Russia maintained one of the greatest winning streaks in global athletics by taking their eighth successive gold medal in this event, although they were pushed much closer than many expected.
It was also a huge personal success for Natalya Nazarova who added her fifth gold medal in the event and alongside her two individual 400m golds has matched the World Indoor record total of seven gold medals also achieved by Mozambique's 800m superstar Maria Mutola.
After the first leg it appeared Russia were cruising to a predictable victory, when Yulia Guschina (52.36) opened up a seven-metre lead from the USA and Belarus who took the baton simultaneously after opening legs from Angel Perkins and Anna Kozak, respectively.
The Russian advantage was maintained by Tatyana Levina (52.37) on the second leg with Belarus and USA still stride for stride at the halfway distance.
However, the Russian advantage was trimmed to four metres after the penultimate leg. Nazarova, in action less than two hours after winning individual silver, was pushed hard by Sviatlana Usovich and the 400m bronze medallist Shareese Woods to around four metres. Nazarova running 52.54.
On the last leg Zykina, the individual 400m champion, surely a little heavy-legged after her earlier exertions faced enormous pressure from Ilona Usovich, the European Indoor silver medallist, who decided to skip the individual 400m to concentrate on the relay.
At the halfway stage on the anchor Usovich trailed Zykina by just two metres with the real possibility Russia could finally lose their iron-like grip on the event.
Perhaps, though, we should have known better. Zykina repelled all Usovich could throw at her down the home straight, running a 50.90 anchor, and held on to take gold in a world lead of 3:28.17. Belarus held on for a magnificent silver in 3:28.90 with USA, also in close attendance, taking bronze in 3:29.30.
Steve Landells for the IAAF