Computational Intelligence in Cardiology and Heart Disease Diagnosis - Computational Intelligence in Biomedical Engineering - page 168

(a) (b)

FIGURE 4.19
A Seca ECG trolley shown on the left and in use for patient ECG monitoring
on the right.

heart's natural pacemaker develops an abnormal rate or rhythm, when the
normal impulse conduction pathway is interrupted, or when another part of
the heart tissue takes over as the pacemaker. Many arrhythmias have no
known cause, whereas others (Coast et al., 1990) can develop from problems
in the cardiac pacemaker, in the ectopic pacemaker sites, or through abnor-
mal propagation of pacing impulses in the cardiac conduction system. Several
risk factors have been identified, including coronary artery disease, high blood
pressure, diabetes, smoking, excessive use of alcohol or caffeine, drug abuse,
and stress. Some over-the-counter and prescription medications, dietary sup-
plements, and herbal remedies are also known to cause arrhythmias. Patients
with this disorder show disruptions in the synchronized contraction sequences
of the heart, which result in a reduced pumping e ciency and giving rise to
various types of arrhythmia disorders are depicted in Figure 4.20. Analysis
for arrhythmias can be undertaken using a 12-lead ECG where onset can be
detected, for example, by an early P wave in the ST segment.
The most common forms of arrhythmia are ectopic beats of a ventricular or
atrial origin, where a common characteristic of the disease is the occurrence
of premature beats (Silipo and Marchesi, 1998). Ventricular ectopic beats
(VEBs) exhibit a different waveshape from the normal QRS sinus rhythm