New research now shows that silent heart attacks are a risk factor for stroke in many adults. Heart attacks may not only cause classic symptoms of pressure and chest pain, but can show very few, if any, recognized symptoms, and this may lead to blood clot formation.
A study conducted by Weill Cornell Medicine and New York-Presbyterian investigators and published in JAMA Neurology found that this type of asymptomatic heart attack, known as a silent heart attack, is associated with a doubled increase of stroke.
Dr. Alexander Merkler was the lead study author. When speaking about the study, he said, “Our study suggests that a silent heart attack may be an independent risk factor for stroke and could lead to future studies that determine which blood thinning treatments would work best in this patient population.”
In the past, research has shown that classic symptomatic heart attacks were known to scar heart tissue, causing abnormal ventricle contractions. This could lead to the formation of blood clots that can travel to the brain. The problem that left researchers puzzled until now is whether these clots also form after silent heart attacks. The issue arises because about 50 percent of all patients don’t experience symptoms, so it is difficult to track.
Strokes of Undermined Cause
It is estimated that over 700,000 people a year are diagnosed with a stroke, but in 20 to 25 percent of these patients, doctors are not able to determine the cause. These are called strokes of undetermined cause. While many physicians agree that these strokes are caused when a distant blood clot travels to the brain, the source of the clot is unclear. “With this lack of information, doctors often can’t give these patients the appropriate care to prevent another stroke from happening,” Dr. Merkler said. “For example, strokes caused by a clot that forms in a neck artery may be treated differently from a clot that forms in the heart.”
Dr. Merkler had hypothesized, based on his own clinical experience, that silent heart attacks could be a risk factor for stroke. This is what lead him to start this research. For the study, Dr. Merkler and his colleagues gathered data from a large group of people from Iceland, ages 67 to 93 years old, who underwent either a cardiac MRI or brain MRI between 2004 and 2007.
They found that out of the 925 participants, 221 had cardiac MRI evidence of heart attack. Of these patients, 67 had experienced a heart attack with symptoms while 153 suffered a silent heart attack. There were 308 participants who showed evidence of stoke in the brain MRI and 93 people who had a stroke of undetermined cause.
This evidence led researchers to find that people with symptomatic heart attacks were twice as likely to suffer from a stroke, while those with silent heart attacks were 1.5 times as likely to have a stoke. They also concluded that a silent heart attack is linked with double the risk of stroke of undetermined cause.
“Anticoagulant drugs that slow blood clot formation by blocking clotting proteins could benefit patients with stroke of undetermined cause who also have evidence of silent heart attack on MRI,” Dr. Merkler said. “Scientists may also want to compare the effectiveness of anticoagulants to antiplatelet medications such as aspirin, which prevent platelets from clumping together,” he added.
The hope is that further studies will confirm these results, so that physicians may use cardiac MRI in patients with stroke of undetermined cause to check whether there is evidence of silent heart attack.