Nine cases of the reaction have been reported, including two in Canada.
Of those nine cases, one was fatal and three others required insertion of a pacemaker.
The department says people should not take new hepatitis C drugs Harvoni or Sovaldi in combination with another antiviral drug and a heart rhythm drug called amiodarone.
Health Canada is working with Gilead Sciences to update the warnings on the packaging of Sovaldi and Harvoni.
Symptoms of the reaction include fainting or nearly fainting, dizziness or lightheadedness, malaise and weakness, shortness of breath and chest pain.