new approach for understanding AV conduction ...in EPS point of view

1. Dr.ahmed Taha Hussein
M.Sc. Cardiology
Zagzig university

2.  Those who suffer from frequent and strong
faints without any manifest cause die
suddenly“ Hippocrates (460 - 375 BC)
 Micheal Bernhard Valentini (1713)

3. Low density
 Tadpole shaped 2 X 5 Na channels
mm High density
 lies beneath the RA L-type Ca
endocardium at the channel
apex of the triangle of
Koch.
 blood supply to the
AVN predominantly
comes from a branch
of the right coronary
artery in 85% to 90%
of patients and from
the circumflex artery
in 10% to 15%

4.  connects with the distal
part of the compact AVN,
perforates the central
fibrous body, and
penetrates the
membranous septum,
along the crest of the left
side of the interventricular
septum, for 1 to 2 cm and
then divides into the right
and left bundle branches.
 dual blood supply from
branches LAD , PDA .

5.  The main function is to delay conduction of
impulse propagated from atrium to ventricle
allowing diastolic time enough for ventricular
filling and atrial contraction.
 limit the number of impulses conducted from
the atria to the ventricles.
 -ve dromotropic response: activating IK(Ach,Ado)
 +ve dromotropic response : activating L-type
Ca channels

7.  AV conduction is
represented on the
surface ECG by
PR
PR interval(120- interval
200 ms).
 PR= (ARA –Ahiss)
+(A-H) .

8.  can be defined as transient or permanent
delay or interruption in the transmission of an
impulse from the atria to the ventricles caused
by an anatomical or functional impairment in
the conduction system.

9.  Congenital …1/22000 LUPUS-mother , CHD.
 Acquired : drug-induced
 CAD
 Rheumatic diseases( AS, Reiter’s, SLE..)
 Infiltrative diseases(amyloidosis , sarcoidosis..)
 Infectious (viral , chagas, TB)
 Neuromyopathies .
 Iatrogenic ( cardiac surgery , RFA)
 Vagally mediated
 Long QT syndromes .

10. LEV’S DISEASE LENEGRE’S DISEASE
 Fibrocalcification of  Primary scelerosing
cardiac cytoskeleton disease of the
 MAC , Aortic Scleorsis conductive system.
 In involvement of the
cytoskeleton

11.  For diagnostic and prognostic value ….
 AV-block is divided into nodal block
 Infranodal block .
 Diagnosis achieved by : ECG ( PR interval , P-R
wave relation , QRS duration)
 Autonomic modulation
 exercise testing .
 EP Study .

12.  Incomplete AV block includes
a. first-degree AV block
b. second degree AV block
c. advanced AV block
 Complete AV block,also known as third degree
AV block

13.  Proximal to, in, or distal to the His bundle in
the
atrium or AV node
 All degrees of AV block may be intermittent or
persistent

14.  PR interval is prolonged 0.21-
0.40 seconds, but no R-R interval
change.

15. First-degree atrioventricular block caused by intranodal
conduction delay

16. First-degree atrioventricular block secondary to His-Purkinje
system (HPS) disease

17. First-degree atrioventricular block caused by intraatrial
conduction delay

18.  There is intermittent failure of the
supraventricular impulse to be conducted to
the ventricles
 Some of the P waves are not followed by a QRS
complex.The conduction ratio (P/QRS ratio)
may be set at 2:1,3:1,3:2,4:3,and so forth

19.  Type I also is called Wenckebach
phenomenon or Mobitz type I and represents
the more common type
 Type II is also called Mobitz type II

20.  typical periodicity
Progressive lengthening of the PR interval until a P
wave is blocked
2.Progressive shortening of the RR interval until a P
wave is blocked
3.RR interval containing the blocked P wave is shorter
than the sum of two PP intervals

21. Infra-Hisian second-degree Wenckebach trioventricular (AV) block. Atrial
pacing in a patient with a normal prolonged atrial–His bundle interval
(AH) but prolonged His bundle–ventricular interval (HV) and right
bundle branch block (RBBB)

22.  ECG findings
1.Intermittent blocked P waves
2.PR intervals may be normal or prolonged,but
they remain constant
3.When the AV conduction ratio is 2:1,it is
often impossible to determine whether the
second-degree AV block is type I or II
4. A long rhythm strip may help

24.  When the AV conduction ratio is 3:1 or higher,the
rhythm is called advanced AV blocked
 A comparison of the PR intervals of the occasional
captured complexes may provide a clue
 If the PR interval varies and its duration is inversely
related to the interval between the P wave and its
preceding R wave (RP), type I block is likely
 A constant PR interval in all captured complexes
suggests type II block

25.  There is complete failure of the
supraventricular impulses to reach the
ventricles
 The atrial and ventricular activities are
independent of each other.
 Ventriculophasic Sinus Arrhythmia :
 intermittent differences in the P-P intervals
based on their relationship to the QRS complex.

26.  In patients with sinus rhythm and complete
AV block, the PP and RR intervals are regular,
but the P waves bear no constant relation to the
QRS complexes

29. Exclude other phenomena

30. Sinus rhythm with normal atrioventricular (AV) conduction. Frequent
premature atrial complexes (PACs; A′) are observed in a bigeminal pattern

31.  HB ectopy that fail to conduct to both Atria and
ventricle .
 Appear like type 2 AV block .
 ECG clues :
 (1) abrupt, unexplained prolongation of the PR
interval .
 (2) the presence of apparent Mobitz type II block in
the presence of a normal QRS
 (3) the presence of types 1 and 2 AV block in the
same tracing
 (4) the presence of manifest junctional extrasystoles
elsewhere in the tracing.

32.  Atrial tachycardia with subsidiary escape focus
from AV junction or ventricle .
 Accelerated idioventricular rhythm .
 Vtach.

33. Echo beat :
 can manifest as “group beating” and be
misdiagnosed as Wenckebach block.
 ECG clues: PR interval , P-wave morphology.
 Atrial tachyarrhythmia with variable AV
conduction .

34.  Pacing is the mainstay of treatment for
symptomatic AV block .
 Identifying transient or reversible causes for
AV conduction disturbances is the first step in
management. Withdrawal of any offending
drugs, correction of any electrolyte
abnormalities, or treatment of any infectious
processes should be considered prior to
permanent pacing therapy.