cannon A wave [L, cane, tube; AS, wafian] , a powerful atrial wave in the jugular venous pulse caused by the contraction of the right atrium against a closed tricuspid valve. Rapid, regular cannon A waves (the “frog sign”) are diagnostic of paroxysmal supraventricular tachycardia. Irregular cannon A waves are seen in atrioventricular (AV) dissociation and are therefore especially helpful in the diagnosis of ventricular tachycardia, which includes AV dissociation in 50% of cases. See also frog sign.
