What is Atherosclerosis?
Atherosclerosis is a long-term inflammatory condition affecting the arteries, and it is responsible for roughly half of all deaths in societies with Western lifestyles. This condition mainly stems from the buildup of low-density lipoprotein, a type of fat, and leftover particles from the fat breakdown process within certain areas of the arteries. These areas usually experience irregular blood flow and are generally located at forked sections within the arteries. Atherosclerosis is a leading cause of atherosclerotic cardiovascular disease (ASCVD), which can lead to heart attacks, strokes, and peripheral arterial disease. This document outlines the biology of atherosclerosis, its consequences, and potential treatments.
What Causes Atherosclerosis?
ASCVD, or atherosclerotic cardiovascular disease, can be caused by many different factors. Some common risk factors include high levels of LDL-cholesterol (the ‘bad’ cholesterol), high blood pressure, diabetes, smoking, age (being a man over 45, a woman over 55), being male, and having a strong family history of the disease. This refers to having a male relative who had the disease before turning 55, or a female relative who had it before turning 65.
Other lifestyle factors, such as not getting enough exercise, being overweight, and eating a diet that’s high in unhealthy saturated and trans-fats, can also contribute. Another factor could be certain genetic mutations that increase your risk.
While having low levels of HDL-cholesterol (the ‘good’ cholesterol) is considered a risk factor, treatments aimed at increasing the levels of this type of cholesterol haven’t been very successful. This has led to some concerns and questions about the role of HDL-cholesterol in terms of ASCVD.
Risk Factors and Frequency for Atherosclerosis
Atherosclerosis often shows no symptoms, making it tough to accurately count how many people have it. This condition is the primary reason for heart and brain diseases. These diseases can lead to ischemic heart disease (IHD) and strokes, which rank as the first and fifth leading causes of death worldwide, respectively.
In the US annually:
- About 610,000 people die from heart diseases, making it the cause of 1 in every 4 deaths.
- Coronary heart disease, a type of disease related to atherosclerosis, claims over 370,000 lives.
- Around 735,000 Americans have a heart attack. Out of these, 525,000 experience their first attack, and 210,000 suffer a recurrent one.
- About 75% of heart attacks are caused by a rupture in the plaque, which is more common in men over 45 and women over 50. The rate of atherosclerosis in women rises after menopause due to the loss of protection from female hormones.
Stroke is the fifth leading cause of death in the US and is the primary reason for severe, long-term disability in adults. Each year, nearly 795,000 people in the US have a stroke, leading to approximately 140,323 deaths. The most common type of stroke, an ischemic stroke, is caused by atherosclerosis-related cardiovascular diseases.
Studies in North America and Europe found multiple risk factors that could lead to or worsen atherosclerosis, like their effects on harmful cholesterol particles and inflammation.
Signs and Symptoms of Atherosclerosis
Your doctor will perform several tests during your examination. These tests include:
- Checking your blood pressure
- Examining your peripheral pulses (pulses that can be felt at the extremities of the body)
- Listening for abnormal sounds, called bruits, in your carotid arteries (located in your neck) and abdomen
- Checking for pulsatile abdominal masses (swelling in the abdomen that pulsates)
- Screening for signs of heart failure
- Inspecting for supra-valvar aortic stenosis (a narrowing of the aorta just above the valve)
- Looking for xanthomas (yellowish, fatty deposits under the skin)
Testing for Atherosclerosis
To evaluate an individual’s risk factors for ASCVD, or atherosclerotic cardiovascular disease, doctors may perform several tests. These can include checking their lipid profile (the levels of LDL-cholesterol in their blood), plasma glucose, and in some cases, high-sensitivity C-reactive protein (hsCRP), which helps detect inflammation in the body. An abdominal ultrasound may also be conducted, particularly in older individuals, to screen for an abdominal aneurysm, which can be a sign of ASCVD.
A simple, but effective, screening test for a condition called peripheral artery disease (PAD) involves using a Doppler device to measure the ankle-brachial index, which is the ratio of the blood pressure in the lower legs to the blood pressure in the arms. The normal range is 1.0 to 1.40. It’s important to note that PAD can signal the presence of ASCVD in other parts of the body, like the heart or brain.
Sonography of the carotid arteries in the neck may be carried out if a patient has a noticeable carotid bruit – an abnormal sound heard through a stethoscope that suggest narrowed blood vessels. Additionally, an ECG, or electrocardiogram, might be performed in specific instances, like a stress ECG, and used to assess the heart’s health. Then, to accurately confirm ASCVD, a calcium score can be calculated using a specific type of CT, or computed tomography, scan known as an electron beam computed tomography (EBCT). This score indicates the amount of calcified plaque in the arteries and is interpreted accordingly to a patient’s age.
Angiography, an X-ray test that uses a special dye and camera to take pictures of blood flow in blood vessels, is seen as the primary method for visualising atherosclerotic lesions in the coronary arteries. However, it should be noted that this is generally reserved for high-risk patients due to its invasive nature and is not routinely used for screening purposes.
In terms of non-invasive options for assessing ASCVD, CT angiography is showing promise. It can detect the presence of low-density plaques, and help predict future acute coronary events. Furthermore, cutting-edge imaging techniques, like cardiovascular magnetic resonance imaging (cardiac MRI), might prove useful in certain patients. However, due to growing healthcare costs, it’s important to weigh the cost of these procedures against their necessity.
Treatment Options for Atherosclerosis
The most effective way to manage ASCVD, or Arteriosclerotic Cardiovascular Disease, is to control the risk factors such as high cholesterol, high blood pressure, diabetes, and others. It’s also important that patients are encouraged to stay active, ideally exercising for 90 to 150 minutes a week. A heart-healthy diet is also key, which means foods low in saturated and trans fats, like red and processed meat, baked goods, and organ meats. Instead, a diet should be rich in fiber, monounsaturated fats, fruits, vegetables, and fatty fish. The recommended salt intake is less than 5 grams a day. Smokers should be motivated to quit and be referred to a program to help stop smoking.
Statins, also known as 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are commonly used to reduce high cholesterol levels, which in turn can lower the chances of cardiovascular issues and death. When it comes to controlling blood pressure, it’s often necessary to use two or more types of drugs like ACE inhibitors, ARBs, diuretics, beta blockers, and calcium channel blockers. It’s important for patients to understand that good blood pressure control can prevent strokes, and the target should be a blood pressure less than 130/85.
As well as a balanced diet and exercise, there are a number of treatments available to manage diabetes. The aim is to keep the HbA1c level below 7%, blood pressure below 130/85, and LDL-cholesterol below 100 mg/dl.
In cases of clinical ASCVD, procedures to improve blood flow, such as angioplasty or a bypass, are often necessary. Thrombolysis, which is the breakdown of blood clots, is another treatment option for conditions such as clots in the brain (Stroke), or acute limb ischemia, which is a sudden lack of blood flow to a limb due to a clot or debris.
What else can Atherosclerosis be?
The process of determining if someone has ASCVD, a type of heart and blood vessel disease, involves ruling out many other potential issues. ASCVD can lead to symptoms such as chest pain, dizziness, leg pain while walking (claudication), and weakness. For doctors to make an accurate diagnosis, they will need a detailed history of your symptoms and they will conduct a thorough physical examination. They may also need to carry out some specific tests, as mentioned earlier, to rule out other similar conditions.
What to expect with Atherosclerosis
Thanks to advances in managing risk factors like high LDL-cholesterol with statin therapy, blood pressure, diabetes, and lifestyle changes like quitting smoking, exercising regularly, and following a healthy diet, people with ASCVD generally have a good prognosis. However, the outcome can worsen if the disease progresses to severe conditions like heart failure, ischemic stroke leading to paralysis and cognitive impairments, or gangrene causing a need for amputation, and the bursting of an abdominal aneurysm.
Possible Complications When Diagnosed with Atherosclerosis
Atherosclerotic Cardiovascular Disease, also known as ASCVD, can show up in several ways. It can occur as:
- Coronary artery disease (CAD), which affects the blood vessels of the heart
- Cerebrovascular disease (CVA), which is related to the blood flow in the brain
- Transient ischemic attack (TIA), also known as a ‘mini-stroke’
- Peripheral artery disease (PAD), which affects blood vessels outside the heart and brain
- Abdominal aneurysms, which is an enlargement of the aorta, the main blood vessel in the body
- Renal artery stenosis, a narrowing of the arteries that carry blood to the kidneys, in men
This article includes information on how to manage risk factors and what tests are needed to check for complications related to ASCVD. More detailed information is available in other chapters in this series.
