Researchers have found that people who survive a heart attack are at much higher risk of sudden cardiac death in the following 30 days.

This new finding indicates that the doctors should closely supervise patients in the month after a heart attack, and that patients should be alert to any signs of trouble.

The first 30 days following a heart attack should be envisioned as a period of healing with heart tissue remodeling, which is conceptually associated with a propensity to experience sudden death.

In their study, the researchers followed the health of almost 3,000 people who had a heart attack from 1979 to 2005. They found that the rate of sudden cardiac death was 1.2 percent in the first 30 days, which is about four times the risk that would have been expected in the general population, after taking age and sex into account.

Over the following 11 months, the rate improved greatly, dropping to a level lower than that usually seen in the general population.

The study also found big improvements in the rate of sudden cardiac death for heart attack patients in the past three decades. They believe that the decline, which was over 40%, is a direct consequence of improved treatment options for people who have just had a heart attack.