A client recovering from lung surgery is being monitored when the rate display settles at exactly 150 and stays there. Not 148, not 153 — 150, unwavering, for twenty minutes. A rate that refuses to vary is itself a clue, because a heart responding to pain, fever, anxiety or movement does not hold a single number. Atrial flutter is an organized, rapid atrial rhythm in which the atria depolarize in a regular circuit at roughly 250 to 350 beats per minute. The atrioventricular node cannot pass impulses that fast, so it blocks most of them and lets through a regular fraction — commonly one in two, one in three, or one in four. That is why the ventricular rate so often lands on a clean division of about 300: around 150, 100, or 75. For the nurse, flutter matters for the same two reasons fibrillation does. A fast ventricular rate shortens filling time and can drop cardiac output, and atria that are not contracting properly form clots that travel. The distinction worth holding is that flutter is *organized and usually...