My aunt passed away last month from sudden cardiac arrest. she had gotten a flu shot 1 week prior followed by bronchitis. could they have contributed?

No: Multiple studies have shown the flu shot is safe and it has never been connected to causing heart attacks. It is a coincidence.

Highly unlikely: Unless your aunt suffered from an anaphylactic shock due to the flu shot (which should have happened within a few hours of the injection), it is highly impossible that the flu shot contributed in any way to the sudden cardiac arrest.

Probably coincidence: Most likely, the cardiac arrest was not in any way related to the flu shot. Cardiac arrest happens randomly - there's no way to predict when or where with precision (which is why it is feared by all). While we can treat underlying medical conditions, sometimes the heart probs are undetected, & sometimes treatment is inadequate. In any case, I am sorry for your loss, but don't blame the flu shot.