Matt, This would be either normal or benign ( normal means everybody has it, benign means that it s abnormal but harmless) I would guess. When you say difficulty breathing, you don t say just how difficult. I would think that it s not very difficult--she doesn t become frightened by it, for example--and therefore her breathing is just a little more difficult than normally, right? That s not too bad. You didn t say how old your gf is nor how long this has been going on, but from your brief description it sounds like PSVT, or Paroxysmal Superventricular Tachycardia. Generally, it s nothing to worry about. There are several forms and causes of it. Stress, alcohol, and caffeine are some external causes, but usually it is caused by what is called a reentrant circuit that causes one of the two nodes in the right atrium to trigger a rapid heartbeat. You have two nodes, the top one is the sinoatrial node, and the lower one is the atrioventricular node. The top one acts as the major pacemaker of the heart, initiating the beat, and the lower one acts primarily as the gatekeeper, letting through the beats the heart really needs. A system of checks and balances in your own heart. Well, the firing of the SA node starts the beat, with the signal traveling down to the AV node and then through the Bundle of His into the ventricles, down some fibers to the bottom (the apex ) of the heart, and then back up the outside. All the previous stuff occurs inside. Well, if there s an extra circuit in there somewhere, the signal can suddenly start circling around and around, causing the top of the heart s rate to accelerate to up to 200 beats per minute (or a little slower). The atria begin beating like crazy. The ventricles often beat at about half or 2/3 of the atrial rate, but the result is a very fast heart rate for a short time, then it suddenly stops and beats normally as if nothing odd happened. Now, normally this does not cause a problem, especially with an interval between episodes as you describe, and no other symptoms like nausea, lightheadedness, or even fainting. If it starts to happen more often, I would begin to become a little concerned and take it to your doctor to see if he would refer you to a cardiologist for an ekg. There are many things an ekg cannot uncover, but there are many things it can, such as a condition called Wolf-Parkinson-White Syndrome (which would cause just what you describe), in which that extra circuit--if there is one--will actually leave a little dip just before the big spike in her ekg, called the QRS Complex. It s very easy to spot if you know what to look for. If so, there still would be nothing to worry about. People live with WPW without incident. Here s one pretty good way to tell if your gf s flutter is PSVT and basically harmless: The Valsalva Manuver. When the rapid heartbeat starts, take a deep breath and strain against it as if you re trying really hard to go to the bathroom, as if you are severely constipated and you re going to show this constipation once and for all just who s boss. Strain like that for 5 to 15 seconds, then breathe normally. If that ends it, all is well. It s PSVT without complications, and she ll be fine. If it doesn t, then watchful waiting may be in order. If the frequency of the episodes increases, go to the doctor. If she develops any other symptoms, go to the doctor. All this assumes that there is no other complicating heart condition. Does she work out? If so, have there been any episodes of shortness of breath, any excessive fatigue, and fainting or dizziness during or immediately following her workout? I would believe at this point that there are none, or you would likely have said so. If that is the case, I think that you have nothing to worry about. As with all cases of the heart (in both senses of the term), be careful, but at this time I think you can rest easy. Hope this helps.