The 77-year-old star's representative has said that she was merely visiting her doctor for a routine checkup, reported Daily Mail online.
"She is fine and well at home," the representative said.
The actress allegedly went to the specialist cardiac unit at the private Wellington Hospital in London. Doctors discharged her from the hospital on the same day, as soon as they were sure that the actress was in a stable condition.
The news raised concern among her fans that she was not able to film "Downton Abbey" further. Fans feared that Smith, who plays the beloved Violet Crawley on the drama, will take doctors' advice to sit the next season out.
Smith is yet to sign up for the fourth season while her co-stars have.
The actress was diagnosed with breast cancer three years ago and has gone through chemotherapy and radiotherapy to treat it. She filmed the sixth "Harry Potter" film while going through the treatment.
