One specific echocardiographic indicator of diastolic function is the Doppler inflow velocity across the mitral valve. The normal mitral inflow pattern consists of early (E) and late (A) filling. With worsening diastolic function comes differences in the E to A ratio.
Grade I: With mild (grade I) diastolic dysfunction, the velocity of early (E) filling goes down, leading to an E/A ratio less than 1.
Grade II: If diastolic dysfunction continues to worsen, the LA pressure will increase, and late (A) filling velocity will go down as well. This causes the E/A ratio to again be >1, in a proportion that looks pretty normal. This is “pseudonormalization” and grade II dysfunction.
Grades III/IV: A further rise in LA pressure causes the E/A ratio to rise even higher. Grade III diastolic dysfunction is usually associated with a E/A ratio of > 2. If the dysfunction is irreversible (i.e. not improved with medical therapy), the diastolic dysfunction is grade IV and associated with higher morbidity & morality.
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Nagueh SF. Echocardiographic evaluation of left ventricular diastolic dysfunction. UptoDate. 2015.