Computational Intelligence in Cardiology and Heart Disease Diagnosis - Computational Intelligence in Biomedical Engineering - page 155

QRS
complex

R

T

PR
segment

ST
segment

P

Q

PR interval

S

QT interval

FIGURE 4.8
QRS complex showing the sinus rhythm regions.

The main features of the QRS wave that depict important information con-
cerning cardiac health are as follows:

a. P wave

b. QRS complex

c. T wave

d. QRS intervals

4.3.1 P Wave
The initial P wave is caused by electrical activity originating from atrial con-
traction (systole). In CVDs, the P wave can become distorted and appear
abnormal as seen, for example, in Figure 4.9. An inverted P wave caused by
positive voltage changing to negative indicates that polarization direction of
the atria is abnormal (Julian et al., 2005). This means that the origin of the
pacemaker signal is not in the SA node, but could come from elsewhere, such
as the atrium or the AV node. If the P wave has a characteristic broadened or
notched look, this indicates a delay in the depolarization of the left atrium,