However, a fourth-round appearance should be enough for Lepchenko to qualify for the US Olympic team, though, while Venus Williams is also set to earn a singles place.
The match was moved from Chatrier to Court 1 but it made no difference to Kvitova who needed exactly an hour to reach her first-ever Roland Garros quarter-final..
Kvitova, who reached the Australian Open semi-finals back in January, will now face Kazakhstan's Yaroslava Shvedova who dumped out defending champion La Na.
Meanwhile, powerful 23rd seed Kaia Kanepi saw off unseeded Dutchwoman Arantxa Rus 6-1 4-6 6-0 to set up a meeting with tournament favourite Maria Sharapova.
The Estonian, forced to rally after dropping the second set to 21-year-old Rus who is ranked 88 in the world, has not been beyond the quarter-finals at any Grand Slam tournament.
Asked whether she thinks she can beat three-time major champion Sharapova, Kanepi replied: "If I play well, of course. Why not?"