Cardiology Flashcards
When is treatment of equine ventricular arrhytmias indicated?
- Multiform VPCs.
- Torsades de pointes/ Wide ventricular tachycardia
- R on T
- Sustained VT with HR >120bpm
- Signs of cardiovascular collapse
Anti-arrhythmics for supra ventricular arrhythmias
Sotalol
Digoxin
Procainamide -IV or oral
Propranolol - IV or oral
Propafenone - IV or oral
Flecainide acetate – IV (or oral)
Amiodarone - IV
Phenytoin – oral
Metoprolol - IV
Quinidine sulphate IV/PO
Anti-arrhythmics for treatment of ventricular arrhythmias
Lidocaine - IV
Magnesium sulfate - IV or NG tube Quinidine - IV or NG tube (Quinidine gluconate discontinued)
Procainamide -IV or oral
Propranolol - IV or oral
Propafenone - IV or oral
Flecainide acetate – IV (or oral)
Amiodarone - IV
Sotalol – oral (or IV)
Phenytoin – oral
Metoprolol - I
Antiarrhythmic classes → Classified by function
Class I: Na channel blockers
Class II: β-blocker
Class III: K channel blockers
Class IV: Ca channel blockers
Class Ia Antiarrhythmic
Procainamide
Procainamide
Procainamide is a fast sodium channel blocker that affects the QRS complex.
Class Ib Antiarrhythmic
Lidocaine
Mexiletine
Lidocaine
Decreases the permeability of the neuron membrane to sodium, which causes inhibition of depolarization, resulting in blocked conduction. No effect on QRS complex.
Class II Antiarrhythmic
Atenolol
Class III Antiarrhythmics
Sotalol
Amiodarone
Sotalol
Sotalol blocks potassium channels and increases the effective refractory period of myocardial cells by prolonging repolarization AND
potent nonselective class II activity (adrenergic antagonist)
Amiodarone
Prolongs action potential and increases effective refractory period of cardiac tissue by blocking potassium channels and slowing repolarization
Drugs Used to Manage Ventricular Tachyarrhythmias
Class Ia: procainamide, quinidine
Class Ib: lidocaine, mexiletine
Class Ic: flecainide, propafenone
Class II: β-blockers: atenolol, propranolol
Class III: d,l-sotalol, amiodarone
Drugs Used to Slow Atrioventricular Nodal Conduction
Class II: β-blockers: atenolol, propranolol
Class IV: calcium channel blockers
Other: digoxin
Purpose of gap junctions within intercalated discs?
Rapid communication junctionns allowing rapid diiffusion of ions allowing easy and fast travel of the action potentials between cardiac muscle cells. This allows the cardiac muscle cells to function as a syncytium.
Control of heart by ANS
Sympathetic = STIMULATION. This results in increased cardiac contractility (2-3 x increased CO). This increased HR is due to increased AV node conduction, due to vagal inhibition.
PS = DEPRESSION. vagal tone. AV and (more) SA node effect resulting in reduceed ventricular pump ~ 50%.
ANS control of heart rhythm
PS (vagal) = reduced HR - Ach - SA/AV nodes.
SNS = increased HR & contractility - NE - atria & ventricles.
Bipolar leads
Two electrodes on different sides of the heart providinign a base-apex current (frontal plane).
Augmented unipolar leads
Frontal plane. 2 negative and 1 positive. aVR/ aVL/ aVF leads
