ATHEROMA: MORPHOLOGY and EFFECTS Brian Angus Pathology Department University of Newcastle upon Tyne Return to Cardiovascular Pathology Index Page

CONTENTS INTRODUCTION DEFINITIONS MORPHOLOGY CONSEQUENCES: VASCULAR ATHEROMA CONTENTS INTRODUCTION DEFINITIONS MORPHOLOGY CONSEQUENCES: VASCULAR CONSEQUENCES: ORGANS The fibrous plaque

INTRODUCTION Atheroma is the single most important cause of morbidity and mortality in Western countries. The most important effects of atheroma are ischaemic heart disease, peripheral vascular disease and cerebrovascular disease. The cause of atheroma is not known, but many risk factors, and factors which accelerate disease development have been identified.

DEFINITIONS Atheroma = Atherosclerosis Athere = porridge. Sclerosis = hardening Atheroma is manifest as the development of deposits of fibrous tissue and lipid on arterial walls.

DEFINITIONS No picture Atheroma is the same as atherosclerosis. However arteriosclerosis is the medical term for hardening of the arteries with advancing age. The media and intima become replaced by fibrous tissue sometimes with calcification. Arteriosclerosis is not often of serious consequence. No picture

THE FATTY STREAK The fatty streak comprises a slightly elevated zone on the arterial wall caused by accumulation of a small number of lipid laden histiocytes, with some free lipid also (not shown). They occur in all societies, even those without a high prevelance of atheroma, but are thought to be the origin of atheroma, as they occur at the same sites.

THE FATTY STREAK .

THE FIBROUS PLAQUE This is the second stage in development of atheroma. Lipid accumulates, free and in foamy histiocytes. Smooth muscle cells migrate from the media and proliferate. Fibrosis develops around the lipid, and forms a cap over the lesion

THE FIBROUS PLAQUE

THE COMPLICATED PLAQUE Ulcers and fissures of the fibrous cap reveal plaque contents, resulting in thrombosis. The plaque may undergo calcification, visible on X-ray. Inflammation associated with the plaque destroys the media which undergoes fibrosis, and is weakened.

PLAQUE MORPHOLOGY Take a closer look at this picture on the next slide. Identify the three stages of development of atherosclerosis.

PLAQUE MORPHOLOGY

ARTERIES AFFECTED All arteries down to 1 mm diameter can be affected. The brachial arteries are spared. The renal arteries are spared (except in diabetes). Maximum atheroma occurs at sites of haemodynamic stress e.g. bifurcations.

VASCULAR CONSEQUENCES Atheroma has the following effects on vessels and the organs/parts served: LUMENAL NARROWING: ISCHAEMIA LUMENAL OCCLUSION: INFARCTION EMBOLISM : ISCHAEMIA AND INFARCTION WEAKENED WALL ANEURYSM Coronary artery thrombosis The following slides show each of these in turn.

VASCULAR CONSEQUENCES: LUMENAL NARROWING Lumenal narrowing results in ischaemia if severe enough. Usually a much greater degree of narrowing is required to cause symptoms than in the diagram. An example is chest pain on exertion due to narrowing of the coronary arteries (angina).

VASCULAR CONSEQUENCES LUMENAL OCCLUSION Lumenal occlusion is due to thrombosis. This will often result in infarction of the part served. An example is myocardial infarction due to thrombosis of a coronary artery.

VASCULAR EFFECTS: EMBOLISM This usually occurs when non occlusive thrombus breaks off and travels with the blood flow until it occludes a distal vessel. A clinical example is transient cerebral ischaemic attacks due to embolism from carotid atheroma. Embolism of lipid rich plaque contents is rare.

VASCULAR EFFECTS: ANEURYSM The commonest site for aneurysm is the abdominal aorta, as shown here. The aorta dilates, becomes filled with lamellated thrombus, and eventually ruptures.

VASCULAR EFFECTS: ANEURYSM The patient with a ruptured aneurysm presents with severe abdominal or back pain, and is often shocked due to blood loss. This is a surgical emergency, and grafting is required.

VASCULAR EFFECTS: ANEURYSM The patient with a ruptured aneurysm presents with severe abdominal or back pain, and is often shocked due to blood loss. This is a surgical emergency, and grafting is required.

ORGAN CONSEQUENCES We will now examine the consequences of narrowing, occlusion and embolism on the principal organs affected, namely the: HEART BRAIN LEGS GUT and KIDNEYS

ORGAN CONSEQUENCES 1 HEART: ANGINA Narrowing of the coronary arteries results in chest pain on exertion - angina.

ORGAN CONSEQUENCES 1 HEART: ANGINA

ORGAN CONSEQUENCES HEART: INFARCTION Thrombotic occlusion of a coronary artery results in myocardial infarction. The photograph shows a 10 day old infarct.

HEART: INFARCTION Myocardial infarct ddddddddddddddddddddddddddddddddddddddd Myocardial infarct

ORGAN CONSEQUENCES BRAIN: INFARCTION Thrombotic occlusion of a cerebral artery results in cerebral infarction. The patient will usually present with neurological deficit and reduced conscious level; the precise features depend on the site and size of the infarct.

BRAIN: INFARCTION

ORGAN CONSEQUENCES BRAIN: TRANSIENT ISCHAEMIC ATTACKS Thrombosis over the carotid arteries may result in release of small emboli. These travel to the brain. The patient suffers transient neurological deficit, or loss of consciousness. These small emboli usually lyse without permanent deficit, but there is always the risk of this.

ORGAN CONSEQUENCES LEG: CLAUDICATION Atheroma of the femoral artery results in reduced blood supply to the lower leg. The patient experiences pain in the calf on walking- claudication. This is relieved by rest and the patient’s progress is punctuated by alternate walking and resting: intermittent claudication.

ORGAN CONSEQUENCES LEG: GANGRENE Thrombosis may develop over an atheromatous plaque in the femoral (or other supplying) artery resulting in infarction of all tissues served (gangrene). This can also occur in severe stenotic atheroma if something else reduces blood flow, e.g. development of cardiac failure.

LEG: GANGRENE

ORGAN CONSEQUENCES GUT: INFARCTION Thrombosis may develop over an atheromatous plaque in one of the mesenteric arteries resulting in infarction. The photograph shows small bowel infarction. University of Utah Small bowel infarction

GUT: INFARCTION University of Utah

ORGAN CONSEQUENCES COLON: ISCHAEMIC COLITIS Lack of blood to the colon results in ischaemic damage short of infarction. The patient has pain and bloody diarrhoea. Narrowed inferior mesenteric artery to colon

ORGAN CONSEQUENCES KIDNEY: HYPERTENSION The renal arteries are usually spared severe atheroma but sometimes, especially in diabetic patients, the origin of the renal artery is affected. The kidney gradually becomes atrophic due to chronic ischaemia. The underperfused kidney releases renin resulting in renal hypertention, with consequent risk of heart failure and stroke. Narrowed origin of left renal artery.

KIDNEY: Atheroma at origin of renal artery

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