I really don’t think you have to worry. The health requirements for a B license are very much lower.
I had a heart attack in March and was told I could drive a car after one week. When they got me to the hospital they took me straight in for a stent operation. The stent was successful but even if it had not been I would have been allowed to drive again after 4 weeks even with a dodgy ticker.
Presumably there was a medical condition of some sort identified on your D4 medical report that caused them to send you for a stress test. Look it up in the guide for Doctors I linked to at #65.
