What do you get when you combine amnesia, that ancient sitcom gimmick, with our contemporary obsession with spoiled, rich, selfish sociopaths like Paris Hilton? Throw in the consequence-free shopping obsession of “Sex & the City,” and you have the oddball premise for the would-be screwball comedy “Samantha Who?” (8:30 p.m., ABC).

Samantha (Christina Applegate) wakes up from a coma with no idea of who she is or what she’s done with her young life. Her glib, self-absorbed mother (Jean Smart) can be seen hovering with a camera, trying to turn Samantha’s plight into a guest spot on “Extreme Makeover.”

Smart’s character isn’t onscreen for five seconds before she seems completely unbelievable, unsympathetic and dumb. If you want to change the channel at this moment, go ahead, but I’m paid to watch this stuff.

We soon learn that Sam was a rather rotten person who cheated on her understanding boyfriend, Todd (Barry Watson), and whose best friend, Andrea (Jennifer Esposito), is a clueless party animal who shows no concern for Sam’s addled condition and no regard for anyone but herself.

In the first episode, Sam shuttles between the apartment of a boyfriend who doesn’t like her and the home of the parents she can’t stand. Where’s “the funny” in that?

The real pity here is that Applegate shows flashes of charm in a role that in another era may have belonged to Carole Lombard or Katharine Hepburn.

Screwball comedies of the 1930s were filled with daffy, spoiled socialites who came to their senses after a blow to the head or the arrival of a good, strong butler or sensible second husband. I’d like to say that the difference between, say, “My Man Godfrey” and “Samantha Who?” is the near-complete absence of sympathetic characters. But the real difference is the complete absence of truly funny characters. As hard as she tries, Applegate can’t save this sitcom on her own.

I should like a show that takes a dim view of selfish materialism, but Samantha’s bratty and now-forgotten life belongs in a much harsher satire, not in a comedy that aspires to the effervescence of a champagne bubble. The chemistry here is entirely wrong. No wonder “Samantha” always feels flat.

¢ The four-part series “The Mysterious Human Heart” (8 p.m. and 9 p.m., PBS, concludes next Monday, check local listings) explores the miracle of our most dependable organ through the stories of three people whose heart conditions brought them to the brink of death.

Tonight’s first hour explores man’s long fascination with the heart and the evolution of cardiac medicine. Part two looks at the electrical impulses that get the muscle to beat more than 100,000 times per day and what happens when that heartbeat loses its rhythm.

Tonight’s other highlights

¢ The Indians and Red Sox meet in Game 3 of the American League Championship Series (6 p.m., Fox).

¢ Diamonds aren’t forever on “Chuck” (7 p.m., NBC).

¢ Behind-the-wheel mayhem on “Everybody Hates Chris” (7 p.m., CW).

¢ Hugh Grant puts a modest car to the test on “Top Gear” (7 p.m., BBC America).

¢ Am I the only viewer having trouble keeping up with all of the new heroes on “Heroes” (8 p.m., NBC)?

¢ The sextuplets turn 3 on “Jon & Katie Plus 8” (8 p.m., TLC).

¢ Dan can’t resist the siren call of 1995 on “Journeyman” (9 p.m., NBC).

¢ The Diamondbacks and Rockies meet in Game 4 of the National League Championship Series (9 p.m., TBS).