When does the E/e' index not work? The pitfalls of oversimplifying diastolic function.

Since the E/e' ratio was first described in 1997 as a noninvasive surrogate marker of mean pulmonary capillary wedge pressure, it has gained a central role in diagnostic recommendations and a supremacy in clinical use that require critical reappraisal. We review technical factors, physiological influences, and pathophysiological processes that can complicate the interpretation of E/e'. The index has been validated in certain circumstances, but its use cannot be extrapolated to other situations-such as critically ill patients or children-in which it has either been shown not to work or it has not been well validated.

Tachycardia after acute deceleration injury.

A 29-year-old man crashed at high speed into another vehicle at traffic lights. He was able to get out of his van but then collapsed after running a few metres. On arrival in the emergency department he was conscious, with a pulse of 140 beats/min and blood pressure of 110/32 mm Hg.