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EVALUATION OF
ANTIARRHYTHMIC DRUGS
Dr. Nitin Shinde
1st Year Resident
LTMMC & GH, Mumbai- 22
DATE- 22-02-2014.
1
CONTENTS
Introduction- Basic Understanding of Arrhythmia & ECG.
Classification Of Drugs
Genetical methods.
Clinical evalua...
SA NODE FIRES AT 60-100
BEATS/SEC
SPREADS THROUGH ATRIA
ENTERS THE AV NODE
(DELAY OF 0.15 SEC)
PROPAGATES THROUGH HIS
PURK...
The Resting Membrane Potential of the cell is -95mV
This ionic gradient is maintained by
Active mechanisms like the
Na+ pu...
Phase 0:
RapidDepolarisation
(Na+ influx)
Phase 1:
Early Repolarisation
(Inward Na+ current
deactivated,
Outflow of K+):
T...
REGULATION BY AUTONOMIC TONE
Parasympathetic/Vagus Nerve
stimulation:
• Ach binds to M receptors, releasing G
protein βγ s...
Cardiac Arrhythmias
7
Arrhythmia means an Abnormal heart
rhythm
Results from the abnormalities of:
 Impulse generation (Rate or Site of origin)...
CLASSIFICATION OF ARRHYTHMIAS
1. Characteristics:
a. Flutter – very rapid but regular contractions
b. Tachyarrhthmia – inc...
MECHANISMS OF CARDIAC ARRHYTHMIAS
(A) Enhanced Automaticity:
In cells which normally display spontaneous
diastolic depolar...
A normal cardiac action potential may be
interrupted or followed by an abnormal
depolarization
Reaches threshold & causes ...
(C) Re-entrant Arrhythmia
Defined as circulation of an
activation wave around an
inexitable object
3 requirements for Re-e...
Unidirectional
Block
Establishment of Re-entrant circuit
13
NORMAL ECG :
P wave – Atrial depolarisation.
QRS wave – ventricular depolarisation.
T wave – ventricular repolarisation.
14
Management Of
Arrhythmias
15
MANAGEMENT
Acute Management
Prophylaxis
Non Pharmacological
Pharmacological
16
NON PHARMACOLOGICAL
Acute
1. Vagal Maneuvers
2. DC Cardioversion
Prophylaxis
1. Radiofrequency Ablation
2. Implantable Def...
PHARMACOLOGICAL APPROACH
Drugs may be antiarrhythmic by:
Suppressing the initiator mechanism
Altering the re-entrant circu...
VAUGHAN WILLIAMS CLASSIFICATION
Phase 4
Phase 0
Phase 1
Phase 2
Phase 3
0 mV
-
80m
V
II
I
III
IV
Class I: block Na+ channe...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Class I – blocker’s of fast Na+ channels
Subclass IA
Cau...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Subclass IB
Weak phase 0 depression
Shortened depolariza...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Subclass IC
Strong Phase 0 depression
No effect of depol...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Class II – β–adrenergic blockers
Based on two major acti...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Class III – K+ channel blockers
Developed because some p...
CLASSIFICATION OF ANTIARRHYTHMICS
(BASED ON MECHANISMS OF ACTION)
Class IV – Ca2+ channel blockers
slow rate of AV-conduct...
26
27
28
Bradyarrhythmias
Resting heart rate of <60/min
Classified as Atrial/AV Nodal/Ventricular
Management:
• Acute→ iv atropine
...
EXPERIMENTAL
EVALUATION OF
ANTIARRHYTHMIC DRUG
ACTION…………..
30
Evaluation of Antiarrhythmic Drug Action
 In-Vitro Models:
1) Isolated guinea pig papillary muscle.
2) Langendorff techni...
EVALUATION OF ANTIARRHYTHMIC DRUGS
32
IN VIVO METHODS
IN-VIVO METHODS :
I. Chemically induced arrhythmia
II. Electrically induced arrhythmia
III. Mechanically induced arrhythmi...
I.CHEMICALLY INDUCED ARRHTHMIA
A large number of chemical agents alone or
in combination are capable of inducing
arrhythmi...
ACONITINE ANTAGONISM IN RATS
PRINCIPLE: Aconite persistently activate sodium
channel.
METHOD:
Continues infusion
in saphen...
EVALUATION
The anti-arrhythmic effect of the test compound is
measured by the amount of aconitine/100 gm animal
(infusion ...
DIGOXIN INDUCED ARRHYTHMIA IN GUINEA
PIGS
PRINICPLE:Over dose of cardiac glycosides induces
ventricular extrasystoles, ven...
METHOD :
Anesthetised male guinea pigs.(Marioth 350-500
gms)
Trachea, jugular vein and carotid artery are
catheterized.
Te...
EVALUATION
 The period until the onset of ventricular extra systoles,
ventricular fibrillation and cardiac arrest is reco...
STROPHANTHIN OR OUABAIN INDUCED ARRHYTHMIA
IN DOG:
Principle :Strophanthin K induces ventricular
tachycardia and multifoca...
METHOD CTD..
Strophanthin K administered by
continuous i.v infusion at a rate of
3mg/kg/min
When the arrhythmias are stabl...
EVALUATION
Ajmalin , quinidine and lidocaine reestablish normal sinus
rhythm at 1 mg/kg ,3 mg/kg iv and 10 mg/kg id.
Test ...
ADRENALINE INDUCED ARRHTHMIA
PRINCIPLE: Adrenaline at high dose may
precipitate arrhythmia.
43
METHOD:
Evaluation: A test compound is said to have
antiarrhythmic effect if the extrasystole disappears
immediately after...
HALOTHANE-ADRENALINE ARRHYTHMIA
Normal pacemaker activity of the heart is under the control
of sympathetic and vagal influ...
METHOD
1% halothane vaporized by 100% oxygen used for
anesthesia
The infusion rate around 2 – 3 µg/kg/min
Intravenous infu...
II.ELECTRICALLY INDUCED ARHYTHMIAS
47
VENTRICULAR FIBRILLATION ELECTRICAL
THRESHOLD
Principle :Ventricular fibrillations can be induced
by various tec. Of elect...
PROCEDURE
↓
Sinus node is crushed and electrical
stimulation is provided with Ag-AgCl
stimulating electrode embedded in a ...
PROCEDURE CTD…
Test drug/ std/control Drugs are
administered through the femoral
vein.
Anodal const. current for 400ms is
...
EVALUATION
To determine VFT :- A 0.2 to 1.8 second train of
50 Hz pulses is delivered 100 ms after every
18thbasic driving...
PROGRAMMED ELECTRICAL STIMULATION INDUCED
RE- ENTRY ARRHYTHMIA
In dogs with old MI reopening of thoracic incision
Bipolar ...
COMMENTS
Since arrhythmias induced by applying premature extra
stimuli
mechanism of generation is thought to be re-entry a...
III.MECHANICALLY INDUCED ARRHYTHMIA
Coronary artery occlusion/reperfusion
arrhythmia
54
CORONARY ARTERY
OCCLUSION/REPERFUSION ARRHYTHMIA
Arrhythmias –induced directly by ischemia and
reperfusion
• Coronary arte...
REQUIREMENTS
Animals – Dogs (20-25Kg)
Anesthetic – Thiobutobarbital sodium (30mg/kg)
PROCEDURE:
Animals – selected
↓
Anest...
Silk suture is placed around LAD
↓
After 45 min(equilibration) – test/std/control-
administered through saphenous vein
↓
A...
EVALUATION
Mortality
Hemodynamics
Arrhythmia
 Ventricular fibrillation
 % animals with VF.
58
CANINE TWO-STAGE CORONARY LIGATION
ARRHYTHMIA
“Two-stage” first stage is the stage of partial occlusion
second stage of pe...
METHOD
In the first stage, isolated LAD surgically isolated
The first ligature was drawn snugly but not tightly around the...
CONTD….
Arrhythmic ratio:
The number of ventricular ectopic beats (/min)
Total QRS complexes (/min).
For example, the arrh...
ADVANTAGES
Produces lesser mortality as compared to complete
occlusion
Very stable arrhythmias, PVC and VT can be obtained...
LIMITATIONS
Cardiac surgery under anesthesia in a sterile environment
is needed
The technique of LAD isolation requires sk...
IV .EXERCISE
INDUCED
ARRHYTHMIA
64
EXERCISE INDUCED VENTRICULAR
FIBRILLATION
PURPOSE AND RATIONALE:
Tests combining coronary constriction with physical
exerc...
• REQUIREMENTS:
Animals – Mongrel dogs (15 -19 kg)
Anesthetic – Sodium pentobarbitone (10mg/kg) i.v.
SURGICAL PREPARATION:...
↓
Pair of insulated silver coated wires – sutured on left
and right ventricles- measure HR (By Gould
biotachometer)
↓
Occl...
EXERCISE-PLUS-ISCHEMIA TEST
68
3-4 weeks after the production of MI
↓
Animals – run on a motor –driven treadmill at speed
6.4 km/hr (o%) grade.
↓
Work lo...
IN VITRO METHOD:
1) Isolated guinea pig papillary muscle.
2) Langendorff technique
3) Acetylcholine & potassium Induced
ar...
1)ANTI-ARRHYTHMIC ACTIVITY IN THE ISOLATED
RIGHT VENTRICULAR GUINEA-PIG PAPILLARY
MUSCLE:
Principle: In right ventricular ...
METHOD:
The heart is removed & placed into a pre-warmed, pre-
oxygenated PSS & right ventricle is opened
The tendinous end...
Pulses are delivered using constant voltage
stimulator and
the developed tension is recorded using
polygraph recorder.
The...
EVALUATION:
Change in Effective Refractory Period (Post treatment minus
pretreatment)
Degree of shift in the strength-dura...
LANGENDORFF TECHNIQUE
75
PRINCIPLE: Heart is perfused in a retrograde direction from
aorta either at constant pressure or at constant flow with
oxy...
PROCEDURE
Animal – Guinea pig (300-500g)
Animal – selected

Sacrificed (stunning)

heart – removed – placed in Ringer’s ...
Ligature – placed around LAD

Test /std/control - administered.

Occluded for 10 minutes

reperfusion

ECG electrode –...
Heart rate measured through chronometer
coupled to polygraph,
Contractile force measured by force transducer.
Incidence an...
80
3)ACETYLCHOLINE & POTASSIUM INDUCED
ARRHYTHMIA
New Zealand White rabbits 0.5 to 3 kg .
The animals are sacrified and heart...
A mechanical record is taken on kymograph.
Controlled arrhythmia are produced and allowed
to continue for 6 to 10 mins.
Af...
Genetic models
83
Mutations in the γ 2 subunit (PRKAG2) of AMP
activated protein kinase produce an unusual human
cardiomyopathy characterize...
HUMAN AND MOUSE CARDIAC GENES
RELATED TO INHERITED ARRHYTHMIA
85
86
Arrhythmia type Experimental model
Wolff Parkinson white
syndrome
Transgenic PRKAG2 model
Atrial Flutter Atrial flutter in...
CLINICAL
EVALUATION:
88
BIOEQUIVALENCE STUDY
Inclusion criteria:
 A healthy male or female 18 to 59 years of age.
 BMI range - 18-35 kg/m2,
 No...
EXCLUSION CRITERIA
Women who are pregnant or breast feeding.
Known hypersensitivity or allergy to drug.
A history or prese...
91
STUDY DESIGNS IN IMPLANTABLE CARDIOVERTER-
DEFIBRILLATOR TRIALS
92
MINIMAL CLINICAL PARAMETERS THAT
SHOULD BE STUDIED AT BASELINE
Left ventricular ejection
fraction
Treatment at enrolment
A...
PRIMARY OUTCOME PARAMETER
Death: Most Important primary outcome.
All-cause death should be classified in the following gro...
95
SECONDARY OUTCOME PARAMETERS
Symptoms and quality of life
Recommended as secondary outcome parameter
No reliable instru...
96
EHRA ATRIAL FIBRILLATION SYMPTOMS
CLASSIFICATION
97
98
ASSESSMENT OF RHYTHM & ECG-BASED OUTCOME
PARAMETERS
AVAILABLE ECG METHODS
•Non-continuous standard ECG recording
Sympto...
CURRENT STATUS OF ANTIARRHYTHMIC DRUGS
Based on results of large Randomized controlled trials
Cardioversion /defibrillator...
CONCLUSION
Although no animal model can accurately
resemble with human disease condition and
species differences also exis...
REFERENCES
Vogel WH, Schölkens BA. Drug Discovery and Evaluation [Internet]. Vogel HG, Vogel WH,
Schölkens BA, Sandow J, M...
102
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Evaluation of antiarrhythmic drugs (1)

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Evaluation of antiarrhythmic drugs (1)

  1. 1. EVALUATION OF ANTIARRHYTHMIC DRUGS Dr. Nitin Shinde 1st Year Resident LTMMC & GH, Mumbai- 22 DATE- 22-02-2014. 1
  2. 2. CONTENTS Introduction- Basic Understanding of Arrhythmia & ECG. Classification Of Drugs Genetical methods. Clinical evaluation. Conclusion. In – Vitro methods: 1) Isolated guinea pig papillary muscle. 2) Langendorff technique 3) Acetylcholine & potassium Induced arrhythmia In-Vivo Methods: Chemically induced arrhythmia Electrically induced arrhythmia Mechanically induced arrhythmia Exercise Induced Arrhythmia 2
  3. 3. SA NODE FIRES AT 60-100 BEATS/SEC SPREADS THROUGH ATRIA ENTERS THE AV NODE (DELAY OF 0.15 SEC) PROPAGATES THROUGH HIS PURKINJE SYSTEM DEPOLARIZES VENTRICLES BEGINNING FROM ENDOCARDIAL SURFACE OF APEX TO EPICARDIAL SURFACE OF BASE Normal Sinus Rhythm 3
  4. 4. The Resting Membrane Potential of the cell is -95mV This ionic gradient is maintained by Active mechanisms like the Na+ pump and Na+/K+ ATPase (Electrogenic) Fixed anionic charges within the cell 4
  5. 5. Phase 0: RapidDepolarisation (Na+ influx) Phase 1: Early Repolarisation (Inward Na+ current deactivated, Outflow of K+): Transient Outward Current Phase 2: Plateau Phase (Slow inward Ca2+ Current balanced by outward delayed rectifier K+ Current) Phase 3: Late Repolarisation (Ca 2+current inactivates, K+ outflow) Action Potential of Cardiac Muscle 5
  6. 6. REGULATION BY AUTONOMIC TONE Parasympathetic/Vagus Nerve stimulation: • Ach binds to M receptors, releasing G protein βγ subunits • Activate Ach dependent K+ current • ↓ slope of Phase 4 Sympathetic stimulation: • Activation of β1 receptors • Augmentation of L-type Ca2+ current and funny currents • ↑ slope of Phase 4 6
  7. 7. Cardiac Arrhythmias 7
  8. 8. Arrhythmia means an Abnormal heart rhythm Results from the abnormalities of:  Impulse generation (Rate or Site of origin)  Conduction  Both 8
  9. 9. CLASSIFICATION OF ARRHYTHMIAS 1. Characteristics: a. Flutter – very rapid but regular contractions b. Tachyarrhthmia – increased rate c. Bradyarrhythmia – decreased rate d. Fibrillation – disorganized contractile activity 2. Sites involved: a. Ventricular b. Atrial c. SA Node d. AV Node Supraventricular 9
  10. 10. MECHANISMS OF CARDIAC ARRHYTHMIAS (A) Enhanced Automaticity: In cells which normally display spontaneous diastolic depolarization (SA Node, AV Node, His- Purkinje System) Automatic behavior in sites that ordinarily lack pacemaker activity 10
  11. 11. A normal cardiac action potential may be interrupted or followed by an abnormal depolarization Reaches threshold & causes secondary upstrokes 2 Major forms: 1. Early Afterdepolarization 2. Late Afterdepolarization (B) Afterdepolarization and Triggered Automaticity 11
  12. 12. (C) Re-entrant Arrhythmia Defined as circulation of an activation wave around an inexitable object 3 requirements for Re-entrant Arrhythmia: 1. Obstacle to conduction 2. Unidirectional block 3. CT>ERP 12
  13. 13. Unidirectional Block Establishment of Re-entrant circuit 13
  14. 14. NORMAL ECG : P wave – Atrial depolarisation. QRS wave – ventricular depolarisation. T wave – ventricular repolarisation. 14
  15. 15. Management Of Arrhythmias 15
  16. 16. MANAGEMENT Acute Management Prophylaxis Non Pharmacological Pharmacological 16
  17. 17. NON PHARMACOLOGICAL Acute 1. Vagal Maneuvers 2. DC Cardioversion Prophylaxis 1. Radiofrequency Ablation 2. Implantable Defibrillator Pacing (Temporary/ Permanent) 17
  18. 18. PHARMACOLOGICAL APPROACH Drugs may be antiarrhythmic by: Suppressing the initiator mechanism Altering the re-entrant circuit 1. Terminate an ongoing arrhythmia 2. Prevent an arrhythmia 18
  19. 19. VAUGHAN WILLIAMS CLASSIFICATION Phase 4 Phase 0 Phase 1 Phase 2 Phase 3 0 mV - 80m V II I III IV Class I: block Na+ channels Ia (quinidine, procainamide, disopyramide) (1-10s) Ib (lignocaine) (<1s) Ic (flecainide) (>10s) Class II: ß-adrenoceptor antagonists (atenolol, sotalol) Class III: block K+ channels (amiodarone, dofetilide,sotalol) Class IV: Ca2+ channel antagonists (verapamil, diltiazem) 19
  20. 20. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Class I – blocker’s of fast Na+ channels Subclass IA Cause moderate Phase 0 depression Prolong repolarization Increased duration of action potential Includes Quinidine – 1st antiarrhythmic used, treat both atrial and ventricular arrhythmias, increases refractory period Procainamide - increases refractory period but side effects Disopyramide – extended duration of action, used only for treating ventricular arrthymias 20
  21. 21. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Subclass IB Weak phase 0 depression Shortened depolarization Decreased action potential duration Includes Lidocane (also acts as local anesthetic) – blocks na+ channels mostly in ventricular cells, also good for digitalis- associated arrhythmias Mexiletine - oral lidocaine derivative, similar activity Phenytoin – anticonvulsant that also works as antiarrhythmic similar to lidocane 21
  22. 22. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Subclass IC Strong Phase 0 depression No effect of depolarization No effect on action potential duration Includes Flecainide (initially developed as a local anesthetic) Slows conduction in all parts of heart, Also inhibits abnormal automaticity Propafenone Also slows conduction Weak β – blocker Also some Ca2+ channel blockade 22
  23. 23. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Class II – β–adrenergic blockers Based on two major actions 1) blockade of myocardial β–adrenergic receptors 2) Direct membrane-stabilizing effects related to Na+ channel blockade Includes Propranolol causes both myocardial β–adrenergic blockade and membrane- stabilizing effects Slows SA node and ectopic pacemaking Can block arrhythmias induced by exercise or apprehension Other β–adrenergic blockers have similar therapeutic effect Metoprolol Nadolol Atenolol Acebutolol Pindolol Stalol Timolol Esmolol 23
  24. 24. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Class III – K+ channel blockers Developed because some patients negatively sensitive to na channel blockers (they died!) Cause delay in repolarization and prolonged refractory period Includes Amiodarone – Prolongs action potential by delaying K+ efflux but many other effects characteristic of other classes Ibutilide – slows inward movement of na+ in addition to delaying K + influx. Bretylium – First developed to treat hypertension but found to also suppress ventricular fibrillation associated with myocardial infarction Dofetilide - Prolongs action potential by delaying K+ efflux with no other effects 24
  25. 25. CLASSIFICATION OF ANTIARRHYTHMICS (BASED ON MECHANISMS OF ACTION) Class IV – Ca2+ channel blockers slow rate of AV-conduction in patients with atrial fibrillation Includes Verapamil – blocks Na+ channels in addition to Ca2+; also slows SA node in tachycardia Diltiazem 25
  26. 26. 26
  27. 27. 27
  28. 28. 28
  29. 29. Bradyarrhythmias Resting heart rate of <60/min Classified as Atrial/AV Nodal/Ventricular Management: • Acute→ iv atropine • Permanent→ Pacemakers. 29
  30. 30. EXPERIMENTAL EVALUATION OF ANTIARRHYTHMIC DRUG ACTION………….. 30
  31. 31. Evaluation of Antiarrhythmic Drug Action  In-Vitro Models: 1) Isolated guinea pig papillary muscle. 2) Langendorff technique 3) Acetylcholine & potassium Induced arrhythmia In-Vivo Methods: Chemically induced arrhythmia Electrically induced arrhythmia Mechanically induced arrhythmia Exercise Induced Arrhythmia 31
  32. 32. EVALUATION OF ANTIARRHYTHMIC DRUGS 32 IN VIVO METHODS
  33. 33. IN-VIVO METHODS : I. Chemically induced arrhythmia II. Electrically induced arrhythmia III. Mechanically induced arrhythmia IV. Exercise Induced arrhythmia. 33
  34. 34. I.CHEMICALLY INDUCED ARRHTHMIA A large number of chemical agents alone or in combination are capable of inducing arrhythmia. 34
  35. 35. ACONITINE ANTAGONISM IN RATS PRINCIPLE: Aconite persistently activate sodium channel. METHOD: Continues infusion in saphenous vein ACONITE 5mg/kg dissolved in 0.1 N HN03 MONITOR LEAD II ECG EVERY 30 SECONDS Anaesthetize with Urathene 1.25 g/kg Test compound 3 mg/kg orally or IV 5 minutes before aconite infusion 35
  36. 36. EVALUATION The anti-arrhythmic effect of the test compound is measured by the amount of aconitine/100 gm animal (infusion duration ), required to precipitate... Ventricular extra systoles. Ventricular tachycardia. Ventricular fibrillation and death. E.g- procainamide 5 mg/kg IV & lidocaine 5 mg/kg IV leads to increase in lethal dose by 65%. 36
  37. 37. DIGOXIN INDUCED ARRHYTHMIA IN GUINEA PIGS PRINICPLE:Over dose of cardiac glycosides induces ventricular extrasystoles, ventricular fibrillation, and finally death. 37
  38. 38. METHOD : Anesthetised male guinea pigs.(Marioth 350-500 gms) Trachea, jugular vein and carotid artery are catheterized. Test grp receives Test drug either orally 1 hr or iv 1 min prior to the infusion while controlol group receieves digoxin infusion only at rate of 85 mg / kg in 0.266 ml/min. until cardiac arrest occurs. Lead III ECG RECORDED 38
  39. 39. EVALUATION  The period until the onset of ventricular extra systoles, ventricular fibrillation and cardiac arrest is recorded.  Total amount of infused Digoxin to induce ventricular extra systoles, or ventricular fibrillation and cardiac arrest is calculated.  Using Student’s t-test the doses of digoxin needed to induce VES, VF and Cardiac arrest respectivelyafter treatment with aniarrhythmic drugs are compared with control receiving digoxin only.  Eg- Standard drugs are lidocaine 3 mg/kg iv . 39
  40. 40. STROPHANTHIN OR OUABAIN INDUCED ARRHYTHMIA IN DOG: Principle :Strophanthin K induces ventricular tachycardia and multifocal ventricular arrhythmia in dogs. METHOD: Dogs of either sex are first anesthetized & artificial respiration is given Two peripheral veins are cannulated for the administration of the arrhythmia inducing substance and the test compound. For intraduodenal administration of the test drug, the duodenum is cannulated.. 40
  41. 41. METHOD CTD.. Strophanthin K administered by continuous i.v infusion at a rate of 3mg/kg/min When the arrhythmias are stable for 10 min, the test substance is administered i.v ( 1.0 and 5.0 mg/kg) or i.d ( 10 and 30 mg/kg) ECG recordings are obtained at 0.5, 1, 2, 5 and 10 min following administration of test drugs and further duration increased if required 41
  42. 42. EVALUATION Ajmalin , quinidine and lidocaine reestablish normal sinus rhythm at 1 mg/kg ,3 mg/kg iv and 10 mg/kg id. Test compound is said to have an ant arrhythmic effect if extra systoles disappear within 15 min . The test drug is considered to have “ NO Effect” if it does not improve strophanthin intoxication within 60 min. Test compound is said to have an ant arrhythmic effect if the extra systoles immediately disappear . If not then the increasing doses are administered at 15 min- intervals. If the test substance does reverse the arrhythmias the next dose is administered after the reappearance of stable arrhythmias. I.D I.V 42
  43. 43. ADRENALINE INDUCED ARRHTHMIA PRINCIPLE: Adrenaline at high dose may precipitate arrhythmia. 43
  44. 44. METHOD: Evaluation: A test compound is said to have antiarrhythmic effect if the extrasystole disappears immediately after drug administration. Dogs (10-11 kg) are anaesthetized with pentobarbitone (30-40 mg/kg ) i.p Femoral vein is cannulated and adrenaline is infused at a rate of 2-2.5 mg/kg via femoral cannula Test drug is administered 3 mins. After adrenaline infusion and Lead II ECG Recorded. 44
  45. 45. HALOTHANE-ADRENALINE ARRHYTHMIA Normal pacemaker activity of the heart is under the control of sympathetic and vagal influences Sympathomimetic drugs are known to increase pacemaker activity Certain anesthetics, are known to highly sensitize the myocardium to catecholamines Dogs and Guinea pigs 45
  46. 46. METHOD 1% halothane vaporized by 100% oxygen used for anesthesia The infusion rate around 2 – 3 µg/kg/min Intravenous infusion of adrenaline Adjusting the infusion speed enough to produce stable vt lasting about 20 min Drugs injected by iv bolus 46
  47. 47. II.ELECTRICALLY INDUCED ARHYTHMIAS 47
  48. 48. VENTRICULAR FIBRILLATION ELECTRICAL THRESHOLD Principle :Ventricular fibrillations can be induced by various tec. Of electrical stimulation like single pulse stimulation , train of pulse stimulation , continous 50 HZ stimulation. Ventricular fibrillation threshold :The minimal current intensity of the pulse train required to induce sustained ventricular fibrillation. Requirement: Animals – Adult dogs (8-12kg) Anesthetic – Sodium pentobarbital (35mg/kg) 48
  49. 49. PROCEDURE ↓ Sinus node is crushed and electrical stimulation is provided with Ag-AgCl stimulating electrode embedded in a Teflon disc sutured to anterior surface of left venticle. Chest cavity is opened Heart suspended in pericardial cradle Artificial respiration – Harvard respiratory pump B.P – monitored Body temperature – maintained by thermal blanket Adult dogs are anaesthetized and heart is exposed. 49
  50. 50. PROCEDURE CTD… Test drug/ std/control Drugs are administered through the femoral vein. Anodal const. current for 400ms is applied through the driving electrode ECG of lead II is recorded 50
  51. 51. EVALUATION To determine VFT :- A 0.2 to 1.8 second train of 50 Hz pulses is delivered 100 ms after every 18thbasic driving stimulus. The current intensity is increased from diastolic threshold. When ventricular fibrillation occurs, the heart is immedietely defibrilleted and allowed to recover for 15-20 mins. VFT is determined before and after administration of test drugs at given time intervals. Compared using student - t Test. 51
  52. 52. PROGRAMMED ELECTRICAL STIMULATION INDUCED RE- ENTRY ARRHYTHMIA In dogs with old MI reopening of thoracic incision Bipolar electrodes sutured on the non- infarcted left ventricle 3 premature extra stimuli applied to induce vt or vf If sustained vt or vf occurred, epicardial defibrillation performed to stop them After 2 control runs, iv bolus injection of drug given Same protocol of arrhythmia induction repeated 52
  53. 53. COMMENTS Since arrhythmias induced by applying premature extra stimuli mechanism of generation is thought to be re-entry around the scar tissue of the old MI. Drug effects demonstrated by the change in severity before and after the drug administration This arrhythmia model can used to demonstrate the proarrhythmic potentials 53
  54. 54. III.MECHANICALLY INDUCED ARRHYTHMIA Coronary artery occlusion/reperfusion arrhythmia 54
  55. 55. CORONARY ARTERY OCCLUSION/REPERFUSION ARRHYTHMIA Arrhythmias –induced directly by ischemia and reperfusion • Coronary artery ligation in anesthetized dog results in:  ↑ in HR  ↑in heart contractility  ↑ in BP  Ventricular arrhythmias 55
  56. 56. REQUIREMENTS Animals – Dogs (20-25Kg) Anesthetic – Thiobutobarbital sodium (30mg/kg) PROCEDURE: Animals – selected ↓ Anesthetized ↓ Artificial respiration – positive pressure respirator ↓ Femoral artery – cannulated and connected to pressure transducer ↓ Chest cavity –opened LAD is exposed ↓ 56
  57. 57. Silk suture is placed around LAD ↓ After 45 min(equilibration) – test/std/control- administered through saphenous vein ↓ After 20 min- ligature of coronary artery is closed for 90 min ↓ Occlusion released – reperfusion period maintained for 30 min. • All the parameters – recorded • At the end – surviving animals are sacrificed by an overdose of Pentobarbital sodium. 57
  58. 58. EVALUATION Mortality Hemodynamics Arrhythmia  Ventricular fibrillation  % animals with VF. 58
  59. 59. CANINE TWO-STAGE CORONARY LIGATION ARRHYTHMIA “Two-stage” first stage is the stage of partial occlusion second stage of permanent occlusion 59
  60. 60. METHOD In the first stage, isolated LAD surgically isolated The first ligature was drawn snugly but not tightly around the artery a state of partial occlusion for 30 min then chest is closed electrocardiogram (ECG) shows only premature ventricular contractions (PVC) then another suture is used to completely occlude the LAD Arrhythmia develops 24-48 hrs after ligation and abate in 3-5 days 60
  61. 61. CONTD…. Arrhythmic ratio: The number of ventricular ectopic beats (/min) Total QRS complexes (/min). For example, the arrhythmic ratio is 0 during the sinus rhythm, while it is 1 during ventricular tachycardia. 61
  62. 62. ADVANTAGES Produces lesser mortality as compared to complete occlusion Very stable arrhythmias, PVC and VT can be obtained which usually appear several hours later Thus resembles late arrhythmias in post mi patients Another advantage :- Drugs administered in a conscious state evaluation cns side effects 62
  63. 63. LIMITATIONS Cardiac surgery under anesthesia in a sterile environment is needed The technique of LAD isolation requires skill Guinea pigs never develop ischemia by in vivo coronary ligation 63
  64. 64. IV .EXERCISE INDUCED ARRHYTHMIA 64
  65. 65. EXERCISE INDUCED VENTRICULAR FIBRILLATION PURPOSE AND RATIONALE: Tests combining coronary constriction with physical exercise may resemble most closely the situation in coronary patients 65
  66. 66. • REQUIREMENTS: Animals – Mongrel dogs (15 -19 kg) Anesthetic – Sodium pentobarbitone (10mg/kg) i.v. SURGICAL PREPARATION: Animals – selected ↓ Anesthetized ↓ Chest cavity – opened ↓ Heart suspended in pericardial cradle ↓ Around left circumflex artery – Doppler flow inducer- to measure blood pressure - Hydraulic occluder - to occlude coronary artery are placed 66
  67. 67. ↓ Pair of insulated silver coated wires – sutured on left and right ventricles- measure HR (By Gould biotachometer) ↓ Occlusion of LAD(Two stage) ↓ Myocardial infarction ↓ After 24 hrs- test drug/std/control - administered During this experiment: • Transdermal fentanyl patch (↓post operative discomfort) • Bupivacaine HCl • Antibiotic therapy(amoxicillin) 67
  68. 68. EXERCISE-PLUS-ISCHEMIA TEST 68
  69. 69. 3-4 weeks after the production of MI ↓ Animals – run on a motor –driven treadmill at speed 6.4 km/hr (o%) grade. ↓ Work load - ↑every 3 min for total of 18 mins(0,4,8,12,16%) ↓ During last minute-treadmill is stopped- left circum flex artery- occluded for additional 1 min. ↓ After 10-20 sec of VF – defibrillation is achieved without any delay by placing large metal plates across animal’s chest. EVALUATION: The exercise plus ischemia test is repeated after administration of the test drug and compared to control (saline) group.The effect of drugs intervention on arrhythmia formation are determined using chi square test with yates correction. 69
  70. 70. IN VITRO METHOD: 1) Isolated guinea pig papillary muscle. 2) Langendorff technique 3) Acetylcholine & potassium Induced arrhythmia 70
  71. 71. 1)ANTI-ARRHYTHMIC ACTIVITY IN THE ISOLATED RIGHT VENTRICULAR GUINEA-PIG PAPILLARY MUSCLE: Principle: In right ventricular guinea pig papillary muscle developed tension (DT), excitability (EX), and effective refractory period (ERP) are measured. 71
  72. 72. METHOD: The heart is removed & placed into a pre-warmed, pre- oxygenated PSS & right ventricle is opened The tendinous end of the papillary muscle is ligated with a silk thread and the chordae tendinae are freed from the ventricle The preparation is mounted in organ bath & experimental conditions are maintained The silk thread is used to connect the muscle to forced transducer and muscles are field stimulated to contract isometrically at a duration of 1 ms. 72
  73. 73. Pulses are delivered using constant voltage stimulator and the developed tension is recorded using polygraph recorder. The force frequency curve is obtained by measuring the developed tension over a range of stimulus frequencies (0.3,0.5,0.8,1.0,1.2 HZ) The percentage change in post treatment versus pretreatment developed tension at 1 HZ is used to quantitate the agents inotropic effect. 73
  74. 74. EVALUATION: Change in Effective Refractory Period (Post treatment minus pretreatment) Degree of shift in the strength-duration curve.i.e.(area between post and pre treatment curve) percentage changes in post treatment developed tension. Duration of action potential. Contraction force. The results of above calculations are to classify the compounds as class I ,III or IV antiarrhythmic agents on the basis of its effect on developed tension, excitability and effective refractory period. EVALUATION MOA OF DRUG EXCITABILITY Na+ Channel Contraction Force Ca+2 Channel Effective Refractory period K + Channel 74
  75. 75. LANGENDORFF TECHNIQUE 75
  76. 76. PRINCIPLE: Heart is perfused in a retrograde direction from aorta either at constant pressure or at constant flow with oxygenated saline soln. Retrograde perfusion closes the aortic valve , just as in situ heart during diastole . The perfusate is displaced through the coronary artery using a canula inserted in the ascending aorta following of the coronary sinus and opened right atrium and flows out via the right ventricle and pulmonary artery. 76
  77. 77. PROCEDURE Animal – Guinea pig (300-500g) Animal – selected  Sacrificed (stunning)  heart – removed – placed in Ringer’s solution (37⁰C)  Aorta – located and cut – cannulated with Ringer’s solution (perfused at 40 mm Hg)  Ligature – placed around LAD 77
  78. 78. Ligature – placed around LAD  Test /std/control - administered.  Occluded for 10 minutes  reperfusion  ECG electrode – pulsatile stimulation, induction of arrhythmia  Heart rate and contractile force measured 78
  79. 79. Heart rate measured through chronometer coupled to polygraph, Contractile force measured by force transducer. Incidence and duration of ventricular fibrillation or ventricular tachycardia is recorded in the control as well as test group. 79
  80. 80. 80
  81. 81. 3)ACETYLCHOLINE & POTASSIUM INDUCED ARRHYTHMIA New Zealand White rabbits 0.5 to 3 kg . The animals are sacrified and heart removed immediately.Atria dissected from other tissue in Ringer’s solution. Fibrillation is produced when atria are exposed to Acetylcholine 3x10-4 g/ml or 0.1 gm potassium chloride. After 5 mins exposure to Ach. Or KCL the atria are stimulated with rectangular pulses of 0.75 ms duration of 10 V. 81
  82. 82. A mechanical record is taken on kymograph. Controlled arrhythmia are produced and allowed to continue for 6 to 10 mins. After rest period of 30 mins test compound is added to bath. Evaluation:- Test compound is found to be effective if fibrillation disappears immediately or within 5 mins following test drug supplementation to organ bath. 82
  83. 83. Genetic models 83
  84. 84. Mutations in the γ 2 subunit (PRKAG2) of AMP activated protein kinase produce an unusual human cardiomyopathy characterized by ventricular hypertrophy and wolf–parkinson white syndrome . Mutations of the K+ channel genes HERG and KVLQT 1 cause the autosomal dominant long QT syndrome, Lande et al., Evaluated a transgenic mouse over- expressing a dominant negative kvlqt 1 isoform, as an in vivo screening model for ikr blocking drugs. Transgenic mice over-expressing the inflammatory cytokine tumour necrosis factor tnf-α (tnf-α mice) in the heart develop a progressive heart failure syndrome . These transgenic animals are more prone to re- entrant arrhythmia. 84
  85. 85. HUMAN AND MOUSE CARDIAC GENES RELATED TO INHERITED ARRHYTHMIA 85
  86. 86. 86
  87. 87. Arrhythmia type Experimental model Wolff Parkinson white syndrome Transgenic PRKAG2 model Atrial Flutter Atrial flutter induced by Ach and rapid pacing. Atrial flutter by aconite. Canine right atrial occlusion injury model. Atrial Fibrillation Atrial fibrillation in the isolated langendorff perfused heart. Canine model of chronic atrial fibrillation. PACAP-27 induced atrial fibrillation. Ventricular Fibrillation Ventricular fibrillation electrical threshold. Canine model of two stage ligation. Ventricular arrhythmia during exercise by ischemia. 87
  88. 88. CLINICAL EVALUATION: 88
  89. 89. BIOEQUIVALENCE STUDY Inclusion criteria:  A healthy male or female 18 to 59 years of age.  BMI range - 18-35 kg/m2,  No significant disease or abnormal laboratory values  Normal 12-lead ECG  Adequately informed of the nature and risks of the study  written informed consent 89
  90. 90. EXCLUSION CRITERIA Women who are pregnant or breast feeding. Known hypersensitivity or allergy to drug. A history or presence of asthma or other pulmonary disease, thyroid disease (hypo- or hyperthyroidism), hepatitis or other liver disease. Any Medical Disease or surgical condition. The presence of abnormal lab values which are considered clinically significant. History of smoking or alcohol within past 1 year. 90
  91. 91. 91
  92. 92. STUDY DESIGNS IN IMPLANTABLE CARDIOVERTER- DEFIBRILLATOR TRIALS 92
  93. 93. MINIMAL CLINICAL PARAMETERS THAT SHOULD BE STUDIED AT BASELINE Left ventricular ejection fraction Treatment at enrolment Antiarrhythmic drugs Rhythm control drugs Rate control drugs Anticoagulation Antihypertensive therapy (special report of angiotensin Receptor inhibition is suggested) Other cardiac medication Concomitant cardiac disease Age, gender Type of AF (first detected, paroxysmal, Persistent, permanent) Duration of AF since first detection Prior antiarrhythmic drug treatment Number of antiarrhythmic drugs tested Number of cardioversions Number of catheter ablations or surgical interventions CHADS2 score Prior antithrombotic treatment Duration of anticoagulation (vitamin K antagonists,other anticoagulant) Anti-platelet treatment (aspirin, clopidogrel, etc) Symptoms due to AF Arrhythmia-related symptoms (EHRA score) Prior stroke/transitoric ischaemic 93
  94. 94. PRIMARY OUTCOME PARAMETER Death: Most Important primary outcome. All-cause death should be classified in the following groups.  Non-cardiovascular, excluding sudden death  Cardiovascular death  Cardiac  Sudden (including arrhythmic, myocardial infarction,others)  Non-sudden  Vascular (e.g. embolic, subarachnoidal bleeds, stroke, other)  Treatment- or procedure-related (is also a serious adverse event) 94
  95. 95. 95 SECONDARY OUTCOME PARAMETERS Symptoms and quality of life Recommended as secondary outcome parameter No reliable instruments to quantify them Sevirity of atrial fibrillation (SAF SCALE) Atrial fibrillation symptoms scale (AFSS) EHRA atrial fibrillation symptoms classification T/t expected to primarily affect symptoms and quality of life
  96. 96. 96
  97. 97. EHRA ATRIAL FIBRILLATION SYMPTOMS CLASSIFICATION 97
  98. 98. 98 ASSESSMENT OF RHYTHM & ECG-BASED OUTCOME PARAMETERS AVAILABLE ECG METHODS •Non-continuous standard ECG recording Symptom-activated ECG (. During triggered visits,.Patient-activated devices) Algorithm-activated (device monitors rhythm) Scheduled Resting ECG Transtelephonic monitoring (24–168 h) Holter recording Loop recorders •Continuous ECG monitoring Pacemakers/implanted defibrillators ECG garment equipped with radio data transmission (E.C.G. GSM-based) ECG-based outcome parameters Freedom from AF (suitable for time-based assessment) Change in AF pattern (e.G. Altered AF burden, altered AF type, Among many others) Proarrhythmia (e.G. Sudden death, ventricular tachycardia, Torsades de pointes, atrial flutter, bradycardia, AV nodal Block) Ventricular rate during AF at rest and during exercise
  99. 99. CURRENT STATUS OF ANTIARRHYTHMIC DRUGS Based on results of large Randomized controlled trials Cardioversion /defibrillator devices as compared to Antiarrhythmic drugs have proved to Be superior in prolonging survival 99
  100. 100. CONCLUSION Although no animal model can accurately resemble with human disease condition and species differences also exist, close similarities with humans suffering from or threatened by arrhythmias can be developed by selecting appropriate model and species. Rather than a single model or experimental technique, combinations of investigations, like isolated heart (langendorff arrangement or working heart), whole hearts in anesthetized or conscious animals, excised cardiac preparations, testing the function can be used. 100
  101. 101. REFERENCES Vogel WH, Schölkens BA. Drug Discovery and Evaluation [Internet]. Vogel HG, Vogel WH, Schölkens BA, Sandow J, Müller G, Vogel WF, editors. Berlin, Heidelberg: Springer Berlin Heidelberg; 2002. P.208-29. Pratt C, Camm A. Evaluation of antiarrhythmic drug efficacy in patients with an ICD. Unlimited potential or replete with complexity and problems? Eur. Heart J. [Internet]. 1999 [cited 2014 Feb 21];1538–52. Mor M, Shalev A, Dror S, Pikovsky O, Beharier O, Moran A, et al. INO-8875, a highly selective A1 adenosine receptor agonist: evaluation of chronotropic, dromotropic, and hemodynamic effects in rats. J. Pharmacol. Exp. Ther. [Internet]. 2013 Jan;344(1):59–67. Nilles KM, London B. Knockin animal models of inherited arrhythmogenic diseases: what have we learned from them? J. Cardiovasc. Electrophysiol. [Internet]. 2007 Sep [cited 2014 Feb 21];18(10):1117–25. Bodhankar S, Bhatt L, Nandakumar K. Experimental animal models to induce cardiac arrhythmias. Indian J. Pharmacol. [Internet]. 2005;37(6):348. Kirchhof P, Auricchio A, Bax J, Crijns H, Camm J, Diener H-C, et al. Outcome parameters for trials in atrial fibrillation: executive summary. Eur. Heart J. [Internet]. 2007 Nov ;28(22):2803–17. 101
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