Ans. is 'c' i.e., Atrial Flutter with Fixed Block The absence of any discernible P waves on ECG together with the presence of Saw Tooth Flutter wave in inferior leads (Leads II, III and AVF) strongly suggests a diagnosis of Atrial Flutter. The presence of a regular rhythm suggests a Fixed Block. Atrial flutter is characterized by rapid atrial rate. The ventricular rate varies depending upon the degree of A. block. The rhythm originates in one atrial focus, resulting from circuit reentry mechanism. On the ECG P waves lose their normal appearance due to the rapid atrial rate. The waves blend together in a sawtooth configuration called flutter waves (the hallmark characteristic of rhythm). The patient develops a regular atrial rhythm. This variation is the ventricular response is irregular Saw tooth P waves (regular atrial rhythm) Irregular Regular ventricular ventricular rhythm rhythm Atrial flutter with variable block Atrial flutter with fixed block