In a heartbeat; When a little girl is struck by a horse and a doctor just happens to be there, every second counts.(Life-Today)

Byline: STEPHANIE EARLS - STAFF WRITER

The heart.

It is the body's most vital muscle.

It is a perfect, four-chambered pump, sending blood pulsing, pulsing, pulsing through the lungs, where it is infused with oxygen, then pumping it out to the organs and tissues of the body.

A body can survive without a kidney or a colon or a lung. But not without a heart. If our heartbeat stops, so do we, organ by organ. After one minute, we pass out. Then we seize. For every minute without a heartbeat, our chances of survival drop by 10 percent. At 10 minutes, brain death.

Electrical impulses within the heart control how often it beats. The number of times it beats each minute depends on age, activity level and health.

The heart of an 11-year-old girl beats between 60 and 105 times a minute.

Though the heartbeat feels like a single thump when you press your fingertips to your wrist, it sounds like a spongy lub-dub through a doctor's stethoscope, as electrical impulses open and shut the upper and lower valves.

After the dub, while the heart recharges, is a fraction of a second of silence. At the tail end of that silence, as the heart scrambles to prepare for the next lub, is a fleeting moment of disorder.

Fifteen milliseconds of it, to be exact.

It's a splinter of a splinter of time, so brief it's hard to fathom. It is three beats of a hummingbird's wings. It is the snap of a camera shutter. It is faster than the blink of an eye.

But in that fifteen milliseconds, the heart is at its most vulnerable. A relatively minor blow to the chest, at just that moment, at just the right spot, can confuse an otherwise healthy heart's rhythm and instantly cause cardiac arrest.

The condition, called commotio cordis, is so rare, almost always fatal, that most doctors, even trauma specialists like Albany Medical Center's John Burton, only read about it in textbooks. Each year, commotio cordis kills between 10 and 20 people, almost all children engaged in youth sports like softball.

The factors leading up to it must be so precise, so phenomenally unlucky, that the odds border on impossible. The chances of being revived, unless a defibrillator is within reach, are nearly nonexistent.

But at a crowded horseback riding competition in Rexford on April 29, the practically impossible happened. Then it happened again.

On that day, Dr. John Burton, a little girl named Delana Ringer and her mom, Suzanne, learned that the time between heartbeats …