Ch 18

Chapter Overview

  • This chapter covers various diseases affecting cardiac function, which can significantly impact overall health and wellbeing:

    • Coronary Heart Disease (CHD)

    • Endocardial and Valvular Diseases

    • Myocardial Diseases

    • Pericardial Diseases

    • Congenital Heart Diseases

Coronary Heart Disease (CHD)

Introduction to CHD

  • Definition: CHD is characterized by insufficient delivery of oxygenated blood to the myocardium, primarily due to obstruction in the coronary arteries caused by atherosclerosis.

  • Sequelae of CHD include:

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

    • Myocardial Infarction: Heart attack resulting from prolonged ischemia.

    • Dysrhythmias: Abnormal heart rhythms that can arise from ischemic conditions.

    • Heart Failure: A state where the heart cannot pump sufficiently, leading to fluid retention and other systemic issues.

    • Sudden Cardiac Death: Unexpected death from cardiac causes, often linked to arrhythmias.

Etiology of CHD

  • Atherosclerosis: Progressive condition causing narrowing of the arterial lumen due to lipid accumulation and inflammation. Several mechanisms may lead to cardiac ischemia, including:

    • Thrombus Formation: Blood clots can obstruct blood flow.

    • Coronary Vasospasm: Temporary spasm of coronary arteries reduces blood flow.

    • Endothelial Cell Dysfunction: Impairs the regulation of vascular tone and blood flow.

Coronary Artery Disease (CAD) / CHD

  • CAD is predominantly a result of atherosclerosis, leading to coronary artery blockage and ischemia.

  • Statistics: CAD is the leading cause of death in the USA, with approximately 75% of coronary-related mortalities attributed to atherosclerosis.

  • Pathophysiology: The disease is driven by inflammatory processes, accumulation of lipids, and fibrous tissue formation, resulting in plaque development.

Mechanisms of Coronary Atherosclerosis

  • Lipids Transport: Lipids play a pivotal role in atherosclerosis, as they are transported in the bloodstream by lipoproteins, influencing risk levels.

    • High-Density Lipoproteins (HDL): Function to transport excess cholesterol from tissues back to the liver, aiding in the clearance of atheromatous plaque.

Types of Lipoproteins

  • Distinct classes of lipoproteins include:

    1. Triglycerides

    2. Phospholipids

    3. Cholesterol

    4. Protein

  • Density Relation: Lipoproteins vary in density based on lipid and protein content:

    • Higher lipid content equates to lower density.

    • Higher protein content results in higher density.

Classification of Lipoproteins

  1. High Density Lipoprotein (HDL)

  2. Intermediate Density Lipoprotein (IDL)

  3. Low Density Lipoprotein (LDL)

  4. Very Low Density Lipoprotein (VLDL)

Fat Digestion, Absorption, and Metabolism: Chylomicrons

  • Chylomicrons: These lipoproteins facilitate the transport of dietary lipids from the intestine to peripheral tissues and the liver, undergoing hydrolysis to yield remnant particles.

Hyperlipidemia

  • Definition: Elevated lipid levels in the bloodstream can lead to adverse cardiovascular outcomes. Major plasma lipids include:

    1. Total Cholesterol

    2. Triglycerides

Risk Factors for Coronary Heart Disease (CHD)

Primary Risk Factors

  • Genetic Predisposition: Family history significantly increases CHD risk.

  • Hypertension: Elevates workload and promotes arterial damage.

  • Cigarette Smoking: Contributes to endothelial injury and promotes atherosclerosis.

  • Dyslipidemia: High LDL and low HDL cholesterol levels heighten risk.

  • Age and Gender: Risk increases with age and varies between sexes.

Secondary Risk Factors

  • Lifestyle Factors: Lack of exercise and obesity contribute to metabolic syndrome.

  • Diabetes Mellitus: Affects blood vessel function and increases cardiovascular risk.

Classification of risk based on LDL

Table of Classifications:

  • LDL Cholesterol Levels (mg/dL) / Classification of Risk

    • <100: Optimal

    • 100 to 129: Optimal or above optimal

    • 130 to 159: Borderline high

    • 160 to 189: High

    • >190: Very high

Recommendations from NCEP for Children and Adolescents

Table of Recommendations:

  • Total Cholesterol Classification / LDL Cholesterol (mg/dL)

    • <170: Acceptable

    • 170 to 199: Borderline high

    • >200: High

Characteristics of Vulnerable Plaques

  • Vulnerable plaques can rupture, leading to complex thrombotic events.

  • Characteristics:

    • Large lipid core associated with instability.

    • Thin fibrous cap lacking resilience under stress.

Pathophysiology of Ischemia

  • Definition: Ischemia signifies a depleted blood supply to the heart, resulting in reduced metabolic viability. Key determinants include:

    • Rate of Coronary Perfusion: Influences oxygen delivery.

    • Myocardial Workload: Increased demand can exacerbate ischemic conditions.

Acute Coronary Syndromes (ACS)

  • Represents a spectrum of conditions resulting from acute coronary artery obstruction, leading to increased myocardial oxygen demand exceeding supply. This results in:

    • Unstable Angina: Sudden and unpredictable chest pain that could precede a myocardial infarction.

    • Myocardial Infarction (MI): Occurs when blood supply is entirely obstructed.