In __________________ there is an irregularity of electrical impulses which cause the atria to beat rapidly which filters down to the ventricle and causes the ventricle to beat fast and irregular as well. When this happens, it is called ____________ with RVR, rapid ventricular response. In the absence of RVR it is called controlled __________. During ____ the atrial rate is usually greater than 300 per minute but what we observe is the ventricular response. The atria pump blood into the left ventricle. This is called the atrial kick and is responsible for about 20% of the cardiac output. During ______________ the atria are just quivering and not pumping.