Tachycardia (increased heart rate)
“Tachycardia” refers to a significant increase of the age-appropriate heart rate. This can be harmless or dangerous, depending on the situation. Persistent Tachycardia or Tachycardia coupled with symptoms like dizziness, fainting or weakness should be medically evaluated.
Cause
The cause of tachycardia may lie within the conduction system of the heart itself or outside of it. For instance, cells in the sinus node (in the right atrium) which normally act as pacemakers can sometimes initiate a faster rhythm. The cause of this is currently unknown. This phenomenon is called sinus tachycardia. If the conduction of electric impulses that normally runs from the sinus node through the atria and the AV node before entering the ventricles is somehow disrupted (e.g. by a so-called atrioventricular block), it is possible that other groups of cells begin to act as pacemakers. Depending on their location, the resulting tachycardia is labelled “supraventricular” or “ventricular”.
Exogenous causes for tachycardia include foods and beverages containing e.g. caffeine, illegal drugs like amphetamines or cocaine, but also medication like beta-mimetics (which are contained in many asthma inhalers), theophylline, nitrates or calcium antagonists. Some foods like nutmeg contain essential oils like myristicine and elemicine which can also cause tachycardia, if consumed in larger quantities.
Tachycardias can be a physiological reaction to sudden decreases in blood pressure. This is called reflex tachycardia. Finally, psychological states such as fear or excitement can cause tachycardias.
Symptoms
Tachycardia can manifest as so-called palpitations (you can feel your heart beat fast). Other possible symptoms include dizziness, shortness of breath, sudden weakness, flutter in the chest, lightheadedness and fainting.
However, the majority of tachycardias occurs more or less without any symptoms and only get diagnosed in the context of routine checkups.
On the other hand, ventricular tachycardias can be an acute danger for the patient and necessitate immediate treatment.
Diagnosis
The normal heart rate in adults lies somewhere between 60 and 100 beats per minute (bpm). It depends on age. Thus, newborns usually have a heart rate of 100 to 150 bpm, which tends to slow down as they grow older. The resting heart rate in older children and adults is usually between 65 and 85 bpm.
The simplest way of evaluating heart rate is pulse palpation. It allows for the evaluation of heart rate and (to some extent) regularity.The most important diagnostic tool after that is ECG. With a standard 12-lead ECG, most tachycardias and arrhythmias can be diagnosed without a doubt. However, this does not yet say much about the cause.If tachycardia appears in episodes and is not present during ECG examination, the method of choice is 24h ECG. For this, the patients receive electrodes on several points of the chest that are connected to a small, portable ECG device. This device continually records electric heart activity and can afterwards be interpreted by the physician.
Treatment Guidelines
In the sign-in area, specialists can find the ESC guidelines for the management of supraventricular tachycardias at:
https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
The guidelines for the management of ventricular tachycardia can be found here:
https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death