12 Lead STEMI Mimics

1. 12 Lead STEMI Mimics

2. Objectives Identify ECG findings that imitate or conceal STEMI Significance of bundle branch blocks (BBB) in the acute coronary syndrome patient Cardiac conditions that can cause ST abnormalities in the absence of ACS

3. Bundle Branch Blocks Produce ECG changes that can imitate or conceal the ECG changes that are associated with Acute Coronary Syndromes (ACS)

4. Bundle Branch Anatomy

5. Bundle Branch Block Significance In cases where an acute MI produces a BBB the mortality rate is higher then in patients without a BBB It is not the presence of the BBB that increases mortality but the fact that the necrosis is more widespread In an ACS patient with a new or presumed new BBB acute reperfusion therapy is indicated

6. Recognition of BBB Wide QRS (greater then 0.12 seconds or 3 small squares) Supraventricular rhythm If both of the above criteria are met suspect a BBB

7. Right or Left BBB? Look at V1 (this method only works in V1) Does the QRS meet the criteria for BBB? If it does follow the steps below: Find the J point Draw a line into the centre of the QRS Draw a line back towards complex point Shade the area in If the arrow points up it is a right BBB, if the arrow points down it is a left BBB

8. Practice ECG # 1 Look for signs of a BBB (wide QRS with P waves present) Determine if the BBB is a left BBB or a right BBB Are there signs of ST elevation present?

9. Answer ECG # 1 QRS > 0.12 seconds P waves present In V1 arrow points down Left BBB No ST elevation present

10. Practice ECG # 2 Look for signs of a BBB (wide QRS with P waves present) Determine if the BBB is a left BBB or a right BBB Are there signs of ST elevation present?

11. Answer ECG # 2 QRS is wide No P waves present (this is a ventricular rhythm) Not a bundle branch block No signs of ST elevation This is ventricular tachycardia

12. Practice ECG # 3 Look for signs of a BBB (wide QRS with P waves present) Determine if the BBB is a left BBB or a right BBB Are there signs of ST elevation present?

13. Answer ECG # 3 Wide QRS and P waves are present Arrow in V1 points up No ST elevation This is a right BBB

14. Other conditions that can mimic or conceal ST elevation Ventricular rhythms (will not be covered here): Paced rhythms Idioventricular rhythms Ventricular tachycardia Premature ventricular complexes Other conditions: Left ventricular hypertrophy Ventricular aneurysm Benign early repolarization Pericarditis Hyperkalemia

15. Left Ventricular Hypertrophy (LVH) Enlargement of the left ventricle often caused by uncontrolled hypertension Recognized by an increase in the amplitude of the QRS complex In LVH the QRS is narrow but has a much greater amplitude then QRS complexes of a normal heart Can cause the ST segment to appear elevated in some leads and to down slope in other leads

16. When to Suspect LVH To determine if LVH is a possibility do the following: Pick the deepest QRS from V1 or V2, in this ECG it is V2 Pick the tallest QRS from V5 or V6, in this ECG it is V5 Count the small boxes for both V2 QRS and V5 QRS (V2 = 30, V5 = 35) Add the number together, if it is greater then 35 suspect LVH (65 for this ECG therefore LVH is suspected)

17. Ventricular Aneurysm May cause ST elevation in leads V1 through V4 in the absence of an acute cardiac condition Generally result from an area of necrosis due to an old infarct which causes the ventricle to bulge out during ventricular contraction

18. Benign Early Repolarization This is a normal ECG variation Completely healthy people can have an ECG that shows ST elevation and tall T waves This condition typically occurs in young healthy males The J point and ST segment are elevated and usually have a �fish hook� appearance Tall upright T waves may also be present

19. Pericarditis An inflammation of the pericardial sac caused by a bacterial or viral infection or a metabolic condition Causes diffuse ST segment changes and may also have a �fish hook� appearance as in early repolarization Different pain pattern then in ACS patients (classic pericarditis pain pattern): Sharp knife like Very localized May radiate to base of neck or between shoulder blades Affected by movement, respiration etc Often pain improves when patient leans forward Pain worsens when supine or semi-fowlers

20. Hyperkalemia Changes to ECG vary depending on potassium level Tall peaked T waves are present throughout the ECG in mild cases With higher potassium levels the QRS will be wide and the ST segment will disappear; P waves will also begin to flatten In severe cases of hyperkalemia P waves will disappear entirely and the QRS will widen and join the T wave to form a Sine wave

21. For More Information on 12 Leads For more information on ST abnormalities: http://www.madsci.com/manu/ekg_st-t.htm For more information on 12 lead ECG and patient presentations: http://www.madsci.com/manu/indexekg.htm ECG Learning Centre: http://library.med.utah.edu/kw/ecg/index.html

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