A young woman with palpitations. Fast, irregular rhythm. Normal axis. Short PR, slurred QRS upstroke—the delta wave of Wolf-Parkinson-White. The shamrock caught it before she arrested.
Maeve smiled. “What does that tell you?”
Dr. Brennan had done it again. Next to a rhythm strip showing a wide-complex tachycardia, he’d drawn another shamrock, this one split into four uneven leaves, each labeled: V rate? , Regularity? , Width? , History? Underneath: “Four questions. Four leaves. One answer.”
They gave adenosine. The tachycardia broke. The underlying rhythm was atrial flutter with 2:1 block and rate-related left bundle branch block. The patient sighed, his chest pressure gone, and asked if he could have some water.
Dr. Maeve O’Reilly had been a cardiologist for twenty-two years, long enough to trust her instincts and short enough to still tremble before a difficult strip. She taught electrocardiogram interpretation to fellows every July, and every July she watched them drown—lost in a sea of squiggly lines, afraid to call a STEMI, afraid to miss one, afraid of the patient whose heart spoke in hieroglyphs.