Heartworm infection with caval syndrome was detected in a thirteen-year-old male cat. However, removal of the heartworms via a jugular venotomy was infeasible because the size of the jugular vein limited our ability to use flexible alligator forceps. Therefore, a right atriotomy using total venous inflow occlusion was performed to remove the heartworms. The procedure was accomplished successfully, and the cat recovered from its symptoms. The present case suggests that right atriotomy using venous inflow occlusion is practical for removal and prevention of rupture of heartworms.