A sudden cardiac arrest.

(Note: I've edited the ages I used for the characters. Am sorry for the inconvenience).

Immediately Chen Lihua entered the hospital, a middle aged nurse at the reception smiled as she greeted her and said, "Dr Chen the chief is looking for you".

Chen Lihua halted in her steps and asked in a surprised tone, "The chief?, are you sure am the one he's looking for?".

Chen Lihua was surprised that the cheif would want to see her, and as for the reason, she had no idea about that.

Normally, the chief would interact with her mother since she was the one who usually spoke with him, instead of her.

And that's the reason she's surprised. The number of times she had interacted with the chief could be counted on one hand. 

And everytime she met the chief, he would smile at her after exchanging short pleasantries.