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Ischemic Heart Disease 165

17. What are the important differential diagnoses of ST
segment elevation in the electrocardiogram?
The two common conditions that produce ST segment
(segment between the end of S wave and beginning of T
wave) elevation in the ECG, and so are usually confused
with acute myocardial infarction are acute pericarditis
and early repolarization syndrome. However, in most
cases, findings in the history and physical examination
help to narrow the diagnostic possibilities (Fig. 4 and
Table 5).

Fig. 4: Typical ST segment elevation in acute myocardial infarction

Table 5: Comparison of ST segment elevation patterns
ECG pattern Myocardial Early Acute
infarction repolarization pericarditis
ST segment shape Convex upward Concave upward Concave upward
Reciprocal changes Present Absent Lead aVR
Location of ST Corresponds Precordial leads Both the limb
segment elevation to area of the and precordial
involved artery leads
Q waves Present Absent Absent
Loss of R wave Present Absent Absent
PR segment Absent Absent Present
depression