Drugs Cardiac Arrhythmias Flashcards
What is the effect of noradrenaline or adrenaline on SAN B-1 adrenoreceptors?
Increases slope
Reduces duration of Phase 4
What is the effect of increased vagal activity to AVN?
Activation of ACh receptors = increased AVN refractoriness = slow HR and reduce CO
What are the causes of arrhythmias?
- Damage to cardiac conducting tissues/nodes
- Congenital
- Drugs
- Electrolyte imbalances - K
What are the rate and rhythm drugs for AF?
- VERAPAMIL - Ca channel blocker
- AMIODARONE - B-adrenoreceptor blocker and K channel blocker
What is the extensive ADR of amidarone?
Predisposes to torsades de pointes
What is the rhythm control drug for AF?
FLECAINIDE - Na channel blocker
What anticoagulants are used in AF?
- Warfarin
- Heparin
- DOACs
What is the MOA of Warfarin?
- Vit K epoxide reductase inhibitor
- Blocks synthesis F II, VII, IX and X
- Monitor via INR or PT time
- Antidote = Vit k
What is the MOA of Heparin?
- Activates anti-thrombin > inhibits thrombin + factor Xa
- Low molecular weight heparin only blocks clotting factor - subtle
- Monitor via APTT
- Antidote = protamine sulfate
What is the MOA of DOACs?
- Rivaroxaban - factor Xa inhibitor
- Dabigatran - thrombin inhibitor
What is seen on the ECG of SVT (AVNRT type)?
- Narrow QRS
- Buried p waves
What are the causes of SVT (AVNRT)?
- Normal structural variant with fast + slow fibres in or near AVN
- Re-entrant arrhythmias only in absence of aberrant arterial impulse trigger
Predisposing factors:
- Caffeine
- Psychosocial stress
- Hyperthyroidism
What are the rhythm control drugs for AVNRT?
- ADENOSINE - hyperpolarises reducing excitability
- FLECAINIDE - blocks conduction in fast re-entrant circuit pathways
What is the rate + rhythm control drug for AVNRT?
VERAPAMIL
What is seen on the ECG of atrial flutter (SVT)?
- Saw tooth flutter waves
- Fast atrial rate - 300bpm
- Narrow QRS