Thanks to google I came across this
What you describe is a classic picture of a very common, very normal (yet often also very aggravating) phenomenon known as premature ventricular contractions (PVCs) or premature atrial contractions (PACs). These occur in almost everyone from time to time, but some of us feel every one while others are totally unaware they are happening. What takes place is this: a tiny area in the upper or lower chambers of the heart becomes momentarily irritable and triggers a heartbeat in advance of the next regular one. The heart, wanting to keep everything in order, pauses for a split second in order for the next regular (sinus) beat to occur. The early beat usually causes the flutter sensation and a sort of "void" sensation that some describe as taking ones breath away for a second. This usually is because the premature beat has occurred when the pulmonary valve of the heart is closed, which makes the early beat more noticeable and provokes the feeling of a need to cough. It is all very simple, and takes place in less than a second, but depending on what part of the heart's cycle it occurs in, it can seem like a rather dramatic and weird sensation.