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NORMAL E/A RATIO |
E = First peak and represents passive ventricular filling in early diastole.
A = Second peak and represents atrial contraction in late diastole.
Mitral
valve E/A ratio (Table) – Rizzo et.al. 1988
Tricuspid
valve E/A ratio (Table) - Rizzo et.al. 1988
Mitral valve E/A ratio (Graph)– Rizzo et.al. 1988
Tricuspid valve E/A ratio (Graph) - Rizzo et.al. 1988
EARLY IN GESTATION |
- A is greater than E (A = 2E at 16 weeks gestation).
- This is due to the low compliance of the fetal ventricular myocardium, and the importance of atrial contraction.
ADVANCING GESTATION (1,2) |
- E increases and reaches A (E/A ratio increases).
- Peak velocity of the E wave increases but the peak velocity of the A wave remains constant (3).
- Maturation of the ventricular myocardium placing less importance on atrial systole.
BIRTH |
- E becomes greater than A.
- Due to the less importance of atrial contraction.
IUGR (1,2) |
- E/A ratio is higher than normal fetuses of similar gestational age.
- This is due to preload impairment without impairment in fetal myocardial diastolic function.
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REFERENCES |
- Reed KL, Anderson CF, Shenker L. Changes in intracardiac doppler blood flow velocities in fetuses with absent umbilical artery diastolic flow. Am J Obstet Gynecol 1987;157:774-779.
- Rizzo G, Arduini D, Romanini C et.al. Doppler echocardiographic assessment of atrioventricular velocity waveforms in normal and small for gestational age fetuses. Br J Obstet Gynaecol 1988;95:65-69.
- Fouron JC, Carceller AM.
Determinants of doppler flow velocity profile through the mitral valve of
the human fetus. Br Heart J 1993;70:457-460.