E/e' ratio
Pronunciation: E over E-prime
The ratio of early mitral inflow velocity to early mitral annular tissue velocity, used to estimate left ventricular filling pressures.
Full Definition
The E/e' ratio (E over e-prime) is a crucial echocardiographic parameter combining pulsed-wave Doppler measurement of early diastolic mitral inflow velocity (E wave) with tissue Doppler measurement of early diastolic mitral annular velocity (e' wave). This ratio provides a relatively load-independent assessment of left ventricular filling pressures and diastolic function. Normal E/e' ratios are typically <8, values of 8-15 suggest intermediate probability of elevated filling pressures, and ratios >15 strongly suggest elevated left atrial pressure. The measurement is obtained by averaging septal and lateral e' velocities, though some guidelines recommend using the lateral e' alone. E/e' correlates with invasively measured pulmonary capillary wedge pressure and has important prognostic implications in heart failure and other cardiac conditions.
Usage
Usage note: Always specify which e' velocity used (septal, lateral, or average); distinguish from other diastolic parameters.
In Context
- "The E/e' ratio was elevated at 18, suggesting increased left atrial pressure." — Diastolic function assessment
- "Normal diastolic function was indicated by an E/e' ratio of 7." — Echocardiography report