'Biological clock' is linked to heart attacks

Scientists on Wednesday said they had uncovered the first molecular proof that the "biological clock" is linked to a type of sudden, fatal heart attack.

Ventricular arrhythmia, or abnormal heartbeat, occurs most frequently after waking in the morning -- and also to a lesser degree in the evening hours -- and causes a high number of deaths.

Reporting in the journal Nature, researchers in the United States said they had uncovered the first molecular link between this risk and circadian rhythm, the term by which biological processes vary according to a 24-hour period.

The finger points at levels of a protein called Klf15, they said.

Previous research has found Klf15 to be a circadian controller -- and, startlingly, is also lacking among some patients with heart failure.

The team created mice that had been genetically engineered to either lack Klf15 or make the protein excessively.

In both cases, the rodents had a much higher risk of arrythmias compared to normal counterparts.

"It is the first example of a molecular mechanism for the circadian change in susceptibility to cardiac arrhythmias," said Xander Wehrens of Baylor College School of Medicine in Houston, Texas.

"If there was too much Klf15 or none, the mice were at risk for developing the arrhythmia."

Klf15 is only one step in a complex molecular cascade, the researchers believe.

It controls another protein, KChIP2, which affects potassium-generated electrical current that flows though heart muscle cells called cardiac myocytes.

When levels of KChIP2 fluctuate, this causes electrical instability in the myocytes.

As a result, the heart muscle's action becomes impaired and it takes longer (or conversely, less time) to empty the ventricle -- the heart's pumping chamber. The heart loses the regularity of the beat and labours to pump blood efficiently.

Co-author Mukesh Jain of the Case Western Reserve University School of Medicine in Cleveland, Ohio said that further work could well uncover other circadian-related causes.

The discovery opens up intriguing paths of research, in pinpointing individuals at risk of nocturnal death and devising drugs to shield them, Jain added.

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No Cancer Benefit From Vitamin B, Omega-3 Supplements in Heart Patients

MONDAY, Feb. 13 (HealthDay News) -- Patients with a history of heart disease will most likely not reduce their risk for developing cancer by taking vitamin B and/or omega-3 fatty acid supplements, a new French analysis suggests.

"In the population we studied, we found no beneficial effects of either B vitamins or omega-3 fatty acids taken over five years on cancer occurrence or cancer-related death," noted study author Valentina Andreeva, who is with the nutritional epidemiology research unit at the University of Paris XIII in Bobigny, France.

Andreeva and her colleagues report their findings in the Feb. 13 online edition of the Archives of Internal Medicine.

To explore the protective potential of B vitamins and fatty acid supplements, the authors did a secondary analysis of data that had been collected in a previous study involving almost 2,000 French men and 500 women.

All were between 45 and 80 years of age, and all had experienced cardiac trouble (heart attack, unstable angina or ischemic stroke) in the year leading up to the start of the study.

In turn, the participants were divided into one of four different groups that consumed a daily supplement regimen involving various types of vitamin B and omega-3 fatty acids at "relatively low supplementation doses."

By the end of the original five-year study, 7 percent of the participants had gone on to develop some form of cancer, and just over 2 percent ultimately died of cancer. The vast majority of cancer cases (including prostate, lung, bladder and colorectal cancer) and deaths occurred among men (81 percent and 83 percent, respectively).

The team unearthed no evidence that any form of vitamin B or omega-3 fatty acid supplement improved cancer outcomes in any way.

The investigators noted that there were some indications that cancer risk might have actually gone up, specifically among women taking vitamin B and/or omega-3 fatty acid supplementation. However, the authors stressed that this observation was based on too few cases to substantiate a firm conclusion, and called for further research involving a larger pool of participants.

"The results of our study suggest that individuals should exercise caution when deciding to take dietary supplements, especially over a long period of time and without a physician's advice," advised Andreeva. "Such supplements constitute active substances and might have adverse effects in some populations. To be on the safe side, individuals should strive to achieve dietary recommendations via healthy, balanced diets."

Joseph Su, the Washington, D.C.-based program director of the division of cancer control and population science within the U.S. National Cancer Institute's epidemiology and genomics research program, said that nothing about the findings struck him as surprising.

"So far, study findings have been very inconsistent," he noted. "But most supplement studies, if anything, have shown no beneficial effect whatsoever. Just like this one. So, I don't think there's anything that can really back up the idea that these supplements can prevent cancer."

However, Vicky Stevens, strategic director of laboratory services at the American Cancer Society in Atlanta, expressed some reservations about the French analysis.

"Compared with other trials, they used much lower levels of supplements," she noted. "From the B-vitamin point of view, dramatically lower. So, it could be argued that they just weren't using high enough levels of supplements to see any effects," Stevens suggested.

"And they used a natural form of folate [vitamin B supplement], whereas other trials use a synthetic form," Stevens added. "But the real problem in being able to evaluate the effects they do see is that they don't have enough people. And it's not really a long enough follow-up period to really see an effect of these supplements on cancer onset. Five years isn't really enough. It can take 10 or 20 years in most cases. So, what they may be seeing is an effect on preexisting abnormalities, but not the impact on cancer onset itself."

Duffy MacKay, a naturopathic doctor and vice president of scientific and regulatory affairs for the Council for Responsible Nutrition in Washington, D.C., agreed.

"When you look at an intervention like this, you're definitely not looking at the role of the supplements at preventing tumors, because the tumors likely started well before the trial," he noted. "So really what the trial is about is giving vitamin B and omega 3 and seeing if they altered the outcome, the progression, of these cancers," MacKay explained.

"And with that you have to realize that cancer is a very complex multi-factorial disease," MacKay stressed. "And two supplements would never be expected to be a successful treatment on their own. I would say, however, that proper nutrition is one of your best allies in terms of wellness, period. And while no one ever claimed these were cancer drugs, if you will, supplements make sense, cancer or no cancer."

More information

For more on vitamins and cancer, visit the American Cancer Society.

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Gauging hype during Heart Month: 5 tests you might not need

NEW YORK (Reuters Health) - February is American Heart Month and consumers will be bombarded with advice to keep their ticker healthy -- whether it's from the American Heart Association's Go Red For Women or the National Heart, Lung, and Blood Institute's The Heart Truth.

Doctors may suggest a screening test to make sure cardiovascular health is in top shape. But if a person lacks symptoms -- like chest pain or shortness of breath -- they might want to hit pause for a second and look closer at the costs and benefits.

The fact is, there is no good evidence that any of the common tests are that helpful if a person is symptom-free.

"If you do a test like a stress test in someone who doesn't have any symptoms, then you are more likely to get a false-positive test than a true positive," said Dr. Malissa Wood, a spokesperson for the American Heart Association.

Such false alarms trigger more unnecessary tests, which often carry significant risks.

"We really want to go based on symptoms," Wood said.

The government-backed U.S. Preventive Services Task Force also advises against routine screening for heart disease for people at low risk.

Even for those at higher risk -- like smokers, diabetics and the obese -- there is insufficient evidence to support routine screening, according to the USPSTF, which bases all of its advice on rigorous science.

Still, groups with ties to drug and heart device makers often recommend the tests routinely, and several companies promote them, to the chagrin of experts in the field.

"There are no 'heart tests' that any asymptomatic man or woman should get," said Dr. Patrick O'Malley, an internist at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. "There are many that are done which they shouldn't get."

Here's a brief guide to the common heart tests:

TEST 1: ECG (EKG)

What is it? An electrocardiogram, or ECG, is simply a readout of your heart's electrical activity recorded by electrodes placed on the chest. It can pick up abnormalities that might, or might not, signal heart disease in the making.

Does it work? ECGs are used to study irregular heart rhythms, heart attacks and other problems. They're also used before some types of surgery, but no trials have looked at whether ECGs help stave off disease in people without symptoms.

What's the harm? An ECG typically costs about $50. Because it's not invasive, the test itself is safe. What someone should worry about is what happens if the results look abnormal. A patient might end up with another test that carries more risks, like a CT scan or a coronary angiogram, during which a catheter is threaded into the heart.

TEST 2: CAROTID ULTRASOUND

What is it? A carotid ultrasound allows doctors to see if the arteries in the neck that supply blood to the brain, called the carotids, are clogged by cholesterol buildups, or plaque. That is considered a risk factor for stroke.

Does it work? This test is used to check the blood flow to the brain. There is no evidence that carotid plaque screening, which is becoming increasingly popular, saves lives. The USPSTF says the harm of routine scans outweighs the benefits.

What's the harm? An ultrasound of the carotids costs between $200 and $300. Routine scans produce more false alarms than "true positives," and may lead to invasive imaging or carotid surgery or stenting. Between one and three percent of patients who get carotid surgery die due to the procedure, and even more suffer strokes from it.

TEST 3: ECHOCARDIOGRAM

What is it? An echocardiogram is a moving ultrasound picture of the heart. It allows the doctor to test how well the heart pumps out blood and whether it has structural problems.

Does it work? While the test might help doctors diagnose conditions like heart failure and atrial fibrillation, it hasn't been proven to help people without symptoms. One recent study found screening for heart disease with echocardiography and other tests didn't change what drugs doctors prescribed, nor people's diet and exercise habits or whether they smoked.

What's the harm? An echocardiogram costs between $200 and $300. Ultrasound scans are generally safe, but can trigger false alarms and may lead to more-invasive tests and treatments later.

TEST 4: STRESS TEST

What is it? To spot signs of pumping problems, a doctor will stress the heart by putting a person on a treadmill or stationary bike while doing an echocardiogram or an ECG. In a nuclear stress test, radioactive dye is injected into the bloodstream to create a better picture.

Does it work? Stress tests can help diagnose heart problems but haven't been shown to be helpful screening tools. Some studies have shown they may miss signs of heart disease.

What's the harm? A stress test may cost anywhere from a few hundred dollars to $1,000. It carries the usual risks of exercise, but largely for people with heart problems -- including very rare cases of heart attack. Some tests will result in false alarms, meaning further procedures with possible complications will be done unnecessarily.

TEST 5: CARDIAC CT SCAN

What is it? CT (computed tomography) scans use high-dose x-rays to get a detailed picture of the heart. In a coronary calcium scan, the doctor looks for calcium deposits in the heart's arteries, which have been tied to an increased risk of heart disease. Patients may also have a dye injected to make it easier to spot blockages.

Does it work? CT scans may help separate women at moderate risk of heart disease into those who would benefit from aggressive treatment and those who wouldn't. But for people without symptoms, CT scans still haven't proved more valuable than medical advice based on well-known risk factors like diabetes and obesity.

What's the harm? The radiation from CT scans, which may cost several hundred dollars, may increase one's cancer risk slightly. When dye is used, about one in 10 people develop kidney damage and some may get thyroid problems, too. False alarms may lead to invasive tests, which carry more risks.

HEALTHY LIVING, NOT TESTS

Experts say the best way to prevent heart disease has little to do with technology and everything to do with lifestyle.

"Tests do not prevent heart disease," said Dr. Rita Redberg, a cardiologist at the University of California, San Francisco. "To prevent heart disease, women (and men) should eat healthy diets with lots of fruits and vegetables, get regular physical activity and not smoke."

The American Heart Association also recommends keeping your blood pressure and cholesterol levels under control, although the USPSTF says there is too little evidence to recommend cholesterol tests when women don't have other heart risks.

(Editing By Peter Bohan)

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