What is Tachycardia?
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 certain point, acceleration 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 may occur 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 has serious health consequences and is linked to a high risk of stroke. If the atrial tachycardia is still rhythmic, it is called 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.
Numerous diseases of the heart may 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)
In addition, some medication, toxins and other diseases like hyperthyroidism may trigger tachycardia.
Those at particularly high risk for tachycardia include:
- Individuals over 60 years old
- People with undiagnosed heart diseases, particularly heart muscle diseases
- People with an overall unhealthy lifestyle: too much stress, smoking, heavy drinking, overweight, lack of exercise
People who have already survived an episode of ventricular fibrillation are at the highest risk of recurrent ventricular fibrillation. Without adequate treatment, about 40 percent of these patients suffer from ventricular fibrillation again within two years after their first episode.1
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.
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 or EKG) will then be conducted to graph your heart´s electric activity. Sometimes, the EKG alone points to the underlying cause of the tachycardia.
For 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 EKG. 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.
1 John et al. Cardiac Arrhythmia 3 Ventricular arrhythmias and sudden cardiac death. Lancet 2012; 380: 1520–29