Some experts think that very few world records will be broken in swimming at this year’s Summer Olympics in London because athletes are no longer allowed to wear high-tech swimsuits. But Dana Vollmer, a UC Berkeley grad who still trains at Cal, may prove them wrong. Which is amazing, considering that Vollmer underwent heart surgery in 2003 to correct a rare disorder that caused her heart to beat 240 times per minute. For years, coaches kept a defibrillator at poolside while she raced. Then, after just missing the 2008 US Olympic team, Vollmer embarked on a relentless training regimen. And next week, when the Games begin, she’ll be the gold-medal favorite in the 100-meter butterfly, and is expected to pick up two more golds in the 400-meter medley and 800-meter freestyle relays. The woman with the balky ticker also could become the first female swimmer to break a world record in the post-high-tech-suit era.