Chapter 15 Arterial Disorders Class Notes (1) PDF

**Chapter 15 Arterial Disorders: General Principles** Basic Concepts - Arteries - Muscular-walled blood vessels - Move blood away from heart - High pressure vessels - Higher the pressure, the greater the resistance the heart must work against - Arte...

**Chapter 15 Arterial Disorders: General Principles** Basic Concepts - Arteries - Muscular-walled blood vessels - Move blood away from heart - High pressure vessels - Higher the pressure, the greater the resistance the heart must work against - Arteriosclerosis - Hardening and narrowing of arteries - Atherosclerosis - Plaque build-up on arterial wall Arterial Wall Composition - Tunica intima - Inner lining of endothelial cells - Damage may lead to arteriosclerosis and atherosclerosis - Tunica media - Smooth muscle - Regulate blood flow - Alpha-adrenergic nerve fibers: vasoconstriction - Beta-adrenergic nerve fibers: vasodilation - Tunica externa (adventitia) - Outer covering Endothelium Function - Fluid filtration, maintain blood vessel tone, semipermeable barrier, neutrophil chemotaxis - Vessel dilation - Nitric oxide (NO) - Vessel constriction - Endothelin - Angiogenesis - VEGF - Diuresis - C-type natriuretic peptide - Clot prevention - Prostacyclin - Clot formation - Thromboxane A2 Endothelial Injury - Leads to arteriosclerosis and atherosclerosis - Attracts WBC's - Initiates inflammation - vWF released increasing platelet aggregation - Foam cells (lipid-rich macrophages) form - NO release inhibited causing vasoconstriction - Plaque formation Blood Flow Regulation - Blood flow inversely related to diameter of vessel - Flow from large diameter to small diameter reduces flow and increases pressure - Resistance affected by vessel diameter, vessel length, and blood viscosity - Blood flow = blood pressure/resistance - Blood flow = CO (cardiac output) - Blood pressure = BP - Resistance = PVR (peripheral vascular resistance) - Cardiac output (CO) - Amount of blood from LV per minute - CO = BP/PVR - BP = CO × PVR - Factors can be adjusted independently - To raise BP: - Increase CO - Increase PVR Turbulent vs Laminar Flow - Laminar - Smooth flow parallel to vessel - Turbulent - Rough flow perpendicular to vessel - Endothelial injury (atherosclerosis) can lead to turbulent flow - "Whooshing" sound known as *bruit* - Sluggish, stagnant, or turbulent blood flow increases risk of thrombus formation Arterial Wall Tension and Distension - Arterial wall tension - Force opposing the distending pressure inside the vessel (smaller vessel, need greater pressure) - Laplace's Law - Intraluminal pressure = tension in wall vessel/radius - Tension=pressure x radius - Hypertension (HTN) - Vessel walls hypertrophy, reducing tension and wall stress - Tension=(pressure x radius)/wall thickness - Compliance - Distending capacity of a blood vessel Blood Pressure Regulation - Systole - Cardiac contraction (left ventricle) - Diastole - Cardiac relaxation - SBP/DBP: 120/80 mm Hg - Pulse pressure - Difference between SBP and DBP - Ideal: approximately 40 mm Hg Cardiac Factors - Stroke volume (SV) - Amount of blood ejected per beat - CO = HR × SV - 4.9 L/min=70 bpm × 70 ml/beat - Approximately 5 L/min at rest Pressure Relationships - CO = BP/PVR or BP = CO × PVR - Flow, resistance, and pressure are all related - Factors can be changed - ANS innervation affects PVR by changing vessel diameter - Changes in PVR affect BP - Changes in BP affect CO - Changes in HR and SV can affect CO and BP Baroreceptors: Neural Regulation of BP - Short-term regulation of BP changes - *Example:* lying down to standing - Located in walls of aorta and carotid arteries - Sense stretch of vessel wall - Send signal to cardioregulatory center - Medulla oblongata and pons - BP too high - Activate PNS - Decrease HR, contractility, vasoconstriction - BP too low - Activate SNS - Increase HR, contractility, vasoconstriction Orthostatic Hypotension - Drop in BP when changing position from lying down to standing - Decreased cerebral perfusion - Dizziness - Possible causes - certain medications (e.g. alpha blockers)  - autonomic neuropathy  - decreased blood volume - age-related blood-vessel stiffness. Renin-Angiotensin-Aldosterone System (RAAS) - Key role in BP regulation - Renin - From JG (juxtaglomerular) cells of kidneys in response to low pressure or perfusion - Converts angiotensinogen (from liver) to angiotensin I - Angiotensin I converted to angiotensin II - ACE (angiotensin-converting enzyme) in the lungs - Angiotension II - Potent vasoconstrictor - Activates aldosterone for adrenal cortex - Aldosterone stimulates sodium and water retention by kidneys to increase blood volume and pressure - Combination of vasoconstriction (angiotensin II) and fluid retention (aldosterone) serve to elevate BP Antidiuretic Hormone (ADH) - From posterior pituitary - AKA: vasopressin - Released in response to drop in BP and/or blood volume or increased blood osmolarity - Increases water reabsorption by kidneys - Raises blood volume and blood pressure Blood Pressure Regulation (image) Natriuresis - Increased urine output when blood volume is elevated - Reduction in blood volume reduces blood pressure - ANP - Atrial natriuretic peptide - Released from atria when they are overstretched - BNP - B-type or brain natriuretic peptide - Released from ventricles - C-type discussed earlier from endothelium **Chapter 15 Arterial Disorders: Modifiable Risk Factors for Atherosclerosis** Effect of Glucose on Arteries - Glucose injures endothelial cells - Glycoslation (aka: glycation) - Forms AGE's (advanced glycosylation end products) - Inflammation and plaque formation may result - AGE's increase endothelin release leading to vasoconstriction - Reason for diabetes mellitus being a risk factor for CAD Other Factors Affecting the Arteries - Free radicals - Damage cell membrane of endothelial cells, causing inflammation - Nicotine - Potent vasoconstrictor, especially coronary arteries; increase BP, SNS activation - Homocysteine - Damages endothelial linings (deficiencies in vitamin B~12~ or folic acid decrease homocysteine breakdown) Lipids - Cholesterol - Ingested from diet; made by liver - Used in cell membrane, hormone synthesis - Triglycerides - Ingested in diet - LDL: low-density lipoprotein (L for lousy) - "Bad" cholesterol as involved in plaque formation in arteries - HDL: high-density lipoprotein (H for happy or healthy) - "Good" cholesterol as it helps excrete cholesterol from body ("reverse cholesterol transport") Dyslipidemia - Associated with cardiovascular disease (CVD) - Associated with elevated LDL - Low levels HDL - Low levels HDL and high triglycerides - Causes of dyslipidemia - Familial hypercholesterolemia (FH) - Diabetes mellitus - Obesity - Hypothyroidism - Sedentary lifestyle - Diet high in sat. fats, alcohol, or excessive simple carbs - Medications: progestins, corticosteroids - Plaque formation along vessel walls - Lipid-filled WBC's (foam cells) - Overt signs and symptoms may be lacking - Review family history and look for risk factors for cardiovascular disease - Xanthoma: cholesterol deposits under skin - Xanthelasma: cholesterol deposits around eyes - Arcus senilis: yellow-white ring around cornea - Diagnosis - Blood sample to evaluate lipids - Rule out causes that may elevate lipids - *Example:* hypothyroidism - Also: hs-CRP; homocysteine levels - ASCVD= Atherosclerotic Cardiovascular Disease Dyslipidemia---Treatment - Lifestyle modifications - Dietary cholesterol less than 300 mg/day - Limit saturated fats - Regular physical activity - Medications - Statins (HMG-CoA reductase inhibitors) - Decrease liver cholesterol synthesis and may also reduce plaque - Bile acid sequestrants - Lower LDL by blocking reabsorption of bile acid in the gut - Cholesterol is key component of bile - Niacin - Lower triglycerides and raise HDL - Risk of increasing insulin resistance in DM - Fibrates - Lower triglycerides and raise HDL Cholesterol Management Guidelines: Risk Calculator: https://tools.acc.org/ASCVD-Risk-Estimator-Plus/\#!/calculate/estimate/ Hypertension - Elevated BP - "Silent killer" - General criteria: - 2 or more BP readings of DBP greater than 80 or SBP greater than 130 mm Hg - Primary HTN: 95% - Etiology unknown - Secondary HTN - Due to underlying disease - *Example:* Cushing's disease - Hypertension Guidelines - Controversy about recommended BP goals for different populations - \~1 in 3 adults in U.S. - Risk factors - Age - African American ethnicity - Obesity - Family history - Diabetes mellitus - Tobacco use - Stress - Excessive alcohol intake - Excess Na+ in diet - Insufficient K+ in diet - Two major pathological effects - High shearing stress on arterial walls - Injury to retina, kidneys, brain, lower extremities - LV hypertrophy (LVH) - Coronary blood supply unable to support additional ventricular tissue - Often no symptoms - Target organ damage may present with headaches, chest pain, vision disturbances, dizziness - Check for disorders and medications known to elevate BP - BP measurement - Seated for 5 minutes - No caffeine, exercise, smoking within prior 30 minutes - 2 measurements: use average - HTN: 2 separate measurements of elevated BP on separate days - Ambulatory BP monitoring may be used Hypertension Assessment - Fundoscopic exam to examine retinas - Chest - Alteration in PMI (point of maximal impact) - Bruits- renal artery stenosis - Peripheral arteries of lower extremities - Temperature, sensation, pulses - Diagnosis - Rule out underlying diseases that may elevate BP, 12-lead ECG, urinalysis (checking for protein in urine which may occur with HTN damage of kidneys), CBC Hypertension---Treatment - Stress reduction and physical activity - Smoking cessation - Medications - Diuretics - ACE inhibitors - ARB's (angiotensin II receptor blockers) - Calcium channel blockers - Beta-adrenergic blockers - Diet: DASH (Dietary Approaches to Stop Hypertension) Limit sodium in diet \< 1500 mg per day - Cheese leading contributor of Na+ in the diet - UPF industry is huge contributor to Na+ intake (3/4 salt is from UPF) - Chicken has high salt level (up to 840 mg per serving of chx breast) - \# 1 source of Na+ for kids is pizza, age 20-50 chicken, over 50 years bread Complications of Hypertension - LVH - May lead to MI or heart failure - Aneurysms - Bulge in weakened area of arterial wall - Cerebral hemorrhage - Hypertensive encephalopathy - Hypertensive retinopathy - Arteriovenous nicking - Renal disease - Glomerular injury **Chapter 15 Arterial Disorders: Atherosclerosis** Atherosclerosis - Result of endothelial injury and inflammation - Lipids, elevated glucose levels, free radicals, shearing force of BP - Gradual process by which atherosclerotic plaques build up on arterial wall - Contributes to CAD, cerebrovascular disease, peripheral arterial disease Atherosclerosis Risk Factors - Gender - Age - Diabetes mellitus - Family history - Tobacco use - Hypertension - Obesity - Lifestyle factors - Sedentary lifestyle - Diet high in saturated fats Atherosclerosis Pathophysiology - Injury to endothelium - Produce adhesion molecules that attract WBC's - Vascular cell adhesion molecule 1 and chemoattractant protein-1 - WBC's differentiate into macrophages and fill with LDL's - Become foam cells - Foam cells store cholesterol until they undergo apoptosis and release lipids into tunica media layer - Inflammatory cytokines attract fibroblasts - Fatty streaks form leading to plaques - Arterial wall becomes less elastic - Plaques calcify and are covered with fibrous platelet cap - Plaque rupture causes bleeding - Plaque can break loose and travel to area and obstruct blood flow - hs-CRP: high sensitivity CRP - Measures CRP levels - CRP associated with inflammation and increased plaque formation Clinical Manifestations of Atherosclerosis - Gradual, so may have no symptoms until end organ dysfunction - Examine for CVD - Obesity, shortness of breath, cyanosis, rapid pulse, elevated BP, weak pulses in extremities, etc. - Bruits - Arteriosclerotic changes to retina Diagnosis of Atherosclerosis - Lipid profile - Cholesterol, TG's, LDL, HDL - Endothelial function assessment - Intracoronary Doppler technique - Ultrasound of brachial artery - C-reactive protein - CRP acute phase protein from liver: inflammation - hs-CRP (high sensitivity CRP): increased levels associated with elevated CVD risk - Homocysteine levels - High levels associated with endothelial injury - Calcium computerized tomography scan - CT scan detects calcified plaques - Cardiac angiography - Radiopaque dye study using cardiac catheterization to examine blocked vessel - Intravascular ultrasonography - Via catheterization provides cross-sectional image of coronary arteries Cardiac Catheterization and Coronary Angiography Atherosclerosis Treatment - Lifestyle Modification - Health diet - Stress reduction - Physical activity - Social connectedness - Specific tx for where atherosclerosis is located but commonly includes stenting or bypass surgery Peripheral Arterial Disease---PAD - Arteriosclerosis and atherosclerosis outside coronary arteries - Most common site: femoral artery above knee - Same risk factors as atherosclerosis - Diabetes mellitus accelerates process - Peripheral neuropathy may be present - Gradual onset - Usually symptoms don't present until 70% occlusion - Intermittent claudication: primary sign - Pain with exertion, relieved by rest - Occlusion decreases oxygenation of tissue, leading to ADP and lactic acid formation - Reducing activity enables oxygen levels to meet metabolic demand, eliminating pain - Metabolic changes in muscle occur with ischemia and reperfusion cycles - Assessment - Examine for signs of arteriosclerosis and atherosclerosis - HTN, hyperlipidemia, diabetes, CAD, MI - Assessment of patient symptoms: pain and numbness with exertion alleviated by rest, etc. - Clinical Manifestations - Examine for diminished or absent pulses (bilateral comparison), palpable coolness, paresthesia, pallor, sensation distal to proximal - Diagnosis - Ankle-brachial index (ABI): compare upper and lower extremity BP - Normal: 1 or slightly greater - Less than 1 indicates PAD - Serum labs: CBC, ESR, CRP, lipids - Arterial plethysmography, conventional angiography, arteriogram, CT scan, MRI, capillary refill time (normal refill less than 2 seconds) - Treatment - Lifestyle modification - Exercise stimulates collateral circulation - Medications - Cholesterol lowering, anti-hypertensive, platelet inhibitors, vasodilators - Thrombolytic agents may be used - Peripheral arterial revascularization (angioplasty and stenting) procedures help restore circulation - Open surgical vascular bypass grafting - Peripheral Arterial Disease Stent with angioplasty image Aneurysm - Weakening of arterial wall causing bulging or dilation - Locations - Cerebral arteries - Sometimes called "berry aneurysms" - Aorta (thoracic or abdominal) - Most common: abdominal aortic aneurysm (AAA) - Commonly caused by arteriosclerotic damage - Also genetic predisposition, infection, vascular disease - Risk factors for rupture - Atherosclerosis, smoking, HTN - Classified by size, shape, location - Aneurysm - Involves all 3 layers of vessel wall - Fusiform shape - All layers of vessel wall dilate equally - Saccular shape - Weakness on one side of vessel - Presentation depends on size, location, and integrity - May be missed until rupture occurs - AAA: may present with abdominal or back pain - May compress organs causing nausea and vomiting - In thin patient, may see pulsatile mass - Deep palpation should not be performed - Bruit may be present - Cerebral aneurysms are normally silent - If rupture: subarachnoid hemorrhage - Diagnosis - Found incidentally - Ultrasonography - Treatment - Lifestyle modifications - Smoking cessation, BP regulation - AAA: periodic follow up (until increases to a certain size) - Surgical treatment may be necessary - Endovascular/endoluminal graft (like a stent) - Open repair Aortic Dissection - Tear in lining between tunica intima and media of aorta leading to a splitting of layers - Blood flows between layers - Potentially lethal - Symptom onset is sudden - Patient hears "ripping" or "tearing" sound - Pallor, tachycardia, BP presentation may be variable depending on dissection location - Signs may include bounding pulse, wide pulse pressure, diastolic murmur, and signs of heart failure - Cardiac tamponade may occur - 20% of cases present with neurological deficit, such as syncope - Diagnosis - ECG, chest CT scan or MRI, transesophageal echocardiogram - Treatment - Surgery Arterial Ulcers - Ischemic skin wounds due to lack of blood flow - Pale, diminished pulses in extremities with delayed capillary refill - Ulcers usually located distally at tips of toes, heel, lateral malleolus - Antibiotics may be needed to prevent infection - Preventive measures to lessen further injury to skin