3-8. OTHER AGENTS USED IN CONGESTIVE HEART FAILURE
a. Beta Adrenergic Blocking Agents. The stimulation of beta-1 receptors in
cardiac tissue causes an increased heart rate often causing an increase in workload of
the heart. As heart failure worsens, the body compensates by stimulating beta
receptors to make the heart pump faster and faster. Consequently, the faster the heart
pumps, the less time the ventricles have to fill and pump efficiently. Beta adrenergic
blocking agents work by blocking this stimulation and allowing less work by the heart by
decreasing the heart rate. Doses are initiated very low and titrated very slowly (over
weeks to months). Large initial doses of beta blockers will actually worsen and produce
heart failure. The most common agents used in the treatment of heart failure include
carvedilol (Coreg) and metoprolol (Lopressor).
b. Spironolactone (Aldactone). Spironolactone is a potassium sparing
diuretic that works by inhibiting aldosterone and causing diuresis. It is useful in the
treatment of edema common in CHF patients.
c. Amiodarone (Cordarone). Amiodarone is an agent used in the treatment
of atrial and ventricular arrhythmias. However, when used in patients who have CHF
and arrhythmias, it has been shown to improve exercise tolerance, decrease
hospitalizations, and improve pump function.
Section II. THE ANTIARRHYTHMIC AGENTS
3-9. REVIEW OF CARDIAC ARRHYTHMIAS
Disorders of impulse information, impulse conduction, or a combination of these
factors produces cardiac arrhythmias (or abnormal heartbeats). These are two types of
arrhythmias that we will consider: flutter and fibrillation.
a. Flutter. Flutter is a very rapid heart rate with rhythm present. Usually the
heart rate is much faster in flutter than it is in simple tachycardia. In flutter, the heart
can beat from 200 to 400 beats per minute.
b. Fibrillation. Fibrillation occurs when there is a very rapid heart beat with no
3-10. THE USE OF ANTIARRHYTHMIC DRUGS
The term antiarrhythmic drugs refer to the agents that suppress abnormal beats or
restore normal cardiac rhythm by depressing various properties of the myocardium
(heart muscle). This is a general mechanism of action for all these drugs. The toxicity
of the drugs will be discussed with each individual drug since it varies with each agent.