Deferiprone (L1) has been shown to remove iron from the heart more efficiently than desferal, but that is not its only purpose. L1 is an excellent iron chelator in general and does perform superior to desferal in studies of long term heart health. However this not not mean that its main purpose is just to remove iron from the heart. It is meant to remove iron from all organs and tissues in the body.
The mechanism of why L1 causes neutropenia in no more than 6-8% of users and the far more serious agranulocytosis (found in less than 1% of users) is not known.
From Cipla's (the manufacturer of Kelfer) site,
Due to the unknown mechanism of deferiprone-induced neutropenia, patients should not take medicinal products known to be associated with neutropenia or those that can cause agranulocytosis.
However, it has been observed that the problem is more prevalent in patients who still have their spleen. This might suggest a reaction in the immune system, rather than any relation to ferritin levels in the heart.
Eponine, you fall into that unlucky less-than-1% category. While patients who develop mild neutropenia may eventually be allowed to resume L1, patients that develop the more serious agranulocytosis, as you did, are not allowed to resume L1 therapy.
I would like to know if there are any sources you know of that suggest that agranulocytosis with L1 may be related to iron levels in the heart.