(7) The refractory period. During this period, cell charges are depolarized
and have not returned to their polarized state. A cell that is electrically "refractory"
cannot receive another impulse until it is repolarized. The refractory period on an EKG
includes the QRS complex and the T wave. The absolute refractory period includes the
QRS and the upslope of the T wave and is NOT a dangerous period. The relative
refractory period may allow depolarization of ventricles. This period occurs on the
downslope of the T wave; it is dangerous if an impulse occurs at this time.
e. Electrocardiogram Uses. The EKG has a variety of uses; for example,
abnormal cardiac rhythms and conduction patterns and following the course of recovery
from a heart attack. Some people carry a Holter monitor to monitor heart electrical
activity. This machine can be carried around by the patient while he goes about his
everyday routines. The Holter monitor is especially useful in detecting rhythm disorders
in the conduction system. It is also useful in correlating rhythm disorders and symptoms
and then following the effectiveness of drugs in dealing with these disorders.
Section III. RHYTHMS/HEART BLOCKS
ANALYSIS OF EKG RHYTHM STRIPS
(1) Determine regularity (also called rhythm) by looking at the R to R interval
(RRI). This interval can be regular or irregular.
(2) The R-R interval is constant for regular rhythm, which means the
distance between the beats, is the same.
Figure 2-7. Regular rhythm.