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Winter can be hard on your heart
Thursday, February 26, 2004BY CHRISTINE V. BAIRD
For those with heart disease, winter is the killing season.
The icy fact is that more heart attacks occur now than during any other time of year. Shakespeare had it right when he wrote of the vengeance in Old Man Winter's "wrathful nipping cold."
"Winter is a dangerous time," said Muhamed Saric, director of the Echocardiography Lab and assistant professor of medicine at University of Medicine and Dentistry of New Jersey. Exposure to chilling temperatures plays a major role in the heart attack spike in places like the Northeast, but staying out of the cold isn't enough: The number of winter heart attacks peaks in warm climates, too.
And women, in particular, should take heed: Studies show that they respond to heart attack symptoms differently than men, often ignoring them until it is too late.
For those with cardiovascular disease, spring's imminence shouldn't cause you to drop your guard. Heart disease is the leading cause of death in the United States, according to the Centers for Disease Control and Prevention, and winter heart attacks are about 20 percent more severe, causing more damage to the heart muscle.
"All of this has been show conclusively, but what is the explanation for it?" Saric said.
For New Jerseyans, a big factor is the cold, which can give a jolt to heart rate and blood pressure, cause clotting and even hypothermia, a condition that arises when body temperature falls below normal.
If the body can't produce enough energy to keep itself warm, "it can kill you," according to the American Heart Association in its recommendations on cold weather and cardiovascular disease.
Heart failure is the cause of most hypothermia-related deaths.
Combine these stresses on the heart with the sudden physical exertions typical of the season, such as shoveling snow or walking through heavy slush, and its workload can sometimes prove too taxing. "Winter and cold bring upon sudden exercise that people are not accustomed to," Saric said. "In New Jersey, everybody drives. Nobody walks."
Staying in good physical shape with a year-round exercise program can mediate the stress. "And when the shoveling comes, take your time," Saric said.
It is particularly important, especially for those with high blood pressure, to go slow in the morning. Studies show that blood pressure ebbs and flows throughout the day, according to the body's natural rhythms, also known as circadian rhythms. In most people, what is known as an "a.m. surge" in heart rate and blood pressure occurs in the hours around awakening. "We have this undulating wave of risk periods, time-wise," said Domenic Sica, chair of clinical pharmacology and hypertension at Virginia Commonwealth University.
The morning hours can be deadly for those with hypertension. Researchers have identified a 49 percent higher risk of stroke, a 40 percent higher risk of heart attack and a 29 percent higher risk of cardiac death in the hours between 6 a.m. and noon. In fact, studies have identified a third cyclical time period, in addition to winter and mornings, when the risk of heart attack or other acute event is greatest: Mondays are more dangerous than any other day of the week.
A person with hypertension has a real problem if he "wakes up Monday morning in the winter and has to shovel snow," said Stephen Glasser, professor of epidemiology at the University of Minnesota. "You have a number of thing coinciding, or colliding, to cause excessive risk."
Such scenarios can be lethal for someone with high blood pressure. "The only other recommendation is not to get up in the morning," Glasser said. "Try telling that to your boss on Monday morning."
One approach to solving the "a.m. surge" dilemma in those with hypertension is chronotherapy. Pharmaceutical companies have begun to formulate drugs that release medication in varying doses over time to correspond with the body's needs. This is different than time-release medications that release an even dose over time. "When we go to sleep at night, our blood pressure drops 25 percent, "Sica said. "You don't need blood pressure medication to be unduly active during this time."
Last year, the Food and Drug Administration approved two chronotherapeutic hypertension drugs, Cardizem LA and InnoPran XL. Both Sica and Glasser worked on developing the former. When taken in the evening, it delivers a higher dose in the morning when blood pressure typically surges.
"It starts making sense to tailor drug delivery," Glasser said.
These drugs are not yet widely prescribed. "It is logical. It sounds right," said Marc Cohen, chief of the division of cardiology at Newark-Beth Israel Medical Center. "The problem is that nobody has ever established -- beyond a shadow of a doubt -- that the delivery system works a whole lot better than the non-delivery system."
A study has established that flu shots have the potential to decrease the number of heart attacks and strokes substantially. The reason: Upper respiratory infections, often found in those with the flu, trigger inflammation in the body that can cause plaque in the arteries to rupture, which leads to blood clots and heart attacks.
This is fairly new news to the medical community. "We are learning more and more that heart attacks and strokes are caused by ruptured plaque," Saric said. Previously, it was thought that they were caused by a plaque buildup blocking the arteries, he said. Plaque is deposits of fat or other substances, including cholesterol, attached to the artery wall.
Now, it is becoming clear that even small amounts of plaque, when ruptured, are dangerous. When plaque bursts, "what lies beneath is exposed to the blood," Sica said. Sticky blood cells known as platelets tend to clump around the exposed area.
"It is like an Italian family at the dinner table," Sica said. "Everybody is congregating." Clots can form and heart attacks can follow.
If those with heart disease got flu shots each year, research has found that in the United States, heart attacks could decrease by 104,500 and strokes by 192,000. The risk of heart attack is tripled in the 10 days following an acute respiratory infection.
Complications of the flu may be one explanation for the puzzling finding that there is a wintertime heart attack peak in warm climates, too. Some other possible factors include overindulging in food and alcohol during the holidays and the accompanying emotional and psychological stress that the season-to-be-jolly can bring. "It's supposed to be fun, but you know better," Glasser said.
Another possibility is the lack of daylight. Sunshine can affect hormones, sometimes significantly if the reduction of light is dramatic.
Whatever the cause, there are certain groups in the population that need to be aware of the increased risks winter brings.
Americans over 65 need to be particularly careful, Saric said. "The older you get, the more pronounced "are the effects of cold weather, flu and other stresses. Additionally, the aging body has more arterial plaque and is more prone to arrhythmia, or irregular heart beat. Epidemiological studies show that ventricular arrhythmias and stroke also peak in winter, regardless of climate, Saric said.
Women, too, need to be mindful of winter's increased risk because heart attacks strike them harder, so to speak. According to the CDC, females in general have poorer outcomes following heart attacks than males do. The percentage of females who die within a year of having a heart attack is 44 percent compared with 27 percent of males.
And women often delay seeking medical treatment. "If a woman gets chest pains, she is more likely to say, 'Gee, I have to finish the laundry first,'" said Cohen. "It sounds stupid, (but) that is the reality."
Studies show that women complain of symptoms less dramatic than stabbing pains to the chest when having a heart attack. Often, they describe nausea, sleeplessness or shortness of breath, those vague symptoms that doctors often dismiss or chalk up to anxiety or being overweight. In an effort to educate women and the medical establishment, the American Heart Association, this month, announced new guidelines for preventing heart disease and stroke in women.
The new recommendations call for a more individualized approach to treating the diseases, with the aggressiveness of treatment linked to whether a woman has a low, intermediate or high risk of having a heart attack in the next 10 years. Cardiovascular disease kills nearly 500,000 women in the United States each year.
So as the snow melts and temperatures rise, don't give in to premature spring fever. Warmer afternoons can quickly turn into brutally cold nights, even after the vernal equinox. The best advice for those with cardiovascular disease is to dress warmly, stay inside if possible and count the days until spring.
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