The Lions failed to lay a glove on the Gorgie side in going down to goals from Michael Smith, Liam Boyce - from the penalty spot - and Alex Cochrane in a one-sided affair.
In a difficult start to the season, Livingston have already faced champions Rangers, Celtic, whom they beat last Sunday, Hibernian, Aberdeen and now Hearts and Martindale fully believes the latter will be challenging for European places this term.
He explained: "I think Aberdeen will still be in and around but I think you can see the top four.
"I think you will be looking at Rangers, Celtic and Hearts and Hibs will be a toss of a coin. That's your top four in my opinion.
"Fifth and sixth I think Aberdeen will be there and it will be a fight between St Johnstone, Dundee United and maybe even ourselves. But I think it will be a flip of a coin.
"But I think the top four are breaking away. I think there's a clear divide.
"I think six or seven teams are playing for 10 upwards. It is a tough league this year, and I think the bigger teams have got stronger.
"I have found it really difficult this time. Hearts and Hibs have kicked on, in my opinion and Rangers and Celtic away from home have always been difficult.
"But I think there is a clear divide in the league now. You can see how the league is going."
Hearts boss Robbie Neilson was delighted with the performances of Barrie McKay and Cammy Devlin.
Both players hit the ground running following their recent arrivals, with McKay involved in two of the goals and Devlin making his full debut.
Neilson admits Hearts' start to the campaign suggests the summer transfer window has been a successful one.
The 41-year-old, whose side remain just one point adrift of leaders Rangers at the summit, said: "When I came in at the start of last season we had the oldest squad in the Championship and the plan was to get the squad a lot younger and more energetic, more mobile.
"The recruitment's been really good this year. Hearts in the Premiership…you're far more appealing than when you're Hearts in the Championship.
"We've managed to recruit the right players, the right types of players. It's nice to be where we are but we're only seven games in and how we respond to the lows will be the next question."