g. Cardiac Arrest. A cardiac arrest is simply the sudden cessation (stoppage)
of the heartbeat. The cause of the stoppage may or may not be known. Treatment of
the cardiac arrest is dependent upon the cause of the arrest.
h. Rheumatic Fever. Rheumatic fever is a streptococcal infection which many
times attacks the valves of the heart. The result is a deformed or weakened valve that
results in a heart murmur.
i. Endocarditis. Endocarditis is an inflammation of the membrane that lines
the heart. Bacteria that repeatedly enter the bloodstream usually cause endocarditis.
The bacteria which causes the endocarditis may enter the bloodstream following a tooth
extraction and, on occasion, is associated with unsanitary intravenous injection
techniques. Diagnosis of endocarditis usually involves the presence of a low fever and
a soft, muffled heart murmur. The valves of the heart are also affected and if not
detected and treated early endocarditis may cause irreversible damage. The treatment
of endocarditis usually centers on bed rest and long term (4-6 weeks) antibiotic therapy.
j. Heart Block. A heart block is defined as a condition in which the cardiac
excitation is slowed or interrupted somewhere in the normal pathway where conduction
takes place. The two primary types of heart block usually seen are the SA or sinoatrial
block and the atrioventricular or AV block. The term "heart block" is somewhat
ambiguous. Usually the block only occurs occasionally and the result is manifested in
only a skipped beat. Generally, the SA block requires no treatment; however, the
prognosis is dependent on the cause and frequency of the block. During the AV block
several or all impulses from the SA node are delayed or blocked in the AV node or
bundle. Obviously, this type of block is much more serious than the SA block.
Treatment of AV block depends upon the cause and the severity of the block. Digitalis
toxicity may cause AV block on occasion.
CARDIOVASCULAR CIRCULATORY PATTERNS
See Figure 2-4 for an illustration depicting cardiovascular circulatory patterns.
a. General. The human cardiovascular system is described as a closed, two-
(1) It is closed because at no place is the blood as whole blood ever
outside the system.
(2) It is two-cycle because the blood passes through the heart twice with
each complete circuit of the body. In the pulmonary cycle, the blood passes from the
right heart, through the lungs, and to the left heart. In the systemic cycle, the blood
passes from the left heart, through the body in general, and returns to the right heart.
(3) It is common for an area of the body to be supplied by more than one
blood vessel, so that if one is damaged, the others will continue the supply. This is