Monday, November 30, 2015

Tachycardia, Fever, and ST Elevation

This patient is approximately 30 years old with some serious baseline illness, and has a history of nonischemic cardiomyopathy.  911 was called for fever and increasing tachycardia.  The patient was too obtunded to report presence or absence of chest pain or discomfort.  The medics recorded this ECG:
There is sinus tachycardia at a rate of 150.  The computerized QTc is 441 ms.  There is 3.0-3.5 mm of ST Elevation at the J-point in V2-V4 (4.5 mm at 60 ms after the J-point) that would normally be called diagnostic of STEMI.

There is no reciprocal ST depression anywhere (which has a poor negative predictive value, but a high positive predictive value).

The medics activated the cath lab.

What do you think?

On arrival, the patient remained tachycardic, was febrile, and was obtunded.  Bedside echo showed very poor LV function.

The patient was not in clinical shock, was warm and well perfused, and did not have pulmonary edema.

There were no previous ECGs for comparison.

An ECG was recorded:
Slightly less tachycardic, and slightly less ST Elevation

What do you think?

We de-activated the cath lab.

The clinical picture did not fit STEMI.  The patient was clearly septic.  There was a previous history of non-ischemic cardiomyopathy.  Tachycardia can greatly exaggerate ST Elevation.

Here is a subsequent ECG:
There is not less tachycardia and less ST Elevation.

The patient ruled out for MI with very low troponin elevations, consistent with sepsis and cardiomyopathy (peak cTnI 0.048 ng/mL with 99% at 0.030 ng/mL).

Learning Points:

1. The ECG must always be interpreted in clinical context.  In a patient with fever one must treat the infection with supportive care and re-evaluate.  When there is no chest discomfort, one must be even more skeptical of ST Elevation and strongly suspect non-ACS etiologies of ST Elevation.
2. Extreme tachycardia can greatly exaggerate ST Elevation
3. STEMI only causes tachycardia to this degree when there is cardiogenic shock
4. Cardiomyopathy can also lead to false positive ECGs.


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