This document discusses screening models for anti-arrhythmic drugs, including both in vivo and in vitro models. For in vivo models, it describes methods using chemically, electrically, and mechanically induced arrhythmias in animals. These involve techniques like aconitine antagonism in rats, digoxin-induced arrhythmias in guinea pigs, and exercise-induced ventricular fibrillation. For in vitro models, it discusses using acetylcholine or potassium to induce arrhythmias in isolated rabbit atria, as well as the Langendorff technique using isolated perfused guinea pig hearts. The screening models are used to test potential anti-arrhythmic drugs and evaluate their ability to prevent or reduce arrhythm

1. NOIDA INSTITUTE OF ENGINEERING AND TECHNOLOGY
Pharmacological Screening of Anti Arrhythmic Drug
Presented by- Submitted to-
Jatin Saini Dr. Saumya Das
M.Pharm (Pharmacology) Associate Professor
1st sem

2. ARRHYTHMIA
 A heart arrhythmia is an irregular heartbeat. Heart rhythm problems occur when the electrical signals that
coordinate the heart's beats don't work properly.
 The faulty signaling causes the heart to beat too fast (tachycardia), too slow (bradycardia) or irregularly..
 Types
• Tachycardia is a fast heart. The resting heart rate is greater than 100 beats a minute.
• Bradycardia is a slow heartbeat. The resting heart rate is less than 60 beats a minute.

3. Screening Model
In vivo Model In vitro Model
1. CHEMICALLY INDUCED ARRHYTHMIA
• Aconitine antagonism in rats
• Digoxin induced arrhythmias in guine pigs
• Strophanthin induced Arrhythmia
• Adrenaline induced Arrhythmia
2. ELECTRICALLY INDUCED ARRHYTHMIA
• Ventricular fibrillation electrical threshold.
• Programmed Electrical Stimulation Induced
Arrhythmia
• Sudden Coronary Death Models in Dogs
3. EXERCISE INDUCED VENTRICULAR
FIBRILATION
4. MECHANICALLY INDUCED ARRHYTHMIA
1. Reperfusion Arrhythmia in Rats
2. Reperfusion Arrhythmia in Dog
1. Acetylcholine or Potassium Induced Arrhythmias
2. LANGENDROFF Technique

4. In vivo Model
1. Chemically Induced Arrhythmia
 Large number of agents alone or combination are capable to induced arrhythmia:
 Anesthetic like Chloroform, ether, Halothane.
 IV Adrenaline, Ouabain alkaloids

5. Aconitine antagonism in rats
Purpose:
Aconitine, its plant alkaloid from roots, it acts persistent on Na+ channels resulting ventricular arrhythmias.
Drugs which have anti-arrhythmetic property can be tested on aconitine intoxicated rats.
Procedure
Male Ivanovas rats (300-400 gm) are used
Anesthetized intraperitonially with urethane (1.25 g/kg)
Aconitine dissolved (5 mcg/kg) in 0.1 N HNO, & infused into rat's saphenous vein 0.1 ml/min
Lead II ECG is recorded every 30 sec.
Test compound injected orally 5 min before Aconitine infusion
Evaluation
Higher dose of aconitine in the test group gives an index of antiarrhythmic activity.
The antiarrhythmic effect of test compound is measured by the amount of aconitine /100g animal.
Higher dose of aconitine is needed as compared with control group.

6. Digoxin induced arrhythmias in guine pigs
Purpose
Overdose of cardiac glycosides, such as digoxin, induces ventricular extrasystoles, ventricular fibrillation, and finally death.
The occurrence of these symptoms can be delayed by antiarrhythmic drugs.
Procedure
Male Marioth guinea pigs (350-500 g) anesthetize with pentobarbitone 35mg/kg intraperitonially
Tracheae, Jugular vein & carotid artery catheterized & animal is maintained on artificial respiration (45 breath/min)
Through jugular vein digoxin is infused at rate 85mcg/kg in 0.266 ml/min until cardiac arrest
ECG recorded with steel needle during experiment
Test drug is administered either 1hr before if orally or 1min before if IV, prior infusion of digoxine
The onset of ventricular extrasystoles, fibrillation, cardiac arrest
Compared results in test & control group
Evalution
Using Student’s t-test, the doses of digoxin needed to induce ventricular extrasystoles, fibrillation, or cardiac arrest,
respectively after treatment with antiarrhythmic drugs are compared statistically with controls receiving digoxin only

7. Electrically induced arrhythmia
 Serial electrical stimulation results in flutter and fibrillation and it is possible to reproduce some of the
main type of arrhythmias of clinical importance. The flutter threshold or the ventricular multiple
response threshold may be determine in anesthetized dogs before or after administration of test
drug.
1. Ventricular fibrillation electrical threshold
2. Programmed Electrical Stimulation Induced Arrhythmia
3. Sudden Coronary Death Models in Dogs

8. Ventricular fibrillation electrical threshold
Purpose
The use of antiarrhythmic drugs in the treatment of ventricular arrhythmias aims to prevent the
development of ventricular fibrillation. Several electrical stimulation techniques have been used to
measure ventricular fibrillation threshold such as
 single pulse stimulation,
 train of pulses stimulation,
 continuous 50 Hz stimulation,
 sequential pulse stimulation

9. Procedure
 Dogs (8-12 kg) anesthetized with pentobarbitone intraperitonially and maintained on artificial
 Chest opened & heart is suspended on pericardial cradle
 SA node crushed & Ag-AgCl stimulating electrode embedded with Teflon disc sutured to anterior
of LV
 Anodal constant current for 400ms is applied through electrode and which was programmed by digital
stimulator
 ECG recorded through lead Il of body ECG monitoring
 To determine Ventricular Fibrillation (VFT) 0.2 to 1.8 s train of 50Hz pulses delivered
 The current intensity of pulse train required to induce sustained ventricular fibrillation is define as VFT
 When VF occurs, heart immediately defibrillate & allow to recover as controlled condition for 15-20
 Test drug administered through femoral vein
Evaluation
VFT is determined before and after administration of test drug & compared by using student T-Test

10. EXERCISE INDUCED VENTRICULAR FIBRILATION
Purpose:
This developed methods to evaluate antiarrhythmic drugs for their activity in cardiovascular parameters
in an exercise-plus ischemia test.
Procedure:
 Mongral dogs (15-19 kg) anesthetized with pentobarbitone IV (10mg/kg)
 Chest cavity opened, heart exposed & supported with pericardial cradle
 Around LCX 20 MHz pulsed Doppler flow transducer & hydraulic accluder are placed
 Pair of insulated silver wire sutured to epicardial surface of both left and right ventricle. ECG & HR is
determined
 Pre calibrated solid state pressure transducer is inserted into left ventricle finally, a two stage
occlusion of LAD is performed
 Leads from cardiovascular instrumentation are tunneled under skin to exit on the back of animal's
neck
 3-4 weeks after the production of myocardial ischemia; animal are walked on treadmill & trained to
lie quietly on lab table during recovery period

11.  Protocol starts with 3 min warm up followed by run at 6.4 km/hr (0% grade)
 Grade is increased every 3min run 0% 4% 8% 12% and 16%
 During last min of exercise LCX is occlusion treadmill stopped & occlusion maintained for additional
1min
 Occlusion is released if VF occurs
 Exercise and ischemia test is repeated after pretreated with test drug & compared with control
reading

12. In vitro Model
 Acetylcholine or Potassium Induced Arrhythmias
 LANGENDROFF Technic

13. Acetylcholine or Potassium Induced Arrhythmias
 New Zealand white rabbits (0.5-3kg) sacrificed and heart removed
 Atria dissected from other tissue in RL and attached with electrode
 Fibrillation produced when atria exposed with Acetylcholine or KCL
 After 5min exposure to Acetylcholine or KCL, atria stimulated with pulses 0.75 ms, usually of 100and
recorded on kymograph
 Control arrhythmia produced for 6-10 min followed by 30 min rest period
 Test compound were added to the bath
 If fibrillation doesn't disappear within 8-10 min, preparation is washed to allowed to normal
concentration.
 Test drug found to be effective If fibrillation is disappears immediately or within 5min

14. LANGENDROFF Technique
 Basic principal involved is that heart is perfused in RETROGRADE Direction from aorta either at constant
pressure or constant flow with oxygenated saline solution. It closes aortic valves, just in situ heart during
diastole. The perfusate is displaced through the coronary sinus and the opened right atrium.
 Procedure
 Guinea pigs either sex 300-500 g
 Heart is removed ASAP and placed in petridish containing RL at 37.0°C Aorta located and cut below the
division
 Cannula inserted into the aorta and tied. Heart is perfused with oxygenated RL
 Heart is transferred to double wall Plexiglass perfussion apparatus maintained 37.0°C
 Ligature is placed around LAD coronary artery occlusion is maintained for 10 min by reperfussion
 Test compound administered through perfusion medium either before or after occlusion.
 Epicardial ECG electrode is used for pulsatile stimulation and induction of arrhythmia [Rectangular pulses
0.75 msec duration, 10 V, 400-1800 shocks/min]
 Small steel hook with string attached to apex of heart and HR measured with chronometer
 Incidence & duration of VF or VT is recorded in control & test group

15. References
 Drug Discoveryand Evaluation: pharmacological assays by H Gerhard Vogel
 http://www.slideshare.net/DrAbhishekVyas/drug-screening-methods-for-antiarrhythmic-
agents?from_m_app=android

16. THANKYOU