module 5

• The rate of contraction must occur at regular interval. However, dogs normally show groups of regularly spaced impulses separated from similar groups by longer interval. This separation occurs regularly in association with breathing. This is termed as "regularly irregular" rate.
• Every sinus impulse must be transmitted through the AV node
• any deviation from the normal heart rate and rhythm is called Arrhythmia
• true or false.Not all arrhythmias are pathologic

  true
• GENERAL CLASSIFICATIONS OF ARRYTHMIA (supraventricular atrial and av nodal)

  paroxysmal atrial tachycardia

  atrial fibrillation

  atrial flutter
• GENERAL CLASSIFICATIONS OF ARRYTHMIA(ventricular)

  premature ventricular contraction

  ventricular tachycardia

  ventricular fibrillation
• Screening for arrhythmia may be done by auscultation
• •Electrocardiography (ECG) is the most specific way to diagnose cardiac arrhythmias
• true or false. jugular pulse is normal

  false
• Drugs in this class are most frequently used to treat ventricular tachyarrhythmias

  Class I - Membrane stabilizing drugs
• its MOA is the blockade of a certain percentage of the fast sodium channels in the myocardial cell membrane

  Class 1
• Members of this class reduced inward Na+ current and bring about

  CLASS 1A
• Quinidine, Procainamide, Disopyramide are example of what class of ANTIARRYTHMIC DRUGS

  CLASS 1A
• Members of this class increase the outward K+ current and bring about the following

  CLASS 1B
• Lidocaine Phenytoin Tocainide are example of what class of ANTIARRYTHMIC DRUGS

  Class 1B
• this class of anti arrythmic drugs Markedly decrease conductivity without changing action potential duration

  Class 1C
• •Encanide Lorcainide Flecainide Propafenone are example of what class of anti arrythmic drug

  Class 1C
• •β-adrenergic blockers. The antiarrhythmic effects of this group results from selective β-adrenergic blocking action (can also increase the outward K+ current and decrease the inward Na+ current).

  Class II
• Propanolol Timolol Metoprolol are what Class

  Class II
• •Their major effect is to lengthen action potential duration and refractory period primarily in the Purkinje fibers and ventricular myocardium

  example are Bretylium Amiodarone

  Class III
• •Block calcium entry into myocardial cells.

  Effectively suppresses ventricular rate in atrial flutter and fibrillation

  •Verapamil Nifedipine


  Class IV
• Direct action of this drug

  •decreases maximal rate of phase 0

  •decreases slope of phase 4

  •decreases spontaneous depolarization of Purkinje fibers, but spares the automaticity of the SA node (controls automaticity)

  •prolongs the effective refractory period of atrial and ventricular myocardium without affecting the normal pacemaker cells (controls atrial fibrillation).

  •For atrial fibrillation in dogs and horses; also for ventricular premature beat

  QUINIDINE SULFATE
• quididine sulfate is orally administered
• •has direct actions similar to quinidine but the indirect effects are not pronounced

  •more effective in controlling ventricular arrhythmias

  PROCAINAMIDE
• PROCAINAMIDE is rapidly absorbed in GI tract
• For ventricular ectopic beats or ventricular tachyarrhytmias

  procainamide
• Improves conduction and shortens action potential duration in Purkinje fibers and myocardiumnot effective in controlling supraventricular arrhythmias

  LIDOCAINE
• lidocaine is absorbed well when given orally
• lidocaine is often mixed with thiamylal for induction of anesthesia
• For severe ventricular ectopic arrhythmias of any cause including digitalis-induced arrhythmias

  lidocaine
• adverse effects of lidocaine Primarily CNS: restlessness, trembling excitement, seizures - can be controlled with diazepam
• cats are extremely susceptible to the adverse cardiovascular effects of lidocaine
• similar to lidocaine; also used as an anti-epileptic

  phenytoin
• phenytoin is rapidly biotransformed in what animal

  dogs
• drug of choice for digitalis-induced ventricular arrhythmias

  phenytoin
• Antiarrhythmic action due to adrenergic blocking effect (decreased spontaneous firing in SA node)

  propanolol
• propanolol produces this kind of adverse effects bradycardia, hypotension, bronchoconstriction; Dangerous to use in congestive heart failure