Just because you’re in the hospital doesn’t mean you’ll quickly get treated if your heart stops beating. About one-third of patients don’t get a potentially live-saving shock within the recommended two minutes. Those who don’t get prompt defibrillation are more likely to die or end up brain damaged or disabled, researchers reported in last week’s New England Journal of Medicine.

Recent attention has focused on getting quicker treatment for heart attacks that occur outside hospitals, and adding defibrillators to public places like airports and schools. The researchers instead looked at what happens inside hospitals and how response time affects survival.

Their study found that 39% of those quickly treated survived to leave the hospital, compared with only 22% of those whose treatment was delayed past the two-minute guideline.

“We still have a lot to learn as to how to deliver treatment in an effective way,” said lead author, Dr. Paul Chan of St. Luke’s Mid America Heart Institute in Kansas City, Mo.

The study used data from a national registry of 369 hospitals that track response times and outcomes. It included 6,789 cases of cardiac arrest caused by an abnormal heart rhythm, the kind most responsive to getting shocked back to a normal heartbeat. Only cases that occurred in intensive care units or regular units were included, not those in the emergency room or during surgery.

More than half of the patients got a jolt from a defibrillator in one minute or less, but it took more than two minutes — sometimes more than 6 minutes — for about 30% to get zapped.

The research showed delays were more likely at smaller hospitals, after-hours, or on weekends, and for patients who weren’t constantly being monitored or were admitted for non-heart problems.