Antiarrhythmic Agents: Cardiac Stimulants and Depressants

1. 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: 60-100 bpm; primary pacemaker • Atrioventricular node: Connects atria and ventricles; 40-60 bpm • Bundle of His and Purkinje fibers: carry electrical impulses from AV node to complete ventricle rate pacing; 15-40 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 betaand 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