drugs for heart failure 18. 1.identify the major risk factors that accelerate the progression to...

Drugs for Heart Failure

18

1. Identify the major risk factors that accelerate the progression to heart failure.

2. Relate how the classic symptoms associated with heart failure may be caused by weakened heart muscle.

3. Identify drug classes that are used for first- and second-choice pharmacotherapy of heart failure.

4. Explain several means by which patients may control their heart failure without drugs.

5. 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• 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

Skin cyanotic and clammyAnxiety, restlessnessUpright posturing Persistent coughRapid breathingTachycardiaEdema of the lower limbs

Signs & Symptoms of Bilateral Failure

• 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

• 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.

• 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 glycosidePrimary action of digoxin

increase in the force of contraction positive inotropic effectallows 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