Complex sentence: His condition was covered by the Portuguese media throughout the day and, before midnight, his death was confirmed, the cause of death being cardiac arrhythmia brought on by hypertrophic cardiomyopathy.
Split into simpler sentences: His condition was covered by the Portuguese media throughout the day. However, before midnight, his death was confirmed, the cause of death being cardiac arrhythmia, brought on by hypertrophic cardiomyopathy.