Sometimes it feels like my heart skips a beat. Its not painful and doesn't last long. Recent normal ekg & normal chest xrays in past. What cause this?

Palpitations. These are caused by many things. Stress, excitement, irritants both physical and chemical, pressure like a hiatal hernia or esophageal push or pull, and primary heart things, the causes are very many in number.
Different causes. Palpitations can be caused by different reasons such as electrolyte or thyroid abnormality or a heart rhythm abnormality which may be missed on a random EKG and a heart monitor is better at diagnosing heart rhythm irregularities.

Related Questions

I'm 17 I have tightness in my chest when I lay down. I feel like my heart skips a beat a lot of times. Had a heart monitor, EKG, and ultrasound normal?

Palpitations. Your test results are reassuring in that they don't show any structural heart disease. Your heart monitor didn't demonstrate any abnormal beats, but if you didn't have any palpitations while wearing a 24 hour monitor, you could wear a loop monitor which records your heart rhythm for weeks and if no dysrhythmia is seen during your complaints, then you will be more reassured. Chest tightness noncard. Read more...