This ECG is from a 54-year-old woman who had an M.I. one week prior to this tracing. She did not receive interventional treatment, as it was not available where she lived when this happened years ago. Her ECG shows the signs of healing injury, as well as probable permanent damage.
Where was this M.I.? The affected leads are all of the precordial leads (V1 through V6), as well as I and aVL. The precordial leads reflect the anterior and low lateral walls of the heart, and Leads I and aVL show us the high lateral wall. This area is perfused by the left coronary artery, and she had a proximal lesion.
What ST and T wave changes are present? All of the leads listed above show a flattening of the ST segments. While they are no longer elevated (the acute injury is over), they are flat and almost convex upward. This shape is usually abnormal, and it has persisted even though the acute injury is subsiding. The T waves in the anterolateral leads are all inverted. This represents reperfusion of the injured tissue. Whether the offending clot is removed by invasive procedure, thrombolytic drugs, or natural degradation, the tissue that is still alive will reperfuse.
What else is abnormal? There are pathological Q waves in V1, V2, and V3, or we could say, "loss of normal r waves". Typically, precordial leads begin with an R wave. Lead V1 often has a small r wave, and the size of the R waves progresses across the chest until V6 is almost entirely upright. This is termed "R wave progression". Loss of the initial R wave in the right-sided chest leads is not always indicative of a "pathological Q wave". Also, a small "septal" q wave can sometimes be seen in V5 and V6. True pathological Q waves represent permanently damaged, necrotic myocardium. Poor R wave progression can be a result of pathological Q waves, or other conditions, including incorrect electrode placement. In this ECG, there appears to be a pathological Q wave in Lead III, as well, but isolated Q waves are not uncommon in Lead III, and this patient's current problem is a resolving anterolateral M.I. We don’t know this patient’s clinical status, but we do know that she was still hospitalized, and in the intensive cardiac care unit.
Is there any good news? Well, this patient has survived a large and dangerous event so far. She is in normal sinus rhythm with a narrow QRS complex and normal intervals.
For a review of the coronary arteries’ distribution, please see the coronary arteries illustration in Heart Art.