This presentation is for all medicos and non medicos related with the study of heart and its functions. Conduction of heart physiology.

1. CONDUCTINGSYSTEMOFHEART
DURGESH.K
ARUNAI MEDICAL COLLEGE & HOSPITAL

2. MYOGENIC HEART
 OUR HUMAN HEART HAS A SPECIAL SYSTEM FOR RHYTHMICAL SELF EXCITATION AND
CONTRACTION .
 AND THIS HAPPENS DUE TO
1. AUTO GENERATION OF ELECTRICAL IMPULSES .
2. CONDUCTION OF THESE IMPULSES .

3. COMPONENTS OF CONDUCTING SYSTEM
o SA NODE ( SINOATRIAL NODE)
o AV NODE ( ATRIOVENTRICULAR NODE )
o AV BUNDLE ( BUNDLE OF HIS )
o RIGHT AND LEFT BUNDLE BRANCHES
o PURKINJE FIBRES

4. SINUATRIAL NODE
 SPECIALISED CARDIAC TISSUE
 FOUND NEAR THE OPENING OF SVC
 AUTORHYTHMIC IN NATURE
 PRODUCES 75 BEATS/MIN
 DIRECTLY CONNECTED WITH ATRIAL CELLS
 CONDUCTION VELOCITY : 0.05 M/S

5. INTERNODAL PATHWAY
 ENDS OF SA NODE CONNECTED WITH
AV NODE VIA INTERNODAL PATHWAYS .
 THERE ARE 3 INTERNODAL TRACTS,
1. ANTERIOR : TRACT OF BACHMAN
2. MIDDLE : TRACT OF WENCKBACH
3.POSTERIOR : TRACT OF THORELS
 CONDUCTION VELOCITY : 1M/S
 DELAY : 0.03 SECONDS

6. ATRIOVENTRICULAR NODE
• FOUND IMMEDIATELY BEHIND TRICUSPID
VALVE
• AUTORHYTHMIC BUT NOT AS OF SA NODE
• ALONG WITH AV BUNDLES IT SHOWS SLOW
CONDUCTION
•AV NODAL DELAY : 0.1 TO 0.2 SECS

7. AV NODAL DELAY
SIGNIFICANCE OF AV NODAL DELAY
HELPS IN CONTRACTION OF ATRIUM
BEFORE VENTRICLES & HELPS IN FILLING OF
VENTRICLES
WOLF PARKINSON WHITE
SYNDROME:
PRESENCE OF ABNORMAL PATHWAY (
BUNDLE OF KENT ) CAUSES SYNCING
CONTRACTION OF ATRIA AND VENTRICLES .

8. AV BUNDLES
 LARGE BUNDLES
 HIGH CONDUCTION VELOCITY ( 1 TO 4M/S)
 NO BACKWARD CONDUCTION TAKES PLACE
 AV NODE TO REST OF VENTRICLES
 IMPULSE REACH AFTER 0.16 SEC FROM SA
NODE
(SA NODAL DELAY + AV NODAL DELAY )

9. PURKINJE FIBRES
 BUNDLE BRANCHES FROM AV BUNDLE
CONTINUES AS PURKINJE FIBRES
 RUNS ALONG INTERVENTRICULAR SEPTUM
AND REACHES OTHER PARTS OF VENTRICLES
 IMPULSE TRANSMITTED FROM
ENDOCARDIUM TO EPICARDIUM
 TOTAL DELAY : 0.06 SECONDS
(DELAY FROM INITIAL PART OF PURKINJE TO
TERMINAL PART + ENDOCARDIUM TO
EPICARDIAL DELAY)

10. ECTOPIC PACEMAKER
 RHYTHMIC IMPULSE GENERATION FROM
OTHER THAN SA NODE
 GENERALLY IN AV BLOCK VENTRICULAR BEAT
WILL BE MAINTAINED NORMAL BY AV BUNDLES
AS IT PRODUCES 15 TO 40 BEATS / MIN
 AFTER SUDDEN BLOCK IT TAKES UPTO 5 TO 20
SECONDS BECAUSE AV BUNDLE LOST ITS
RHYTHM FROM SA NODE
 DURING THAT TIME PATIENT MAY GET FAINTED
 IF THE TIME INCREASES IT MAY LEAD TO DEATH

11. OVERALL CONDUCTION OF HEART
SA NODE
0.00 sec
INTERN0DAL
BRANCHES
AV NODE
0.03 sec
BUNDLE OF
HIS
0.16 sec
PURKINJE
FIBRES
0.19 sec

12. CLINICAL ASPECTS
1. A – V BLOCK :
FAILIURE OF CARDIAC IMPULSE TO PASS FROM
ATRIA TO VENTRICLES VIA AV NODE
2. VENTRICULAR ESCAPE :
INTENSE VAGAL STIMULATION RESULTING IN AV
BLOCK WHICH IS COMPENSATED BY SELF
GENERATED IMPULSES OF VENTRICLES
3. WOLF PARKINSON WHITE SYNDROME
4. STOKES ADAMS SYNDROME

13. THANKYOU