Treatment Of Dysrhythmia Flashcards
Mention treatment of bradycardia
Atropine, cardiac pacing, isoprenaline (transiet)
Mention the Vaughan Williams classification of dysrhythmic drugs with example
Class I: Na channels blockers (Ia: procainamide, Ib: lidocaine, Ic: propafenone)
Class II: beta-blockers
Class III: K channel blockers (amiodarone)
Class IV: Ca channel blockers (verapamil)
Non-classified: adenosine & digoxin
Mention the effect of Na channel blockade & the effects specific to each subclass wuth resoect to strength if association
Dec Vmax & delay conduction. Dec phase 4 slope & dec automaticity. Inc ERP.
Ia, moderate dissociation rate, moderate conduction blockade, moderate dec of autorhythmicity
Ib, rapid dissociation from normal tissue, minimal effect
Ic, slow diss, marker effect
Mention effect of subclasses of Na ch blockers on K channel
Ia, block K channels in both, thus increase APD & ERP
Ib, inc K efflux from fast fibers, thus dec ADP & ERP
Ic, no effect
Mention effect of subclasses of Na ch blockers on AVN
Ia, inc ADP/ERP
Ib, no effect
Ic, inc ERP by BB action
Mention effect of Na ch blockers on ADP/ERP
Ia, ^ADP/^^ERP
Ib, vvADP/vERP, as both effects affect ERP in opposite directions, while only one factor acts on ADP dec it, no effect in AVN
Ic, ADP/^ERP
Mention effects of subclasses of Na ch blockers on ECG
Ia, prolong P-R, Q-T intervals & QRS
Ib, no effect on P-R, shortens QT
Ic, prolong P-R & QRS
Mention autonomic effects of Class Ia agents & its clinical implication
Antimuscarinic, ganglion blockade, alpha blockade.
Paradoxical inc in AVN conduction res in ventricular tachycardia in AF (blocked by digoxin, BB, verapamil)
Mention cardiac effects of Class Ia
Negative inotropic & prolonged QT sydrome
Mention general adverse effects of Class Ia
Cardiotoxicity (hypotension, slow conduction, Trosade de Pointes
Thromboembolism
GIT disturbance
GR: Class Ia may precipitate thromboemblism
Stagnation of blood in atria in long standing AF, RES in thrombus formation & showers of emboli on return to sinus rhythm & improvement of contractility
Mention specific adverse effects of members of Class Ia
Procainamide, lupus like syndrome
Quinidine: thromobocytopenia & cinchonism
Disopyramidine: heart failure, urine retention & glaucoma
Mention mechanism of action & uses of Lidocaine
Has minimal effects on normal tissue but selectively blocks inactivated sodium channels in ischemic & depolarized tissue —> marked conduction block & dec autorhythmicity
Used in V tachycardia in cardiac surgery or M. infarction & digitalis induced arrhythmia
Mention adverse effects of lidocaine
- Cardiac: it is the least cardiotoxic anti-arrhythmic drug, but still it may may precipitate cardiac arrest or worsen impared conduction
- CNS: perioral parasthesias, dizzines, temors, convulsions.
Mention therapeutic uses & adverse effects of propafenone
U: SV & V arrhythmias
AE: arrhthymias, AV block, heart failure, taste disturbances, constipation, bronchospasm, dizziness, blurred vision.
Describe mechanism of action of BB in treatment of arrhythmia
Des SAN & AVN activity & slope of phase 4
Mention therapeutic uses & adverse effects of BB
U:arrhythmias due to symp overactivity, arrhythmias following MI, IV esmolol for Termination (not control) of PSVT
AE: aggravate heart failure, heart block, aggravate bronchial asthma
Describe mechanism of action of Class III agents (amiodarone)
K channel blockade: delays repolarization, blocks reentry
Na channel blockade: suppress ectopic foci, slow conduction
CCB: coronary & peripheral VD, dec sinus rate & AVN conduction
Mention therapeutic uses of Class III
Broad-Spectrum, ventricular & SV arrhythmias including WPWS.
GR: Amiodarone is given as a LD followed by maintainance dose.
Because full effect is reached after a lag period of 1-3 weeks as it has long t half.
Mention two most prominent drug interactions of amiodarone
Displaces digoxin from PP
Inhibits warfarin metabolism
Mention adverse effects of Class III agents
- Cardiac: bradycardia, heart block, hypotension
- Corneal microdeposits
- Thyroid dysfunction
- Inc liver enzymes
- Pulmonary inflitrates & fibrosis
- Peripheral neuropathy & myopathy
- Photosensitivity
Mention a drugs related to amiodarone, its advantage & uses & adverse effects
Dronedarone, devoid of iodine Similar to amiodarone not used in NYHA class iv HF Inc Torsade de Pointes
Describe pharmacodynamic action of class vi agents and its uses
Block Ca++ current in slow fibers
Dec SAN & AVN activity
Dec phase 4 slope
U: Supraventricular arrhythmias: AF & Af, termination of PSVT
Side effects of class vi agents
- Paradoxical acceleration of conduction in WPW syndrome leading due to blockade of AV conduction
- Aggravate HF
- Adverse effects of CCBs
Describe the pharmacodynamic action of adenosine & uses
Binds A1 receptors, opens K+ channel, hyperpolarization, dec Ca++ influx
Dec SAN rate & AVN conduction & inc ERP
U: Termination of PSVT
Mention side effects of adenosine
- Chest pain & dyspnea (A1 action, CI asthma)
- Headache and flushing (A2 action, VD)
- Sinus bradychardia, arrest or AV block (CI AV block)
Write a note on broad therapeutic classification of antiarrhythmic drugs
For V arrhythmia, lidocaine, phenytoin, mexillitine
For SV arrhythmia, verapimil, adenosine, digoxin
For V & SV, caused by symp overactivity: BB
Broad-spectrum: class Ia & Ic & III [WPW syndrome]
Uses of MgSO4
Digitalis induced arrhythmia associted with hypomagnesia
Torsades de Pointes
AF & Af treatment
DC in hemodynamically unstable patients
In stable patient:
Pharmacological cardioversion:
Procainamide (+digoxin, BB or verapamil to block AVN)
Maintenance of rhythm after cardioversion
Propafenone (+verapimil), Amiodarone, sotalol
Ventricular rate control
BB, verapamil/diltiazem , digoxin
Anticoagulants: to avoid thromboembolism
