Routine Activities May Stress The Hearts Of People With Heart Disease

November 09, 1998

American Heart Association meeting report:

DALLAS, Nov. 9 -- Routine daily activities -- driving a car, housework or even getting out of bed in the morning -- can trigger a shortage of blood supply, increasing the risk of a heart attack for people with heart disease, according to a study presented today at the American Heart Association's 71st Annual Scientific Sessions.

The study's lead author Prakash C. Deedwania, M.D., chief of cardiology at the VA Medical Center, Fresno, Calif., says previous research has shown that vigorous activities such as snow shoveling can trigger a sudden heart attack, especially in individuals who have heart disease.

The new research shows that even moderate physical exertions can lead to dangerous shortages in blood supply to the heart, a condition called ischemia. Because of the sudden stoppage of blood flow, a person having a heart attack will feel chest pain and shortness of breath. However, individuals with ischemia don't always experience these typical warning signs. Thus, they may continue to exert themselves, he says.

"It is well recognized that the majority of ischemic episodes -- up to 80 percent in some studies -- are not associated with chest pain," he says. "It is not entirely clear why some people experience pain and others do not. However, it has been suggested that a history of prior heart attack, bypass surgery or other diseases might cause numbing of the heart. Also there may be variations in how a person perceives pain.

"The fact that the ischemia is 'silent' doesn't make it any less dangerous. If anything, the individual's lack of awareness may make it even more dangerous than a heart problem you can feel," says Deedwania who is also a professor of medicine at the University of California, San Francisco, and at Stanford University.

"The message to people with heart disease is not necessarily to avoid these activities, but to be sure to continue their therapies, take proper medications and be cautious."

The study included 97 people, all of whom had heart disease or had experienced a prior heart attack. On two or three occasions per individual, researchers measured the heart's electrical activity of each participant using a 24- to 48-hour-long continuous electrocardiogram. Abnormal electrical activity indicated ischemia, which means that the demand for oxygen-rich blood to the heart exceeded the supply. The study notes that most of the ischemic episodes were preceded by heart rate increases, which in turn increased the heart's demand for oxygen. For people with damaged hearts the increased demand for oxygen may be exaggerated because even though their heart is beating faster, no more blood is being pumped through.

Individuals in the study also kept detailed diaries of their daily routines in which they recorded more than 2,200 separate activity episodes among them. Researchers found that the most stressful activities were driving, housework and yardwork. Other high-risk tasks included talking on the phone and watching television.

"Driving was very stressful for the patients, especially when they were rushing, in heavy traffic or trying to find a parking spot," Deedwania says. "During 210 monitored driving episodes, there were 22 incidents of ischemia -- more than 10 percent -- but only one individual had chest pain."

Recorded episodes of yard work (mowing, gardening, etc.) and housework (vacuuming, mopping, etc.) produced similar percentages of silent ischemic incidents in the study participants.

In 175 walking episodes, 29 cases of ischemia were recorded, but 20 percent of these individuals experienced chest pain. "People are probably more aware of ischemic symptoms while walking than they are when their attention is focused on house or yard work," Deedwania says.

Ischemic incidents were high among individuals who got out of bed abruptly just after waking up in the morning, and ischemia was even recorded 50 times during an estimated 300 recorded periods of sleep.

"Both blood pressure and heart rate can go up during REM (rapid eye movement) sleep," Deedwania explains. "Getting up too suddenly may be a factor in the high number of heart attacks that occur in the early morning."

To minimize the risk associated with getting out of bed, individuals with known heart disease should never jump out of bed when they first wake up.

"Take it slowly," Deedwania advises. "Give your body a chance to adjust." Beta-blockers, drugs that can reduce heart rate and blood pressure, have proven to be highly protective against ischemia, Deedwania says, "and mild regular exercise can condition the heart to minimize the risk."

Co-authors are Enrique Carbajal, M.D., and James Oakley, B.S.

American Heart Association

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