The document discusses various types of bradycardia and atrioventricular (AV) blocks as seen in ECG readings. It details classifications such as first-degree AV block, Mobitz type I and II second-degree AV blocks, and complete heart block, including their characteristics, clinical implications, and diagnostic approaches. The document emphasizes the significance of recognizing these conditions in patients and the potential need for further monitoring or interventions.

1. ECG IN BRADYCARDIA
KUSH KUMAR BHAGAT
MD, DM CARDIOLOGY (GOLD MEDALIST)
CONSULTANT INTERVENTIONAL CARDIOLOGY AND
ELECTROPHYSIOLOGY
FELLOWSHIP IN CARDIAC ELECTROPHYSIOLOGY, PACING AND
COMPLEX AFRRYTHMIA

3. Sinus node dysfunction
• Sinus bradycardia: Rate less than 60/Min
• Sinus pause: Sinus node depolarizes >3 s after the last atrial depolarization
• Sinus node arrest: No evidence of sinus node depolarization

4. • Tachycardia-bradycardia (“tachy-brady”) syndrome: Sinus bradycardia, ectopic
atrial bradycardia, or sinus pause alternating with periods of abnormal atrial
tachycardia, atrial flutter, or AF.
• The tachycardia may be associated with suppression of sinus node automaticity
and a sinus pause of variable duration when the tachycardia terminates.
• Chronotropic incompetence: Broadly defined as the inability of the heart to
increase its rate with increased activity or demand, in many studies translates to
failure to attain 80% of expected heart rate reserve during exercise.

5. SINUS BRADYCARDIA

6. Sinus pause: Sinus node depolarizes >3 s after the
last atrial depolarization

7. Sinus node arrest: No evidence of sinus node depolarization

8. Tachycardia-bradycardia (“tachy-brady”) syndrome

9. FIRST DEGREE AV BLOCK
First-degree atrioventricular block: P waves associated with 1:1 atrioventricular conduction and a PR interval >200 ms (this is
more accurately defined as atrioventricular delay because no P waves are blocked)
Atrioventricular block

10. Beat 1 is normal.
 Beat 2 shows first-degree AV delay, with a more gradual slope than normal in the AV
nodal tier.

12. Second Degree AV BLOCK
Second-degree heart block (intermittent AV block)is present when some
atrial impulses fail to conduct to the ventricles.
It is divided into two types:
A. Mobitz Type 1.
B. Mobitz Type 2.

13. Mobitz type I second-degree AV block (AV Wenckebach
block) is characterized by progressive PR interval
prolongation prior to block of an atrial impulse.
The pause that follows is less than fully compensatory (i.e., is
less than two normal sinus intervals), and the PR interval of the
first conducted impulse is shorter than the last conducted atrial
impulse prior to the blocked P wave.
Usually the difference between the longest and shortest PR
intervals exceeds 100 ms.
This type of block is almost always localized to the AV node and
associated with a normal QRS duration, although bundle branch
block may be present.
It is seen most often as a transient abnormality with inferior
wall infarction or with drug intoxication, particularly digitalis,
beta blockers, and occasionally calcium channel antagonists.
MOBITZ TYPE I BLOCK

14. WENCKEBACH PHENOMENON
Wenckebach AV cycle (type 1 second-degree block) is shown.
As the PR interval progressively increases from left to right in the figure,
the slope of the line in the AV nodal region is progressively less steep until
it fails to propagate at all after the fourth P wave (small line perpendicular
to sloping AV nodal conduction line), after which the cycle repeats.

16. In Mobitz type II second-degree AV block, conduction fails
suddenly and unexpectedly without a preceding change in PR
intervals
 It is generally due to disease of the His-Purkinje system and is
most often associated with a prolonged QRS duration.
When Mobitz type II block occurs with a normal QRS duration, an
intra-His site of block should be expected.
It is important to recognize this type of block because it has a
high incidence of progression to complete heart block with an
unstable, slow, lower escape pacemaker. Therefore, pacemaker
implantation is necessary in this condition.
Mobitz type II block may occur in the setting of anteroseptal
infarction or inthe primary or secondary sclerodegenerative or
calcific disorders of the fibrous skeleton of the heart.
Mobitz Type II Block

17. 2:1 AV BLOCK
SINUS RHYTHM WITH 2:1 AV BLOCK(Infra His Block).
QRS morphology is consisted with Bifasicular block (RBBB
and left posterior fasicular block).

18. Third-degree atrioventricular block (complete heart block): No evidence of atrioventricular conduction

20. Advanced, high-grade or high-degree atrioventricular block:
≥2 consecutive P waves at a constant physiologic rate that do not conduct to the ventricles with evidence for some
atrioventricular conduction

22. Q&A Session

24. The ECG shows:
• Sinus rhythm
• Prolonged PR interval of 280 ms (best seen in leads V1, V2)
• Normal axis
• Normal QRS complexes
• Normal ST segments and T waves
Clinical interpretation
• Sinus rhythm with first degree block.

25. What to do
• First degree block does not cause any haemodynamic impairment, and by itself is of
little significance.
• However, when a patient has symptoms which might be due to a bradycardia (in this
case dizziness), there may be episodes of second or third degree block, or possibly
Stokes-Adams attacks, associated with a slow ventricular rate.
• The appropriate action is therefore to request a 24 h ECG tape-recording in the hope
that the patient will have one of her dizzy turns while wearing it.
• It would then be possible to see whether or not the dizziness was associated with a
change in heart rhythm.
• First degree block itself is not an indication for permanent pacing or for any other
intervention.

26. Choose the correct diagnosis for this ECG:
A. I degree AV block.
B. II degree Mobitz type I block.
C. II degree Mobitz type II block.
D. Complete heart block.

27. Explanation:
Mobitz typeI block is also known as AV Wenckebach.
The 3 rules of classic AV Wenckebach are:
1) the PR interval lengthens until a nonconducted P wave occurs.
2) the RR interval of the pause is less than the two preceding RR intervals.
3) the RR interval after the pause is greater than the RR interval just prior to
the pause.
Unfortunately, there are many examples of atypical forms of Wenckebach
where these rules don't hold.
ANS : II degree Mobitz type I block.

29. What does this ECG shows:

30. ANS: AF with complete heart block.
This ECG shows:
The underlying rhythm is AF with slow regular ventricular
response consistent with CHB.
QRS complex shows LVH with left axis deviation.

32. The ECG shows:
• Regular narrow complex rhythm at 35/min
• P waves sometimes, but not always, visible just before the QRS
complexes
• PR interval, when measurable, is always short but varies
• Height of R wave in lead V4 plus depth of S wave in lead V2 = 45 mm
• Normal QRS complexes and ST segments.
• Peaked T waves, especially in lead V4

33. Clinical interpretation
• The short PR interval raises the possibility of pre-excitation, but the interval varies,
and in the
• first complex of leadsV1-V3 no P wave can be seen.
• The slow, narrow, complex rhythm suggests atrioventricular nodal escape.
• Here there is a pronounced slowing of SA node, presumably due to athletic training,
and an accelerated idionodal rhythm has taken over.
• This pattern used to be called a 'wandering atrial pacemaker'. The tall R waves are
perfectly normal in young fit people, and so are the peaked P waves.
What to do
• This is a normal variant in athletes, and no action is required.

34. Choose the correct diagnosis for this ECG:
A. I degree AV block.
B. II degree Mobitz type I block.
C. II degree Mobitz type II block.
D. Complete heart block
E. WPW Preexitation syndrome

35. Note the short PR interval and the delta wave (initial slurring) of the QRS complex

36. • 35 yr old female
• Asymptomatic from cardiac point of view
• To be operated for gallstones
• Routine ECG showed bradycardia

38. 2:1 AV BLOCK
UNDERWENT 24 HR HOLTER MONITERING HAD INTERMITTENT CHB
(CONGENITAL CHB)
MANAGEMENT??

40. • THANK YOU

41. Choose the correct diagnosis for this ECG:
A. I degree AV block.
B. II degree Mobitz type I block.
C. II degree Mobitz type II block.
D. Complete heart block
E. WPW Preexitation syndrome.

42. The constant PR interval distinguishes this from type I AV block.
Mobitz II 2nd degree AV block is usually a sign of bilateral bundle branch disease. One of the two
bundle branches is completely blocked (note the wide, negative S in V1 = LBBB). The
nonconducted sinus P waves are most likely blocked in the other bundle (ie, the right bundle)
which exhibits 2nd degree block.
Although unlikely, it is possible that the P waves are blocked somewhere in the AV junction such
as the His bundle.

43. 2 : 1 AV BLOCK