ECG Review: Reciprocal Acuity
By Ken Grauer, MD
Figure. ECG obtained from an 86-year-old woman with new-onset shortness of breath.
Clinical Scenario: The ECG shown in the figure was obtained from an 86-year-old woman who presented with new-onset shortness of breath. How would you interpret this tracing? Can you explain the title of this ECG review?
Interpretation: Despite the absence of chest pain, the ECG in the figure is highly suggestive of acute infarction. The title of this ECG review tells all. The rhythm is sinus at a rate of 65 beats/minute. The PR and QRS intervals are normal, and the QT is borderline prolonged. The mean QRS axis is approximately +40°. There is no evidence of chamber enlargement. An incomplete right bundle-branch block (RBBB) pattern is present.
Although there is no ST elevation in lead II, the inferior leads otherwise show changes suggestive of acute infarction (small q waves are seen in leads II and aVF, a larger Q wave is seen in lead III, and T waves in leads III and aVF appear to be hyperacute in that they are peaked and accompanied by slight but definite ST elevation). Support that these changes in leads III and aVF are truly acute is forthcoming from the "mirror-image" picture of reciprocal ST depression and T wave inversion in the high lateral and lateral precordial leads (leads I, aVL, and V4, V5, and V6, respectively). The mirror-image nature of these changes can be most easily appreciated by turning the tracing over and holding it up to the light—which results in the ST segment and T waves of leads III and aVF now taking on the appearance of the ST segment and T waves of leads I, aVL, V4-V6—and vice versa. The clinical significance of recognizing reciprocal ST-T wave changes such as these is that this finding strongly suggests acuity of the process.
(Dr. Grauer, Professor and Assistant Director, Family Practice Residency Program, University of Florida, ACLS Affiliate Faculty for Florida, Gainesville, is on the Editorial Board of Emergency Medicine Alert.)