ECG leads act like cameras focusing on different walls of the heart. By identifying which leads contain pathologic Q waves, clinicians can pinpoint where the old damage is located. Septal and Anterior Infarctions

: T-waves may remain inverted or become upright and "flattened" over time.

Damage to the side of the heart often involves the Circumflex artery. Lateral MI: Q waves in leads I, aVL, V5, and V6. Inferior Infarctions

The diagnosis of an Old Myocardial Infarction on ECG relies heavily on identifying pathological Q waves and associated abnormalities in R-wave progression. These findings serve as a historical record of previous myocardial damage. When interpreting an ECG with these findings, it is crucial to compare it to prior tracings, as Q waves typically appear within hours to days of an acute event and remain permanently.

In a healthy heart, the R wave (the upward spike) gets progressively taller from lead V1 through V5. If a patient has had an anterior MI, the R waves may remain small or "stunted" across the precordial leads. This is known as Poor R Wave Progression (PRWP). Persistent ST Elevation (Ventricular Aneurysm)

Use this guide as a at the bedside or during ECG review. Always compare with prior ECGs and imaging to confirm scar, because not all Q waves = old MI, and not all old MI = Q waves.