A 56-year-old man is brought to the emergency department by ambulance complaining of shortness of breath, chest tightness, and profuse diaphoresis. The patient reports that he had a heart attack "sometime in his late 40s." The patient takes lisinopril, atorvastatin, and a baby aspirin daily. He was given two doses of nitroglycerin by paramedics in the field. An electrocardiogram is ordered, oxygen is provided by nasal cannula, and intravenous access is obtained.
Which of the following electrocardiogram results would indicate irreversible necrotic tissue damage to this patient's heart?
A) Deep Q waves
B) Inverted T waves
C) ST segment depression
D) ST segment elevation
E) The presence of U waves
A) Deep Q waves
Deep Q waves are a classic electrocardiogram finding in necrotic or irreversibly damaged cardiac tissue because action potentials cannot propagate across the necrotic area, therefore the net vector of ventricular depolarization travels away from this area.
Answer B: Inverted T waves, is incorrect. Inverted T waves and ST segment depression are characteristic of the earliest signs of reversible myocardial ischemia.
Answer C: ST segment depression, is incorrect. ST segment depression and T-wave inversion are characteristic of the earliest signs of reversible myocardial ischemia.
Answer D: ST segment elevation, is incorrect. ST segment elevation corresponds to a reversible myocardial lesion.
Answer E: The presence of U waves, is incorrect. U-waves are a non-specific finding commonly observed in hypokalemia.
Key Learning Point
Electrocardiographic findings of Q waves indicate necrotic or irreversibly damaged cardiac tissue through which action potentials cannot propagate.
