I have had this for years. My doctor caught it once on an EKG and said it was PVC, or Premature Ventricular Contraction. The heart starts to beat, decides not to, then beats harder the next beat to make up for it. Or something like that--I'm not a doctor, but that's how he explained it to a layperson. Later, I had an echocardiogram and they found I had a thickened mitral valve which was prolapsed, but it's not a life-threatening problem. Your mom should see a doctor to rule out anything dangerous, but it sure sounds exactly like what I've had for at least 26 yrs. Oh, and they put me on Lopressor and it helped a lot, but I still get those funny PVC's when I'm sick or extra tired.