When Michael “Fuj” Fujinaka started medical school two years ago he received a stethoscope. But he was not taught how to use it until his third year of school.

“Basically every medical student uses a stethoscope. But you don’t learn how to use it until your third year,” said the Stockton, Calif. native, who is in his third year at the University of California, San Diego School of Medicine.

Fujinaka said his desire to better educate medical students about how to detect and diagnose troubling heartbeats — and his strong interest in the iPhone — led him to create the iMurmur application. The title of the application refers to an abnormal heartbeat.

With a reported 10,000 downloads so far, iMurmur has become one of the most popular medical applications ever created for the iPhone. The Yonsei said his target market includes medical students, doctors, emergency medical technicians and paramedics.

“I was looking for something that a lot of people could use, something that was not really technical. I hope it can help people,” said Fujinaka, who developed the idea for the application in March.

He said iMurmur is designed to simulate the heart sounds that medical staff would encounter in a clinical setting.

“It’s like a real patient. You can practice listening to it hundreds of times before getting into a clinic,” said Fujinaka, who graduated from Claremont McKenna College in 2007 with a double major in economics and molecular biology.

Fujinaka said iMurmur’s interactive nature allows users to quiz themselves as they listen to heart sounds. The screen simultaneously displays a diagram of the murmur.

“If you hear a lub-lub or a woosh sound, there is a pictorial diagram,” said Fujinaka, who is the son of vegetable farmers.

The application also includes a reference library, which enables users to listen to specific heart murmurs.

Fujinaka said the creation of iMurmur involved creating appropriate diagrams and finding the right sounds.

“I did a lot of the diagram work, making sketches. And I had to get licenses to use the sounds,” he said.

Fujinaka and business partner, Alan Gardner — who worked on the application as a developer — created iMurmur.

Once Fujinaka and Gardner were happy with the application, they submitted it to Apple in July.

“Apple is very hands off. You make the application and you submit it. You don’t know why they accept or deny it,” Fujinaka said.

The application, which was made available on Apple’s iPhone Website at the end of July, has remained among the top 20 applications. Fujinaka said there have been more than 10,000 sales to 25 countries. He did not disclose how much he has made from the application, which costs $2.99 to download.

“Not bad for a kid out of Stockton,” said Fujinaka, adding that he has a strong interest in working in the field of pain medicine.

Fujinaka recently sold iMurmur to the electronic stethoscope manufacturer Thinklabs Medical, based in Centennial, Colo.

Clive Smith, CEO of Thinklabs Medical, said iMurmur was a great match for his company, which works with medical schools and teaching hospitals.

“The software augments medical education and contributes to the learning process. It’s a good diagnostic tool for students to learn heart sounds,” Smith said.

Weijen Chang, assistant clinical professor of medicine at the UCSD School of Medicine, agreed.

“I’ve used (iMurmur) and it’s a lot of fun,” Chang said. “I think it’s great that medical students are making applications to help their understanding.”

He said the application is a major advancement, a far cry from the old days of reading a medical reference book.

“This is the wave of the future. It helps students to understand murmurs better. And you don’t have to go to the library. You can just go to your phone,” Chang said.

He said although he teaches heart murmurs to students in bedside settings.

“This is a good complement to teaching at the bedside.”

“This application fills in the gaps in cases where you can’t find a patient with every single murmur,” Chang said.

Fujinaka said he is pleased with iMurmur’s success, adding that his entrepreneurial spirit was strongly influenced by his father and grandfather.

“After the war, my grandfather had nothing. He started over in farming. My dad and grandfather were always looking ahead,” he said. “So I’ve learned to always keep an eye out for opportunities to do something different. And this has worked out nicely.”