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P A R T 8
Drugs acting on the cardiovascular system
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Calcium channel blockers block muscle contraction
in smooth muscle and decrease the heart’s workload,
relax vasospasm in variant angina and possibly block
the proliferation of the damaged endothelium in
coronary vessels.
■■
Individuals on calcium channel blockers need to be
monitored for signs of decreased cardiac output and
response, including slow heart rate, hypotension,
dizziness and headache.
■■
The potassium channel opener, nicorandil, promotes
arterial dilation and vascular smooth muscle
relaxation, reducing both preload and afterload.
KEY POINTS
CHAPTER SUMMARY
■■
CAD, a leading cause of death in Australia and
New Zealand and most Western nations, develops
when changes in the intima of coronary vessels
lead to the development of atheromas or fatty
tumours, accumulation of platelets and debris, and a
thickening of arterial muscles, resulting in a loss of
elasticity and responsiveness to normal stimuli.
■■
Narrowing of the coronary arteries secondary to the
atheroma buildup is called atherosclerosis.
■■
Narrowed coronary arteries eventually become
unable to deliver all the blood that is needed by the
myocardial cells, causing a problem of supply and
demand.
■■
Angina pectoris, or “suffocation of the chest”, occurs
when the myocardial demand for oxygen cannot
be met by the narrowed vessels. Pain, anxiety and
fatigue develop when the supply-and-demand ratio is
upset. Types of angina include stable, unstable and
variant angina.
■■
MI occurs when a coronary vessel is completely
occluded and the cells that depend on that vessel for
oxygen become ischaemic, then necrotic and die.
■■
Angina can be treated by drugs that either increase
the supply of oxygen or decrease the heart’s
workload, which decreases the demand for oxygen.
■■
Nitrates and beta-blockers are used to cause
vasodilation and to decrease venous return and
arterial resistance—effects that decrease cardiac
workload and oxygen consumption.
■■
Glyceryl trinitrate is the drug of choice for treating
an acute anginal attack. It is available in various
forms.
■■
Beta-blockers prevent the activation of sympathetic
receptors, which would normally increase heart
rate, increase blood pressure and increase cardiac
contraction. All of these actions would increase the
demand for oxygen; blocking these actions decreases
the demand for oxygen.
■■
Calcium channel blockers block muscle contraction
in smooth muscle and decrease the heart’s workload,
relax vasospasm in variant angina and possibly block
the proliferation of the damaged endothelium in
coronary vessels.
■■
The potassium channel opener, nicorandil, promotes
arterial dilation and vascular smooth muscle
relaxation, reducing both preload and afterload.
meals
to alleviate GI upset
; environmental
controls, such as limiting light, maintaining
temperature and avoiding excessive noise and
interruptions,
which could aggravate stress and
increase myocardial demand
; and taking safety
precautions, such as providing periodic rests and
assisting with ambulation if dizziness occurs,
to
prevent injury.
■
■
Offer support and encouragement
to help the
person deal with the diagnosis and the drug
regimen.
■
■
Provide thorough teaching, including the name of
the drug and dosage prescribed; measures to avoid
adverse effects and prevent anginal attacks; actions
to take when an attack occurs; warning signs
of problems, and signs and symptoms to report
immediately; and the need for periodic monitoring
and evaluation
to enhance knowledge about drug
therapy and to promote compliance.
Evaluation
■
■
Monitor response to the drug (alleviation of signs
and symptoms of angina, prevention of angina).
■
■
Monitor for adverse effects (hypotension, cardiac
arrhythmias, GI upset, skin reactions, headache).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
■
■
Evaluate the effectiveness of the teaching
plan (person can name drug, dosage, proper
administration, adverse effects to watch for,
specific measures to avoid them and the importance
of continued follow-up).
