Hayden Panettiere's split from Milo Ventimiglia was "so out of left field".

The 36-year-old actress dated Milo, 48, for about two years while co-starring alongside him on Heroes, the hit TV show, and Hayden has now shared details of their 2009 break-up, which caught Hayden totally off-guard.

The actress - who recently came out as bisexual - told Us Weekly: "It was so out of left field, nothing that big or explosive had happened. Nothing had really gone wrong. Nobody cheated.

"I remember the look on his face being pure shock at how visceral and massive my negative reaction was, and he immediately took it back."

Hayden explained that Milo initially asked to get back together because he was so overwhelmed by her reaction.

The Hollywood star said: "One hundred percent it was only because I was over the toilet, hysterically crying. It was like my world had crumbled."

Despite their eventual split, Hayden insists she's always been wholeheartedly committed to all of her relationships.

The actress - who has Kaya, 11, with ex-partner Wladimir Klitschko - explained: "Every relationship I've ever been in, I invested my whole self in. I saw him as my partner and that it was going to hopefully keep going and evolving and lead to marriage."

However, Hayden recalled harbouring doubts about her relationship with Milo at the time.

She said: "It was a point of contention that I was unable to put the 'I' in front of 'love you' and at the time, I didn't realise or understand why it made me feel so uncomfortable.

"I could only say 'love you' in a casual way. Being older, he was much more aware of what that meant. And that said a lot."

Meanwhile, Milo previously framed their romance as a learning experience.

The actor - who is now married to model Jarah Mariano - told MR PORTER: "There are things that happen to you in your life that shape who you are.

"Everything I've been through from jobs to friendships to partnerships, everything has built me to who I am. You learn from it. You learn a better way of doing things. It wasn't until my mid to late twenties that the job wears on you, relationships wear on you.

"But I wouldn't change a thing."