Therapy and drugs for arrhythmia

Question 1

classes of antiarrhythmics according to Vaughan-William classification

Answer 1

IA, IB, IC, II, III, IV, V

Question 2

class IA

Answer 2

only present in non nodal cells. moderate sodium channel blood, thus reducing amplitude of AP and conduction velocity- quinine, procainamdie, dispyramide

Question 3

class IB

Answer 3

only present in non nodal cells . weak sodium channel blood, thus reducing amplitude of AP and conduction velocity- lidocaine, mexiletine, tocainide

Question 4

class IC

Answer 4

only present in non nodal cells . strong sodium channel blood, thus reducing amplitude of AP and conduction velocity- flecainide, propafenone

Question 5

class II

Answer 5

B- blockers, B- adrenergic receptor antagonism. blocks sympathetic stimulation of the heart. prolongs phase 4 depolarisation, shortens phase2. First line for atrial fibrillation. atenolol, bisoprolol, propranolol

Question 6

class III

Answer 6

prolong refractoriness (slow K flow out of cells). increase action potential duration. used for difficult to treat dysrythmias- life threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter- resistant to other drugs.sustained ventricular tachycardia - amiodarone, bretylium, sotalol

Question 7

class IV

Answer 7

calcium channel blockers bind to L type voltage gated calcium channels, depress phase 4 depolarisation in SA and Av nodes shorten phase 2, used for paryoxysmal supra ventricular tachycardia and rate control for atrial fibrillation and flutter - diltiazem, verapamil

Question 8

class V

Answer 8

other- digoxin, adenosine. have properties of several classes

Question 9

amiodarone

Answer 9

class III. most likely to be used for ventricular tachycardia and sometimes supra ventricular tachycardia. many interactions with other drugs eg digoxin, has lots of side effects

Question 10

side effects of amidarone

Answer 10

thyroid, pulmonary fibrosis, slate grey pigmentation, corneal deposits, LFT abnormalities

Question 11

digoxin

Answer 11

cardiac glycoside, increases vagal tone, complex effect on cardiac action potential- reduces refractory period, increases intracellular calcium, used for difficult to control AF, atrial flutter, SVT, heart failure. very long half life 36-48 hours, commonly used in elderly, monitor potassium levels and for toxicity. effect of digoxin is measured by heart rate

Question 12

digoxin toxicity

Answer 12

nausea, vomiting, xanthopsia, bradycardia, tachycardia, arrhythmias. shown from reverse tick appearance of ST segment in lateral leads. more serious if potassium levels are low

Question 13

treatment of digoxin toxicity

Answer 13

stop digoxin, if levels very high and risk of signifiant arrhythmia then give digibind- which is digoxin immune antibody by binding with digoxin and forming complex molecules and excreted in urine

Question 14

adenosine

Answer 14

slows conduction through AV node, used to convert paroxysmal supra ventricular tachycardia to sinus rhythm. very short half life, only administered as fast IV push, may cause systole for a few seconds, feeling of impending doom. avoid with patients with asthma