Heart Failure and Antidysrhythmics

Posted by e-Medical PPT Saturday, October 27, 2012
Drug Therapy for Heart Failure
Occurs when heart cannot pump enough blood to meet tissue needs for oxygen and nutrients
May be impaired contraction (systolic dysfunction)
May be impaired relaxation and filling of ventricles (diastolic dysfunction)
May be both

Causes of Heart Failure
Dysfunction of contractile myocardial cells and endothelial cells
Endothelium dysfunction results in build-up of atherosclerotic plaque, growth of cells, inflammation and activation of platelets
Result—CAD, hypertension leading to heart failure

Other Causes of Heart Failure
Hyperthyroidism
Fluid overload
Certain anti-dysrhythmic drugs
Drugs that cause excessive retention of sodium and water

Classification of Heart Failure
Class I—ordinary activity does not cause S/S
Class II—slight limitations, asymptomatic at rest. Activity does result in fatigue, palpitations, dyspnea or anginal pain
Class III-marked limitation of physical activity. Less than ordinary activity causes fatigue, palpitations, dyspnea or angina
Class IV—any physical activity results in discomfort, s/s at rest.

Antidysrhythmics
Used to prevent and manage cardiac dysrhythmias
Dysrhythmias (aka arrhythmias) are abnormalities in heart rate or rhythm
Can interfere with perfusion of body tissues

Cardiac Electrophysiology
Heart has specialized cells with intercalated discs
Electrical activity resides in specialized tissues that can generate and conduct an electrical impulse
Conductivity is much faster in heart tissue
Sequence:  stimulation from impulse, transmission, contraction of atria and ventricles and relaxation of atria and ventricles

Automaticity
Heart’s ability to generate an electrical impulse
Can occur in any part of conduction system
SA node has highest degree of automaticity so highest rate of electrical discharge, thus,  is primary pacemaker
Impulse dependent on sodium and calcium into a myocardial cell and potassium ions moving out of cardiac cells

Cardiac Dysrhythmias
Can originate in any part of conduction system
Result from disturbances in impulse formation or conduction defects
Abnormal impulse formation--Automaticity allows for other than the SA node to depolarize given certain conditions—may be 2ndary to hypoxia, ischemia, lyte imbalance, acid-base disturbances
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