In-Depth Notes on Cardiac Glycosides, Antianginals, and Antidysrhythmics

Learning Objectives

  • Understand the mechanisms of action for major cardiac medication classes:

  • Cardiac glycosides

  • Antianginal drugs

  • Antidysrhythmic drugs

  • Describe agents used to treat heart failure.

  • Identify and describe signs and symptoms of digitalis toxicity.

  • Apply the Nursing Process regarding cardiac medications.

Overview of Heart Failure

  • Definition: Heart failure (HF) occurs when the heart becomes weakened and enlarged, losing its ability to pump blood effectively.

  • Pathophysiology:

  • Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)

  • Preload and Afterload affect heart function:

    • Right-sided HF backs up blood in the periphery.

    • Left-sided HF backs up blood into the lungs.

Mnemonic: Remember the right and left side by the phrase "Right to the body, Left to the lungs."

  • Stages of Heart Failure:

  • Stage I: High risk for HF without symptoms or structural disease.

  • Stage II: Cardiac changes present with no symptoms.

  • Stage III: Structural heart disease with symptoms (e.g., fatigue, shortness of breath).

  • Stage IV: Severe heart disease with marked symptoms at rest.

Tip: Use the acronym "H-SSS" (Hi-Staging Symptoms) to recall the stages from no symptoms to severe symptoms.

Nonpharmacologic Treatment for Heart Failure

  • Dietary restrictions: Limit salt and saturated fat intake.

  • Lifestyle changes: Limit or avoid alcohol, and stop smoking.

  • Encourage mild exercise.

Tip: Think "SLIDE" for nonpharmacologic treatments - Salt restriction, Lifestyle changes, Increase exercise, Decrease alcohol.

Lab Tests for Heart Failure

  • Atrial Natriuretic Peptide (ANP): Normal range 20 - 77 ng/mL.

  • Brain Natriuretic Peptide (BNP): Desired value < 100 pg/mL, positive > 100 pg/mL.

Mnemonic: Remember "A for ANP and B for BNP", with corresponding ranges being 20-77 and <100.

Cardiac Glycosides: Digoxin

  • Source: Derived from purple and Grecian foxglove.

  • Mechanism of Action:

  • Positive inotropic effects: Increases myocardial contractility and improves circulation.

  • Negative chronotropic effects: Decreases heart rate.

  • Negative dromotropic effects: Slows the conduction velocity through the heart.

Mnemonic: "P-N-N" (Positive to contract, Negative to rate, Negative to conduction) for digoxin's effects.

  • Pharmacokinetics: 60-80% absorption, renal excretion, long half-life (30-40 hrs) leading to potential toxicity.

  • Clinical Uses: Heart failure, atrial fibrillation.

  • Side Effects:

  • Common: Bradycardia, dysrhythmias, gastrointestinal disturbances, headache, vision changes (blurred/yellow).

Tip: Remember the "5 B's of Digoxin": Bradycardia, Blurred vision, Breast pain, Bloating, and Back pain.

  • Signs of Digoxin Toxicity:

  • Nausea, vomiting, fatigue, vision disturbances, and bradycardia.

  • Toxicity Management:

  • Antidote: Digoxin immune fab.

Drug Interactions and Nursing Process for Digoxin

  • Drug Interactions:

  • Diuretics (increased risk of hypokalemia leading to toxicity).

  • Antacids (reduce digoxin absorption).

  • Nursing Interventions:

  • Monitor heart rate, hold if < 60 BPM, check for signs of HF and toxicity.

  • Assess lab values, especially potassium and renal function.

  • Patient education: Adherence to therapy, signs of toxicity.

Tip: "Monitor to Maintain" – always monitor heart rate and potassium levels.

Anti-Anginal Drugs

  • Types: Nitrates, beta blockers, calcium channel blockers.

  • Mechanism of Action: Relieve angina by increasing blood flow and decreasing myocardial oxygen demand.

  • Nitrates:

  • Used for immediate relief from angina, available in multiple forms (sublingual, IV, etc.).

  • Common side effects: Headaches, hypotension.

  • Beta Blockers:

  • Reduce heart rate and workload on the heart; side effects include bradycardia.

  • Calcium Channel Blockers:

  • Used to treat stable and variant angina by promoting vasodilation.

Tip: Remember "N-B-C is the ABC for Angina" (Nitrates, Beta blockers, Calcium channel blockers).

Antidysrhythmic Drugs

  • Classification:

  • Class I: Sodium channel blockers (1A, 1B, 1C).

  • Class II: Beta blockers.

  • Class III: Prolong repolarization.

  • Class IV: Calcium channel blockers.

  • Nursing Assessments:

  • Monitor ECG, vital signs, evaluate for abnormal rhythms, and educate about medication adherence.

Mnemonic: Use "S-B-P-R" (Sodium, Beta, Prolong, Calcium) to recall antidysrhythmic classes.

Conclusion Key Points

  • Cardiac glycosides like digoxin can cause serious side effects; require careful monitoring and patient education.

  • Antianginal and antidysrhythmic medications have distinct actions and implications for treatment.

  • Proper assessment and knowledge of drug interactions are essential in managing patients with cardiac conditions.

Review Questions and Answers

  1. What is the definition of heart failure, and how does it affect cardiac output?

    • Heart failure (HF) is when the heart becomes weakened and enlarged, losing its ability to pump blood effectively, leading to a decreased cardiac output.

  2. Describe the stages of heart failure and the symptoms associated with each.

    • Stage I: High risk for HF without symptoms or structural disease.

    • Stage II: Cardiac changes present with no symptoms.

    • Stage III: Structural heart disease with symptoms like fatigue and shortness of breath.

    • Stage IV: Severe heart disease with marked symptoms at rest.

  3. What lifestyle changes can be recommended for patients with heart failure?

    • Dietary restrictions (limit salt and saturated fat), avoiding alcohol, stopping smoking, and encouraging mild exercise.

  4. What are the normal and abnormal ranges for Atrial Natriuretic Peptide (ANP) and Brain Natriuretic Peptide (BNP)?

    • ANP normal range: 20 - 77 ng/mL; BNP desired value: < 100 pg/mL, positive > 100 pg/mL.

  5. Explain the mechanisms of action of digoxin and its common side effects.

    • Digoxin increases myocardial contractility (positive inotropic), decreases heart rate (negative chronotropic), and slows conduction through the heart (negative dromotropic). Common side effects include bradycardia, dysrhythmias, gastrointestinal disturbances, headache, and vision changes.

  6. How can digoxin toxicity be identified and managed?

    • Signs include nausea, vomiting, fatigue, vision disturbances, and bradycardia. Management involves administering the antidote, digoxin immune fab.

  7. What are the different types of anti-anginal drugs, and how do they work?

    • Types include nitrates (increase blood flow), beta blockers (reduce heart rate and workload), and calcium channel blockers (promote vasodilation).

  8. Discuss the importance of patient education regarding cardiac medications and potential drug interactions.

    • Patient education is crucial for adherence to therapy, recognizing signs of toxicity, and understanding drug interactions that can enhance or inhibit the effects of cardiac medications.