Cardiac Pharmacology: Key Concepts and Terminology

Lecture Overview

• Aimed at understanding key concepts related to cardiac medications, especially those with dual purposes.
• Duration: Short lecture covering key foundational concepts.

Modifying Cardiac Function

• Situations requiring modification: Hypertension, heart failure, or a combination.

Ways to Affect Cardiac Function

1. Timing of the heart
   • Example: Metronome ticking represents heart rate (fast/slow).
   • Chronotropic: Pertains to the heart rate.
2. Force of Contraction
   • Strength of the cardiac muscle contraction.
   • Inotropic: Pertains to the force of contraction.
3. Vascular Resistance
   • Affects how hard the heart has to work.
   • Indirect effects on cardiac function.

Direct and Indirect Cardiac Effects

• Direct effects: Drugs affecting heart muscle or nervous tissue within the heart (chronotropic, inotropic).
• Indirect effects: Drugs affecting workload and resistance the heart has to work against.

Key Terminology

• Chronotropic: Affects the rate of the heart beat.
  • Positive chronotropic: Increases heart rate.
  • Negative chronotropic: Decreases heart rate (affects SA node).
• Inotropic: Affects the force of heart muscle contraction.
  • Positive inotropic: Increases force of contraction.
  • Negative inotropic: Decreases force of contraction.
• Dromotropic: Affects the speed of electrical conduction in the heart.
  • Positive dromotropic: Speeds up conduction.
  • Negative dromotropic: Slows down conduction (can lead to AV block, ventricular fibrillation).

Detailed Concepts

• SA and AV Nodes: Essential for heart beat and timing regulation.
• Negative Dromotropic Effects: Slows transmission from SA to AV node, leading to possible dysrhythmias or AV block.
  • Adverse Events: Dysrhythmia (adverse effect); AV block/ventricular fibrillation (adverse event).

Drugs and Cardiac Effects

• Inotropic: Digitalis (digoxin), isoproterenol, epinephrine, propranolol.
• Chronotropic: Acetylcholine, certain hypertension drugs.
• Dromotropic: Verapamil, anti-seizure medications.

Clinical Applications

• Dual-purpose drugs: Used for heart failure and hypertension.
  • Dependent on drug’s primary and secondary effects.
• Selection Criteria: Based on desired direct or indirect effects, inotropic, chronotropic, or dromotropic characteristics.

Conclusion

• Essential to understand chronotropic, inotropic, and dromotropic terms for clinical application and drug selection.
• Revisit these concepts when studying specific cardiac drugs later on.

Note: This is a foundational lecture, critical for understanding future lectures on specific cardiac drugs.