Bradycardia = slow heart rate Tachycardia = fast heart rate Fibrillation = fast, uncoordinated beats — a quivering
Some common arrhythmias include:
Supraventricular tachycardia is a burst of
rapid heartbeats that originates in your heart's upper chambers. The bursts
usually begin and end suddenly. Episodes can last seconds to days.
Atrial flutter is when the heart's upper
chambers flutter, beating rapidly. Atrial flutter is often associated with damage
to the heart caused by a faulty heart valve.
Atrial fibrillation is a very common arrhythmia, affecting mainly older people.
In atrial fibrillation, the heart's upper chambers beat very fast (300 to 600
beats a minute) and chaotically. The ventricles also speed up, resulting in
an irregular and often rapid heart rhythm.
Wolff-Parkinson-White syndrome, named after
the physicians who first described it, is caused by an extra electrical pathway
that develops between the heart's upper and lower chambers. This extra pathway
allows too many electrical impulses to reach the ventricles, speeding up the
Ventricular tachycardia is when faulty electrical
signals that arise from your heart's lower chambers cause your ventricles to
beat too fast. Ventricular tachycardia is almost always associated with heart
disease or recent heart attack and can deteriorate to the most serious form
of fast heartbeat — ventricular fibrillation.
Ventricular fibrillation is considered a
medical emergency. Chaotic electrical signals through your heart's lower chambers
cause your heart to suddenly quiver uselessly and cease pumping. Most people
lose consciousness seconds later and require some type of immediate emergency
medical assistance, such as CPR. Unless the heart is shocked back into a normal
rhythm by a device called a defibrillator, ventricular fibrillation results
in sudden death.
Long QT syndrome is an inherited arrhythmia,
involving a defect in the ventricles. QT refers to a pattern seen on an electrocardiogram
— a test that measures the electrical impulses of the heart. These impulses,
read from electrodes attached to the chest, are recorded as waves. The different
peaks and valleys of these waves are designated by letters — P, Q, R,
S and T. The Q-to-T interval represents the firing and resting of the ventricles
during each heartbeat. Doctors measure this interval and can tell if a QT interval
takes a normal amount of time or takes too long and results in rapid heartbeats.
Sick sinus syndrome is when the heart's sinus
node isn't firing right, your heart rate slows down or slows down and then speeds
up. Sick sinus syndrome, which is common in older people, is considered a type
of bradycardia. This arrhythmia sometimes accompanies atrial fibrillation.
Heart block occurs when the electrical pathways
that run between your heart's upper and lower chambers and through your heart's
lower chambers become blocked, slowing the transmission of electrical impulses
through the heart. The result is a very slow heart rate (bradycardia).
Premature beats are the most common arrhythmia,
premature beats—which affect a large number of people, especially older
Americans—are benign and are often described as "flip-flops."
Caffeine and stress increase the occurrence of premature beats.