Download Drugs for Heart Failure

18
Drugs for Heart Failure
1.
2.
3.
Identify the major risk factors that accelerate the progression
to heart failure.
Relate how the classic symptoms associated with heart failure
may be caused by weakened heart muscle.
Identify drug classes that are used for first- and secondchoice pharmacotherapy of heart failure.
4.
5.
Explain several means by which patients may control their
heart failure without drugs.
For each of the classes listed in the Drug Snapshot, identify
representative medications and explain the mechanism of
drug action, primary actions, and important adverse effects.
6.
Categorize heart failure drugs based on their classification
and mechanism of action.
Heart failure is closely associated with disorders such as chronic
hypertension, coronary artery disease and diabetes.
Weakening of the cardiac muscle is a natural consequence of
aging, the process can be accelerated by a number of
disorders that are related to heart failure.
• The inability of the ventricles to pump enough blood to meet the
body’s metabolic demands.
• Treatment goals
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Prevent,
Treat, or
Remove the underlying causes,
Improve quality of life,
Extend life expectancy.
The central cause of heart failure is weakened heart muscle.
Normal Physiology:
 The right side of the heart receives blood from the
venous system and sends it to the lungs
 Blood receives oxygen and looses carbon dioxide
 Blood returns to the left side of the heart and sends
it to the rest of the body
 The amount of blood received by the right side of
the heart should exactly equal that sent out by the
left side of the heart. If this does not occur HF can
occur
• Preload
• Before the chambers of the heart contract (systole), they are filled to their
max capacity with blood.
• The degree to which the heart fibers are stretched just prior to contraction
is preload
• The more they are stretched, the more forcefully they will contract.
• Strength of contraction is called contractility.
• Afterload
• The pressure in the aorta that must be overcome for blood to be ejected
from the left side of the heart and ultimately to the entire body
Signs & Symptoms of Bilateral Failure
Skin cyanotic and
clammy
Anxiety, restlessness
Upright posturing
Persistent cough
Rapid breathing
Tachycardia
Edema of the lower
limbs
• Skin cyanotic and
clammy
• upright posture /
leaning forward /
persistent cough
• rapid breathing
• ALL forms of CHF lead
to decreased oxygen
to the tissues
 Causes decreased blood
to the lungs
 edema of lower limbs
leads to blood backing
up in venous circulation
 fast heart rate
The three primary characteristics of heart function are force of
contraction, heart rate, and speed of impulse conduction.
• Force of Contraction
• Ability to change the force of contractions is the goal of pharacotherapy
• Ability to increase the strength of contraction is called the positive
inotropic effect
• Fundamental characteristic of cardiac glycosides
• Heart Rate
• A faster heart works harder but not necessarily more efficiently
• A slower heart has a longer time to rest between beats, decreasing the
workload on the heart.
• Speed of Impulse Conduction
• Slowing the conduction speed will cause the heart to beat slower,
decreasing the workload of the heart
The specific therapy for heart failure depends on the severity of
the disease.
• Stop using tobacco
• Limit salt (sodium) intake and be sure to eat foods rich in
potassium and magnesium
• Limit alcohol consumption
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Implement a medically supervised exercise plan
Learn and use effective ways to deal with stress
Reduce weight to an optimal level
Limit caffeine consumption
Angiotensin-converting enzyme (ACE) inhibitors are the preferred
drugs for heart failure.
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Affect the renin-angiotensin-aldosterone system
Lower blood pressure
Reduce the workload on the heart
Reduce peripheral edema
• Increase cardiac output.
• Very effective
• Relatively low potential for serious adverse
effects First-choice drugs in the treatment of HF.
• “pril” drugs
• Watch for a dry cough
Diuretics relieve symptoms of heart failure by reducing fluid
overload and decreasing blood pressure.
• Commonly used for the treatment of HF
• Few adverse effects
• Effective at increasing urine flow, lowering
blood volume, and reducing edema and
congestion.
• Reduce fluid overload and lower blood pressure
• The workload on the heart is reduced
• Cardiac output increases
• Usually prescribed in combination with ACE
inhibitors and other HF medications
Cardiac glycosides increase the force of myocardial contraction
and were once the traditional drugs of choice for heart failure.
 Aka: digitalis glycoside
 Primary action of digoxin
 increase in the force of contraction
 positive inotropic effect
 allows the weakened heart to eject more blood per
beat - increasing cardiac output.
• A second important action
• slow electrical conduction through the heart.
• fewer beats per minute.
• Reduced heart rate, combined with more
forceful contractions, allows for much
greater efficiency of the heart.
Cardiac Glycosides
• Adverse Effects
•Margin of safety for toxicity is very small
• narrow “therapeutic window”
•Vomiting / diarrhea
•Extreme bradycardia (can be fatal)
• Pulse rate should be between 60-100 bpm
•Loss of appetite
• Very sensitive to low potassium levels
• low K+ leads to increased dig. toxicity at any concentration
• Serum digoxin levels should be monitored
• When taking furosemide (Lasix), a diuretic, monitor very closely.
Lasix is a K-wasting diuretic. Low levels of K potentiate dig toxicity
• digoxin levels over 1.8ng/ml are toxic
• Arrhythmias/dysrrhythmias
• Green halos around lights
• Confusion-you must know your patients
mental state to be able to recognize
confusion
• Arrhythmias !!! In children is the first sign
of “dig” toxicity
Cardiac Glycosides
• Antidote
• Digoxin immune fab (Ovine (sheep))
• Binds with digoxin preventing it from
reaching tissues
• Onset less than 1 minute
• Given IV
Beta-adrenergic blockers are used in combination with other
drugs to slow the progression of heart failure.
• Block the cardiac actions of the
sympathetic nervous system
• Slowing the heart rate
• Reducing blood pressure
• Workload on the heart is decreased
Vasodilators reduce symptoms of heart failure by decreasing
cardiac workload.
• Two direct-acting vasodilators
• Hydralazine (Apresoline)
• Isosorbide dinitrate (Isordil)
• Act directly on vascular smooth muscle
• Relax blood vessels
• Lower blood pressure.
Phosphodiesterase inhibitors and other miscellaneous drugs are
used for short-term therapy of advanced heart failure.
• Block the enzyme phosphodiesterase in cardiac and smooth
muscle.
• Increases the amount of calcium available for myocardial contraction.
• Two main actions that benefit patients with HF:
• An increased force of contraction (positive inotropic response)
• Vasodilation