By Dr. Ian Riddock, MD, SMGOR Eastside Clinic
Stroke is a devastating event, that is caused by when blood flow to an area of the brain is disrupted. Strokes represent the third leading cause of death in developed countries, and the leading cause of permanent disability. More than three quarters of strokes are first-time events occurring without warning. Ischemic stroke, a type of stroke caused by a loss of blood flow, accounts for 80%. The rest are hemorrhagic, or due to bleeding inside the brain. An ischemic stroke can be thought of as a “brain attack”, like a heart attack, from sudden blockage of blood flow from either a clot forming on top of a ruptured cholesterol plaque (like a pimple on the inside of an artery) or from a clot traveling from elsewhere (typically the heart) and getting lodged in a brain artery. If the event causes permanent brain tissue damage, it is called a cerebral infarction, like a myocardial infarction (heart attack). The disability a patient suffers is related to the area of the brain impacted. If it resolves before it causes permanent damage it is called a” transient ischemic attack” or TIA. Some call it a “mini-stroke”. Though a TIA does not cause permanent disability, it should not be taken lightly, as it is a clue to underlying treatable disease such as carotid artery disease, atrial fibrillation or a shunt (hole) in the heart which may allow clots from other parts of the body to travel into arteries of the brain.
Risk factors for stroke are similar to heart disease. High blood pressure is the most common risk. Others include cigarette smoking, diabetes, high cholesterol, abdominal obesity, unhealthy diet, inactivity, alcohol, stress and other factors leading to the development of a heart arrhythmia called atrial fibrillation. Atrial fibrillation, or AFib, accounts for 15% of all strokes. It is a rapid and irregular heartbeat where the top chambers, called atria, quiver instead contracting normally with the rest of the heart. This causes blood to coagulate and form clots. These clots tend to collect in the left atrial appendage, an elongated windsock-like structure. Eventually these clots make their way from the left atrium into the left ventricle (pumping chamber of the heart) where they can be ejected into the brain. The likelihood of this event occurring in someone with atrial fibrillation is anywhere from 1-10% each year depending on age, gender and other cardiovascular risk factors the patient may have.
When someone survives a stroke or TIA they undergo a battery of tests to confirm the type of stroke and to look for a cause. These may include CT or MRI scans of the brain, ultrasounds of the carotids and heart, as well as labs looking at cholesterol and clotting factors. In some cases, the heart rhythm is monitored for at least 24 hours to look for AFib. Unfortunately, AFib may only announce its presence sporadically. The duration of monitoring necessary for detecting atrial fibrillation is unknown, but longer monitoring over a period of 2-4 weeks with skin patches over the heart, or even months to years with a small implantable device placed under the skin can significantly increase detection of AFib.
Detecting AFib is important because the treatment is different than if stroke is caused by a ruptured cholesterol plaque in a carotid artery, for instance. In the latter case, cholesterol medications as well as antiplatelet agents such as aspirin or clopidogrel are used. In the case of AFib, anticoagulants (blood thinners) such as warfarin, dabigatran, rivaroxaban, apixaban or edoxaban are used. Aspirin is just not very effective at preventing clot formation in AFib, but there is a higher risk of bleeding with anticoagulants.
In cases where the search leads to the discovery of cholesterol plaque buildup in the carotid arteries, routine and advanced lipid testing may uncover genetic causes of accelerated unstable plaque development. Proper identification and treatment of these disorders may prevent relatives from having a stroke and/or prevent another devastating stroke in that individual.
In all cases a healthy lifestyle that includes physical activity, wholesome diet, avoidance of tobacco/nicotine, and no more than moderate alcohol use can prevent both initial strokes and recurrence after the initial event
While TIA and stroke are frightening and disabling events, they do not have to occur again. Knowledge of the underlying cause coupled with appropriate therapy can eliminate this disease.
Ian Riddock, MD
Dr. Riddock is board certified in internal medicine, cardiovascular diseases, clinical lipidology and cardiovascular computed tomography. He is also a certified specialist in clinical hypertension through the American Society of Hypertension. Dr. Riddock has special interest in preventive cardiology, clinical lipidology, personalized risk assessment, heart failure, chronic angina and clinical research.