WASHINGTON (CNN) -- Vice President Dick Cheney had a blood clot in his left leg checked out by his doctor at George Washington University Medical Center on Tuesday morning, his spokeswoman told CNN.

"The ultrasound was reassuring and showed that the clot is gradually resolving," Megan McGinn said. "His blood thinning medication was found to be in the desired range.

"The vice president's doctors advised him to continue the current course of treatment."

The appointment was put on the schedule early in the day, and he has since "returned to the White House to resume his normal schedule," she said.

Cheney first complained of discomfort in his leg after an overseas flight in early March. Doctors performed an ultrasound at that time and found a deep venous thrombosis, or DVT, in his lower left leg, McGinn said. He was put on blood-thinning medication and returned to work soon after.

After experiencing some discomfort on March 20, Cheney went to the GWU medical facility for another ultrasound on the clot. That imaging revealed no extension or complication.

Cheney has had a history of heart ailments -- including four heart attacks dating back to 1978 -- and was briefly hospitalized in January 2006 after suffering shortness of breath.

In September 2005, he underwent surgery to remove an aneurysm in an artery behind his right knee.

-- CNN's Erika Dimmler and Ed Henry contributed to this report