Once Mark was diagnosed, despite medication, his health began to deteriorate when he developed an intolerance to the medication that he was taking to help control the arrhythmias.
Ar ôl i Mark gael diagnosis, ac er gwaethaf meddyginiaeth, dechreuodd ei iechyd ddirywio pan ddatblygodd anoddefgarwch i’r feddyginiaeth a oedd i fod i helpu i reoli’r arrhythmia.