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ECG 101 AMI with LBBB or PPM

Understand the significance of Left Bundle Branch Block (LBBB) and Pacemaker (PPM) in ECG interpretation with relevant examples. Learn diagnostic criteria for acute MI, AMI indications, and more.

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ECG 101 AMI with LBBB or PPM

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  1. ECG 101AMI 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

  5. 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

  6. Acute MI and LBBB

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

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

  9. Examples • Inappropriate concordance in V1 in patient with LBBB • Inappropriate concordance in V6 in patient with LBBB • Exaggeration of appropriate discordance in lead V1 in patient with LBBB

  10. 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

  11. 68 year old Male with Chest Pain • ST segment depression in lead V3 • Example of inappropriate concordance

  12. AMI with LBBB - Examples

  13. 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

  14. 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

  15. 74-year-old woman with LBBB

  16. 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

  17. PPM Review

  18. AMI with PPM

  19. 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

  20. 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

  21. 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

  22. 68-year-old man with dyspnea

  23. 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."

  24. 64-year-old-man with a dual chamber pacemaker

  25. 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%

  26. Presyncope with Dual Chamber Pacemaker

  27. 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

  28. Review

  29. 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

  30. 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

  31. 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

  32. Questions?

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