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Chapter 6 Parameter Monitoring
User Manual of Veterinary Monitor --41--
Chapter 6 Parameter Monitoring
6.1 ECG
6.1.1 ECG Measuring Principle
I. Brief Description of ECG
The heart has its own special electrical conduction system. It is situated within heart walls and consists of
specially differentiated myocardial cells. The function is generating and conducting excitations, and
maintaining and governing normal heart rhythms. The cardiac conduction system consists of atrionector,
internodal tracts, atrioventricular bundles, atrioventricular junctions, Kent-His bundles, bundle branches and
Purkinje‘s fibers, as shown in Figure 6.1:
Figure 6.1 Special Cardiac Conduction System Diagram
The myocardium is constituted of innumerable myocardial cells, atrionector generates an excitation, which
conducts toward the atrium and ventricle to cause progressive excitations of the entire heart in accordance
with certain pathways and time interval. The changes of electrical potentials in the direction, pathway,
sequence, and time in the process of excitation of each part of the heart follow a certain rule. Since a animal
body is equivalent to a volume conductor, these electrical changes will eventually spread to the body surface.
Given that a great number of electrical signals are generated by the heart at the same time, they can be
recorded as functions of time through electrodes that are placed on the surface of the chest or limbs, and this
recorded curve is called electrocardiogram (ECG).Electrocardiograph (ECG) is a representation of changes
of bioelectricity in the process of generating, conducting and recovering excitations of the heart. The changes
of bioelectricity of myocardial cells are the source of ECG.
ECG is an abbreviation for electrocardiogram. An normal ECG includes P-waves, QRS complexes and
T-waves. A P-wave is originated from the potential change when the atrium depolarizes before its
contraction. A QRS complex is originated from the potential change when the ventricle depolarizes before its
contraction, and a T-wave is originated from the potential change when the ventricle repolarizes, the
amplitude of T-wave should not be lower than 1/10 of that of R-wave in the same lead, T-wave is abnormal
which means Myocardial ischemia or damage.
Atrionector
Right Atrium
Atrioventricular
Node
Right Bundle
Branch
Right Ventricle
Left Atrium
Kent-His Bundles
Left Bundle Branch
Left Posterior
Muscle Bundle
Left Ventricle
Left Anterior
Muscle Bundle
Purkinje's Fibers