I’m a 30-year-old woman and have recently undergone several tests due to swelling in my legs (pedal edema), which still occurs but varies in severity. My blood work — including CBC, thyroid, kidney, and liver function tests — all came back normal. A 2D echocardiogram also showed no abnormalities. However, I’ve recently started experiencing shortness of breath with exertion. Yesterday, while brisk walking, my oxygen saturation dropped to 91%, but it returned to 99% within a second of stopping. Is this kind of fluctuation normal, or should I undergo further evaluation for potential heart issues such as heart failure?