I had the exact issue andrewr refers to on my last medical. Despite a “normal” ECG when undertaking my Class 1 medical, I was more than surprised/concerned to receive documents from CASA AVMED requiring me to see a cardiologist & obtain a Stress Echocardiogram due to abnormalities identified in my ECG. The end result being that AVMED were assessing another person’s ECG (same surname as mine) that did have an issue.
No apology, no nothing & the person who really did have the ECG issue is probably blissfully flying around totally unaware he has an issue...