a decrease in calcium levels may cause cardiac flaccidity. It should be noted that
calcium level alterations rarely reach the point where these effects can be seen.
c. Sodium. Sodium is another essential electrolyte involved in cardiac
function. However, sodium imbalances are usually manifested in some of the other
systems before cardiac problems arise. If sodium levels are increased above normal
depressed cardiac function occurs. Sodium levels are of concern in congestive heart
failure because of the edema that can certainly aggravate congestive heart failure.
Persons having congestive heart failure must carefully monitor their sodium intake in
that too much sodium can cause an excessive fluid accumulation in the tissues. This
fluid accumulation causes the heart to work harder in order to compensate for the water.
d. Magnesium. Magnesium is an essential electrolyte involved as a cofactor
in many enzyme systems. It is also closely linked to regulating intracellular potassium
and calcium content. High magnesium levels may affect heart rate, cardiac conduction,
and blood pressure. Hypotension, vasodilation, bradycardia, heart block, and cardiac
arrest can occur with increasing levels. Low magnesium may cause cardiac
arrhythmias and may play an important role in atypical ventricular tachycardia (torsades
de pointes). Attempting to replace potassium is difficult if an existing magnesium or
calcium deficiency is also present.
Cardiac disorders are some of the top killers in the United States. A variety of
medications are used in the treatment of these conditions.
a. Bradycardia. Bradycardia is a slow heart rate. Generally, bradycardia
refers to a heart rate less than 60 beats per minute. This condition is sometimes
referred to as sinus bradycardia because the decrease in heart rate is usually attributed
to a decrease in the activity of the sinoatrial node. An increase in vagal tone is probably
the cause of most cases of bradycardia. In most cases, bradycardia is not serious.
Bradycardia is often observed in sleeping persons and in young athletes. There are no
symptoms of bradycardia unless it is severe. For simple bradycardia, no treatment is
usually needed; however, severe bradycardia may be treated with atropine.
b. Tachycardia. Tachycardia means a rapid heart rate. Generally,
tachycardia refers to a heart rate more than 100 beats per minute. Tachycardia can be
caused by a number of disorders (for example, hyperthyroidism, vagal suppression,
sympathetic nervous system stimulation, emotional responses, and exercise). The
usual treatment of tachycardia is aimed at removing its cause.
c. Arrhythmia. Arrhythmia is a term that is used to refer to any abnormal
heartbeat (that is, missed beats or extra beats). There are two types of arrhythmias that
will be discussed in this subcourse: flutter and fibrillation.