Jackson was admitted to the hospital and given oxygen as well as a diuretic, to help remove fluid from his lungs. Diagnostic testing showed that his mitral valve was not working at full capacity. This caused the tendons in his heart, called chordae tendineae, to rupture. In a larger dog, this may have been a fatal event, but Jackson's small body was able to compensate until he received treatment.
His heart will never return to normal, but proper medication, lifestyle management, and regular checkups have helped him maintain a good quality of life. He also receives plenty of tender loving care!
Happy Valentine's Day, Jackson!