Acute MI: Recognition and ECG Changes

 

Acute MI: Recognition

•         Clinical history of ischemic-type chest discomfort

•         Initial evaluation ideally should be accomplished within 10 minutes

•         Changes on serially obtained ECG tracings

•         Rise and fall in serum cardiac markers

Acute MI:  ECG Changes

ECG-  Diagnostic Criteria

STEMI:

Q waves , ST elevations, hyper acute T waves; followed by T wave inversions.

Clinically significant ST segment elevations:

> than 1 mm (0.1 mV) in at least two anatomical contiguous leads

 or 2 mm (0.2 mV) in two contiguous precordial leads (V2 and V3)

–        New LBBB

–        Indicates area of myocardial necrosis

–        Note: LBBB and pacemakers can interfere with diagnosis of MI on EKG

ECG

•         NSTEMI:

–        ST depressions (0.5 mm at least) or T wave inversions ( 1.0 mm at least) without Q waves in 2 contiguous leads with prominent R wave or R/S ratio >1.

–         Isolated T wave inversions:

•         can correlate with increased risk for MI

•         may represent Wellen’s syndrome:

–        critical LAD stenosis

–        >2mm inversions in anterior precordial leads

•         Unstable Angina:

–        May present with nonspecific or transient ST segment depressions or elevation

Correlation of ECG Changes and Areas of Damage

ECG Lead Changes	Area of Myocardium	Coronary Artery
II, III, AVF	Inferior	RCA
V1 to  V2	Posterior	RCA
V2 to V4	Anteroseptal	LAD
V3 to V5	Anterior	LAD
I, AVL	High Lateral	LCX