They were given intelligence tests and had their heart monitored for several hours, among other diagnostic procedures to see how they would react to sudden surprises.

Once seated in the Chair, the contestant found themselves looking up at a large video screen on which the host's image was displayed, as well as the information for the current question.

The third question involved recalling information from a series of images that appeared on the screen above them and required the player to remember something specific or particular details about one image, the fifth required the player to list items pertaining to a given category, and the seventh involved choosing which event occurred first or last (this question type would be eliminated later in the show's run).

The game prematurely ended when a contestant answered a single question incorrectly, lost all of their money due to redlining, or committed a third violation of the countermeasure rule.

Correctly answering every question awarded the contestant all of the money in their account, for a potential top prize of $250,000 if they had no redlining penalties.

Precautions were taken to ensure the contestant's safety during these events, such as a pane of heavy plastic being set just in front of their face as McEnroe served.

In the original New Zealand version, for the second Heartstopper, the contestant must answer 7 rapid-fire questions in a 60-second bonus round on one of the three categories shown on the screen above them.

Once during the rest of the game, they could exercise this option after a correct answer; if they missed a question or received their third violation of the countermeasure rule, they would leave with the money won up to the "stabilize" point.

In the British version of the show, a contestant would be required to stabilize after correctly answering the fifth question if they had not yet done so by that point.

If a contestant tried to close their eyes or perform some other task in an attempt to lower the heart rate, the host gave a warning.

On January 29, 2002, just a week before Mackerer's $224,600 win, another player, Dean Sheffron,[6] reached the last question with a total of $132,200 but lost it all due to redlining.