We are sometimes asked "does DicomObjects support ECG" (or EKG depending on where you are in the world!)
The answer is that we support it (as we for all SOP classes) for reading/writing/transmission as well as giving you the ability to create it and to extract data element values from it.
We do not offer explicit rendering (there are just TOO many variables, and we spend days handling every possible option of line thickness, colour etc.) but the ECG data is readily available, and quite simple to put into the graphing package of your choice.
Note that ECG usage in DICOM is now very rare, having effectively been abandoned in favour of SCP, and I think I've seen one single copy in the last 10 years.