Does an ivc filter only catch a blood clot that would travel to the lungs?

That's main function: The main purpose of the IVC filter is to protect the lungs from blood clot reaching them. The filter will also prevent blood clots from reaching the right atrium of the heart, however, this is not the main concern as the clot normally travels quickly through the heart into the pulmonary artery of lungs where it gets stuck in the narrowing pulmonary arteries. This is termed pulmonary embolism.