0071643192.pdf

EXAM

■ Findings are often nonspecific and may include pallor, diaphoresis, and
tachypnea.
■ Listen for new heart murmur (mitral regurgitation).
■ 15% of patient with proven MI have reproducible chest pain on exam.
■ Look for signs that increase risk for heart disease or suggest an alternate
diagnosis.

DIFFERENTIAL

■ PE, aortic dissection, pericarditis, tension pneumothorax, musculoskeletal
pain, gastroesophageal reflux (a diagnosis of exclusion, rarely the correct
answer on boards), esophageal rupture

DIAGNOSIS

ECG Findings Suggestive of MI

■ Hyperacute T waves
■ Earliest ECG finding
■ Transient
■ Differential includes hyperkalemia, LVH, pericarditis
■ ST segment elevation
■ “Domed” or upwardly concave
■ Occurring inregional distribution
■ Dynamic—waxing and waning with time
■ May be associated with evolving Q waves (infarct)
■ Reciprocal ST segment depression
■ Changes in region electrically opposite that of injury
■ Indicates a larger area of injury, lower ejection fraction, and ↑mortality
■ T-wave inversions in regional distribution
■ May occur before or after ST elevation
■ Wellen’s T waves—deep symmetric or biphasic T wave inversions in
the anterior precordial leads suggest LAD lesion
■ Differential includes LVH, BBB, pacer, myocarditis, and pericarditis
■ New LBBB
■ In presence of preexisting LBBB or ventricular-paced rhythm:
■ ST segment elevation >5 mm
■ ST segment depression >1 mm in lead V 1 , V2,or V 3
■ ST segment elevation with concordance
■ An LBBB follows the Law of Appropriate Discordance: It is appro-
priatefor the ST segment elevation/depression to be discordant
with the direction of the primary QRS vector.

Differential Diagnosis of ST Elevation on ECG:

■ Left ventricular (LV) aneurysm
■ History of prior MI
■ ECG with anterior (usually) Q waves and ST elevation
■ ST without dynamic or reciprocal changes
■ Can be visualized on echocardiography
■ Early repolarization (see Figure 2.12)
■ Characterized by no more than 3 mm of J-point elevation in the pre-
cordial leads with an upwardly concave morphology
■ Rarely seen in leads V 1 and V 2

CARDIOVASCULAR EMERGENCIES

ECG findings suggestive of MI:

■Hyperacute T waves

■ST segment elevation

■Reciprocal ST segment

depression

■T-wave inversions in

regional distribution

■New LBBB

Hyperacute T waves are the

earliest ECG finding of STEMI.