Atrial arrhythmia Atrial fibrillation 2008-03-25T06:29:00Z The ventricular response to atrial fibrillation is irregularly irregular because of the large number of atrial impulses that transit the atrioventricular node, making the ventricle partially refractory to further impulses. Atrial fibrillation can cause a number of manifestations including excessive ventricular response with angina pectoris or hypotension in susceptible individuals, syncope, systemic embolization, fatigue, or anxiety. These features should be coded separately. HP:0005179 SNOMEDCT_US:49436004 HP:0005110 An atrial arrhythmia characterized by disorganized atrial activity without discrete P waves on the surface EKG, but instead by an undulating baseline or more sharply circumscribed atrial deflections of varying amplitude an frequency ranging from 350 to 600 per minute. Quivering upper heart chambers resulting in irregular heartbeat HP:0001715 UMLS:C0004238