Veterinary Cardiovascular Therapeutics

Introduction

• This presentation discusses cardiovascular therapeutics.
• A veterinary pharmacologist, Dr. Martin Hawes, is delivering the lecture.
• The presentation covers learning objectives related to cardiovascular diseases, treatments, and different drug classes.

Learning Outcomes

• State the fundamental functional problems caused by cardiovascular diseases.
• Describe and cite examples of medication classes used for cardiovascular diseases in animals.
• Explain and differentiate between compounds that modify heart rate.
• Identify medications that modify heart rate and rhythm, differentiating between commonly used drugs.
• Identify peripherally active compounds that enhance cardiovascular disease treatment.
• Provide examples of drug applications for common animal diseases (dogs, cats, and horses).

Links to other modules

• VMS1005: Heart and Blood Flow
• VMS1006: Cardiac System
• VMS2004: Response to chronic increase in load

Functional Problems of the Cardiovascular System

• Lecture discusses various cardiovascular system functional issues.

Drugs Affecting Cardiac Function

• Drugs that affect myocardial cells directly: Antidysrhythmic drugs, Cardiac glycosides, and other inotropic drugs
• Drugs that affect cardiac function indirectly (reduce pre/afterload): Drugs acting on the RAAS, Diuretics, Calcium channel blockers

Drugs that affect myocardial cells directly (Antidysrhythmic Drugs)

• This section details different classes of antidysrhythmic drugs (Classes I-IV).
  • Class I: Sodium channel blockers (e.g. quinidine, procainamide, lidocaine, mexilitine, flecainide, propafenone)
  • Class II: Beta-blockers (e.g. propranolol, atenolol, metoprolol)
  • Class III: Potassium channel blockers (e.g. amiodarone, sotalol)
  • Class IV: Calcium channel blockers (e.g. verapamil, diltiazem)
• The cardiac action potentials (phases) are used to illustrate the mechanism of action.

Cardiac Glycosides and Other Inotropic Drugs

• Derived from foxgloves, these drugs (e.g., digoxin) increase the force of contraction and decrease heart rate.
• They are used to treat heart failure and supraventricular tachyarrhythmias.
• A narrow therapeutic window exists, and close monitoring is vital.
• Digoxin is more sensitive in cats than dogs

Inodilators (e.g., Pimobendan)

• These drugs have both a positive inotropic (increases contractility) and vasodilatory effect.
• Pimobendan is a phosphodiesterase III inhibitor.
• Important in mitral valve disease.

Other Drugs That Increase Myocardial Contraction (e.g., Dobutamine)

• Dobutamine is a direct-acting synthetic catecholamine with positive inotropic effects used to treat hypotension during surgery.

Main Mechanisms of Blood Pressure Regulation

• The presentation provides diagrams illustrating the regulation mechanisms.

Renin-Angiotensin-Aldosterone System (RAAS)

• The RAAS is essential for heart failure development.
• Involves vasoconstriction (e.g., ACE inhibitors and ARBs) and sodium retention (e.g., diuretics).
• Angiotensin II receptor blockers are used in human patients to treat CHF, but not in animals.

Diuretics

• These drugs are classified and their effects on renal excretion discussed.
  • Osmotic agents (mannitol)
  • Loop diuretics (furosemide, torsemide)
  • Thiazides
  • Aldosterone antagonists
  • ADH antagonists

Thiazide Diuretics

• Less powerful than loop diuretics.
• Act by binding to sodium-chloride co-transporter.
• Used in end-stage heart disease.

Calcium Channel Blockers (e.g., Amlodipine)

• Amlodipine blocks calcium channels in vascular smooth muscle.
• Used for antihypertensive treatment in cats and dogs.
• Slow onset and waning of effect

Congestive Heart Failure (CHF) - Dogs and Cats

• Different types of CHF with corresponding treatment strategies are discussed for individual animal types.
• Mitral Valve Regurgitation, Dilated Cardiomyopathy, etc.

Key Points Summary

• Presents a concise recap of learning objectives.

Further Reading

• Key resources for further study are cited.