Show Notes: Classic PE: Pleuritic chest pain, shortness of breath, tachycardia, and S1Q3T3 after starting an oral contraceptive on a long flight to get chemo. Large PE Misses: About 20 percent of PEs are painless and probably about 50 percent of the large ones are painless, but this is rarely taught. The logic is that there is collateral circulation. Large PEs almost always cause SOB, however. These PEs often mimic ACS or sepsis due to tachycardia (rare in ACS) or low blood pressure, ischemic ECG changes, and elevated troponin/BNP/WBC. A bedside echo can really help if the patient is unstable, as can an ECG. Look for a dilated RV on the echo. Look for a new right axis or T-wave inversion in both inferior and anterior leads on the ECG because both of these are rare in ACS. Small PE Misses: Pleuritic chest pain only. The logic is that there is no collateral circulation so there is a lung infarct,

which causes pain. No SOB, normal vitals, normal ECG, no known risk factors. Use PERC or D-dimer if you don't have a more likely diagnosis. You may know the PERC, but do you also know the exclusion criteria? (https://bit.ly/3L7NRUz.) Too Many Chest CTs: COVID is a more likely diagnosis most of the time for PERC so don't dimer them unselectively! The logic is how many PEs have you and your colleagues diagnosed with a mildly elevated D-dimer or when you had a better explanation for symptoms but you were just CYA? Better than logic is logic and literature: Use age-adjusted D-dimer and YEARS criteria to minimize unnecessary CT. Both are validated and can be used in pregnant patients as well. (https://bit.ly/3L7NRUz.) Also know the causes of false-negative D-dimer (on thinners, symptoms less than a week).