“We undertook this project after we observed that many inpatient deaths due to congestive heart failure seemed to occur in the early morning,” says lead author José Fabri Jr., M.D., an assistant physician at Brazil’s Heart Institute (InCor), University of São Paulo Medical School. “We decided to investigate the distribution of deaths to see if they really were more frequent at certain times of the day. Gender differences were unexpected.”
The mechanism behind this type of pattern may lie in the daily biological ebb and flow of hormone levels and body processes known as circadian rhythm. Circadian rhythm refers to patterns that occur on a 24-hour cycle such as sleeping, waking and hunger at certain times of the day. Earlier studies on patients who were not hospitalized have found that heart attack and sudden death tend to peak during the few hours after waking. For congestive heart failure, nighttime appears to be more risky, according to this study, which is the first to find gender differences in circadian patterns.
Fabri’s group studied the deaths of 508 patients – 308 men and 200 women ages 14 to 93, average age 59 – hospitalized with terminal heart failure. They received standard treatment for their condition, which includes bed rest, diet and treatment with ACE inhibitors, diuretics and digoxin for chest pain. The researchers found that men were most likely to die near dawn, between 5 a.m. and 6:59 a.m., and also between 11 p.m. and 11:59 p.m., but women were most at risk only during the early morning hours.
“Heart failure in men is usually more severe than in women. This clinical characteristic may affect circadian patterns, and may be related to our findings,” Fabri says. There is also the possibility that differences in hormonal patterns between men and women also may account for these findings, but too little is known about such differences to make any guesses, he says.
The body undergoes many cyclical changes during the day that can increase heart attack risk, Fabri says. Heart rate, blood pressure and probably even the heart’s ability to contract – all determinants of oxygen demand – peak between 7 a.m. and noon. Blood levels of norepinephrine and renin activity – both of which help vessels constrict – also peak during that time.
Earlier studies have shown that congestive heart failure patients have abnormalities in their circadian patterns for blood pressure and heart rate, Fabri says. Heart rate and blood pressure generally “dip” overnight, but this is often not the case in people with heart failure.
Further studies should help clarify the mechanisms tied to these circadian patterns in heart failure death and perhaps even lead to new drugs that could modify them, he says. For instance, the Beta-Blocker Heart Attack Trial (BHAT) found that beta-blocker drugs are linked to a 44 percent reduction in the incidence of sudden cardiac death during the morning hours.
Beta blockers are not commonly used in heart failure patients; however, recent studies report that these drugs may help treat heart failure, Fabri says.
Co-authors are: Rogerio S. Depaula, M.D.; Desiderio Favarato, M.D.; Antonio C. Pereira-Barreto; M.D.; and Alfredo J. Mansur, M.D.
CONTACT:
For information Nov. 10-14,
contact Karen Hunter or Darcy Spitz
at the Hilton Anaheim Hotel
(714) 251-5801
Abstract 3116 (Poster)
NR01 – 1359 (SS01/Fabri)