E is for Equality
- Is RV as big or bigger than LV?
- Normal ratio ~0.6:1 (in A4C)
- 1:1 or greater is definitely abnormal
Acute symptoms – possible pulmonary embolism (PE)
- Not perfectly sensitive (small PEs)
- Not perfectly specific (RV strain from COPD, etc.)
The third E is for equality and this is really trying to estimate if the right ventricle is as big or bigger than the left ventricle. So normally the RV:LV ratio should be about 0.6 to 1 and this is classically measured in the apical four chamber view across the tips of the valves. We choose 1:1 as being abnormal because if you're getting the view correctly, it’s definitely abnormal when the ratio exceeds 1, when the RV is equal to or greater than the LV. We use this to really tell us if someone with acute symptoms such as shortness of breath or chest pain may have a pulmonary embolism. Large PEs will show signs of right ventricular strain and can be a big help in terms of diagnosis, prognosis, and therapy. Keep in mind however, that right ventricular strain is not sensitive for PE because you can certainly have small PEs that don't show any signs on echo and it’s also not perfectly specific in the sense that you can have RV strain from more chronic conditions such as COPD, pulmonary hypertension, things like that.