This case provides an excellent example of how to correlate Systematic Interpretation of an ECG with the clinical scenario. My approach to this case begins with Descriptive Analysis, in which I sequentially assess Rate — Rhythm — Intervals — Axis — Chamber Enlargement — and, Q-R-S-T Changes. Regular sinus rhythm is present at a rate of about 70/minute. All intervals (PR, QRS duration, QT) are normal. The axis is leftward (since net QRS deflection in lead aVF is negative) — but not leftward enough to qualify for LAHB (left anterior hemiblock).  The axis is approximately -15 degrees. There is no chamber enlargement. This leaves us with assessment of Q-R-S-T Changes.

Q-R-S-T Changes: QS complexes are present in lead III, and in leads V1,V2. A small but-definitely-present initial positive deflection (r wave) is seen in lead V3. Transition is slightly delayed (the R wave only becomes taller than the S wave is deep between V4-to-V5). ST segments are coved ("frowny"-shape) in leads V4,V5,V6. There appears to be 1-2 mm of J-point ST depression in these leads, followed by symmetric T wave inversion. T wave inversion actually begins in lead V3. It is also seen in the high lateral limb leads (leads I and aVL). The ST segment is depressed in lead II. There is no ST segment elevation.

Clinical Impression: The patient in this case is a 52-year old man with a history of severe coronary disease, prior infarction, and multiple previous stent placements. He presents with new chest pain. Clearly, the J-point ST segment depression, ST segment coving, and symmetric T wave inversion in multiple leads may indicate ischemia. This ischemia could be new. That said, we have no idea if the ECG findings on this tracing are new or longstanding — since we have not been provided with any prior (baseline) ECGs on this patient for comparison. Given his medical history — even if the above ECG findings were not new, prompt evaluation (ie, with cardiac catheterization) might still be in order. If these ECG findings are new — then the indication for cardiac catheterization is that much stronger.

Selected Comments: The QS complexes seen in this tracing are not diagnostic of prior infarction. Even large Q waves (or QS complexes) in lead III and/or lead aVF may sometimes be seen in patients who have not had prior infarction. In the absence of any Q wave in the other inferior lead (lead II) — we merely report the QS complex in lead III as a descriptive finding of uncertain significance. If no such QS complex was present in lead III prior to this patient's myocardial infarction — then recognition of a new QS complex in lead III after his infarction may serve as a marker of previous necrosis, but not otherwise.

Similarly, the presence of QS complexes in leads V1 and V2 is not diagnostic of prior septal or anteroseptal infarction. That's because a definite small positive deflection (r wave) IS present in lead V3. Statistically, the finding of a QS complex in leads V1,V2 but not V3 is far more likely to be due to body habitus or lead misplacement, than it is to be a marker of prior infarction. Only when no r wave at all is seen in leads V1, V2 and V3 in a patient without LVH or QRS widening due to bundle branch block — does it become more likely than not that the patient has had prior anterior infarction. Therefore, we simply note the presence of a QS complex in leads V1 and V2 in this case — and, leave it to clinical correlation to determine if this is or is not likely to be a significant finding.

Finally, regarding ischemia — we note a series of suggestive ECG findings. Not only is there symmetric T wave inversion in anterolateral leads — but the J-point is clearly depressed below the baseline in leads V4,V5,V6; as well as in lead II. In addition, the ST segment is coved ("frowny"-configuration) in lateral chest leads. In view of the clinical history in this case — it is no surprise that cardiac catheterization showed acute disease.

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NOTE: For quick review of the Systematic Approach to ECG Interpretation discussed above — Please Check Out my ECG Blog #93 —

• For review of which leads may normally show Q waves or T wave inversion — Please Check Out my ECG Blog #79 —
• Finally, for full discussion in the form of a video on QRST Changes and the Systematic Approach — Please view my ECG Video #15 — If you click on SHOW MORE below this video on the YouTube site, you’ll see a complete linked Contents!