Obesity Paradox - Lower Rates of Sudden Cardiac Death

I find that studies that conflict with "long standing common medical
sense" have the potential to provide new directions for insight and new
knowledge. This may be one. "Everybody knows that obesity is bad for
the heart". May not be fully true.


http://www.urmc.rochester.edu/news/s...ex.cfm?id=2791

As Girth Grows, Risk of Sudden Cardiac Death Shrinks

Study Reaffirms “Obesity Paradox�: Obese patients at lower risk of
sudden cardiac death compared to non-obese patients

March 16, 2010

Obesity has long been identified as a risk factor for cardiovascular
disease and heart failure. But, a new study conducted by researchers at
the University of Rochester Medical Center found that being skinny
confers no advantage when it comes to the risk of dying suddenly from
cardiac causes.

Scientists found that non-obese heart failure patients – including
overweight, normal and underweight patients – had a 76 percent increase
in risk of sudden cardiac death compared to obese heart failure
patients. Normal and underweight patients showed a startling 99 percent
increase in risk for sudden cardiac death compared to obese patients.

The results were presented today at the American College of Cardiology
Annual Scientific Session in Atlanta. The study, by researchers from one
of the world’s leading groups on sudden cardiac death, is the first to
assess the relation between BMI and the risk of sudden cardiac death.

“This study is important because it not only answers questions regarding
the risk of sudden cardiac death in different types of heart failure
patients, but poses several new questions that need to be explored,�
said corresponding study author Ilan Goldenberg, M.D., research
associate professor of Medicine in the Cardiology Division. “Why do
obese heart failure patients see a risk advantage? Why do normal weight
patients have a significantly different risk profile than those who are
slightly overweight? These are important questions that may have
treatment implications in the future.�

The researchers at the University’s Heart Research Follow-Up Program
examined the risk of sudden cardiac death in 1,231 patients who had
suffered at least one prior heart attack and had been diagnosed with a
low ejection fraction, a measurement of how much blood is pumped from
the heart with each beat. Their analysis found that decreased BMI or
body mass index was associated with a large increase in the risk of
sudden cardiac death. These findings highlight the “obesity paradox,� a
phenomenon long recognized by cardiologists that, once afflicted, obese
heart failure patients fare better than their slimmer counterparts. This
study adds to a growing body of conflicting data regarding the relation
of BMI to outcome in patients with heart failure.

“When we started this study we were hoping the data would disprove the
obesity paradox,� said Bonnie Choy, co-lead author and a second year
medical student at the University’s School of Medicine and Dentistry.
“Our study is the first to create and analyze subcategories within
non-obese patients, looking at overweight, normal and underweight
patients, but even with this advanced analysis we still the saw an
inverse relationship between BMI and sudden cardiac death.�

The science behind the obesity paradox in the heart failure population
is unresolved, but some researchers believe timing may have something to
do with it. One possible explanation is that the long-term negative
effects of conventional risk factors, such as increased BMI, may be
overwhelmed by the short-term effects of other factors on heart failure
mortality. In addition, survival advantages that exist in obese patients
with heart failure may, in the short term, outweigh the harmful effects
of increased BMI.

“Obese patients are hard on their bodies; many don’t eat right, don’t
exercise, and many smoke,� explained Eric Hansen, co-lead author and
also a second year medical student at the University of Rochester. “If
their bodies are surviving this bad treatment then perhaps they are
better equipped, from a genetic standpoint, to live with heart failure.�

Compared to the overweight, normal and underweight patients, obese
patients were younger, had a higher ejection fraction, higher blood
pressure, diabetes and were more likely to be smokers. BMI was
calculated as weight in kilograms divided by the square of height in
meters for all study participants. The clinical definition of obesity –
BMI ≥30 kg/m2 – was used. Overweight patients fell into the 25 to 29
kg/m2 range of BMI values and normal/underweight patients fell into the
25 kg/m2 range of values.

In addition to evaluating the relationship between BMI and sudden
cardiac death, researchers assessed the effect of BMI on the benefit of
implantable cardioverter defibrillator (ICD) therapy. An implantable
cardioverter defibrillator is a medical device about the size of a pager
that is surgically implanted in the chest under local anesthesia. The
device detects irregular and potentially fatal heart rhythms
(arrhythmias), which often lead to sudden cardiac death, and shocks the
heart back into a normal rhythm. Researchers found that implantable
cardioverter defibrillator therapy was more effective in the non-obese
patients with lower BMI values who were at higher risk for sudden
cardiac death. These findings may help identify patients who would get
the most benefit from an ICD – patients with a lower BMI.

Sudden cardiac death claims up to 330,000 American lives every year,
accounting for about half of all cardiac deaths. Sudden cardiac arrest,
a condition in which the heart suddenly and unexpectedly stops beating,
leads to sudden cardiac death if it is not treated within minutes. Most
cases of sudden cardiac arrest are due to abnormal heart rhythms that
can result from blockage of coronary arteries or scarring from a prior
heart attack. Certain drugs can also trigger abnormal rhythms and death.

In addition to Goldenberg, Choy and Hansen worked closely with
Cardiology faculty members Arthur J. Moss, M.D., and Wojciech Zareba,
M.D., Ph.D., to complete this study.