Is There Any Link Between Sensitivity To Potassium And Esophageal

Is there any link between sensitivity to potassium and esophageal spasms? My husband has had issues with heartburn for years and lately he had been having severe pain in his sternum that sounds like esophageal spasms. He has been to a cardiologist, had an echo stress test and CT scan that ruled out heart problems. Recently we find that these episodes seem to occur when he eats raw spinach and it doesn't make sense to me what about spinach would trigger these attacks.