finally, ectopic beats (beats located away from the normal position) could be a sign of
electric instability of the ventricles. Such heartbeats are an important sign since they
may indicate that more serious dysrhythmias such as ventricular tachycardia or
ventricular fibrillation may develop.
Section II. ELECTROPHYSIOLOGY
a. Heart Cells. Two types of cells are found in the heart: electrical cells and
mechanical cells. The heart's conduction system is mare-up of electrical cells. These
cells have the ability to begin and transmit electrical activity in the heart. Myocardial
cells (the mechanical cells) make up the bulk musculature of the heart. When an
electrical stimuli reaches these cells, the cells contract. An electrical impulse stimulates
the mechanical action of the heart causing the heart to pump effectively. If the electrical
system of the heart does not function properly, arrhythmias (a mechanical activity) may
Figure 2-1. Electrical cells and mechanical cells.