kchendrix,
Premature ventricular contractions or PVCs are also known as "extrasystoles." They are "extra" heartbeats. They arise from an irritable area in the heart's lower pumping chambers (the ventricles). PVCs interrupt the normal heart rhythm and cause an irregular beat. This is often felt as a "missed beat" or a "flip-flop" in the chest. PVCs are often harmless, but when they occur very often or repetitively, they can presage more serious rhythm disturbances.
I also experience these occasionally. I was diagnosed with mitral valve prolapse twenty years ago. Things that can trigger them are caffeine, cigarettes, alcohol and chocolate. I avoid these things. But do have a piece of chocolate occasionally, can€™t totally live without that. I also try to eat a healthy varied diet and supplement with minerals. Especially magnesium, which helps normalize the heartbeat.
