The 101-year-old leader of Ashkenazi haredim has fluid in his lungs and according to one report, a cardiac ejection fraction of 20%.
Rabbi Yosef Shalom Elyashiv
The good thing about Rabbi Elyashiv's condition is that it can reverse itself. By this I mean that it can moderate and stabilize on its own in ways that are difficult to predict and which don't appear to be due to medical intervention. (That said, the medical intervention he's getting is absolutely necessary.)
The bad thing is that he is 101-years-old, quite frail, and his kidneys are probably very weak, which makes it less likely that Rabbi Elyashiv's condition will moderate and stabilize.
That said, my father lived for several years with an ejection fraction like that, so it isn't impossible.
Doctors have allowed Rabbi Elyashiv to remain at home.
According to Arutz Sheva, Rabbi Elyashiv attended a brit (ritual circumcision ceremony) in the synagogue ajoining his home today and acted as sandek, meaning he held the baby during the actual circumcision.
Yeshiva World notes that the wedding of his last unmarried grandchild is scheduled for tomorrow evening. At this point, it does not appear that Rabbi Elyashiv will be strong enough to attend.
Rabbi Elyashiv's aides are asking people to pray for HaRav Yosef Shalom ben Mousha.