 60 rpm in non-athletic subjects, could be a problem, too. Causes are: Heart tissue damage related to aging: Damage to heart tissues from heart disease or heart attack: Heart disorder present at birth (congenital heart defect): Infection of heart tissue (myocarditis): A complication of heart surgery

Underactive thyroid gland (hypothyroidism): Imbalance of chemicals in the blood, such as potassium or calcium: Repeated disruption of breathing during sleep (obstructive sleep apnea): Inflammatory diseases, such as rheumatic fever or lupus

Medications, including some drugs for other heart rhythm disorders, high blood pressure, and psychosis

Heart block (atrioventricular block)
This is a situation where the electrical signals originating in upper chambers is blocked reaching the lower chambers, thus slowing the conduction.
In all situations of suddenly reduced pulse rate, you need to see your doctor as complications such as fainting spells and sudden cardiac arrest can occur.

Conclusions: If you consider yourself a healthy person you need to check your pulse frequently and if there is any abnormality please do not ignore, consult your doctor.
When you check your blood pressure keep a record of your pulse, too. This is very important for future guidance.

Hope this article will benefit you to influence your good health.

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