The Centers for Disease Control and Prevention (CDC) estimates that 720,000 individuals in the U.S. have heart attack per year and for these patients, their chances of survival often depend on how quick they are given the necessary treatment.

A new study, however, suggests that patients who had heart attack and managed to arrive at the hospital during business hours are more likely to receive more immediate treatment and are likely to survive than their counterparts who arrive at the hospital on weeknights, weekends and holidays.

For the study published in the journal Circulation: Cardiovascular Quality and Outcomes on July 29, Jorge Saucedo, from the NorthShore University Health System in Evanston, Illinois, and colleagues examined the treatment and survival of patients who had ST-elevation myocardial infarction and were treated at one of the 447 hospitals in the U.S. between January 2007 and September 2010.

ST-elevation myocardial infarction, or STEMI, is a severe type of heart attack that is caused by prolonged period of blood supply blockage that affects a large area of the heart. This type of heart attack involves a substantial risk of death and disability and requires immediate treatment.

Over 27,000 of the patients involved in the study arrived at the hospital past regular business hours while nearly 16,000 arrived at the hospital during business hours. The researchers found that the patients who arrived at the hospital during working hours waited 56 minutes, on average, to have angioplasty, a procedure that involves inflating a small balloon to open blocked arteries, while those who arrive at night or on weekends had to wait an average of 72 minutes.

Saucedo said that the slower door-to-balloon times during off hours likely has something to do with staffing as hospital catheterization laboratories, where angioplasties are done, often do not have staff at night.

Although the waiting times during and after business hours are within the recommendation of the American Heart Association of no longer than 90 minutes wait for angioplasty, the researchers have found that patients who arrive at the hospital past business hours have 13 percent elevated risks of dying from any cause compared with those who arrive during normal business hours. 

"In contemporary community practice, achievement of quality performance measures in patients presenting with ST-segment-elevation myocardial infarction was high, regardless of time of presentation," Saucedo and colleagues wrote. "Door-to-balloon time was, however, slightly delayed (by an average of 16 minutes), and risk-adjusted in-hospital mortality was 13% higher in patients presenting off-hours."