By Ken Grauer, MD
The electrocardiogram (ECG) in the figure was obtained from a woman with dyspnea and marked hypertension, but who had no chest pain. How would you interpret this ECG? Should you activate the cath lab?
Interpretation: There is marked artifact on today’s tracing. While still possible to interpret this ECG, artifacts to this degree render assessment of P wave morphology and ST-T wave changes more challenging. There are two additional “technical issues” to address with this tracing:
- The presence of a prominent negative component to the P wave in lead V1 — as well as the rSr’ complex in this lead — suggests that the lead V1 (and possibly lead V2) electrodes may have been placed one or two interspaces too high on the chest.
- Finally, it looks as if the S-wave amplitude in leads V2 and V3 (and possibly in other chest leads) may have been “cut off.” The practice in many prehospital systems in the United States is to use ECG monitors that automatically “truncate” amplitude when either the R wave or S wave in a given lead attains
10 mm in size.
Looking closely at the lowest point of the S wave for the first two QRS complexes in lead V2 shows a small, but definite, space between the descending and ascending limbs of the S wave. This confirms that the true S-wave amplitude has been shortened (limited) by the automatic amplitude cutoff used on this ECG machine.
The relevance to today’s case of recognizing this automatic S wave “cutoff” after reaching 10 mm is that deeper S waves than what are displayed on today’s ECG are consistent with definite voltage for left ventricular (LV) hypertrophy (LVH).
- ST-T wave changes of LV “strain” typically manifest as ST-T wave depression in one or more of the lateral leads (consistent with the ST-T wave picture that we see in leads V5 and V6 of today’s tracing).
- Sometimes, instead of taller, lateral lead R waves, patients with LVH show a similar amplitude effect, but in oppositely-directed leads. For example, right-sided leads V1 and V2 often manifest deeper S waves when there is LVH (i.e., deeper S waves in leads V1 and V2 suggest there is more electrical activity directed away from these right-sided leads — toward the enlarged LV).
- Similarly, instead of the ST-T wave depression that is typically seen in lateral leads with LV “strain” in a patient with LVH, there may be ST-T wave elevation in the anterior leads (i.e., the “mirror-image opposite” picture of LV “strain” in leads V5 and V6 may be seen as ST elevation in anterior leads).
Impression: Given the very deep anterior S waves that appear to have been cut off in today’s tracing, the ST-T wave elevation that we see (which is most marked in lead V2) probably reflects LV “strain” in this anterior lead from this hypertensive patient with marked LVH. There otherwise appear to be no acute changes on today’s ECG.
Note: For more information about this case, visit https://tinyurl.com/KG-Blog-424.
The electrocardiogram (ECG) in the figure was obtained from a woman with dyspnea and marked hypertension, but who had no chest pain. How would you interpret this ECG? Should you activate the cath lab?
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