The Vietnamese star swimmer won her second medal at the FINA/Airweave Swimming World Cup 2015, which concluded the same day in Moscow.
The 19-year-old finished in 4:40.79, second to defending FINA World Cup champion Katinka Hosszu, who clocked 4:36.35 to win the gold medal.
Vien was 0.48 second faster than her Hungarian rival during the first 100m of the butterfly stroke section, and was only left behind when the race entered the second lap (200m-300m), when swimmers competed in the breaststroke.
The Vietnamese swimmer was nearly one second faster than the bronze medal winner, France’s Lara Grangeon, who finished in 4:41.54.
Vien’s best performance in the 400m individual medley was 4:38.78, which she achieved at the 16th FINA World Championships 2015, running from July 24 to August 9, in the Russian city of Kazan.
The Vietnamese swimmer also competed in the women’s 400m freestyle, but failed to pass the qualifying round.
She finished 15th in the qualifying round in 4:24.77, way slower than Vietnam’s national record of 4:08.66, which she set at the 28th Southeast Asian Games in Singapore in June.
Vien thus left the Swimming World Cup with two medals, with a bronze won in the women’s 200m individual medley category on Tuesday.
It was the first-ever World Cup medal to be taken home by a Vietnamese swimmer.
FINA, or the International Swimming Federation, is the international governing body of swimming, diving, water polo, synchronized swimming and open water swimming.
The event in Moscow is the first out of eight legs of the 2015 FINA/Airweave Swimming World Cup, with the seven others set to be held separately in Paris-Chartres, Hong Kong, Beijing, Singapore, Tokyo, Doha and Dubai.
The total cash prize for the Swimming World Cup is nearly US$2 million, according to FINA.
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