Heartbeat tournament decks are based on combos using Heartbeat of Spring and Early Harvest to generate a massive amount of mana to cast a game winning spell. The deck was piloted by Maximillian Bracht for a top 8 finish at Pro Tour Honolulu.
The basis behind the deck is to use Heartbeat of Spring to accumulate large amounts of mana, then through Early Harvest, Weird Harvest, and Drift of Phantasms, acquire an X-spell such as Invoke the Firemind or Maga, Traitor to Mortals with enough mana to play it. Most of the other cards are either fixers to improve the chances of going off, as getting the combo is called, or counters to ensure that opponents don't interfere with the combo via countermagic or destruction.
The sideboard is what is often called the "Man Plan", which involves taking out the combo pieces and siding in various more aggressive creatures. The sideboard also has mass removal in the form of Savage Twister and Pyroclasm. When used, the Man Plan works by tricking your opponent into siding out the mass removal and winning via beatdown.