Felt nauseous and short of breath during exercise. Diagnosed with GERD after normal chest x ray, ECG echo stress test. Panic attack GERD or heart?

Most commonly GERD. with normal CXR,ECG and echo, findings are less likely cardiac. Exercise has been known to trigger reflux. Figure out if its your routine (crunches on a full stomach), or diet (aggravating foods, coffee, OJ). Try some PeptoBismol before exercise to see if chnages. Keep a diary of when it happens, how you feel, and what you had to eat that morning. It will give you and your doc the best picture.