Cardiovascular Disease 3 and 4 PDF

Cardiovascular Disease 3 and 4 Friday, 1 November 2024 21:17 Vascular Disease Endothelium Endothelial cells form the inner most lining (single cell layer thick) of the blood vessels. - Endothelium is mechanosensitive (it can sense how blood flows over it and the pressure of the flow),...

Cardiovascular Disease 3 and 4 Friday, 1 November 2024 21:17 Vascular Disease Endothelium Endothelial cells form the inner most lining (single cell layer thick) of the blood vessels. - Endothelium is mechanosensitive (it can sense how blood flows over it and the pressure of the flow), this allows it to adjust to changes in the blood flow. - Actively help regulate vascular tone which means it can signal blood vessels to vasodilate (widen) or vasoconstrict (narrow). - It is the key regulator of vascular homeostasis. - It responds to physical and chemical signals in the body making a wide range of factors that help regulate the processes shown here. - Pulse wave velocity Blood vessel health is measure using pulse wave velocity which tells us about arterial stiffness using ultrasound. Pulse wave velocity measures the speed of arterial pressure waves traveling along the aorta and large arteries. It is calculated by dividing distance with pressure wave transit time at the two points of recording arteries. Atherosclerosis Atherosclerosis is a condition where lipoproteins build up inside the walls of the arteries which causes formation of plaque at the specific sites of the arterial tree tough endothelial (intimal) activation, inflammation, necrosis, fibrosis and calcification. It leads to narrowing of blood vessels which makes them more susceptible to formation of thrombi and plaque rupture. And there is obstruction of blood flow to peripheral organs, including heart, brain and/or lower extremities. (reduce/completely stopped blood flow to these organs). In a carotid artery plaque scan which is often done using ultrasound red represents normal flow, Yellow is high velocities and Blue is very high velocities. Endothelial response to shear stress It is highly responsive to shear stress (frictional force made by blood flow over its surface). Shear stress plays important role in health of blood vessels by influencing behaviour and health of endothelial cells in the ways that help prevent or promote CVD. Endothelial response to shear stress changes depending on the type of blood flow it experiences. It can be disturbed flow (irregular and disturbed) or laminal flow (steady and smooth). Vascular calcification Most individuals age 60+ have calcium deposits withing the arterial walls. It can accumulate in different ways either Intimal (deposit in intima) and/or medial(deposit in media layer). Increasingly recognised as a serious problem, in 1982 only 16 papers, today over 4000 Leads to vessel stiffness and increased BP. Consequences of atherosclerosis - Ischaemic heart disease (angina) Obstruction and/or spasm of the coronary arteries decreases the oxygen supply to the myocardium causing angina. Symptoms are precipitated by exercise, stress and cold. Unstable angina may result in a eventual myocardial infarction, so treatment with nitrate, Ca2+ channel or beta blockers in advise in the 1st instance. - Acute myocardial infarction Occurs when one of the coronary arteries become occluded by an embolus (blood clot), leading to heart muscle ischaemia (lack of oxygen). Severity depends on the size and location of the blocked coronary artery Clinical presentation of the chest pain, shortness of breath, weakness and anxiety Serum troponin is also be elevated (indicates cardiac muscle death). (used for diagnosis) - In-stent restenosis (stent is a small tube in the artery to keep it open) Risk of in-stent restenosis is when the artery starts to narrow again Due to neointimal hyperplasia which is the growth of new tissue inside the stent caused by injury from the stent placement. Injury to the artery wall triggers vascular smooth muscle cell (VSMC) proliferation which can re block the artery. Drug-eluting stents have been developed to inhibit proliferation to prevent re-narrowing. But a side effect is that it takes months for re-endothelialisation. Treatment of coronary artery disease: bypass Coronary artery bypass graft (CABG) is performed in patients with advanced atherosclerosis and/or multi-vessel disease. The procedure involves grafting (taking) a vessel from another part of the body, often the saphenous vein or internal mammary artery (IMA), to bypass the CA blockage. The increased blood flow to the heart muscle reduces the chance of myocardial infarction. Grafting can be performed as a single (one artery is bypassed), double, triple and even quadruple procedure Consequences of atherosclerosis Ischaemic stroke Ischaemic stroke occurs when blood supply to a part of the brain is compromised. This can occur due to a thrombus that has developed locally in the brain or from a plaque rupture elsewhere, commonly the internal carotid artery. Symptoms depend on the area of the brain affected Acute treatment with tissue plasminogen activator (tPA), a thrombolytic agent, can reduce the adverse effects of the stroke. Ongoing treatment with anticoagulants and carotid endarterectomy may be indicated. Identifying vulnerable carotid plaques is important to prevent complication such as stroke. Patients referred after displaying symptoms including dizziness, visual disturbances, memory loss etc.. Which can reduce blood flow to the brain. Duplex utilises ultrasound technology to provide a 2D image of the carotid artery and Doppler sonography to measure flow. If ultrasound shows more than 70% stenosis (artery significantly narrowed), patient will require carotid endarterectomy surgery but like other invasive surgical procedure this carries certain risks as well. Consequences: peripheral vascular disease PVD involves the obstruction of large arteries not within the coronary, aortic arch vasculature or brain. Often occurs due to atherosclerosis blockages in the lower extremities and leads to acute and chronic ischaemia (lack of blood supply to affected areas). Symptoms include claudication (pain in legs or buttocks during physical activities), colour changes in the limb and wounds and ulcers that are slow-healing or do not heal at all. In severe cases PVD can result in loss of limb Mortality rates are increased after foot ulcer development. With around 50% dying withing 5 years of developing a diabetic foot ulcer (NICE guidelines). Consequences: aortic aneurysms Pro-atherogenic (high blood pressure, high cholesterol, smoking, inflammation) stimuli induce stiffening of aorta. This results in weaking and bulging of the aortic wall. In the most cases there are no symptoms, other than occasional pulsating mass in the abdomen. AAA rupture is extremely serious and usually fatal (>80% of cases) All men over 65 are invited for ultrasound screening in the UK. At-risk (those with a large or fast-growing aneurysm) patients can undergo grafting to increase the stability of the aorta.