A tachycardia is defined as a very fast heartbeat of more than 100 beats per minute. Physical effort, excitement or stress naturally accelerates the heartbeat without any underlying health problem.
Up to a specific point, rise of the heart´s activity increases cardiac output, or the volume of blood pumped by the heart. Beyond this point, however, the heartbeat is too fast to fill the ventricles with enough blood and cardiac output is reduced.
Tachycardia can happen only in the atria (the heart’s upper two chambers) or only in the ventricle (the heart’s lower two chambers).
Atrial tachycardia is not in itself life threatening, but also has serious health consequences and is linked to a high risk of stroke. If the atrial tachycardia is still rhythmic, it is referred to as atrial flutter.
During an atrial fibrillation, the activity of the heart muscle cells is arrhythmic and chaotic. During a ventricular tachyarrhythmia, better known as ventricular fibrillation, the heart chambers can no longer contract.
They lose their ability to pump blood due to the disorderly and irregular electrical activity in the muscle cells. Ventricular fibrillation causes cardiac arrest within minutes and is one of the most common causes of sudden cardiac death.
What causes tachycardia?
Various diseases of the heart can pathologically accelerate the heart rhythm or cause arrhythmias. These include:
- Diseases of the heart muscle (cardiomyopathy, myocarditis)
- Coronary artery disease
- Heart attack
- Heart failure
- Diseases of the impulse conduction system
- Congenital heart rhythm disorders (e.g. Long QT-Syndrome, WPW, Brugada)
In addition, some medication, toxins and other diseases like hyperthyroidism may trigger tachycardia.
How is tachycardia diagnosed?
To diagnose a tachycardia, the physician has to learn about your medical history. They will ask you under what circumstances the tachycardia and associated symptoms have occurred. He will listen to your heart sounds and measure your pulse. An electrocardiogram (ECG) will graph your heart´s electric activity. Sometimes, the ECG alone points to the underlying cause of the tachycardia.
For an effective long-term therapy, it is crucial that the underlying cause of the disorder is found. To that end, different examinations and tests are necessary.
These examinations may include blood tests, X-ray, ultrasound and/or specific examination of the blood vessel system. Infrequently occurring tachycardia may be detected by a long-term ECG. Besides portable Holter monitors there are devices which can be inserted under the skin.
Insertable heart monitors are very useful for observing the heart’s electric activity over a long period of time, even years.
What are the symptoms of tachycardia?
Inexplicable, self-limiting tachycardia without any further symptoms may be harmless. It is recommended, however, to see a physician for a medical examination because the event may have been caused by a serious underlying health problem and arrhythmias may worsen without adequate treatment.
If the heartbeat is permanently accelerated over 100 beats per minute, you must seek medical advice. You should visit a physician as soon as possible if the arrhythmia is accompanied by symptoms like giddiness, dizziness, shortness of breath, or a light pressure in the breast.
Symptoms like fainting (syncope), breathlessness, cramping or breast pain indicate an emergency requiring immediate medical treatment.