1. Scott E. Ewing DO Lecture #9
ECG 101 AMI with LBBB or PPM
Scott E. Ewing DO
Lecture #9

2. Review - LBBB

3. LBBB

4. LBBB – Definition QRS duration ≥120 ms
Small or absent initial R waves in right precordial leads (V1 and V2) followed by deep S waves
Broad, notched R waves in lateral precordial leads (V5 and V6) and usually leads I and aVl
Prolonged intrinsicoid deflection (>60 ms) in V5 and V6
Secondary ST-T wave changes

6. LBBB Significance
Complete LBBB may be associated with a normal, leftward, or rarely rightward axis
LBBB may mask or mimic the pattern of underlying myocardial infarction
LBBB a marker of underlying organic heart disease
Hypertensive heart disease
Severe coronary disease
Cardiomyopathy
Valvular disease

7. Acute MI and LBBB

8. Uncomplicated LBBB
Appropriate discordance in uncomplicated LBBB (note ST elevation in leads V1 to V3)

9. Diagnostic Criteria
If doubt persists, serial electrocardiograms may show evolving changes

10. Examples Inappropriate concordance in V1 in patient with LBBB
Exaggeration of appropriate discordance in lead V1 in patient with LBBB

11. Acute MI and LBBB
Note ST segments are elevated V5 and V6 (inappropriate concordance) and grossly elevated (> 5 mm) V2, V3, and V4
Note ST segment depression in leads III and aVF

12. 68 year old Male with Chest Pain
ST segment depression in lead V3
Example of inappropriate concordance

13. AMI with LBBB - Examples

15. Interpretation: Inferior AMI with LBBB
Sinus bradycardia and LBBB with primary ST-T wave changes
LBBB morphology with primary biphasic and inverted T waves in leads 2, 3 and aVF
Uncomplicated bundle branch blocks should have "secondary" T wave changes
Inverted T waves suggest that a "primary" or ischemic process is evolving in the inferior distribution
Pt had a myocardial infarction with a CK of 700 and 21% MB fraction

17. Interpretation: Anterior AMI with LBBB
Evidence of prior and possibly evolving MI superimposed on LBBB
Prior MI is indicated by Q waves as part of a qR in I and V6
Notching of the ascending limb of the S wave in the mid-left chest leads consistent with prior MI (Cabrera's sign)
Biphasic T waves in the mid-left chest leads raise consideration of evolving ischemia/MI
Statement that "LBBB precludes diagnosing MI" is not correct
Yet, LBBB often does mask changes of prior or acute MI

18. 74-year-old woman with LBBB

19. Interpretation: LBBB with Anterior AMI
Evidence of acute/evolving anterior ischemia/MI superimposed on the LBBB
Primary T wave inversions in V2-V4, rather than the expected discordant (upright) T waves in leads with negative QRS
Although this finding is not particularly sensitive for ischemia/MI with LBBB, such primary T wave changes are relatively specific
Note: prominent voltage with LAA and leftward axis here with LBBB are consistent with underlying LVH

20. PPM Review

23. AMI with PPM

24. Typical VPR - altered ventricular activation from right to left, producing broad, negative QS or rS complex in leads V1-V6
Large monophasic R wave is encountered in leads I and aVL and occasionally leads V5 and V6
QS complexes frequently encountered in leads II, III and aVF
As with LBBB, ST-T wave configurations are discordant with QRS complex

25. VPR demonstrating lateral AMI
Leads I and aVL demonstrate concordant ST segment elevation that is not appropriate for VPR
Dynamic changes compared to prior ECG

26. Diagnostic Criteria Discordant ST segment elevation > 5 mm
Concordant ST segment elevation > 1 mm
ST segment depression > 1 mm V1, V2, or V3
Most useful criteria is discordant ST elevation of 5 mm or more

27. 68-year-old man with dyspnea

28. Interpretation: VPR with AMI
VPR with underlying complete heart block (P waves march through)
Superimposed current of injury with hyperacute ST-T changes inferiorly and laterally with reciprocal change V1-V3 consistent with acute infero-postero-lateral ischemia/ MI
Pacemaker patterns, like LBBB, often mask acute or chronic MI
Sometimes the ischemic changes "show through."

29. 64-year-old-man with a dual chamber pacemaker

30. Interpretation: VPR with Possible AMI
AV sequential pacing (see lead V1)
QRS complexes do not show a typical LBBB pattern
Instead, the lateral leads (I, aVL, V5, V6) show prominent Q waves with QR-type complexes
Persistent ST elevations in V5 and V6
Underlying anterior MI / ventricular aneurysm-type pattern in the presence of the paced ECG
Ischemic heart disease, s/p prior MI(s), with very severe LV dysfunction, LVEF about 20%

31. Presyncope with Dual Chamber Pacemaker

32. Interpretation: AV Sequential Pacing with Inferior AMI
Markedly elevated J point and convex ST segment elevations inferiorly, with reciprocal changes in I, aVL, and V2
Pacemaker is dual chamber with intermittent A-V sequential pacing alternating with A-sensed V-paced rhythm
Ventricular paced ECGs are usually not interpretable for ischemia
However, just as with an intrinsic LBBB, >5 mm ST segment elevation in right precordial or inferior leads, and especially ST depressions/T wave inversions in leads with QS or rS complexes, are highly suggestive of ischemia

33. Review

34. LBBB Review QRS duration ≥120 ms
Small or absent initial R waves in right precordial leads (V1 and V2) followed by deep S waves
Broad, notched R waves in lateral precordial leads (V5 and V6) and usually leads I and aVl
Prolonged intrinsicoid deflection (>60 ms) in V5 and V6
Secondary ST-T wave changes

37. Interpretation: NSR With LBBB
Hypertrophic obstructive cardiomyopathy with chronic LBBB
Note evidence of LAA
Most patients with LBBB have LVH
Presence of LAA with LBBB is also strongly suggestive of underlying LVH
Note: there is some baseline artifact here that at times simulates a pacemaker stimulus--however the patient did not have an electronic pacemaker and the P waves and wide QRS are due to native conduction entirely

39. Interpretation: SR with LBB and AMI
ST segment deviates in the same direction as the major QRS deflection (concordant) in the inferior leads
In the setting of LBBB, concordant ST segment deviation is indicative of acute infarct
Remember: ST segment deviation secondary to LBBB alone is discordant with the major QRS deflection
ST segment is depressed when the major QRS deflection is positive
elevated when the major QRS deflection is negative

40. Questions?