Case Report: 62-year-old man with shortness of breath after taking antibiotic

Human lung tissue with pulmonary embolism under a microscope. (©ChrWeiss,AdobeStock_244529421)

EKG in PE from The Emergency Medicine 1-Minute Consult

EKG results

A 62-year-old male with history of coronary artery disease and prior coronary bypass surgery eight years ago, plus a history of anxiety and chronic obstructive pulmonary disease (COPD), presents to the emergency department after having two days of intermittent shortness of breath since starting cephalexin (Keflex) for a skin infection three days ago. He denies any chest pain, fever, new rash or cough. He states the shortness of breath seems to get worse about an hour after taking cephalexin (Keflex).

Exam: Vital signs are normal.  Exam is otherwise normal.  Specifically, there is no rash, oral swelling, rales or wheezing.

Initial differential diagnosis: Anxiety, allergic reaction, pulmonary embolism, acute coronary syndrome, COPD exacerbation

EKG read (see image on the right):

1. Sinus rhythm with occasional premature ventricular contractions (PVCs)
2. Possible inferior infarct, age undetermined

Do you agree with the read?

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The computer read is correct, but there is also some non-specific T-wave inversion and flattening in the inferior and lateral leads. The heart rate is also on the high side, but still <100.

CASE CONCLUSION

Patient had a large mobile deep vein thrombosis in the left leg, which was asymptomatic, and multiple pulmonary embolisms in bilateral upper and lower lobes. Straightening of the interventricular septum was seen, but no massive right ventricular enlargement.

DISCUSSION
Always be aware of medications causing symptoms but make it a diagnosis of exclusion when there are more dangerous considerations. This patient has multiple reasons he might be short of breath, but with no wheezing, an allergic reaction or COPD exacerbation are unlikely to be the cause. Even mild wheezing could be his baseline. Acute coronary syndrome and pulmonary embolism should be high on the differential diagnosis for someone with dyspnea and clear lungs.  Both are often painless. This is well known for acute coronary syndrome (ACS), but less so for pulmonary embolism, where about 20% of cases are painless.

EKG findings in pulmonary embolism are not well understood by many clinicians who think that tachycardia and S1Q3T3 (suggesting right heart strain) are the most important things to look for.  About 75% of patients with pulmonary embolism will have a normal heart rate and 60% will have a heart rate under 90. See highlighted area from sample page on the right for most common new EKG findings in pulmonary embolism and their relative incidence. These include the 4 Ts: inverted T waves, flat T waves, Tachycardia and Totally normal. Rarer findings include RBBB >R or L axis, poor R-progression (S1S2S3), among others highlighted in the image on the right.

Another important pearl in diagnosing PEs is that small PEs typically have pleuritic pain but little more. Vitals and EKG will typically all be totally normal. Large PEs are paradoxically the ones that are most likely to be painless which is likely to occur because there is no lung infarction due to collateral circulation. Large PEs, though, often painless are more likely to cause abnormal vitals and EKG findings, which often mimic those in ACS. Large PEs may also cause elevations in troponin, BNP and WBC counts, thus masquerading as ACS, congestive heart failure (CHF) or sepsis.

CASE LESSONS

• Your first reaction to a patient who offers you a benign cause for their symptoms should be: “I hope you’re right, but let’s make sure it’s not anything more dangerous.”

• Painless pulmonary embolisms are quite common and usually occur with larger pulmonary embolisms. Painless PEs are more proximal and thus, less likely to cause lung infarction. Unlike with myocardial infarction (MI), this is just as frequent in younger patients.

• Tachycardia occurs in only 25% of PEs.  If you use HR >90 it’s probably closer to 40%. This patient had a HR in the mid 90s.  A totally normal EKG is just as common. Most common are inverted or flat T-waves (about 30% each).

About the Author

Dr. Pregerson is chief editor of http://EMresource.org, an emergency medicine website that includes a free EM ultrasound library, EM cases of the month, EM pocket references and more.

Peer Review: Dr. Stephen W. Smith of Dr. Smith’s ECG Blog.