9.1: Cardiac Arrthymia Drugs Flashcards
In cardiac myocytes, which ion has its highest concentration inside the cells?
K+
What happens in each phase of a fast cardiac action potential?
As VGSCs open, Na floods in make the cell positive
K+ starts to leave but Ca2+ also enters resulting in a plateau phase
K+ leaves and the membrane is hyperpolarised
What type of drugs are class 2 anti arrhythmic drugs?
Beta blockers
What arrhythmia can amiodarone predispose to?
Torsades de pointes
Due to QTc prolongation
What can atropine be used for?
Bradycardia
When is digoxin mainly used?
In atrial fibrillation, atrial flutter, heart failure
How does digoxin work?
Cardiac glycoside Inhibits Na/K-ATPase So intracellular Na accumulates This inactivated NCX So intracellular Ca2+ accumulates This lengthens the cardiac action potential and increases the contractility
What are some precautions with digoxin?
Renally excreted, so CI in renal failure
Narrow TI, can cause hyperkalaemia, so cardiac monitoring necesssary
How is adenosine administered?
Rapid IV bolus with a half life of seconds
What carrythmias can amiodarone be used for?
Many, widespread
Especially ventricular
What are some side effects of amiodarone?
Lots of serious ones Nausea Vomiting Tremor Photosensitivity Pulmonary fibrosis Constipation Hepatic injury Optic neuritis
What is the action of class 1 anti arrhythmics?
Na channel blockers
E.g. lidocaine, flecainide
How does amiodarone work?
K+ channel blocker
Prolongs phase 3 of the AP (as less permeability to K+)
