Tachycardia (fast heart beat)
Overview - When to see a cardiologist - Associated symptoms - Causes - Treatment
Overview
Tachycardia is the medical term for a fast heart beat. The heart rate is strictly controlled by a complex balance of nerves and hormones which respond to the demands of the body. Usually, the heart rate is precisely matched to the needs of the body so that a person at rest will have a low heart rate and a person doing exercise, or recovering from exercise, will have a faster heart rate. However, the systems controlling the heart rate only work when the hormones of the body are in balance, there is enough water in the body (“circulating volume”) and the heart electrics are functioning normally. When any of these systems go wrong, this can cause the heart rate to be higher than normal, and this can be felt as a tachycardia.
When to See a Cardiologist
It is normal to be aware of your heart rate, and for this to be faster than normal during exercise and while recovering from exercise. However, most of us are fairly in tune with what is a “normal” heart rate for us during exertion, and if the rate suddenly changes or recovers differently from usual, this may indicate a new medical problem.
It is important to distinguish whether a tachycardia is caused by the normal heart electrics going faster than usual (“sinus tachycardia”) or by abnormal electrical signals within the heart (“arrhythmia”). A cardiologist can help you tell the difference, either by asking targetted questions or more likely by doing ECG tests to record the heart’s electrical activity during episodes of tachycardia.
Even if it isn’t possible to record an ECG during symptoms (for example if episodes are very short, or happen very infrequently) a cardiologist can do tests to tell if the heart is otherwise normal, and assess how risky the tachycardia is likely to be. This assessment is usually based on the descriptionn of the palpitations - how long, how fast, and whether accompanied by other symptoms - as well as whether the heart shows any other abnormalities.
Associated Symptoms
Some very rapid tachycardias can cause the blood pressure to drop, leading to lightheadedness and sometime even syncope (passing out). This is more likely to happen with tachycardias originating in the lower chambers of the heart (ventricular tachycardia), or any tachycardia that goes above about 180bpm.
Termination of a tachycardia can also cause syncope. This is due to termination pauses, where the sudden drop in heart rate leads to a pause in the heart beat.
Other symptoms that may be associated tachycardia include:
Chest pain (angina) - this is more likely if there is other heart disease present
Breathlessness - particularly at very high heart rates
Lightheadedness (presyncope)
Causes
A fast heart beat can be caused by a wide variety of cardiac diseases, as well as medical conditions outside the heart.
Non-cardiac conditions that can raise the heart rate include:
Anaemia - this common condition occurs when the blood count is lower than usual. Anaemia usually has to be fairly severe to cause tachycardia.
Thyroid disease - overactivity of the thyroid gland (hyperthyroidism) commonly causes tachycardia, which may either be sinus tachycardia or a fast arrhythmia.
Lung disease - long-term lack of oxygen in conditions such as chronic obstructive pulmonary disease (COPD) and other pulmonary diseases can cause a persistently elevated heart rate.
Lack of physical fitness - people who do less cardio exercise tend to have higher resting heart rates than people who are more physically fit. However the difference is usually small and it is rare to notice this as a symptom. Changes in fitness levels, however, may cause changes in resting heart rate over time and this can give rise to notifications and warnings from wearable devices.
Heart conditions that lead to a rise in heart rate, either intermittently or persistently, include:
Inappropriate sinus tachycardia (IST) - this is a condition of cardiovascular autonomic dysfunction where the heart rate is consistently too high, but the heart rhythm is otherwise normal, and there is no other medical condition found to be causing the high heart rate. This is generally a diagnosis of exclusion, i.e. when other possibilities are ruled out, this diagnosis remains as the explanation.
Postural tachycardia syndrome (PoTS) - another form of cardiovascular autonomic dysfunction in which the heart rate rises disproportionately on moving to a standing position, and remains elevated. Management involves retraining the mechanisms that govern heart rate and blood pressure regulation as well as medication to suppress the heart rate rise for some patients.
Supraventricular tachycardia (SVT) - a family of abnormal heart rhythms caused by an extra electrical connection in the heart which, under the right conditions allows the heart to race. Attacks are usually dramatice with a sudden onset and offset.
Wolff-Parkinson-White syndrome (WPW) - this condition is the cause of some supraventricular tachycardias. Unlike most SVT, in WPW, the patient is born with one or more extra electrical connections in the heart and this is usually visible on a straightforward resting ECG. The combination of a characteristic finding on the resting ECG plus a story of palpitations or tachycardia in the past is enough to diagnose WPW.
Atrial fibrillation (AF or AFib) - this condition is the most common heart rhythm abnormality wordwide, affecting 1.5m people in the UK. A further 1.5m may have the condition but be unaware. AF always causes an irregular heart beat and in most sufferers this is felt as tachycardia and palpitations.
Atrial flutter - this condition is a semi-organised form of atrial fibrillation. Whereas AFib causes chaotic electrical activity in the upper chambers of the heart and a chaotic, ireregular heart beat, atrial flutter causes a consistent and regular racing in the upper chamber using the same electrical short circuit around 300 times a minute.
Ventricular tachycardia (VT) - this is a racing rhythm originating in the lower chamber of the heart. VT can be dangerous especially if it is caused by scarring in the heart from heart attacks or ischaemic heart disease.
Treatment
Different causes of tachycardia may have widely varying treatments, and so getting expert advice and the right diagnosis is crucial to making sure the right treatment is offered.
Non-cardiac disease
If tachycardia is found to be due to non-cardiac diseases such as hyperthyroidism, anaemia, or lung disease, it is usual to be referred on to specialists in these conditions.
Sinus tachycardia and autonomic dysfunction
Where the problem is within the heart, but the rhythm is found to be sinus tachycardia, then this may not require much or any treatment. Where treatment is needed, it will usually focus on issues outside the heart such as hydration and blood pressure support.
Other arrhythmias
For electrical problems within the heart causing tachycardia there are nearly always three options:
Lifestyle measures - aimed at reducing the drive for arrhythmias to start. Depending on the precise arrhythmia diagnosis this may include getting blood pressure under control, losing weight or avoiding alcohol and caffeine. Some arrhythmias have very specific triggers for example bending over, or sudden frights or shocks. In which case avoiding these triggers where possible can be really useful way of managing the problem.
Medications - usually with antiarrhythmic drugs to suppress the rhythm abnormality and to promote a normal heart rhythm. Common drugs given for heart rhythm control include beta blockers such as Bisoprolol, calcium channel blockers such as Verapamil, sodium channel blockers such as Flecainide, and multi-active drugs such as Amiodarone or Digoxin.
Ablation procedures - almost all arrhythmias can now be targeted with a surgical approach called ablation. Ablation procedures aim to reduce or even completely cure some arrhythmias. The success rates and safety profiles of ablation procedures vary widely depending on which arrhythmia is being targeted. SVT ablation and flutter ablations for example, completely cure the problem in well over 90% of cases. An AF ablation on the other hand is unlikely to be completely curative but can achieve a great reduction in symptoms, lasting many years.
It is common for a combination of all three approaches to be used. For example to manage atrial fibrillation a cardiologist may recommend weight loss and alcohol reduction, as well as taking a beta blocker or Flecainide daily. If symptoms were still intrusive despite these measures then an AF ablation may be discussed.