Palpitation is a subjectively unpleasant feeling caused by irregular or accelerated heartbeat. It is a very common problem and almost everyone has experienced it. The good news is that vast majority of palpitations means nothing serious. Occasional irregularity in heart rhythm is normal and sometimes it may be perceived as unpleasant pounding sensation. Despite that, it is good not to underestimate patients’ complaints and, especially by the elderly, at least check their pulse or do a simple ECG examination.
For better understanding of the following text we should know more about heart conduction of electrical impulses. Electrical impulses cause contractions of heart muscle. In normal conditions these impulses arise in regular frequency in one particular location in the right heart atrium. This location is referred to as sinoatrial node (SA node). Out of here, the signal spreads across atrial musculature. Transmitting of the signal into heart ventricles is possible only through a single place called atrioventricular node (AV node). Except for atrioventricular node, heart atria and ventricles are electrically isolated. Proper impulse spread is as follows: SA node => atrial musculature => AV node => ventricular musculature. In this case we talk about a normal sinus heart rhythm. Let just add that almost every part of myocardium has the ability to emit electric signals. When there is a problem in sinus node, other muscle cells of heart atria can retake its function and start to emit the signal. Even ventricular muscle cells are able to do so, but these are unable to reach higher frequency.
The causes of palpitations are numerous and most of them are completely harmless. I divided them into three basic groups according to ECG findings. There are, of course, even other possibilities of dividing them.
I. Accelerated, but otherwise normal heartbeat
Heart rate is quicker than usual, but ECG shows us normal ECG rhythm. Electrical conduction in heart works correctly. Accelerated heart beat is in this case mostly a response to a outer or inner stress situation. We mark this situation as sinus tachycardia.
Particularly neurasthenic young girls may feel palpitations caused by stress, excitement and so on. The ECG usually shows only normal, but accelerated heart beat. The condition improves by itself or after administering some tranquilizers.
Physical exertion is associated with heart palpitations. It is a natural reaction; the heart beats faster to supply working muscles with more oxygen.
When level of glucose in blood goes down, defense mechanisms are activated including heart rate acceleration. Hypoglycemic state affects mainly people with diabetes who use insulin or oral anti-diabetic medication.
Lack of hemoglobin causes decreased ability of blood to transport oxygen. The heart responds by accelerating contractions to increase oxygen transport.
Overproduction of thyroid hormone is associated with increased heart rate and unpleasant palpitations. In addition, symptoms occur like heat intolerance, sweating, weight loss, increased appetite, etc. The ECG shows a normal accelerated heart rate and in blood tests we can discover increased thyroid hormones levels.
Note: Increased concentration of thyroid hormones can also cause heart rhythm disorder known as atrial fibrillation (more in part III).
Some medications can accelerate heart rate, for example some drugs used to dilate bronchi and some antidepressants.
Extrasystoles are electric impulses in heart that occur in addition to otherwise normal and regular rhythm. We can also describe them as “premature contractions”. Such extrasystole can emerge in any part of atrium or in a ventricle. ECG detects them quite easily and usually allows distinguishing atrial and ventricular extrasystoles. Extrasystoles are from time to time quite normal and for most people they are asymptomatic. Some people, however, perceive these premature contractions unpleasantly as strong or irregular beats. As a treatment, drugs from group of so-called beta-blockers are administered to stabilize and gently slow the heart rate leading to relief.
III. Arrhythmias associated with accelerated heartbeat
ECG changes include accelerated rhythm associated with arrhythmia presence. Arrhythmias are typical by abnormal heart electric signal emission or conduction.
This includes the entire group of rhythm disorders that are associated with accelerated heartbeat. Compared to sinus tachycardia (see above I) these arrhythmias usually emerge suddenly and often without a visible causative factor. The issue of these disorders is very complex and will not be further deepened in this article. Let’s just mention one important example, so-called atrial fibrillation. Atrial fibrillation is one of the most common arrhythmias. It is caused by chaotic electric impulse spread in atrium leading to irregular heartbeat and tachycardia or bradycardia. It is easily diagnosed by ECG. Causative factors of atrial fibrillation are numerous (low oxygen supply to the heart, heart failure, valvular heart disease, overactive thyroid gland, etc.). Although atrial fibrillation is not a life threatening condition, it may cause serious complications when untreated (see related article).
These are lethal arrhythmias where the electric impulse arises in muscle cells of heart ventricles. This pathology causes extremely quick ventricle contractions. Ventricular tachycardia can cause palpitations, but usually it leads to unconsciousness. Ventricular tachycardia can return back to normal rhythm, but in some cases it changes into fatal arrhythmia known as ventricular fibrillation. Electric defibrillation is in such case the only way how to save affected person’s life.
We shall begin with medical history and physical exam with measuring pulse. ECG is the essential diagnostic method that can show us the majority of pathological conditions causing palpitations. When a person suffers palpitations, it is advisable to check thyroid hormones blood levels as thyroid disorders are very common. If ECG is normal and patient complains about only sporadic palpitations, it is wise to provide long-term Holter monitor.