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[The Q wave in the electrocardiogram: necrosis or an electrically inactive area? Myocardial pseudoinfarct]
R A Franken1, M A Assef, F de P Stella
1Faculdade de Ciências Médicas da Santa Casa de São Paulo.
Insights
Transient metabolic disturbances, not necrosis, may cause reversible Q-wave myocardial infarction (MI) on ECG. This finding suggests alternative explanations for ECG changes in patients with normal cardiac enzyme levels.
Area of Science:
- Cardiology
- Electrophysiology
- Pathophysiology
Background:
- Q-wave myocardial infarction (MI) on electrocardiogram (ECG) typically indicates irreversible myocardial necrosis.
- Diagnosis often relies on ECG changes and elevated cardiac biomarkers like creatine kinase-MB (CKMB).
Observation:
- Six patients with Q-wave MI on ECG showed improvement with Q-wave disappearance.
- These patients had normal plasma levels of creatine phosphokinase (CPK) and CKMB.
- Underlying conditions included coronary disease, metabolic alterations, acute myocarditis, and ischemic stroke.
Findings:
- The study proposes that transient metabolic disturbances, rather than necrosis, can lead to reversible myocardial dysfunction.
- This dysfunction may create an 'inactive electrical zone' by increasing the resting transmembrane potential, rendering myocardial cells unresponsive to electrical stimuli.
- This mechanism explains Q-wave resolution without evidence of infarction.
Implications:
- Re-evaluation of diagnostic criteria for Q-wave MI may be necessary, especially in cases with normal cardiac biomarkers.
- Transient metabolic disturbances should be considered in the differential diagnosis of ECG abnormalities.
- This could lead to more accurate patient stratification and management, avoiding unnecessary interventions for presumed infarction.
Abstract:
Six patients with Q-wave myocardial infarction in the ECG, two with coronary disease, two with metabolic alterations, one with acute myocarditis and another with ischemic stroke had an improvement of ECG tracings with disappearance of the Q wave. All had normal plasmatic levels of CPK and CKMB. It is believed that metabolic transitory disturbance of the myocardium increases the rest transmembrane potential turning the cell nonresponsive to electrical stimulus and without mechanical activity (inactive electrical zone, not a necrosis zone, which is an anatomo-pathological diagnosis).