Heartbeat

Our heart starts beating soon after we are conceived (long before we are born) and continues uninterrupted until we die.

The heart is a hollow organ with 4 chambers, 2 atria and 2 ventricles. The walls of these chambers are made of muscle. It is the contraction of this muscle which constitutes a heart ‘beat’. The electrical impulse that initiates each heart beat starts in the sinus node, located in the right atrium (the upper right heart chamber). This electrical current spreads to the top chambers (atria) of the heart, then to the lower chambers (ventricles), causing the muscles to contract and blood to be pumped.

While the heart has it's own natural pacemaker (the sinus node), the rate at which it fires is influenced by nerves from the brain, and hormones such as adrenaline in the bloodstream.

Pulse rate

The rate at which the heart beats, known as the pulse rate, can vary considerably. A resting heart rate between 60 and 100 beats per minute is normal for adults. (Children's hearts beat faster than than those of adults). Generally speaking, the more efficient the heart, the lower the resting heart rate. Athletes can have resting heart rates around 40 beats per minute. People taking medicines such as beta-blockers or some types of calcium channel blockers, may have pulse rates lower than 60 beats per minute. A faster than normal heart rate is known as tachycardia and a lower than normal heart rate is called bradycardia.

Factors that can influence the pulse rate are:

  • Air temperature: when it's warm or humid, pulse rate can increase by 5-10 beats/minute.
  • Medicines: e.g. beta-blockers, thyroid medicines, pseudoephedrine (found in many cough and cold preparations);
  • Exercise;
  • Emotions, such as stress, anxiety, extreme happiness or sadness;
  • Stimulants, such as caffeine, amphetamine-like drugs and cocaine;
  • Alcohol.

Just as important as the rate of the heartbeat is its rhythm. Usually this is very regular, rather like the ticking of a clock, with the same time between beats.

Palpitations

Sometimes the heart rhythm is disturbed and becomes irregular. When this happens the affected person may suddenly be aware of their heart beating, something commonly referred to as palpitations.

In most instances palpitations are not serious and do not mean there is anything seriously wrong with the heart. We have all experienced the sensation of our hearts suddenly beating rapidly when we get an unexpected shock.

Noticing heart palpitations can be a frightening experience. If it's very brief and once in a blue moon it can be ignored. But if it happens frequently, or is accompanied by symptoms such as lightheadedness, faintness, breathlessness or chest pain, visit your doctor to have it checked out.

Extra beats (ectopic beats)

Sometimes, for no apparent reason, the heart gives an ‘extra’ beat which may be noticed. This is called an ectopic beat and, unless it happens often, is usually harmless. It is sometimes due to too much caffeine or alcohol. Ectopic beats are quite common.

Arrhythmias

Arrhythmias are an abnormal heart rate which may also be accompanied by an abnormal rhythm. There are various types, some are intermittent and some are continuous.

Atrial fibrillation

Atrial fibrillation (AF) is one type of arrhythmia. Many older people have this arrhythmia. In atrial fibrillation, the heartbeat is 'irregularly irregular'. In other words there is no pattern and when the pulse is felt it seems quite chaotic with beats happening willy nilly and can be very fast. People with AF usually feel pretty well but they are at risk of blood clots forming inside the heart's chambers, leading to stroke. For this reason it is often necessary to take the anti-clotting drug warfarin on a permanent basis.

When to see the doctor

Your pulse is an indicator of your health, so any changes or irregularities should be investigated by your doctor. Sometimes, they can be a sign of problems with the heart. A wide variety of things can be to blame, many of which are harmless or easily treated.

Palpitations are a particular concern if the associated change in heart rate or rhythm means the heart is not pumping enough blood to keep the rest of the body, particularly the brain, functioning normally. This can result in light-headedness, faintness or blackout.

See your doctor if:

  • You have recurring bouts of an irregular heartbeat, such as frequent bursts of feeling a rapid heart rate for no reason;
  • Your resting heart rate is consistently above 100 beats per minute or below 60 beats per minute, especially if you have dizziness, shortness or breath, or feel faint.

One of the frustrations for people with heart irregularities is that they always seem to go away when you visit the doctor. A good idea is to try to keep a record of the attacks. This can often be done by recording the rate and pattern of your pulse. To feel your pulse, press the first 2 fingers of one hand on the opposite wrist just below the skin crease under the base of the thumb.

If you can ‘tap out’ the abnormal rhythm when you go to see your doctor it can be a great help. However, this is often difficult, and investigations such as plain ECG and wearing a portable monitor that records your pulse for 24 hours or more are often necessary to determine the nature of the irregularity. Some of these include an event monitor, so you can press a button when you have the symptom and your doctor can see if it correlates with an abnormality of heart rhythm.

References

1. Mayo Clinic. Heart rate: what’s normal? Reviewed Sept 2012. http://www.mayoclinic.com/health/heart-rate/AN01906 (accessed Aug 2013).
2. Mayo Clinic. Tachycardia. Reviewed May 2011. http://www.mayoclinic.com/health/tachycardia/DS00929/DSECTION=symptoms (accessed Aug 2013).
3. American Heart Association. All about heart rate (pulse). Updated Oct 2012. http://www.heart.org/HEARTORG/Conditions/More/MyHeartandStrokeNews/All-About-Heart-Rate-Pulse_UCM_438850_Article.jsp (accessed Aug 2013).
4. Patient.co.uk. Arrhythmias (abnormal heart rhythms). Last checked Sept 2011. http://www.patient.co.uk/health/arrhythmias-abnormal-heart-rhythms (accessed Aug 2013).
5. Patient.co.uk. Palpitations. Last checked Nov 2012. http://www.patient.co.uk/health/palpitations (accessed Sept 2013).
6. British Heart Foundation. Abnormal heart rhythms. http://www.bhf.org.uk/heart-health/conditions/abnormal-heart-rhythms.aspx (accessed Sept 2013).
7. Merck Manual Home Health Handbook. Overview of abnormal heart rhythms. Last review Nov 2012. http://www.merckmanuals.com/home/heart_and_blood_vessel_disorders/abnormal_heart_rhythms/overview_of_abnormal_heart_rhythms.html#top (accessed Sept 2013).
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