Lecture Notes: Drugs Affecting the Cardiovascular and Hematological System

Cardiac Cycle Summary

• Systole: Ventricles contract, increasing pressure, closing mitral and tricuspid valves, and opening aortic and pulmonic valves for blood ejection.
• Diastole: Ventricles relax, mitral and tricuspid valves open, blood flows from atria to ventricles.
• Blood Flow:
  • Unoxygenated blood returns via vena cava to right atrium, moves to right ventricle, and is sent to lungs for oxygenation.
  • Oxygenated blood returns to left atrium, moves to left ventricle, and is ejected to the body via the aorta.
• Stroke Volume: Amount of blood ejected from the left ventricle per contraction (approx. 75 ml).

Factors Affecting Stroke Volume

• Preload: Stretching force on ventricular muscle, affected by venous return and atrial contractility.
• Contractility: Force of ventricular contraction, affected by catecholamine concentration.
• Afterload: Resistance the left ventricle must overcome to eject blood; compared to pushing fluid through a straw vs. a hose.

Cardiac Output

• Definition: Volume of blood leaving the left ventricle per minute.
• Factors: Stroke volume and heart rate.

Heart Failure

• Mechanisms: Chronic sympathetic activation, renin-angiotensin-aldosterone system (RAAS), systemic vasoconstriction, sodium retention.
• Drug Therapy: Aims to improve cardiac function and decrease workload on the heart.

Drugs for Congestive Heart Failure

• ACE Inhibitors and ARBs: Interrupt RAAS, decrease fluid and sodium retention.
• Beta Blockers: Decrease oxygen requirements, workload of the heart.
• Calcium Channel Blockers: Slow heart rate, decrease contraction force.
• Digoxin: Increases myocardial contraction force, requires monitoring for toxicity.
• Diuretics: Decrease fluid retention.

Specific Medications

ACE Inhibitors

• Captopril: Inhibits conversion of angiotensin I to II, decreases vasoconstriction and aldosterone.
• Uses: Hypertension, heart failure treatment.
• Adverse Effects: Cough, hyperkalemia, angioedema.

Beta Blockers

• Propranolol (Non-selective): Blocks beta-1 and beta-2 receptors, decreases heart rate and contraction force.
• Metoprolol (Selective): Primarily affects beta-1 receptors, focused on heart.
• Uses: Hypertension, angina, arrhythmias.
• Adverse Effects: Bronchospasms (non-selective), hypotension.

Cardiac Glycosides

• Digoxin: Increases force of contraction, decreases heart rate.
• Uses: Heart failure, atrial fibrillation.
• Adverse Effects: Toxicity potential, bradycardia.

Newer Drug Classes

Nesiratide

• Function: Vasodilator, reduces cardiac preload and afterload, promotes diuresis.

ARNI (Angiotensin Receptor Neprilysin Inhibitors)

• Entresto: Combines neprilysin inhibition with ARB effects, reduces fluid retention and blood pressure.
• Uses: Chronic heart failure not responsive to other treatments.

Important Concepts

• Inotropic, Chronotropic, Dromotropic Effects:
  • Inotropic: Force of muscle contractions.
  • Chronotropic: Heart rate.
  • Dromotropic: Conduction speed through AV node.

Nursing and Patient Education

• Monitoring: Blood pressure, heart rate, signs of toxicity, electrolyte balance.
• Education: Importance of medication adherence, signs of adverse effects, lifestyle changes.
• Emergent Situations: Understanding risks of abrupt medication discontinuation, potential impacts on heart rate and blood pressure.