Fig. 5.1
ST segment changes in superacute phase
Acute Phase (Hours/Days to Weeks)
[ECG Recognition]
1.
Inverted T wave
2.
ST elevation with obliquely straight morphology/convex
3.
Pathological Q wave
Subacute Phase (Weeks to Months)
[ECG Recognition]
1.
Inverted T waves but smaller, ST segment at baseline
2.
Pathological Q wave
Recovery Phase (Several Months Later)
[ECG Recognition]
1.
T wave upright without changes anymore
2.
ST segment at baseline without more change
3.
Pathological Q wave
Besides, the ECG can tell the location of myocardial infarction based on the leads in which the basic patterns of myocardial infarction present.
1.
Inferior wall: leads II, III, and aVF
2.
Anterior wall: leads V1, V2, V3, V4, V5, and V6
3.
Lateral wall: leads V5, V6, I, and aVL
4.
Posterior wall: leads V7, V8, V9, or V1, V2 with R waves and peaked T waves
5.
Right ventricle: leads V3R, V4R, V5R, and V6R
The hexaxial reference system and axes of the chest leads may help us memorize the location of myocardial infarction (Fig. 5.5).
Fig. 5.5
The hexaxial reference system and the axes of chest leads
Using what you learned above, analyze the following practice strips and find out the location and phase of myocardial infarction (Figs. 5.6, 5.7, 5.8, and 5.9).
Fig. 5.6
Acute anterolateral infarction. ST segment elevation in leads I, aVL, and V2 to V6
Fig. 5.7
Subacute anterior myocardial infarction. Inverted T waves, ST segment at baseline, pathological Q wave in leads V1 to V5
Fig. 5.8
Superacute inferior myocardial infarction. ST segment elevation in leads II, III, and aVF and tall and peaked T wave
Fig. 5.9
Acute inferior myocardial infarction. ST segment elevation in leads II, III, and aVF
5.2.1.2 Early Repolarization Syndrome
Early repolarization syndrome is a common disease in clinical settings that can be revealed by ECG. It refers to a 0.1 mV elevation of J point (the border of the ending of QRS complex and the beginning of ST segment in at least two neighboring leads).
Two common types of ECG variant can be discovered in early depolarization syndrome: smooth transition from QRS complex to the ST segment instead of a sharp turn, called J point, and the other for a deflection or upright wavelet between QRS complex and ST segment, called J wave (Fig. 5.10).
[ECG Recognition]
1.
J point elevation and J wave formation: mainly in leads V2 to V5, occasionally seen in leads II, III, and aVF. When the J wave is present in leads V1 and V2 and QRS complex changes to rSr′ pattern, the ECG may resemble the right bundle branch block variant.
2.
Concave ST elevation is commonly seen in chest leads and inferior leads. Elevation in chest leads is more than that in inferior leads, usually within a 0.5 mV gap. A tall and peaked T wave could also present.
3.
The beginning of QRS complex is slow but the declining part is fast, or with a notch or deflection. The QRS complex’s amplitude improves while duration is shortened.
5.2.1.3 Acute Pericarditis
Acute pericarditis is an acute inflammation of the pericardium, both visceral and parietal layer. It might occur with myocarditis and endocarditis or as the only cardiac impairment. ECG of patients with acute pericarditis is dynamic, as shown in Fig. 5.11.
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