Earlier this week, Waterville resident Samantha Fields traveled roughly 200 miles to the Foster Hospital for Small Animals in North Grafton, Massachusetts, so her foster dog, a 17-month-old American foxhound named Addie, could undergo intensive heart surgery.

The surgery — aimed at correcting a deformity of the heart and lungs that slows blood flow — failed to correct the problem.

“It was disappointing,” said Fields, who raised close to $9,000 for Addie’s surgery. “I had hoped that after the procedure she would be much better.”

The duo isn’t giving up, though, and they plan to return to the Tufts University specialized animal hospital in two to three weeks for another procedure, Fields said.

“It’s going to be an open-chest procedure, versus this one was done with a catheter,” she said. “So it’s going to be a longer stay, harder and longer recovery, but I’m in this for the long haul with her, so I’ll make sure it gets done.”

The money raised via Facebook and GoFundMe pages should be enough to cover the additional surgery, although Fields said she might need some additional money for medications, laboratory work and other incidentals.

Fields has fostered Addie since May, and the two share a special bond in that they both have heart conditions. Fields, who has diastolic heart failure, recently moved to Waterville from Colorado, where the high altitude forced her to be on oxygen full time.

She said the dog has been doing well since the surgery Wednesday, which failed because the blockage in Addie’s pulmonary valve was too thick and surgeons couldn’t pass a catheter through the area aimed at widening it and easing blood flow, Fields said. The next procedure she is scheduled to get is called a patch graft, and while it offers Addie a chance at an improved life, it is risky. Without the surgery, veterinarians have estimated that Addie will live for only a few months.

“Basically, they say she will either make it through the surgery and do really well, or she won’t make it through at all,” Fields said.

For now, Addie is doing well — she has been sleeping and eating since the pair returned to Waterville on Friday and is looking “happy-go-lucky,” Fields said.

Fields agreed to foster Addie for the Humane Society Waterville Area and said she hasn’t decided yet whether she will adopt Addie permanently until after her second surgery. She said she loves caring for the dog, and her only hope is that if the surgery goes well, Addie might get adopted by a family that could offer her a big backyard to run around and play in.

In the meantime, she said she doesn’t mind caring for Addie during her period of limited activity.

“My original thing has always been that I want what’s best for Addie,” Fields said.

Rachel Ohm — 612-2368

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Twitter: @rachel_ohm