Atherosclerosis

Overview

By Tina Shahian, PhD

Atherosclerosis is a hardening of the arteries that results from a buildup of plaque. Plaque is made up of cholesterol, fat, calcium, clotting agents, cell debris, and other substances normally found in circulating blood. These substances accumulate at specific sites along the arteries and, over time, restrict or fully block blood flow to downstream organs, such as the heart, brain, and limbs. This process becomes accelerated when part of the plaque unexpectedly breaks off, or forms a blood clot. 

Illustration of an artery cross section showing plaqueDepending on the location of the plaque and the extent of blockage, other complications may result. Plaque buildup in the coronary arteries, which deliver blood to the heart, can lead to coronary heart disease – the primary cause of deaths in the Untied States. Reduced or halted blood flow to the heart may cause a heart attack. Plaque in the carotid arteries (carotid artery disease), which deliver blood to the brain, can cause a stroke. A blockage in the major arteries (peripheral artery disease) causes pain and numbness in the limbs and pelvis, while blockage in the renal arteries (chronic kidney disease) affects kidney function. An aneurysm is a bulge in the artery wall that can be lethal if it bursts.  

Atherosclerosis can be managed (and prevented) with lifestyle changes and medical intervention. Every year approximately 380,000 Americans die from coronary heart disease.

 

Causes and Risk Factors

Atherosclerosis can begin during childhood and progress slowly into adulthood. It is not clear what triggers the plaque-forming substances to deposit on the arteries, but damaged or scarred sites are thought to play a role. The following can damage the artery walls or promote plaque formation:

  • High cholesterol. High levels of low-density lipoprotein (LDL) cholesterol increase the chance of plaque formation. Unlike high-density lipoprotein (HDL) cholesterol, LDL cholesterol transports fat into the arteries, and attracts macrophages that further grow the plaque.
  • High fat. Elevated levels of triglycerides (a type of fat) in the blood increase the risk of atherosclerosis.
  • High blood pressure. Chronic high blood pressure can damage the coronary arteries and lead to atherosclerosis.
  • Smoking. Smoking promotes plaque formation by damaging the arteries.
  • Inflammation. Inflammation due to injury or another underlying condition enhances the chance of developing atherosclerosis.
  • Family history. The risk of atherosclerosis in higher for individuals with a family history of heart disease.

Symptoms

Atherosclerosis may not produce symptoms until it is at an advanced stage, at which time medical attention is needed. Symptoms vary depending on the affected artery.

  • Coronary arteries. Atherosclerosis in arteries that carry blood to the heart may cause chest pain and pressure – also symptoms of a heart attack.
  • Carotid arteries. Atherosclerosis in arteries that carry blood to the brain can lead to numbness in the limbs, droopy facial muscles, dizziness, and difficulty speaking.
  • Peripheral arteries. Atherosclerosis in arteries that carry blood to the arms, legs, and pelvis can cause pain while walking, numbness and, in men, erectile dysfunction.
  • Renal arteries. Atherosclerosis in arteries that carry blood to the kidneys can cause kidney failure.

Diagnosis

common, external and internal carotid arteriesThe first step in diagnosing atherosclerosis is a physical exam. During the exam, a doctor listens for abnormal sounds in the arteries and looks for a decreased pulse in the limbs, both of which are evidence of restricted blood flow. Additional tests are performed to assess heart function and gain a closer view of the arteries.

  • Blood tests. Elevated levels of cholesterol, fat, sugar, and certain proteins are detectable in the blood and can be associated with atherosclerosis.
  • Electrocardiogram. An electrocardiogram (EKG) measures electrical signals that pass through the heart, and can identify an irregular heartbeat or a past heart attack.
  • Imaging. A chest X-ray, computed tomography (CT) scan, and magnetic resonance angiography (MRA) allow closer visualization of the heart and arteries for evidence of plaques.
  • Blood pressure tests. The ankle/brachial index test looks for blockage of the arteries in the limbs by comparing the blood pressure between the ankle and the arms; normally, blood pressure in the ankle measures the same or higher than in the arm. A Doppler ultrasound can also measure blood pressure at various points in the body.
  • Stress test. This test monitors the heart’s performance while under stress, which is in the form of exercise (treadmill or stationary bicycle), or induced with medication. Abnormalities in the heart rate, rhythm, and overall function are easier to detect when the heart is pumping blood at a fast rate.
  • Angiography. During an angiography, a dye is injected into the arteries through a thin catheter. X-ray imaging allows for visualization of the flow path of the dye, which mimics that of the blood, as well as any blockages along the way.

 

Treatment

A combination of lifestyle changes, medication, and surgery may be used to treat atherosclerosis or slow its progression.

  • Lifestyle changes. Regular exercise; maintaining a healthy weight; and a diet high in fruits and vegetables, but low in cholesterol, fat, and salt help slow atherosclerosis. Avoiding smoking helps prevent plaque-promoting damage to the arteries.
  • Medication. Prescription medications can help slow or stop disease progression. Drugs known as statins and fibrates are used to lower plaque-promoting LDL cholesterol, while boosting HDL cholesterol levels. Anti-platelet drugs reduce platelet aggregation and clotting in the arteries, which slows the growth of plaques and minimizes the risk of a complete blockage. Beta blockers, angiotensin-converting enzyme (ACE) inhibitors, calcium channel blockers, and water pills (diuretics) all help lower blood pressure, reducing burden on the heart.
  • Surgery. When lifestyle remedies and medication fail to curb disease progression, surgery is used to physically eliminate plaque from the affected artery. During an angioplasty, a deflated balloon is delivered to the site of blockage where it is inflated to push back the plaque. Then, a mesh tube (stent) may be installed to act as a physical barrier against future plaque buildup. A carotid endarterectomy is performed to dissolve plaque from the arteries in the neck. Thrombolytic therapy helps prevent a heart attack or stroke by dissolving blood clots and restoring blood flow to the heart and brain, respectively. Coronary artery bypass grafting improves blood flow to the heart by using veins from other parts of the body to redirect blood past the blocked site.

Prevention

The best way to prevent atherosclerosis is by staying physically active, maintaining a healthy weight, and making smart food choices – that is, eating plenty of fruits and vegetables and avoiding foods high in cholesterol, fat and salt. It is also important to avoid smoking and stress-inducing activities. Individuals with a high risk of developing heart disease may consult their physician to determine the ideal preventative plan.

Sources

  • “Atherosclerosis”. American Heart Association. Apr 2014. Retrieved Jun 6, 2014. http://www.heart.org/HEARTORG/Conditions/Cholesterol/WhyCholesterolMatters/Atherosclerosis_UCM_305564_Article.jsp.
  • "Atherosclerosis ". Mayo Clinic. Mayo Foundation for Medical Education and Research. May 2014. Retrieved Jun 6, 2014. http://www.mayoclinic.org/diseases-conditions/arteriosclerosis-atherosclerosis/basics/definition/con-20026972.
  • “What is Atherosclerosis”. National Heart, Lung, and Blood Institute. NIH. Jul 2011. Retrieved Jun 6, 2014. https://www.nhlbi.nih.gov/health/health-topics/topics/atherosclerosis/.
  • “Thrombolytic therapy”. Medline Plus. Jun 2012. Retrieved Jun 6, 2014. http://www.nlm.nih.gov/medlineplus/ency/article/007089.htm
  • “What Are Arthritis and Rheumatic Diseases?” National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). NIH. Jul 2009. Retrieved Jun 2, 2014. http://www.niams.nih.gov/Health_Info/Arthritis/arthritis_rheumatic_ff.asp#a.