This seems to fit.

"La técnica más utilizada para la evaluación de la función diastólica del ventrículo izquierdo (VI) es la ecocardiografía transtorácica. A pesar de su amplio uso desde hace décadas, la evaluación de la función diastólica del VI y, sobre todo, la clasificación del grado de disfunción diastólica (DD) por medio de este método no está libre de controversia. [...]
En segundo lugar, pocas diferencias se observaron entre los pacientes previamente clasificados con disfunción diastólica grado II y III utilizando las nuevas recomendaciones con respecto a las previas."
https://secardiologia.es/multimedia/blog/10093-disfuncion-di...

"Relationship Between Left Atrial Volume and Diastolic Dysfunction in 500 Brazilian Patients [...]
The prevalence of DD in this sample was 33.8% (grade I: 66%, grade II: 29% e grade III: 5%). LAVI increased progressively according to DD grade: 21 ± 4 mL/m2 (absent), 26 ± 7 mL/m2 (grade I), 33 ± 5 mL/m2 (grade II), 50 ± 5 mL/m2 (grade III) (p < 0,001)."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3998172/

"For the age‐ and sex‐specific criteria, we categorized individuals as having: normal LV diastolic function, no abnormal measures; mild DD, 1 abnormal measure; moderate DD, 2 abnormal measures; and severe DD, 3 abnormal measures."
https://www.ahajournals.org/doi/full/10.1161/JAHA.117.008291

Here are the new 2016 American Society of Echocardiography classification guidelines:
https://www.asecho.org/wp-content/uploads/2016/03/2016_LVDia...


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Note added at 1 hr (2019-01-31 06:39:29 GMT)
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Sorry, it should be the other way round when expanded in English: grade III (or severe) diastolic dysfunction. I was mechanically following the order of the abbreviated form. You also find "type III" with the same meaning as "grade III".