German to English Medical Medical: Cardiology DPD scan

This is the first one in a list of "further empfohlene Maßnahmen" for a patient with myocardial infarction. The whole item:

Ambulanter DPD-Scan, Ltst. 3L (Fragestellung: xxx kardiale Speichererkrankung)

with xxx standing for something that is illegible.

I found out what a DPD scan is, but I can find no indication what "Ltst. 3L" might stand for. This is a report from an Austrian hospital. Any ideas anyone?

Thanks for your help, as always!