CAD MI

Coronary Artery Disease Overview

Definition

Coronary Artery Disease (CAD) refers to a class of diseases that impact the blood vessels supplying the heart, known as the coronary arteries. This condition results from the buildup of atherosclerotic plaque within these arteries, leading to reduced blood flow and oxygen supply to the heart muscle.

Conditions Included

CAD encompasses a variety of clinical conditions, including but not limited to:

  • Angina: Chest pain due to reduced blood flow to the heart muscle.

  • Myocardial Infarction (MI): Often referred to as a heart attack, it occurs when blood flow to a part of the heart is blocked for an extended period.

  • Valvular Heart Disease: Involves damage to heart valves that affects blood flow through the heart.

  • Aortic Aneurysms: Abnormal bulges in the aorta that can lead to life-threatening hemorrhages.

  • Stroke: A disruption of blood flow to the brain that can be caused by a blockage from plaque or a clot.

  • Carditis: Inflammation of the heart muscle and surrounding structures.

  • Peripheral Artery Disease (PAD): Narrowing of the peripheral arteries, often affecting the legs.

  • Heart Failure: A condition where the heart cannot pump enough blood to meet the body’s needs.

  • Arrhythmias: Irregular heartbeats resulting from CAD.

  • Thromboembolic Disease: Conditions related to thrombus (clots) that can block vessels and lead to ischemia.

  • Hypertensive Heart Disease: Damage to the heart caused by high blood pressure.

  • Congenital Heart Disease: Structural heart defects present from birth that may lead to CAD.

  • Venous Thrombus: Blood clots forming in veins that can impact circulation.

  • Rheumatic Heart Disease: Damage to the heart from rheumatic fever.

  • Cardiomyopathy: Disease of the heart muscle affecting its size, shape, or thickness, often leading to heart complications.

Statistics on CAD

  • Prevalence: CAD is the most common cause of cardiovascular disability and death in the U.S. and worldwide.

  • Demographics: More prevalent in men than women, with a ratio of 4:1 in younger ages; by age 70, this ratio balances out to 1:1, highlighting increased risk for women post-menopause.

Risk Factors for CAD

Modifiable Factors:

  • Elevated blood homocysteine levels: High levels can damage blood vessels and lead to clot formation.

  • Hypoestrogenemia in women: Lower estrogen levels after menopause increase CAD risk.

  • High LDL to HDL ratio (> 5): An unbalanced cholesterol ratio contributes to plaque buildup.

Etiopathogenesis of CAD

Progressive Disease Process:

  • A gradual process where irregularly distributed lipid deposits (atherosclerotic plaque) form in the coronary arteries, reducing their elasticity and ability to supply blood to the heart.

Key Contributors:

  • Abnormal lipid metabolism: Disturbances in lipid processing can lead to increased cholesterol levels.

  • Excessive cholesterol/saturated fat intake: Diets high in saturated fats contribute to plaque formation.

  • Genetic predisposition: Family history of heart disease increases individual risk.

Formation of Plaque:

  • Plaque consists of lipids, connective tissue, smooth muscle cells, and glycosaminoglycans. The earliest lesion is identified as a fatty streak, which can evolve into a fibrous plaque as inflammation and damage progress.

Pathophysiological Mechanism

  • Genetic Predisposition: Inherited factors can elevate risk levels for CAD through mechanisms like inflammation and endothelial function.

  • Lifestyle & Behavior: Unhealthy diet, lack of exercise, and smoking can increase LDL cholesterol levels.

  • Endothelial Injury: Damage to the endothelial layer of blood vessels allows LDL cholesterol entry, leading to plaque buildup and other processes such as platelet aggregation and smooth muscle cell proliferation.

  • Chronic Endothelial Injury: Persistent endothelial damage is essential for plaque formation and subsequent CAD progression.

Clinical Manifestations of CAD

Common Symptoms:

  • Myocardial Ischemia: Reduced oxygen supply leading to angina or chest pain.

  • Myocardial Infarction (MI): Complete oxygen deprivation leading to tissue necrosis.

  • Congestive Heart Failure: The heart's inability to manage blood flow can lead to various systemic symptoms.

  • Sudden Death: Can occur due to fatal arrhythmias caused by compromised coronary circulation.

Myocardial Ischemia

  • Imbalance: Occurs when the oxygen supply to the myocardium does not meet its demands.

  • Angina: Can be reversible and is often triggered by exertion, stress, or heavy meals.

Coronary Occlusion:

  • A blockage of more than 70% in coronary arteries typically leads to ischemia.

Types of Angina:

  • Stable Angina: Predictable pattern triggered by exercise, subsides with rest.

  • Unstable Angina: Occurs at rest, may last longer, and is less responsive to treatment, indicating an impending myocardial infarction.

  • Prinzmetal Angina (Variant Angina): Caused by vasospasm, can occur at rest, often at night.

  • Atypical Angina: May present not just as pain but as discomfort or fatigue.

Implications for Physical Therapists

  • Increased vigilance is necessary for any discomfort above the waist during increased activity, which should be evaluated as potential angina.

Diagnosis of CAD

  • Clinical Presentation: A thorough history and physical examination to identify stable or unstable angina.

  • Exercise Stress Test: Evaluates angina symptoms by mimicking stress conditions, with ECG changes (e.g., ST segment depression) potentially indicating ischemia.

  • Further Tests: Cardiac catheterization or coronary angiography provide detailed images of heart and coronary vessels for diagnosis and planning treatments.

Myocardial Infarction (MI)

Definition

An MI occurs when the myocardium is deprived of oxygen for an extended period, leading to irreversible tissue damage and necrosis.

Common Cause

  • Prolonged ischemia: Often results from a blood clot (occlusive thrombus) formed over a ruptured atherosclerotic plaque.

Zones of Myocardial Injury

  • Zone of Infarction: Dead tissue resulting from lack of blood supply.

  • Zone of Ischemia: Tissue that is not getting enough blood.

  • Zone of Injury: Tissue that is still viable but compromised in function.

Diagnosis of MI

Clinical Presentation

  • Typical symptoms include sharp, chest pain that is not relieved by rest or nitrates; discomfort may also refer to other regions such as the jaw or arm.

ECG Findings:

  • ST Elevation (STEMI): Characterized by an elevation in ST segment followed by T wave inversion.

  • NSTEMI: Presents with T wave inversions; definitive diagnosis requires lab results confirming elevated cardiac biomarker levels.

Lab Tests:

  • Troponin I: Most specific marker for myocardial injury; levels increase soon after injury.

  • CK-MB: Enzyme indicating myocardial muscle injury that also rises following MI.

  • Myoglobin: Appears early but lacks specificity for heart muscle damage.

Complications Following MI

  • Infarct extension: Additional heart muscle damage may occur after the initial event.

  • Arrhythmias: Abnormal heart rhythms that can arise immediately or later.

  • Myocardial rupture: Rare but can occur if inflamed tissue degrades.

  • Ventricular dysfunction: Impaired pumping ability of the heart following significant tissue loss.

Management of MI

Emergency Response:

  • Initial management includes Basic Life Support (CPR) and the administration of medications such as Nitroglycerin, Oxygen, and Aspirin.

Surgical Options:

  • Percutaneous Transluminal Coronary Angioplasty (PTCA): Expanding blocked arteries via balloon catheter, sometimes placing a stent (PTCA with stents).

  • Coronary Artery Bypass Grafting (CABG): Bypasses blocked arteries to restore blood flow to the heart.

Conservative Management:

  • Emphasis on cardiac rehabilitation, lifestyle modifications (diet, exercise), and regular monitoring.

Medications for MI Management

  • Nitroglycerin: A vasodilator that relieves angina by improving myocardial blood flow.

  • Aspirin: Reduces clotting risk; associated risks include gastrointestinal bleeding.

Other Antiplatelet/Antithrombotic Drugs:

  • Clopidogrel (Plavix), Dipyridamole, and Ticagrelor are notable medications used to prevent thrombus formation.

Thrombolytics in MI Treatment:

  • Streptokinase: Dissolves clots but carries a risk of hemorrhage.

  • Numerous other thrombolytic agents exist to facilitate rapid clot dissolution, enhancing myocardial salvage during acute MI situations.