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 ...

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 ...