Myocardial Infarction and the ECG MEHDI BAKHSHI MSN PhD ICNS

Paul D. Sherry, M.D. Parkside Cardiology Financial Disclosure 9/2/2010 neither I, nor any member of my immediate family, within the last 12 months, have had a financial relationship with any proprietary entity producing health care goods or services.

Myocardial Infarction and the ECG Very brief ECG basics Definition of ST elevation Definition of a significant Q wave Localizing the area involved in the MI Some ECG cases Pseudo infarcts

Definition of Acute M.I. 2007 Joint Task Force of the European Society of Cardiology, ACC, AHA A clinical event consequent to the death of cardiac myocytes that is caused by ischemia

An acute MI can occur with a normal ECG The most important tool early on in diagnosing an MI is still the history. Diagnosis of an acute or old anterior MI with a LBBB can be difficult if not impossible Remember the value of serial ECGs in acute coronary syndromes

The Three Bipolar Limb Leads

Precordial Leads and the location of V4R

Current of Injury Patterns

What is significant ST elevation? Elevation of the origin of the ST segment at its junction (J point) with the QRS complex of ≥ 1 mm in two or more limb leads or precordial leads V4 to V6 Or ≥ 2 mm in two or more precordial leads V1 to V3

Current of Injury during balloon inflation in the left anterior coronary artery Wagner, Galen: Marriott’s Practical Electrocardiography, 10th edition, page 176

What is the difference between a physiologic Q wave and one that indicates an infarction?

ECG time intervals

Physiologic Q waves are less than or equal to .02 sec Except for lead III, AVR and V1, Q waves greater than or equal to 0.4 seconds are abnormal.

Myth Q waves always mean transmural infarct Non Q wave infarcts always are subendocardial Q waves tell you there has been an infarct Q waves don’t tell you about pathology

Septal Q waves in the inferior and anterolateral leads II, III, avf, V3-V6

Reciprocal Changes The ECG recorded from one side of the electric field of the heart will be seen in an upside-down mirror image on the other

Reciprocal Changes

Localizing Infarcts on the 12 Lead ECG Lateral - Cx Ant – sep - LAD Anterior - LAD Lateral - Cx Inferior - RCA Lateral - Cx Ant – sep - LAD Anterior - LAD Lateral - Cx Inferior - RCA Inferior - RCA