The Olympic silver medallist, holder of the previous record, had been leading Olympic and world champion Daniel Gyurta with 50m to go before being caught in the final two lengths.
But less than a month after having his heart restarted, Jamieson still managed to knock more than a second and half off his old British record, touching home in 2:01.43minutes.
Germany's Marco Koch was in third, with fellow Brit Andrew Willis fourth in an English record of 2:02.99mins.
Jemma Lowe, who won 200m butterfly bronze earlier in the meet, also picked up a silver medal in the 100m butterfly.
The 23-year-old lowered her Welsh record to 56.32seconds to touch home behind Sweden's world champion Sarah Sjostrom.
Elsewhere Chris Walker-Hebborn sealed the first major short course medal of his career, as he set a new personal best in the 100m backstroke to tie for third with France's Camille Lacourt in a time of 49.74secs.
And Aimee Willmott set a new English record of 4:25.37mins to take bronze in the 400m individual medley, behind Spain's Mireia Belmonte Garcia and Hungary's Katinka Hosszu, while Hannah Miley was fourth for Great Britain.
Siobhan-Marie O'Connor, winner of silver and bronze in Denmark, competed in her third individual final of the week finishing tenth in the 200m freestyle while Sophie Allen lowered her own British record to 1:05.65mins when she finished seventh in the 100m backstroke.
Fran Halsall missed out on a medal in the 50m freestyle by just 0.08secs when she finished fourth.
And it was a similar story when she returned alongside Allen, Lowe and O'Connor for the 4x50m medley relay, although they did break the British record, clocking a time of 1:46.56mins.