A 68-year-old man presents to a rural clinic with severe substernal chest pain. He is diagnosed with an acute ST-segment elevation myocardial infarction (STEMI). Due to limited resources and transport delays, definitive revascularization is significantly delayed, allowing the infarction to follow its natural clinical course. Arrange the following electrocardiographic (ECG) changes in the typical chronological order in which they appear during the evolution of an untreated acute transmural myocardial infarction.
- 1Appearance of hyperacute (peaked) T waves
- 2ST-segment elevation
- 3Formation of pathologic Q waves with T wave inversion
- 4Normalization of the ST segment with a persistent Q wave
Answer
The correct chronological order is: 1) Appearance of hyperacute T waves, 2) ST-segment elevation, 3) Formation of pathologic Q waves with T wave inversion, 4) Normalization of the ST segment with a persistent Q wave.
The natural progression of ECG changes in an acute transmural myocardial infarction begins within minutes with hyperacute (peaked) T waves representing early ischemia. This is followed rapidly by ST-segment elevation due to transmural injury currents. Over the next several hours to days, pathologic Q waves form as myocardial tissue undergoes necrosis, and T waves invert. Finally, over days to weeks, the ST segment normalizes, but the pathologic Q waves generally persist as a permanent electrical marker of the old infarction.
Step-by-Step Solution
Key Concept
Chronological evolution of electrocardiographic changes in an untreated acute transmural myocardial infarction.
Estimated Time:1m 0s