Drugs Affecting The Rhythm & Output of The Heart

Drugs Affecting The Rhythm & Output of The Heart

Digitalis Overview

  • Classification: Cardiac glycosides, antiarrhythmic agents.
  • Function: Improve myocardial function, increase cardiac output by strengthening contraction.
  • Chemical Composition: Contains steroid, sugar, and lactone.
    • Sugar: Increases solubility, alters absorption.
    • Lactone: Responsible for cardiotonic properties.
  • Sources: Derived from foxglove plants (Digitalis purpurea and Digitalis lanata).

Effects of Digitalis

  1. Cardiac Effects:
    • Elevates Na and K concentrations, increases calcium influx, enhancing myocardial contractility.
    • Decreases heart rate via vagal stimulation, affecting S.A. Node activity.
    • Alters conduction through the Bundle of His leading to decreased ventricular impulses.
    • Results in increased cardiac output and reduced symptoms of heart failure.

Indications for Use

  • Conditions Treated:
    • Supraventricular tachycardia.
    • Atrial fibrillation (controls, does not cure).
    • Acute or chronic heart failure.
    • Cardiogenic shock.

Contraindications

  • Avoid in cases of:
    • Heart block.
    • Ventricular tachycardia or fibrillation.
    • Renal impairment.

Digitalization Process

  • Digitalization: Administering digitalis until optimal cardiac effects are achieved, tailored per patient.
    • Initial loading dose followed by a maintenance dose.

Common Drugs:

  • Digoxin: Primary glycoside, therapeutic but toxic at higher levels; effect seen in 1-2 hours I.V.
  • Lignocaine: Antiarrhythmic that decreases heart muscle excitability.
    • Treats abnormal pulse rhythms; I.V. with side effects like drowsiness and convulsions.

Nursing Considerations for Digitalis

  1. Monitor Pulse: Check apical pulse before administration; hold if <60 bpm.
  2. Watch for Toxicity: Identify signs (headaches, visual disturbances, GI symptoms).
  3. Electrolyte Monitoring: Keep an eye on serum K+ levels; administer potassium if low.
  4. Side Effects Awareness: Include nausea, vomiting, bradycardia, etc.
  5. Patient Education: Advise on dietary potassium intake and signs of overdose.

Other Cardiotonic Drugs:

  1. Dopamine: Increases contractility and improves renal function.
  2. Isoprenaline: Targets beta receptors to raise heart rate; side effects include tachycardia and hypertension.

Management of Congestive Cardiac Failure (CCF)

  • Combines lifestyle changes and pharmacological treatment.
    • Key Medications:
    • ACE Inhibitors: Relax blood vessels to reduce workload.
    • Beta Blockers: Decrease heart rate and improve efficiency.
    • Diuretics: Reduce fluid retention, improving cardiac function.
    • Digoxin: Enhances heart contraction; monitor closely for toxicity.