Most “sudden” cardiac arrests are not sudden, in the sense that most patients have visited a doctor or gone to a hospital during the two weeks before they happen.

Researchers used a Danish registry of 28,955 out-of-hospital cardiac arrests recorded from 2001 to 2014 to track the patients’ interactions with doctors and hospitals in the year preceding the event.

They found that 57 percent of them had contacted either a doctor or a hospital in the two weeks before their arrest. The data was presented at the annual meeting of the European Society of Cardiology.

Over the year before the event, patient visits to the hospital increased gradually to 7 percent in the week before the event, from 3 percent a week one year earlier. Contacts with their doctors, either in person or by phone, followed a similar pattern, increasing to 54 percent in the week before the arrest from a relatively constant 26 percent a week the rest of the year. About 14 percent of the general population contacted their doctors over the same period.

The lead author, Nertila Zylyftari, a researcher at Copenhagen University Hospital, said that the study did not have the data to identify specific warning signs of cardiac arrest. Still, she said, “there are these additional health care contacts, and that means there is a chance for focusing more on identifying those at risk in future studies.”