Can we help?
Follow up on thismonth's He@lthLINK
Phone Numbers
Directory assistance
(203) 688-4242
Patient information
(203) 688-4177
Adult emergency
(203) 688-2222
Children's emergency
(203) 688-3333
Admitting
(203) 688-2221
Children's admitting
(203) 688-3331
Mailing address:
Yale-New Haven Hospital
20 York Street
New Haven, CT
06510-3202
|
May 2007
News this month A new study reveals that even a slight impairment of heart function may increase a person’s risk of stroke. While other studies have shown that heart failure boosts stroke risk, this study suggests that any level of heart muscle impairment, even asymptomatic muscle dysfunction, may lead to ischemic stroke. An ischemic stroke is a brain attack in which a blood clot blocks a blood vessel in the brain. It is a major cause of impairment and death in the United States, with an yearly incidence of 700,000. The study, led by Marco R. Di Tullio, MD, a professor of clinical medicine at Columbia University, was the first to compare the level of left ventricular dysfunction (LVD) in people who had survived strokes to that of the general population. LVD refers to a deficiency in the heart’s ability to pump oxygenated blood to the rest of the body. “The link between LVD
and stroke risk was not
significantly different for
women than it was for men.”.
The study group comprised 588 participants in the Northern Manhattan Study (NOMAS), a large epidemiological study begun in 1990 at the Neurological Institute of New York to investigate stroke risk factors in various ethnic groups. About half of the subjects in Dr. Di Tullio’s study had experienced first-time ischemic strokes and half had not. The stroke patients were identified through daily screening of admissions, discharges and head CT scan logs at NewYork-Presbyterian Hospital/Columbia University Medical Center, where 80 percent of all patients with stroke in northern Manhattan are hospitalized. The control group, found through random-digit telephone dialing, matched the stroke patients in terms of age, gender and ethnicity. Each subject in the study had undergone an echocardiogram, which is a heart ultrasound that uses ultrasonic waves to test heart function. The study revealed a 24.1 percent incidence of left ventricular dysfunction in stroke patients compared to 4.9 percent in the control group. Echocardiograms showed moderate to severe LVD in 13.3 percent of stroke patients compared to 2.4 percent of people in the control group, and mild LVD in 10.7 percent of stroke patients compared to 2.4 percent of the stroke-free control group. An association between impaired heart function and stroke was present in people of all ages. It was present in people of all races, even though frequency of traditional stroke risk factors, such as hypertension, varies between racial groups. The link between LVD and stroke risk was not significantly different for women than it was for men. It remained significant even when other risk factors, such as diabetes and smoking, were taken into consideration. The study’s authors observed that their findings seem to contradict the common notion that the greater the severity of LVD, the higher the risk for stroke. Instead, they concluded that doctors should assume that patients with even mildly reduced left ventricular ejection fractions have a significantly increased risk of stroke. The ejection fraction (EF) is a measure of how efficiently the heart is pumping. It describes the percentage of the blood in the left ventricle that is pushed out into the arteries with each beat of the heart. For this study, the investigators considered an EF of greater than 50 percent to be normal, an EF of 41 to 50 percent to be mildly dysfunctional, an EF of 31 to 40 percent to be moderately impaired, and an EF of 30 percent or less to be severely decreased. The study was funded by the National Institute of Neurological Disorders and Stroke, and it was published June 2, 2006, in Stroke: the Journal of the American Heart Association. The researchers plan to study stroke-free people over time to identify more specific patterns in left ventricular dysfunction and stroke risk.
The Yale New Haven Stroke Center is
working to promote a national education
campaign based on the acronym F.A.S.T.
If you experience or notice someone
with Facial numbness or weakness, Arm
or leg numbness or weakness, or Speech
difficulty, then it’s Time to dial 911.
Yale-New Haven Hospital is home to a certified Primary Stroke Center
|
|
 We still don’t know if LVD causes stroke We’ve known for a long time that there’s a link between left ventricular dysfunction and stroke. This study puts a finer point on it: even mild LVD – not just moderate to severe LVD – is linked to ischemic stroke across a multiethnic population. But the study does not suggest a causative link, and it doesn’t add dramatically to the body of literature we already have. “Future studies are needed
to evaluate treatment
strategies for patients with
all degrees of LVD with
regard to stroke prevention.”
Most importantly, it does not suggest any improvements on our approach to stroke prevention. No study to date has definitively shown that using blood thinners, other than aspirin, decreases the incidence of stroke in patients with left ventricular dysfunction. The risk factors for LVD are very similar to the risk factors for stroke. They include bad cholesterol levels, high blood pressure, hypertension, diabetes and atrial fibrillation. We aggressively treat those risk factors already with statins, blood pressure drugs, diet modification, and antithrombotics, such as aspirin and Coumadin®. But does LVD cause stroke? The study does not answer that question. Left ventricular dysfunction refers to a decrease in the heart’s ability to pump oxygen-rich blood to the rest of the body. The efficiency of the pumping action is described by an ejection fraction (EF): the percentage of the blood in the left ventricle that is pushed into the arteries with each heart beat. The authors of the study considered an ejection fraction of more than 50 percent to be normal, an EF of 41 to 50 percent to be mildly dysfunctional, an EF of 31 to 40 percent to be moderately impaired, and an EF of 30 percent or less to be severely decreased. What they found was what we’d expect: LVD of any degree was more common in people who have had ischemic strokes than in people who have not. The novel finding of this study is that mild LVD appeared to raise the risk of stroke as much as moderate to severe LVD. Dr. Di Tullio’s study, which is a case-control study, is liable to bias. Cases and controls are often not well matched, particularly in a small trial such as this. This can make results of case-control studies difficult to generalize. In addition, the strokes were not stratified according to stroke sub-type, such as embolic, small vessel disease, cryptogenic, etc. It would be interesting to know if LVD was equally present in all stroke subtypes or in selected ones, particularly as one would generally expect LVD to lead to an increase in embolic strokes rather than the other subtypes. Should this study change the management of stroke patients or of patients with left ventricular dysfunction? Trials evaluating the effect of anticoagulation with Coumadin® in patients with LV dysfunction are ongoing and will, we hope, answer the current questions regarding optimal medical therapy to prevent stroke in patients with LVD. This trial suggests that patients with mild LVD should also be included. In the meantime, aggressive management of established stroke risk factors remains the optimal therapy. This includes controlling patients’ blood pressure and lipids, treating atrial fibrillation appropriately, using anticoagulation when necessary, and advising patients to quit smoking, exercise regularly and adopt a low-fat, low-cholesterol diet. It also means teaching patients to seek prompt medical attention if they experience difficulty breathing, focal numbness or weakness, or heart palpitations. The study is interesting, but it doesn’t dramatically change what we already know or suggest a new approach to patient care. It does, however, suggest that future
studies are needed to evaluate treatment
strategies for patients with all degrees of
LVD with regard to stroke prevention.
Dr. Stephen Possick is affiliated with Cardiology Associates of New Haven.
|
