Samuels (28) revealed on Sunday she had heart surgery to correct an irregular heart beat just two weeks before competing in Saturday's world championship race in London.
Former world champion triathlete Samantha Warriner had career-saving heart surgery last December to control a similar condition.
Samuels needed to finish in the top 10 on Saturday to qualify for the Olympics. Instead, she finished 40th, three minutes behind Helen Jenkins of Britain, who won in 2hr 34sec.
Samuels and May said a bout of flu before the race had a bigger effect on Samuels' race than the surgery.
Samuels said in an email she decided no-one needed to know of her heart condition, diagnosed in May as right ventricular outflow tract tachycardia.
The condition meant her heart raced uncontrollably when exerting more than 80% of her energy levels.
"I wasn't getting enough oxygen that my muscles needed, resulting in the inability to continue until it settled or simply collapsing if I kept going," Samuels said.
The problem kept emerging as Samuels practised a fast run off the bike and found herself "falling in a heap".
"Training and racing was beginning to get compromised by it more and more frequently," she said.
Samuels' husband, Steve Gould, said from Wanaka yesterday her condition was obvious to television viewers when she raced in Takapuna earlier this year.
A fast burst of speed at near 100% exertion was needed at the start of the run to keep up with the front-runners, he said.
"She ran 800m and her heart rate was 230-240 and she felt her heart was going to explode. You could see when her vision went because she put her hands out in front of her face... It took about two minutes to settle down," Gould said.
The London race was "a hard one for her because it was her pinnacle race" and the timing of surgery had not been great but they had taken the view it had to be done, Gould said.
It took several months to diagnose the problem, he said, with doctors inserting a monitor about the size of a USB stick into Samuels' chest to record her heart beats in January.
The couple had not been able to afford private surgery earlier and when her name came up on the public waiting list in July, she was overseas and had 72 hours' notice to fly back to New Zealand.
Gould supported Samuels in surgery, which involved feeding wires from her groin to her heart to deliver drugs to replicate the arrythmia before cauterising eight to 10 spots inside her heart. Samuels was conscious for the procedure, Gould said.
Samuels is excited about her future now the surgery is behind her, particularly because she knows she was achieving highly at 80% intensity (she recently won the Alcatraz Triathlon and was 10th in the Kitzubuhel world series race).
Her new goal is to qualify for the Olympics next April in Sydney, where the course suits her strong cycling abilities.
"Watch this space. I am on a mission now. Get rid of the flu and test out this heart... and one less thing to worry about when I am on the start line.
"From now on I am hopefully back to pushing 100% in training and racing and that excites me a lot!" Samuels said.
Dr May said the diagnosis of heart conditions in high-performance athletes could often be tricky and controversial.
There was evidence some endurance and ironman athletes who did very high workloads for long periods of time were doing damage to their hearts but that was not the case with Samuels, she said.
Samuels' heart was structurally normal and the condition was best described as a "common problem in an uncommon person" and Samuels was not doing harm by continuing, Dr May said.
Warriner's condition was supraventricular tachycardia and she also returned to training and racing quickly but has switched to long-distance triathlons.
Samuels will remain in Europe to train and race before returning to Wanaka in mid-September.
