Narveson (3-4) began his career as a Cardinals draft pick, but he's played an important role in Milwaukee's rotation and stymied his former team after losing to St. Louis on May 8.
Braun's two-run homer made it 4-0 in the fifth and Hart started the sixth with another drive just as smoke started to billow in right field from a concession stand's malfunctioning popcorn machine.
Tony La Russa managed his 5, 000th game for the Cardinals, but there was little he could have liked from this one after St. Louis managed just six hits.
The Brewers improved to 23-9 at home.
At Philadelphia, Roy Halladay tossed seven masterful innings to become the first nine-game winner in the majors, and Placido Polanco hit a grand slam as Philadelphia beat Chicago.
Halladay (9-3) gave up six hits and struck out nine to earn his first win against the Cubs. The Phillies and San Francisco are the only teams he hasn't beaten.
Domonic Brown also homered for the National League East-leading Phillies. Antonio Bastardo got the final out for his second save.
At Miami, Logan Morrison and Mike Stanton each hit a two-run homer to help Florida beat Arizona and end an eight-game losing streak.
John Buck also homered and drove two runs for the Marlins, who had seven of their 13 hits go for extra bases.
Florida's 13 hits were its highest total since it had a season-high 14 against the Dodgers on May 28.
Miguel Montero and Xavier Nady hit back-to-back homers for the Diamondbacks, who have lost four of five. Joe Saunders (3-6) gave up five runs and 10 hits in six innings.
At Denver, Jhoulys Chacin pitched eight shutout innings as Colorado pounded Los Angeles' Chad Billingsley for 13 hits.
Chacin (7-4) stifled a Dodgers lineup missing slugger Matt Kemp (hamstring), and the Rockies scored five times in the fifth on six straight singles. The decisive rally was sparked by two uncharacteristic errors by the Dodgers, the best-fielding team in the major leagues.
Chacin allowed three harmless singles, struck out nine and walked three, handing over a 6-0 lead to a bullpen that nearly frittered it away. Third baseman Chris Nelson's throwing error opened the doors for the Dodgers' big ninth inning.
Kemp had a pinch-hit drive for his NL-leading 19th homer and Aaron Miles delivered a two-run single before Huston Street closed out his 19th save in 21 tries.
At Houston, Freddie Freeman and Alex Gonzalez homered on back-to-back pitches during Atlanta's four-run third inning, and the Braves earned their fourth consecutive victory.
Freeman's two-out, two-run shot off fellow rookie Aneury Rodriguez (0-4) landed several rows up in the second deck in right field and gave Atlanta a 4-0 lead. Gonzalez sent the next pitch into the Crawford Boxes in left field.
Chipper Jones and Eric Hinske also homered for Atlanta, which tied its season high for runs. Freeman and Gonzalez combined for six RBIs.
Matt Downs hit a two-run homer in the ninth for Houston, which has dropped six of seven. Michael Bourn had a triple and two doubles while tying a career high with four hits.
At Pittsburgh, Dillon Gee remained undefeated and Jose Reyes homered among his three hits as New York downed Pittsburgh for its fifth win in six games.
Gee became the first Mets rookie starter to improve to 7-0, and New York has won all nine of his starts. He allowed one run and eight hits in a career-high eight innings.
