TORONTO - Zach Herold's soccer dream is dead. But thanks to a pre-season medical, the 17-year-old Toronto FC defender still has his whole life ahead of him.

The young American has been forced to retire after being diagnosed with hypertrophic cardiomyopathy (HCM), which causes abnormal thickening of part of the heart muscle.

Strenuous exercise for HCM sufferers can trigger a potentially fatal irregular heart rhythm, or arrhythmia.

The heart condition has been linked to the deaths of such athletes as Windsor Spitfires captain Mickey Renaud, Russian hockey player Alexei Cherepanov and Cameroon soccer star Marc-Vivien Foe.

"Announcing my retirement from soccer at this age is something I never, ever thought would happen to me," Herold said in a statement Monday.

"This news was very hard to take but I know it’s the best decision for me and my health," he added.

Herold, who turns 18 on June 7, will be honoured in a ceremonial coin toss in Toronto before Saturday's MLS game against the New England Revolution.

Dr. Christine Lawless, head of cardiology for Major League Soccer, says HCM is found in about one in 500 people.

Herold did not show any major symptoms or have a family history of HCM. But an abnormality on a pre-season electrocardiogram (EKG or ECG) raised a red flag.

"Once you get on the right track, it's not that difficult to diagnose," Lawless said on a media conference call.

Herold was drafted in the second round, 24th overall, in the January MLS draft in Philadelphia. He had risen through the ranks of U.S. junior teams, and was with the American under-20 team at the Copa Chivas in Mexico in January.

"He's athletic, he's fast and he's one of the best products in the country," Mo Johnston, Toronto FC's director of soccer, said after drafting Herold.

But the six-foot 165-pounder from Port St. Lucie, Fla., never got to play in a Toronto uniform. Herold underwent a medical the day he arrived at BMO Field and the results concerned team doctor Ira Smith. More tests followed, both in Canada and the U.S., with Herold unable to play in the meantime.

Smith says Herold's condition should not impact his daily life, although he will face exercise restrictions "indefinitely."

"It's one of those conditions where you don't really have a choice," Smith said. "It's not a 'If you do this, then this.'

"We do not want you to do any exercise in professional athletics because it puts a risk to your life, basically."

Lawless said MLS prospects undergo a physical at the scouting combine before the draft but do not undergo EKG tests until they join a team.

"In Zac's case, it wouldn't have been picked up until that electrocardiogram was done," she said.

While Herold was part of the U.S. junior program, Lawless said earlier tests may not have caught Herold's condition.

"It's a peculiar disease because it's based in genetics. And these genes become expressed especially during adolescence and young adulthood. So somebody could have a totally normally EKG when they're 14 years old. And a totally abnormal EKG when they're 18 years old."

The MLS medical safety net that caught Herold's condition is part of a FIFA initiative, following the death of Foe at the 2003 Confederations Cup and several other players.

In 2006, FIFA instituted a cardiac screening program. MLS followed suit two years later, with Herold the second player to test for HCM.

"The effort is very life-saving," said Lawless. "We've come a long long way. I don't know what would have happened to those players if they had continued to play. I don't know if we would have seen another Marc-Vivien Foe incident."

Lawless said Herold had been devastated by the medical news. But she said his attitude towards the future was positive.

"He has some very interesting ideas on what he'd like to do with his future."

NOTES — Real Salt Lake forward Alvaro Saborio was voted Major League Soccer Player of the Week by the North American Soccer Reporters. Saborio scored two goals in Real Salt Lake’s 3-1 victory over the Houston Dynamo.