"Gastrocardiac syndrome" might be considered outdated in the medical world (not sure what they mean by that), but it's been a real thing for me. I started getting clued up on the vagus nerve because of frequent weird heartbeats (which turned out to be PVCs and PACs that my cardiologist diagnosed after I bought my own portable ECG thingy to catch them), especially when I bent over or lay on my side. After finding out I had a hiatal hernia and starting on omeprazole, those odd heartbeats dropped a ton, like by 90%.