1. Antiarrhythmic Agents: Cardiac Stimulants and Depressants
Chapter 16
Antiarrhythmic Agents: Cardiac Stimulants
and Depressants

2. The Heart
Four-chambered organ located in the upper left thoracic cavity
Purpose
Pumps the blood around the body so that oxygen
and nutrients can be distributed to all areas of the
body
Maintains the blood pressure at an acceptable level
Generates and conducts electrical impulses
Heart rate is controlled by the autonomic nervous
system

3. The Heart Main pacemakers of heart:
Sinoatrial node: bpm; primary pacemaker
Atrioventricular node: Connects atria and ventricles; bpm
Bundle of His and Purkinje fibers: carry electrical impulses from AV node to complete ventricle rate pacing; bpm

4. Cardiac medications
Increase /decrease the force of the myocardial contraction
Increase / decrease the heart rate
Increase / decrease the conduction of electrical impulses through the myocardium

5. Congestive Heart Failure (CHF)
Cardiac glycosides
-Digoxin
-Treat arrhythmias

6. Cardiac Glycosides
Derived from natural sources; treatment for heart failure:
cardiac distention-inability to pump the full blood volume
cardiac hypertrophy-prolonged stretching
sodium and water retention-decreased renal blood flow
Results in weight gain, edema, shortness of breath, and pulmonary congestion

7. Digoxin Decreases electrical conduction Negative Dromatotropic Effect
Increases time spent in diastole
Increases the force of the myocardial contraction
Positive inotropic action
End result: slows and strengthens contractions

8. Digoxin: Dose Considerations
Duration of action
Method of administration
Other
Physical size of the client
Other medications
Renal or hepatic function
Advanced age
Presence of other illnesses

9. Digoxin Low therapeutic index
Toxicity can be life-threatening; occurs in 10-20% of patients
Many drug-drug, drug herbal interactions
Routine monitoring of serum potassium and digoxin levels

10. Digoxin: Adverse Effects
Gastrointestinal effects
Nausea and vomiting
Anorexia
Diarrhea
Cardiac effects
Cardiac arrhythmias
Neurological effects

11. Cardiac Glycoside Toxicity
Predispose to cardiac glycoside toxicity
Hypokalemia
Renal impairment
Rapid IV administration

12. Cardiac Glycoside Toxicity
Treatment
Stop the drug
Physical assessment
Check potassium level
Administer if needed
Monitor heart rate
Administer antiarrhythmics

13. Nursing Considerations
Apical pulse for 1 minute. Hold if HR < 60 bpm
Report changes in heart rhythm
Assess for symptoms of toxicity
Monitor digoxin blood levels
Monitor for drug-drug and drug-herbal interactions
Educate : signs of toxicity and how to monitor pulse rate .

14. Antiarrhythmic and Antidysrhythmic Drugs
Grouped together according to their similar actions
Work three ways:
Decrease automaticity of cardiac tissues in the ectopic sites
Alter rate of conduction
Alter refractory period of cardiac muscle between consecutive contractions

15. Antiarrythmic Agents Dependent on: type of dysrhythmia
presence of other conditions
safety of the drug
onset and/or duration of drug action
Administered IV until patient stabilized, then oral agents given
Arranged into classes

16. Antidysrhythmic Medications
Class 1 (1A, 1B, 1C): decrease the influx of sodium ions, stabilizing membranes
Class 2: decrease contractility, B/P, AV node conduction
Class 3: Prolong action potential, refractory period
Class 4: Decrease myocardial contractility, 02 demand

17. Antidysrhythmics Quinidine gluconate – Class 1 Lidocaine – Class 1B
Dilantin – Class 1B
Propranolol – Class 2
Verapamil HCL – Class 4
Digoxin – Class 4

18. Adverse Effects GI upset Cardiovascular disorders Hypersensitivity
Hypotension
Bradycardia
Lightheadedness

19. Nursing Considerations
Take patients apical pulse for one minute
Record rate and rhythm of the heartbeat
Assess allergies
Monitor blood pressure
Patient should be supine when administering IV agents .

20. Beta-adrenergic Blocking Agents
Block the hormone epinephrine
Inhibit beta and beta2 sympathetic receptors
Reduce heart rate
Reduces contractility
Slow electrical conduction
Decrease the blood pressure

21. Beta-Adrenergic Blocking Agents
Adverse effects
Cause bronchoconstriction
Can cause heart failure
Examples: propranolol (Inderal), esmolol, bretylium tosylate (Bretylol)

22. Calcium Channel Antagonists
Reduce the influx of calcium into the cell:
Prevention of reversal of spasms of the coronary blood vessels
Coronary artery dilation
Reduction of myocardial oxygen consumption
Example: Verapamil .

23. Adverse Effects Vasodilation may cause: Hypotension Edema Dizziness
Headache
Slower myocardial conduction may cause:
Bradycardia
Heart failure
Other effects:
Constipation, diarrhea, nausea, fatigue

24. Patient Education Ensure understanding of drug regime
Review signs to report to their health care provider
Instruct patient how to take their pulse
Remind them of the importance for proper follow-up
Encourage questions