A 29-year-old woman has a known history of palpitations from a diagnosis of supraventricular tachycardia that usually terminates when she performs a Valsalva maneuver. Today, she presents to the ...

I'm lying on my back with my legs in the air and thumb in my mouth, blowing out hard. But it's not working. My heart is still going a million miles an hour. I'd experienced episodes of rapid heartbeat ...