A healthy heart beats at a rate of 60 to 100 times per minute. It may beat faster under some conditions — such as exercise, fear, stress, anxiety or fever — but that’s normal. When your heartbeat speeds up for no apparent reason, however, that may be a sign of an abnormally rapid heartbeat — a condition called tachycardia (tachy means fast; cardia refers to the heart). Tachycardia can cause the heart to beat faster than 100 beats per minute, in some cases racing up to 400 beats per minute.
Most Dangerous Rapid Heart Rhythms
Sudden rapid heartbeats originating in the ventricles are the most dangerous arrhythmias. Ventricular tachycardia, a rapid yet steady beat is dangerous in its own right. Worse, it can turn into ventricular fibrillation, or VF, which is characterized by irregular and chaotic rapid heartbeats. Because the fibrillating ventricular muscle cannot contract and pump blood to the brain and vital organs, VF is the number one cause of sudden cardiac death. Without immediate emergency treatment of an electric shock to restore normal rhythm, an individual loses consciousness within seconds and dies within minutes.
Types of Arrhythmias
Understanding some common terms in the language of cardiac arrhythmias helps sort through the types of rhythm problems. An arrhythmia is any abnormality in heart rhythm. Arrhythmias are categorized in three main ways:
Rate If the heart rate is rapid, or greater than 100 beats a minute, it is considered a tachycardia. Alternatively, a slow heart rate, below 60 beats a minute, is known as a bradycardia.
The location of the problematic electrical circuit helps define the arrhythmia. For instance a rhythm is called supraventricular if it originates above the ventricles (lower chambers). So, the problem is most likely in the upper chambers (atria). It follows that a ventricular arrhythmia is the result of a problem in the lower chambers (ventricles).
The nature of the heartbeat, whether it is steady or chaotic, is another key to categorizing an arrhythmia. A rapid beat that is irregular and chaotic may be a type of fibrillation, or quivering beat.
Types and Causes of Rapid Heartbeat
Tachycardia usually is caused by a problem with the electrical system that flows from the upper to the lower chambers of the heart and triggers the heartbeat.
Supraventricular tachycardia (SVT) – This type of tachycardia originates in the upper chambers (the name supraventricular means above the ventricles). In most cases, SVT is not dangerous; however, if episodes happen frequently, the heart muscle can be weakened over time.
Ventricular tachycardia (VT) – This more dangerous type of tachycardia starts in the lower chambers, or ventricles. VT can be life threatening. Without treatment, ventricular tachycardia can lead to ventricular fibrillation, a severely irregular, rapid and ineffective beating of the ventricles that is the most common cause of cardiac arrest.
Symptoms of Rapid Heartbeat
Some people with tachycardia feel no symptoms. Others experience one or more of these common symptoms:
Shortness of breath
Dizziness or lightheadedness
Changes in vision
Fainting or feeling faint
If you experience a rapid heart rate, get it checked out by a medical professional as soon as possible. If you have serious symptoms, such as fainting or chest pain, call 9-1-1 immediately for emergency medical attention.
Diagnosis and Treatment
To help determine the type of tachycardia and the most appropriate treatment, a heart rhythm specialist will ask about the symptoms and patterns of your rapid heartbeat, including:
The rhythm pattern — regular or irregular
Patterns of onset (such as food or activity triggers)
Whether it starts and stops suddenly or gradually
What makes it stop, if anything
Length of a typical episode
What it feels like (racing, fluttering, pounding, etc.)
To confirm the diagnosis, you may need other heart tests, such as:
An electrocardiogram (EKG or ECG)
A long-term recording of your heart rhythms (Holter monitor)
An electrophysiology (EP) study
Treatment options for SVT may include medications or catheter ablation procedures.
For VT, ablation may be coupled with an ICD (implantable cardioverter defibrillator). Ablation may reduce the frequency of VT episodes, minimizing the number of shocks the ICD may need to deliver to the heart.