Cuffs and collars aren’t a life-or-death matter, but they’re becoming a close second for Dr. Roderick Tung.

Tung, a 35-year-old L.A. cardiologist, balances his time between heart surgery and promoting his line of dressy Italian sport shirts sold under the label “Tung.”

Now, as the label catches on with luxury retailers such as Nieman Marcus and Gary’s of Newport Beach, Tung finds his fashion-design hobby fast becoming a second career.

“I find myself on the fence between growing this into a big business versus just keeping it fun,” said Tung, who designs, markets and picks the fabrics for the shirts.

A Northwestern Medical School graduate with no formal design training, Tung launched the line of hand-stitched $295 shirts just a couple of years ago. So how is the M.D. winning over the luxury fashion crowd?

It doesn’t hurt that he’s a frequent customer at L.A. boutiques such as Traffic and the recently closed Lisa Kline. He began shopping at the stores when he came to Los Angeles for cardiology training in 2004. As he grew more discerning of his attire, he began drawing up some shirt designs for fun. Tung describes his shirts as a mixture of sleek Italian design with British sartorial accents.

Soon enough, Tung began corresponding with a tailor in Italy he found online. He visited the country with about 10 designs in 2009, paid the tailor to have them made and received a shipment of his first 60 shirts a couple of months later. Traffic and Kline took the first batch on consignment for the fall 2009 season and sold them out, prompting Tung to scale up production. He had 495 shirts made for the current winter season.

Tung wouldn’t divulge how much he’s invested to date, but said he spent about $20,000 on “tuition” to learn the business, get those first shirts made and launch his website.

All the while, he’s been an assistant professor at the Ronald Reagan UCLA Medical Center, where he consults with patients and does minimally invasive surgery, such as installing pacemakers.

Tung has no plans to drop his cardiology career, but after going home at night, he designs shirts, keeps in touch with Italian suppliers and arranges meetings with department store buyers. Tung, who visits Italy during his four weeks of vacation, expects to turn a profit within the year.

Ilse Metchek, president of the California Fashion Association, said Tung has found a good opportunity with his apparel.

“There is a big market for high-end sport shirts, especially in California,” she said.