FIGURE 86.4 Narrow complex tachycardia due to atrial flutter: This shows atrial flutter at 240 BPM Flutter waves are subtle, but may be discerned in a 2:1 ratio to QRS complexes especially in lead V1 through V4 and in the right-sided chest leads V3R and V4R FIGURE 86.5 Atrial flutter with 3:1 and 4:1 atrioventricular block If AV conduction occurs in a 1:1 or 1:2 ratio (as in Fig 86.4 ) adenosine may make flutter waves more visible as seen here