Common Characteristics of Cardiac Arrhythmias
Under normal, healthy conditions the human heart beats 60 to 100 times a minute. In the course
of a day, the heart pumps an equivalent of 2,000 gallons of blood, carrying essential oxygen and
other nutrients to all of the body's cells. Ultimately, the brain coordinates this complex process,
but the heart also has its own semi-independent power station. Most of this electrical activity
is carried out by pacemaker cells located in the upper right-hand portion of the heart muscle
known as the sinus node. From the sinus node, beat impulses are relayed to other areas of the heart
via special groups of interlocking relay cells.
To have a properly functioning heart, all four of the heart's chambers must receive the beat signal
in the proper sequence. The chambers are divided into the right atrium and ventricle and the left
atrium and ventricle. The pair on the right side of the heart pumps oxygen-depleted blood coming back
from the rest of the body into the lungs for fresh oxygen. The pair on the left side moves freshly
oxygenated blood returning from the lungs to the many organs of the body.
Many factors affect the heart rate, or the number of heartbeats per minute. The rate goes up when we
exercise or are emotionally aroused, and goes down when we rest or sleep. Irregularities, however, also
can originate within the heart itself. This type of disturbance is known as an arrhythmia, and it can
not only affect the rate at which the heart beats but also its pattern of beating.
Most people experience skipped beats or minor palpitations from time to time; these generally are of
no medical significance. Other types of arrhythmias, however, are potentially quite serious.
