An arrhythmia is a change in the rhythm of your heartbeat. When the heart beats too fast, it's called tachycardia. When it beats too slow, it's called bradycardia. An arrhythmia can also mean that your heart beats irregularly (skips a beat or has an extra beat).

Tachycardia

Tachycardia is an abnormally rapid beating of the heart, defined as a resting heart rate of over 100 beats per minute.

There are three types of tachycardia, each with its own specific symptoms/causes.

Sinus tachycardia

Sinus Tachycardia is due to rapid firing of a the sinoatrial (sinus) node, which is the natural pacemaker of the heart. A person with Sinus Tachycardia will see his or her heart rate increases rapidly with minimal exertion; the rapid heart rate may be accompanied by symptoms of palpitations, fatigue, and exercise intolerance. Sinus Tachycardia is not associated with an abnormal electrical pattern on the electrocardiogram. Anyone can suffer from Sinus Tachycardia, but it is most often seen in young women in their late 20s or early 30s. In addition to the most prominent symptoms of palpitations, fatigue and exercise intolerance, Sinus Tachycardia can also be associated a drop in blood pressure upon standing, blurred vision, dizziness, tingling, shortness of breath, and sweating.

Paroxysmal atrial tachycardia

Like Sinus Tachycardia, Paroxysmal Atrial Tachycardia is symptomized by bouts of rapid, regular heart beating, but in the case of Paroxysmal Atrial Tachycardia (sometimes called PAT), the rapid heart beating originates elsewhere in the atrium, or upper chamber of the heart, rather than in the sinoatrial (sinus) node. Paroxysmal Atrial Tachycardia occurs and ends suddenly. The heart rate is usually between 160 and 200 beats per minute. It can occur without any heart disease being present. It is usually more annoying than dangerous and is caused by a premature atrial beat that sends an impulse along an abnormal electrical path to the ventricles. Other causes stem from anxiety, stimulants, overactive thyroid, and in some women, the onset of menstruation. Other symptoms include lightheadedness, chest pain, palpitations, anxiety, sweating, and shortness of breath.

Ventricular tachycardia

Ventricular tachycardia is an abnormal heart rhythm that is rapid, regular and originates from an area of the ventricle, the lower chamber of the heart. Ventricular tachycardias are most commonly associated with heart attacks or scarring of the heart muscle from previous heart attacks and are life threatening. It can occur in the absence of apparent heart disease, but often develops as an early or a late complication of a heart attack, during the course of a general weakening of the heard (called cardiomyopathy), heart disease affecting the heart valves, an inflammation of the heart muscle, and following heart surgery. Ventricular tachycardia can also result from anti-arrhythmic medications (an undesired effect) or from altered blood chemistries (such as a low potassium level), pH (acid-base) changes, or insufficient oxygenation.

Dangers of tachycardia

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Heart Rhythm Society

Tachycardia is harmful for two reasons. First, when the heart beats too rapidly, it performs inefficiently (since there is not enough time for the ventricles to fill completely), causing blood flow and blood pressure to diminish. Second, it increases the work of the heart, causing it to require more oxygen while also reducing the blood flow to the cardiac muscle tissue, increasing the risk of ischemia and resultant infarction.

Diagnosis

Proper diagnosis is very important, however, since the severity of tachycardia ranges greatly. A careful description of the episode will aid the doctor.

Symptoms include:

Note: Symptoms may start and stop suddenly. In some cases, there are no symptoms.

Diagnosis is not always easy, because the event is usually over by the time the patient sees a doctor.

In addition to the above symptoms, Tachycardia resulting in loss of consciousness may occur. Ventricular tachycardia is a potentially lethal arrhythmia and may result in an absent pulse. If the rapid heart rate is still occurring, an electrocardiograph will show the condition. If the event is over, physicians often recommend a period of ambulatory electrocardiographic monitoring (called Holter monitoring) to confirm the diagnosis. An intracardiac electrophysiology study or blood chemistries and other tests may also be performed.

Treatment

Treatment varies with the symptoms, the situation, and the underlying cardiac disorder. No treatment may be required in cases of non-life threatening tachycardia.

Ventricular tachycardia may become an emergency situation and may be require CPR, electrical defibrillation or cardioversion (electric shock), or intravenous anti-arrhythmic medications.

Non-emergency treatment can take several paths. An electrophysiologist may recommend one of three options: