Clinical Manifestations & Complications of Atherosclerosis

In the beginning stages of atherosclerosis, it is often asymptomatic  i.e. there are no overt signs nor symptoms, often for decades. Symptoms and signs develop when the atherosclerotic plaques begin to restrict blood flow.  The manifestations often are associated with organs that are affected by the reduced blood flow as well as possible signs of lipid accumulation in the blood and other organs.

Screening for atherosclerosis development

As it takes years for atherosclerotic plaques to develop, subtle changes in physical exams and composition of blood can suggest the risk of atherosclerotic plaque formation.  The following physical & blood tests are commonly performed to assess for each stage of plaque formation:

Medical history:  looking for possible damage to endothelium (e.g. familial history, exposure to smoke, alcohol, stress, etc)

Blood pressure:  looking for damage to vessels due to high blood pressure

Blood test:  Lipid panel (e.g. Total cholesterol, High vs low density lipoprotein): looking for the amount of cholesterol and fats in circulation as they contribute to foam cell formation and hence, plaque formation

Blood test:  Fasting glucose & HbA1C:  looking for untreated hyperglycemia (diabetes) which can injure the blood vessels. See Diagnosis of Diabetes for more detail.

Complications of Atherosclerosis

Acute ischemic attack of the heart: angina & myocardial infarction

Atherosclerosis of the coronary arteries will slowly reduce prefusion to heart tissue. As the tissue is starved, pain and loss of function (contraction and electrical excitability) will ensue.  This cardiac pain, also known as angina, can occur upon exertion (i.e. stable angina) because the plaque prevents sufficient blood flow to meet the increased demand in exertion.  However, as the plaque grows, blood flow will be insufficient for the demand of everyday life – manifesting in unpredictable pain known as unstable angina.

As mentioned, atherosclerotic plaques are at risk for rupture which would cause serious alterations in blood flow.  A full blockage of blood flow – whether due to the ruptured plaque or the ensuing clot – will result in infarct and tissue hypoxia of all the cardiac tissue downstream of the blockage.  In addition to ‘crushing’ pain of the infarct, there will be decreased blood flow to the entire body – often manifesting in lack of mobility, nausea, and loss of consciousness. There will also be electrical disturbances in the cardiac tissue which can be recorded on EKGs. Myocardial infarction is a life-threatening event without medical intervention.

Acute ischemic attack of the brain:  stroke or transient ischemic attack (TIA)

Similar to myocardial infarct, a complete blockage to any cerebral arteries will manifest in a stroke. Clinical manifestations of a stroke would be acute changes in both neurological and cognitive abilities (see Signs and symptoms of restricted blood flow due to atherosclerosis).  ..See  for more detail Pathophysiology of Neuromuscular Control: CNS Issues in the Motor Cortex (Traumatic Brain Injury & Ischemic Stroke).

Transient Ischemia Attack (TIA) are referred to as “mini strokes” where the blockage of blood flow is unpredictable  with all of the aforementioned changes in neurological and cognitive abilities – but appears to resolve in a short amount of time. This is usually attributable to the brain’s vasculature’s amazing ability of rerouting blood. For more detail see Circulation and the CNS.

Thrombosis of Atherosclerotic Aorta

The formation of a clot is one of the common clinical outcomes of severe atherosclerosis. Thrombosis-induced ischemia can result in heart attack or stroke, depending on location. Clot formation as a result of atherosclerosis in coronary vessels can block the blood flow to the heart, and cause tissue damage as a result of hypoxia. Similar scenarios can occur anywhere along the vascular tree, including the brain (stroke), lower limb (peripheral artery disease), etc.

Aneurysm of Atherosclerotic Aorta

Severe atherosclerosis can progress towards aneurysm, where the muscular layer of the vessel weakens and creates a bulge that can rupture and lead to internal bleeding.

The increased resistance of a growing atherosclerotic plaque causes a backup of blood immediately upstream of the plaque.  If a weakening of the arterial wall begins, a bulging deformity forms, known as an aneurysm.  Aneurysms of the thoracic and abdominal aorta are the most common, but aneurysms can occur in any artery.

Depending on the location, most aneurysms are asymptomatic when small.  When symptoms to occur, they are non-specific (e.g. pain in a general area) unless they happen to compression an adjacent structure (e.g. optic nerve in the cause of a brain aneurysm). As aneurysms grow, then cause visceral pain, often described as steady and deep.  Some mistake abdominal aneurysms for a back ache. 

Aneurysms can become apparent if there is an abnormal prominent pulsation – especially in the case of abdominal aortic aneurysms. Rapidly enlarging aneurysms that are about to rupture can be tender in the area. With auscultation, a bruit (abnormal turbulent blood flow) may be audible over the aneurysm. There will also be signs of decreased blood flow to organs downstream of the dissection (e.g. feet will be pale & cool due to lack of blood). 

Aortic Dissection

As a result of damage to the tunica media during atherosclerotic plaque formation, a weakening and separation between the tunicas develop.  This can lead to aortic dissection which involves a tear in the tunica intima causing a separation of the intima and media layers. This creates a false channel for blood flow which does not reach its end destination (ie organs). Aortic dissection can occur anywhere along the aorta. Symptoms include an abrupt “tearing pain” along the area of the dissection. Because the aorta runs anterior to the spine, this pain can be confused for back pain. As well, there will be decreased blood flow to organs downstream of the dissection.