Therapy for arrhythmias Flashcards
What is the most common arrhythmia?
Atrial fibrillation
What arrhythmia has f waves?
Atrial fibrillation - fine oscillations from baseline
F on atrial flutter
What classification system is used for anti-arrhythmic agents?
Vaughan-Williams classification
I - Na channels (Ia, Ib, Ic) II - symp NS inhibitors III - K channels IV - Ca and AV node V - other/unknown mechanism
Name some Ia type anti-arrhytmics
Moderate Na blockade, delay repolarisation
Quinidine
Procainamide
Disopyramide
Name some Ib type anti-arrhythmics
Weak Na blockade, accelerate repol.
Tocainide
Mexiletine
Phenytoin
Lidocaine
Ventricular dsyrhythmias
Name some Ic type anti-arrhythmics
Strong Na blockade, no effect on repol.
Encainide
Flecainide
Propafenone
Moricizine
Severe ventricular dsyrhythmias, AF, atrial flutter
Name some II type anti-arrhythmics
Affect sympathetic NS signalling
Beta blockers: atenolol, bisoprolol, propranolol
Name some type III type anti-arrhythmics
Affect K+ channel to prolong repolarisation
Amiodarone
Bretylium
Sotalol
Name some type IV anti-arrhythmics
Affect Ca channel and AV node
Verapamil
Diltiazem
Paroxysmal SVT, atrial flutter and AF
Name some type V anti-arrhythmics
Others, don’t fit into any 1 class only
Digoxin - cardiac glycoside, inhibits Na/K pump, increased Ca for contraction
Adenosine - slows AV conduction
Describe the mechanism of action of digoxin
Cardiac glycoside, inhibits Na/K ATPase to increase levels of Ca for contraction
Used for heart failure and AF
Describe signs of digoxin toxicity
ECG - reverse tick of ST segments Nausea and vomiting Xanthopsia - yellow vision Bradycardia/tachycardia Arrhythmias
How do you treat digoxin toxicity?
Stop immediately (long half life) Give digibind (digoxin antibody)
Why must care be taken with class III drug amiodarone?
Many DDIs, especially with digoxin
Side effects include:
- thyroid issues
- pulmonary fibrosis
- grey appearance of skin
- corneal deposits
- LFT abnormalities
Describe amiodarone toxicity
Interstitial disease of lungs
Respiratory distress
Solitary pulmonary fibrotic masses
Blue-gray colouring of the skin
Describe the mechanism of action and indication of adenosine
Slows AV conduction, can cause systole for a few seconds before restoring normal HR
For paroxysmal SVT
IV, short half life
List some anti-coagulants used for arrhythmias
Warfarin - vit K1 oxide reductase inhibitor Dabigatran - thrombin inhibitor Rivaroxaban - Xa inhibitor Apixaban - Xa inhibitor Edoxaban - Xa inhibitor
What are the general indications for anticoagulation?
Atrial fibrillation - stroke
DVT/PE
After surgery
Immobilisation - prophylactic
What clotting factors are inhibited by warfarin?
Decreases clotting activity of II, VII, IX and X
What enzyme metabolises warfarin?
CYP450
What drugs increase warfarin activity?
Aspirin Sulphonamides Cimetidine Antibiotics - macrolides Heparin Disulfiram
What drugs decrease warfarin activity?
Barbiturates
Phenytoin (Ib) - don’t use together
Vitamin K - watch diet when on warfarin
Cholesyramine
How do you monitor warfarin therapy?
International normalised ratio - calculation of standardised prothrombin time
INR in normal people = 1
Therapeutic INR = 2.5-4 (want it increased so clotting is reduced)
reduce vitamin K in diet and alcohol
What are some adverse effects of warfarin?
Bleeding Teratogenic - chondrodysplasia (1st and 3rd) Retroplacental bleeding Intracerebral foetal bleeding Many DDIs
How do you assess bleeding risk in those on warfarin?
CHADS2 score
C= CHF 1 H = hypertension 1 A = age >75 1 D = DM 1 S2 = stroke 2
Each score relates to % risk of bleeding
What are the characteristics of an ideal anticoagulant?
Oral No need for monitoring No interaction with drugs/food Given once/twice a day at fixed dose As effective as warfarin Safer than warfarin
GONNAS
