Cardiovascular Pharmacology, Contrast Media, and Clotting Cascade

Vocabulary review covering Class I-IV cardiac medications, contrast media characteristics, the clotting cascade phases, and clot-affecting pharmacological agents.

Class I - Sodium Channel Blockers

A class of drugs (subdivided into IA, IB, and IC) that inhibit the cellular exchange of sodium in cardiac pacemaker cells, reducing action potential conduction and decreasing heart rate; commonly represented in the cath lab by Lidocaine.

Class II - Beta Blockers

Medications that directly influence and slow overall conduction through the heart's electrical system (including the SA node and AV node), resulting in a slowed heart rate; commonly seen examples include Lopressor (metoprolol) and Propranolol.

Class III - Potassium Channel Blockers

Drugs that inhibit the cellular exchange of potassium in pacemaker cells, slowing the rate of repolarization and prolonging action potentials and effective refractory periods to decrease heart rate; examples include Amiodarone (Pacerone) and Dofetilide (Tikosyn).

Sotalol (Betapace)

A medication categorized under both Class II and Class III that functions as a potassium channel blocker and a non-selective beta blocker, used to slow heart rate, decrease myocardial contractility, and treat ventricular arrhythmias and atrial fibrillation or flutter.

Class IV - Calcium Channel Blockers

Drugs that inhibit the cellular exchange of calcium in pacemaker cells, affecting depolarization (contraction) by relaxing smooth muscle cells within cardiac musculature, decreasing vessel resistance, and lowering blood pressure; examples include Verapamil and Diltiazem (Cardizem).

Radiolucent

The property of blood and blood vessels, owing to their composition of low density molecules, that causes them to be unseen under x-ray without the aid of contrast media.

Contrast Medium

A viscous, radiopaque fluid utilized to visualize a specific structure or fluid within an x-ray field/image, distinct from a dye because it does not colorize or stain.

Hydrophilicity (ionicity)

One of the four main properties of contrast media, referring to its tendency to dissolve in water, which makes it kinder on the patient's body.

Viscosity (Contrast Media)

One of the four main properties of contrast media, describing the fluidity of the agent and how well it flows through a blood vessel.

Osmolarity/Osmolality (Contrast Media)

The number of osmoles of solute in a kilogram (weight) or liter (volume) of solvent, dictating movement across semipermeable membranes and correlating to how contrast molecules permeate vessel walls versus staying in the body longer.

Clotting Cascade: Phase 1

The initial clotting stage where platelets contact a vessel break, activate, and stick together with the aid of prothrombin (which sheds a component to transform into thrombin), creating a porous platelet plug.

Clotting Cascade: Phase 2

The second clotting stage where fibrinogen activates by shedding a component to transform into fibrin, which creates a protein mesh that covers and supports the porous platelet plug to solidify it into a clot.

Anticoagulants

Agents that work against clot formation by reducing the blood's ability to clot, a category that encompasses both antiplatelets and thrombin inhibitors.

Antiplatelets

Anticoagulants that inhibit clot formation by targeting phase 1 of the clotting cascade; examples include Acetylsalicylic Acid (Aspirin), Aptifibatide (Integrilin), Tirofiban (Aggrastat), Clopidogrel (Plavix), Plasugrel (Effient), Ticagrelor (Brillinta), Abciximab (Reopro), and Cangrelor (Kengreal).

Thrombin Inhibitors

Anticoagulants that inhibit clot formation by targeting phase 2 of the clotting cascade, blocking thrombin's signal to convert fibrinogen into fibrin; examples include Bivalirudin (Angiomax), Heparin, Enoxaparin (Lovenox), and Dabigatran (Pradaxa).

Thrombolytics

A class of drugs that strive to break down an existing thrombus; common examples in the cath lab include Alteplase or Activase (tPA) and Reteplase (Retevase).