Cardiovascular - Acute Coronary Syndromes Midterm Notes PDF

3 1 CARDIOVASCULAR – Acute Coronary Syndrome (ACS) and Myocardial Infarc7on 1. Acute Coronary Syndrome (ACS) Acute Coronary Syndrome (ACS) refers to a spectrum of condi1ons caused by a sudden reduc1on in bl...

3 1 CARDIOVASCULAR – Acute Coronary Syndrome (ACS) and Myocardial Infarc7on 1. Acute Coronary Syndrome (ACS) Acute Coronary Syndrome (ACS) refers to a spectrum of condi1ons caused by a sudden reduc1on in blood flow to the heart, which includes Unstable Angina (UA), Non-ST-Segment Eleva@on Myocardial Infarc@on (NSTEMI), and ST-Segment Eleva@on Myocardial Infarc@on (STEMI). Most Likely Cause Cause: o Rupture of atherosclero@c plaque in a coronary artery. o Forma@on of a coronary thrombus (blood clot) at the site of the plaque rupture or erosion. o Atherosclerosis is the underlying cause of most ACS cases, and the rupture of unstable plaques ini1ates the thrombo1c process. Pathophysiology 1. Plaque Rupture or Erosion: o Plaques with thin fibrous caps rupture due to shear stress, releasing lipid-rich material into the bloodstream. o Rupture exposes subendothelial proteins, triggering platelet adhesion, ac@va@on, and aggrega@on. 2. Thrombus Forma@on: o Platelets aggregate and form a platelet plug. o The coagula1on cascade is ac1vated, leading to fibrin deposi@on and development of a more stable thrombus. o This thrombus can par@ally or completely occlude the artery. 3. Reduced Blood Flow and Ischemia: o Par1al or complete blockage of coronary blood flow leads to myocardial ischemia (oxygen starva1on of the heart muscle). o If ischemia persists, it results in myocardial infarc@on (heart aOack). Disease Transmission Transmission: o Not transmissible. ACS is caused by atherosclerosis, plaque rupture, and thrombus forma1on. o No infec1on or communicable agent is responsible for the development of ACS. Risk Factors Modifiable Risk Factors Hypertension: High blood pressure increases the risk of endothelial injury, promo1ng atherosclerosis. Dyslipidemia (High LDL, Low HDL): LDL cholesterol deposits within the artery walls and contributes to the forma1on of plaques.  2 Smoking: Increases oxida1ve stress, reduces nitric oxide (vasodilator), and accelerates atherosclerosis. Diabetes Mellitus: Chronically high glucose levels damage endothelial cells, increasing the risk of plaque forma1on. Obesity: Central obesity is associated with metabolic syndrome, which increases the risk of coronary artery disease (CAD). Physical Inac@vity: Lack of exercise promotes obesity and metabolic syndrome. Poor Diet: Diets high in saturated fats and trans fats increase LDL cholesterol levels. Non-Modifiable Risk Factors Age: Risk increases with age (men > 45 years, women > 55 years). Sex: Males have a higher risk compared to premenopausal women; however, postmenopausal women have an increased risk due to estrogen loss. Family History: Family history of early coronary artery disease (before age 55 in men, 65 in women) increases risk. Ethnicity: Certain ethnic groups (e.g., African, Asian, First Na1ons) have a higher predisposi1on to cardiovascular disease. 2. Myocardial Infarc@on (MI) Myocardial Infarc@on (MI), also known as a heart aOack, occurs when blood flow to a part of the heart muscle is blocked for an extended period, resul1ng in 1ssue death (necrosis). Most Likely Cause Cause: o Complete occlusion of a coronary artery due to a thrombus that forms following plaque rupture. o Thromboembolism from the rupture of an atherosclero@c plaque in the coronary artery. o Persistent ischemia and subsequent myocardial necrosis define an MI. Pathophysiology 1. Plaque Rupture or Erosion: o Similar to ACS, the rupture of an atherosclero1c plaque exposes subendothelial collagen and 1ssue factor, triggering platelet ac@va@on. 2. Thrombus Forma@on: o Platelets release thromboxane A2, which promotes vasoconstric@on and further platelet aggrega@on. o Ac1va1on of the coagula1on cascade leads to the genera1on of fibrin, forming a thrombus. 3. Coronary Artery Occlusion: o If the thrombus completely occludes the artery, blood flow to the downstream myocardium is stopped. o Lack of oxygen causes myocardial ischemia, and within minutes, cardiac muscle cells begin to die (necrosis). 4. Myocardial Necrosis:  3 o Infarcted cells die and are replaced by fibrous scar @ssue, which is non- contrac1le. o The heart undergoes ventricular remodeling, where hypertrophy occurs in remote areas of the heart to compensate for lost contrac1lity. Disease Transmission Transmission: o Not transmissible. MI is caused by internal processes such as plaque rupture, thrombus forma@on, and myocardial ischemia. o No infec1ous or communicable agent is responsible for MI. Risk Factors Modifiable Risk Factors Hypertension: High blood pressure increases arterial shear stress, leading to plaque rupture. Dyslipidemia: High LDL cholesterol promotes the development of atherosclero1c plaques. Smoking: Increases oxida1ve stress, promotes platelet aggrega1on, and reduces nitric oxide availability, increasing clot risk. Diabetes Mellitus: Increases oxida1ve stress and promotes endothelial dysfunc1on. Obesity: Obesity is linked to metabolic syndrome, which increases the risk of cardiovascular disease. Physical Inac@vity: Increases risk factors for metabolic syndrome. Poor Diet: Diets rich in saturated fats increase LDL cholesterol levels, contribu1ng to plaque forma1on. Non-Modifiable Risk Factors Age: Risk increases with age (men > 45 years, women > 55 years). Sex: Males are at higher risk of MI compared to females before menopause. Family History: A family history of early coronary artery disease increases risk. Ethnicity: Certain ethnic groups, including African, Asian, and First Na@ons, have a higher predisposi1on to MI. Summary Table Criteria Acute Coronary Syndrome (ACS) Myocardial Infarc@on (MI) Thrombus, complete occlusion of Cause Plaque rupture, thrombus forma1on coronary artery 1. Plaque rupture → 2. Thrombus 1. Plaque rupture → 2. Complete Pathophysiology forma1on → 3. Ischemia occlusion → 3. Necrosis Transmission Not transmissible Not transmissible Smoking, diabetes, hypertension, Risk Factors Same as ACS dyslipidemia, obesity