Cardiac Glycosides, Antianginals, and Antidysrhythmics

Pathophysiology and Management of Heart Failure

• Heart failure occurs when the heart muscle weakens and enlarges, ultimately losing its ability to pump blood adequately.

• Compensatory mechanisms eventually fail, leading to congestion in the lungs and periphery.

• Classification of Heart Failure:

  • Right-sided failure: Blood backs up into the periphery.

  • Left-sided failure: Blood backs up into the lungs.

• Nonpharmacologic treatment for heart failure:

  • Limit salt intake.

  • Limit saturated fat intake.

  • Limit or avoid alcohol intake.

  • Stop smoking.

  • Perform mild exercise.

Cardiac Glycosides: Digoxin

• Primary uses include the treatment of Congestive Heart Failure (CHF) and atrial arrhythmias.

• Mechanism of action:

  • Inhibits sodium-potassium ATPase.

  • Positive inotropic effect: Increases myocardial contractility, stroke volume, and cardiac output, resulting in increased blood flow and decreased preload.

  • Negative chronotropic effect: Decreases the heart rate.

  • Negative dromotropic effect: Decreases the conduction of heart cells.

• Side effects of Digoxin:

  • Dizziness, weakness, and headache.

  • Abdominal pain.

• Adverse reactions:

  • Bradycardia.

  • Cardiac dysrhythmias, such as premature ventricular contractions (PVCs).

• Signs of Digoxin Toxicity:

  • Anorexia, nausea, and vomiting.

  • Blurred vision and visual illusions (specifically white, green, or yellow halos around objects).

  • Delirium.

• Drug-Drug Interactions:

  • Potassium-wasting diuretics: Increase the risk of digoxin toxicity due to hypokalemia.

  • Cortisone: Leads to sodium retention and potassium release, increasing toxicity risk.

  • Antacids: Decrease the absorption of digitalis.

• Contraindications:

  • Ventricular dysrhythmias.

  • Bradycardia.

  • Hypokalemia.

  • Renal disease.

Nursing Process for Digoxin

• Assessment measures:

  • Obtain a baseline pulse rate and perform an apical pulse check for one full minute.

  • Review medical and medication history.

  • Monitor electrolytes.

  • Assess for signs and symptoms of CHF, atrial arrhythmia, edema, and abnormal lung sounds.

  • Assess for evidence of digitalis toxicity.

• Nursing Interventions:

  • Monitor serum digoxin levels: The therapeutic range is $0.5$ to $2\,ng/mL$. Levels over $2.2\,ng/mL$ are considered toxic.

  • Monitor serum potassium levels and report hypokalemia ($< 3.5\,mEq/L$).

  • Evaluate for peripheral and pulmonary edema indicating CHF.

• Patient Teaching:

  • Take the medication at the same time every day.

  • Take the pulse daily; notify a healthcare provider if the rate is less than $60\,bpm$ or above $100\,bpm$.

  • Report signs of digoxin toxicity immediately.

  • If taking a diuretic, take potassium supplements as prescribed.

  • Encourage high-potassium foods: dried fruits, fruit juice, vegetables, and potatoes.

Types of Angina

• Classic (Stable) Angina: Occurs with predictable stress or physical exertion.

• Unstable (Preinfarction) Angina: Occurs frequently with progressive severity unrelated to activity; it is unpredictable regarding stress, exertion, and intensity.

• Variant (Prinzmetal/Vasospastic) Angina: Occurs while the patient is at rest.

Antianginal Drugs: Nitrates

• Action: Promotes vasodilation and decreases both preload and afterload.

• Nitroglycerin formulations for acute anginal pain:

  • Sublingual (SL): Works in $1$ to $3$ minutes and lasts for approximately $30$ minutes.

  • Aerosol spray.

  • Intravenous (IV).

• Formulations for prevention:

  • Topical (ointment or transdermal patch).

  • Oral extended-release capsules and tablets.

• Side effects: Headache, flushing, dizziness, weakness, and syncope.

• Adverse reactions: Hypotension.

• Contraindications: Increased intracranial pressure and severe hypotension.

• Cautions: Use with caution in patients with hepatic disease.

• Interactions: Alcohol, other antihypertensive medications, and other vasodilating drugs.

• Guideline: Do not abruptly discontinue nitroglycerin.

Antianginal Drugs: Beta Blockers and Calcium Channel Blockers

• Beta Blockers:

  • Used for prevention of angina.

  • Action: Block the action of epinephrine and norepinephrine, allowing heart vessels to relax and dilate; decreases workload and oxygen demands.

  • Side effects: Dizziness, depression, fatigue, sexual dysfunction, and peripheral edema.

  • Adverse reactions: Bronchospasms, bradycardia, and hypotension.

  • Caution: Do not abruptly discontinue.

  • Cardioselective Beta Blockers (e.g., Atenolol): Act strongly on beta1 receptors, decreasing heart rate while avoiding bronchoconstriction. Preferred for patients with COPD.

  • Nonselective Beta Blockers (e.g., Propranolol, Nadolol, Pindolol): Decrease heart rate but can cause bronchoconstriction.

• Calcium Channel Blockers (e.g., Diltiazem, Verapamil):

  • Used for prevention of angina.

  • Action: Relax coronary arteries and decrease coronary artery spasms (effective for variant angina); reduce cardiac workload and oxygen demands.

  • Side effects: Dizziness, flushing, headache, peripheral edema, and fatigue.

  • Adverse reactions: Hypotension and bradycardia.

Nursing Process for Antianginal Drugs

• Assessment measures:

  • Obtain baseline vital signs.

  • Review medication and medical history.

  • Assess pain level for acute episodes, including frequency and severity of attacks.

• Nursing Interventions:

  • Monitor vital signs.

  • Position the patient sitting or lying down during the first administration of a nitrate.

  • Apply topical patches or paste using gloves.

  • Apply topical forms to a clean, dry area with little hair (e.g., the back of the arm).

  • Administer SL nitroglycerin if chest pain occurs: Give one tablet every $5$ minutes for up to $3$ doses, evaluating pain between each dose.

  • Monitor effects of fast-acting nitroglycerin (SL and IV).

  • Store medications away from light.

• Patient Teaching:

  • Sit down and rest when chest pain occurs before taking nitroglycerin; call 911 if pain is not relieved or worsens.

  • Store nitroglycerin in its original container away from heat, moisture, and light.

  • Rotate patch or paste application sites to avoid hairy areas (thighs or arms are acceptable).

  • Acetaminophen may be used for relief of nitrate-induced headaches.

  • Do not stop beta blockers or calcium channel blockers abruptly; monitor heart rate and blood pressure.

Antidysrhythmic Drugs: Classifications and Mechanisms

• Group 1: Sodium (Fast) Channel Blockers:

  • Subclass IB: Lidocaine. Used for ventricular dysrhythmias. Side effects include edema, nausea, vomiting, and dizziness.

  • Mechanism: Blocks sodium influx to slow conduction.

• Group 2: Beta-Adrenergic Blockers:

  • Example: Acebutolol hydrochloride. Used for treatment of PVCs and hypertension. Side effects include dizziness and headache; adverse reactions include hypotension and bradycardia.

  • Mechanism: Block epinephrine and norepinephrine, reduce calcium entry, and decrease conduction velocity, automaticity, and recovery time.

• Group 3: Drugs that Prolong Repolarization (Potassium Channel Blockers):

  • Example: Amiodarone hydrochloride.

  • Uses: Life-threatening ventricular tachycardia ($V\text{-tach}$) and ventricular fibrillation ($V\text{-fib}$) unresponsive to other drugs.

  • Action: Increases refractory (recovery) time and prolongs the duration of the action potential.

  • Side effects: Fatigue, confusion, dizziness, GI distress (nausea, vomiting, constipation).

  • Adverse effects: Pulmonary toxicity, elevated liver enzymes, dysrhythmias, hypotension, bradycardia, neuropathy, tremors, and blue-gray skin discoloration.

• Group 4: Calcium (Slow) Channel Blockers:

  • Examples: Verapamil (used for angina, dysrhythmias, PSVT, and hypertension) and Diltiazem (used for angina, PSVT, atrial flutter/fibrillation, and hypertension).

  • Mechanism: Block calcium influx, slow conduction velocity, decrease myocardial contractility, and increase refraction in the atrioventricular node.

Nursing Process for Antidysrhythmics

• Assessment measures:

  • Obtain baseline vital signs and ECG.

  • Monitor for palpitations and compare apical and radial pulses.

  • Check cardiac enzymes if ordered.

• Nursing Interventions:

  • Monitor for hypotension and bradycardia.

  • Monitor lung sounds.

  • Administer IV push (IVP) medications slowly.

  • Keep the patient on a cardiac monitor to observe for abnormal ECG patterns.

• Patient Teaching:

  • Monitor blood pressure, pulse, and ECG if using wearable electronic devices.

  • Do not stop any cardiac drug abruptly.

  • Beta blockers may take $1$ to $3$ months to achieve full effect.

  • Report palpitations or slow heart rate to the healthcare provider.

  • Rise from a sitting or lying position slowly to prevent falls.

  • Avoid alcohol, caffeine, and tobacco.

Questions & Discussion

• Question: A patient has angina pectoris. The patient’s BP is $100/60\,mm\,Hg$. The nurse administers nitroglycerin $0.4\,mg$ sublingual (SL). It is most important for the nurse to assess the patient for the development of what condition?

  • Response: Hypotension. A side effect of nitroglycerin is hypotension owing to the vasodilation of blood vessels.

• Question: A nurse is administering digoxin, $0.125\,mg$, to a patient. Which nursing interventions will the nurse implement?

  • Response: The nurse should check the apical pulse rate before administration, monitor the patient’s serum digoxin level, and instruct the patient to report a pulse rate less than $60$. Patients should also be advised to eat foods high in potassium and avoid taking antacids with digoxin as they decrease absorption.

• Question: A patient is ordered to receive digoxin to treat congestive heart failure. The nurse is most concerned about which assessment finding?

  • Response: A heart rate of $56\,beats/min$. The apical pulse should be taken for a full minute and should be greater than $60\,beats/min$. The prescriber must be notified if it falls below this threshold.

• Question: A nurse is preparing to administer digoxin to a patient. Which laboratory result is the nurse most concerned about: Sodium $138\,mEq/L$, Potassium $3.0\,mEq/L$, Digitalis level $1.8\,ng/mL$, or BNP $200\,pg/mL$?

  • Response: Potassium $3.0\,mEq/L$. A low serum potassium level (hypokalemia) enhances the action of digoxin and can cause digitalis toxicity.

• Question: When administering antianginal drugs, the nurse identifies which as the most common response?

  • Response: Hypotension.

• Question: The nurse should teach the patient to report which of the following to the health care provider immediately if experienced after taking nitroglycerin: Dizziness, Faintness, Headache, or Persistent pain?

  • Response: Persistent pain. While dizziness, faintness, and headache are known side effects related to vasodilation, persistent pain indicates the possibility of acute coronary syndrome.

• Question: Which drug is a calcium channel blocker used for the treatment of dysrhythmias: Diltiazem, Esmolol, Flecainide, or Sotalol?

  • Response: Diltiazem. Esmolol and Sotalol are beta blockers, while Flecainide is a sodium channel blocker.

• Question: A patient with angina and a long history of severe chronic obstructive pulmonary disease is ordered beta blocker therapy. Which beta blocker would be most effective for this patient: Propranolol, Nadolol, Pindolol, or Atenolol?

  • Response: Atenolol. Atenolol is a cardioselective beta blocker that acts strongly on the beta1 receptor to decrease heart rate while avoiding the bronchoconstriction that nonselective beta blockers (propranolol, nadolol, pindolol) can cause.