Muirhead, a four-time world junior champion, claims she feels like she has a target on her back after her victory in December's European Championships.
And she only just escaped with a narrow 8-7 win over Russia's Anna Sidorva.
"At the Europeans we started pretty slowly and got better and better, our aim was to play this championship strong from the start and we've done that," said Muirhead.
“We did well at the Europeans and when you come into an event like this, you always have a huge target on your back.”
Hosts Canada, Germany, Sweden, Switzerland and the Czech Republic also won their opening matches in Lethbridge.
Canadian-born German skip Melanie Robillard admitted her relief after guiding her rink to a 6-3 win over Denmark.
Robillard is stepping in for veteran Andrea Schöpp and admitted her last-minute preparations had been stressful.
“I’m really happy it’s over and I’m really happy we won," she said.
"It’s been pretty stressful. I’m trying to keep calm but I was actually really nervous when I started that game."