Pharm --Heart Phys/Antiarrhythmic Flashcards
This class of antiarrhythmics work on voltage gated Na channels (activated state)
Class 1 – Na channel blockers
This class of antiarrhythmics work on voltage gated K channels
Class 3 – K channel blockers
This class of antiarrhythmics work on voltage gated Ca channels
Class 4 – Ca channel blockers
This class of antiarrhythmics work on sympathetic innervation?
Class 2 – B-blockers
This class of antiarrhythmics work on voltage gated Na channels by depressing phase 0 and proloinging repolarization?
Class 1A
This class of antiarrhythmics work on voltage gated Na channels shortens repolarization?
Class 1B
What parts of the heart exhibit fast-response action potentials?
Myocardium: Atrium, Ventricle, His-Purkinje
What parts of the heart exhibit slow-response action potentials?
SA node, AV node
What heart cells have excitation threshold around:
- -65mV
- -35mV
- -65mV = myocardial cells
- -35mv = nodal cells
How is heart membrane potential affected by:
- -Hypokalemia?
- -Hyperkalemia?
- -HypOkalemia –> hyperpolarizes, increases threshold (more current required)
- -HypERkalemia –> depolarizes, decreases threshold (less current required)
What is normal [K+] range?
3.5mM - 5.5mM
Do the following K+ concentrations Increase or decrease excitability?
- -[K] less than 3.5
- -[K] 5.5-7mM
- -[K] over 7mM
- -[K] less than 3.5 –> increase excitability (but, hyperpolarizes + increase threshold)
- -[K] 5.5-7mM –> increase excitability (decrease threshold)
- -[K] over 7mM –> decrease excitability (but, depolarizes + increase threshold b/c Na current inactivation)
What 3 things are different about an action potential elicited during the relative refractory period?
- -Needs higher than normal stimulus
- -Reduced amplitude
- -Reduced duration
What current determines depolarization in:
- -Myocardium?
- -Nodes?
- -Myocardium = I(Na) – sodium
- -Nodes = I(Ca, L-type) – calcium entering
List the conduction velocities from slowest to fastest
- -Atria
- -AV node
- -His - bundle branch (BB)
- -Purkinje fibers
- -Ventricles
- -AV node –0.05m/s
- -Atria –0.5m/s
- -Ventricles –0.5m/s
- -His-BB –2m/s
- -Purkinje fibers –4m/s
What channel do you block to prevent cardiac contraction
L type Ca+ channel
What measurement is analogous to cardiac preload?
EDV –End diastolic volume
What measurement is analogous to cardiac afterload?
TPR – Total peripheral (vascular) resistance
Sympathetic control of cardiac contractility is by what receptor? What G-coupling?
B1 adrenergic – Gs coupled
Parasympathetic control of cardiac contractility is by what receptor? What G-coupling?
M2 muscarinic – Gi coupled
What kind of shift (left/right) of the slope on the Pressure/Volume loop graph indicates:
- -Positive inotropy
- -Negative inotropy
- -left shift (increase slope) = positive inotropy
- -right shift (decrease slop) = negative inotropy
What are the 2 causes of systolic dysfunction?
- -Volume overload
- -Dilated cardiomyopathy
What are the 3 causes of diastolic dysfunction?
- -Pressure overload
- -Hypertrophic cardiomyopathy
- -Restrictive cardiomyopathy
In ECG, what are the causes of:
- -ST segment elevation?
- -ST segment depression?
- -ST elevation = transmural infarct, coronary vasospasm (Prinzmetal)
- -ST depression = subendocardial ischemia, exertional (stable) angina
What ECG finding in:
- -Bigeminy?
- -Trigeminy?
- -Bigeminy = PVC after every sinus beat
- -Trigeminy = PVC after every 2 sinus beats
What type of heart block?
- -No P-R association
- -Increasing PR interval w/ dropped beat
- -Fixed PR interval w/ dropped beat
- -Prolonged PR interval w/ 1:1 association
- -No P-R association = 3rd Degree
- -Increasing PR interval w/ dropped beat = 2nd Degree, Mobitz Type 1
- -Fixed PR interval w/ dropped beat = 2nd Degree, Mobitz Type 2
- -Prolonged PR interval w/ 1:1 association = 1st Degree
What type of arrhythmia can be caused by hypothyroidism or sleep apnea?
Bradycardia
What are the 2 most common SVTs (supraventricular tachycardias)
- -AV node reentry – dual AV node conduction pathways (2/3 of SVTs)
- -Bypass tract reentry – AV node and bypass tract reentry (1/5 of SVTs)
Polymorphic, long QT syndrome that is either congenital (14 genes) or acquired (drug induced).
What is it?
Torsades de Pointes
What is atrial rate and regularity in:
- -Atrial Flutter
- -Atrial Fibrillation
- -Atrial flutter = 250-300b/m, regular, no ventricular transmission
- -Atrial fibrillation =400-600b/m, irregular
What arrhythmia rhythm is the leading cause of thrombotic stroke?
Atrial fibrillation
On ECG, what kind of bundle branch block causes:
- -Left axis deviation
- -Right axis deviation
- -Left axis deviation = left ANTERIOR fascicle
- -Right axis deviation = left POSTERIOR fascicle
What is slow automatic ventricular rhythm w/ abnormal QRS caused by ectopic ventricular pacemaker origin?
Parasystole
Fast AV accessory pathway starting in bundle of Kent
ECG: short PR interval, delta wave, wide QRS
What is it?
Wolf-Parkinson-White Syndrome – Atrioventricular Reciprocating Tachycardia
Cinchonism is an adverse effect of what drug?
Quinidine – Class 1A antiarrhythmic
What drug class prefers depolarized (ischemic tissue) Na channel blockade?
Class 1B antiarrhythmics – Lidocaine, mexiletine
What antiarrhythmic drug is not used in the US anymore because of potential fatal bone marrow aplasia and pulmonary fibrosis?
Tocainide – Class 1B antiarrhytmic
What antiarrhythmic class can cause heart block?
Class 1C
The most common non-cardiac effect of this antiarrhytmic drug is blurred vision
Flecainide – Class 1C
What antiarrhythmic class is contraindicated in WPW syndrome?
Class 2
What is the primary drug o choice for sustained VT, VF and is useful against most all arrhythmias (except digitalis toxicity)?
Amiodarone – Class 3 (K channel block)
What drug is a thyroxine analog that mimics all antiarrhythmic classes and has a half life of 80 days?
Amiodarone
This drug a natural nucleoside,Gi-coupled, and has a half life of 10 seconds used to terminate PSVT
Adenosine
Magnesium can be used to prevent what?
Recurrent Torsades de Pointes (TdP)
Differentiate between Long QT Syndrome [1, 2, 3] by triggers:
- -Sleep, auditory, post-partum
- -Exercise, emotion
- -Rest, sleep, bradycardia
- -Sleep, auditory, post-partum = LQT2
- -Exercise, emotion = LQT1
- -Rest, sleep, bradycardia = LQT3
Differentiate between Long QT Syndrome [1, 2, 3] by treatment:
- -I(Na) “window” current block
- -[K+] therapy
- -B-Blockers
- -I(Na) “window” current block = LQT3
- -[K+] therapy = LQT2
- -B-Blockers = LQT1
Which Class 4 Antiarrhythmics are not effective at anti-arrhythmia, but useful in anti-anginal and anti-HTN? Why?
DHPs (dihydropyridines) – Nifedipine, Amlodipine, Felodipine, Isradipine
–Preferentially block vascular smooth muscle Ca channels
What are 4 1st line drugs used for rate control in acute and chronic A-fib or A-flutter?
- -Verapamil
- -Diltiazem
- -B-blocker
- -Digoxin
This antiarrhythmic drug is:
- -Na/K pump inhibitor
- -Has vagotonic effect
- -Has low theraputic index
- -Can cause blurred or yellow vision
- -Is a positive inotropic agent for heart failure
- -Is a cardiac glycoside
Digoxin