Cardiovascular System Notes

Cardiovascular System Overview

• Course: ANP300, University of Pretoria, Department of Anatomical Pathology, and National Health Laboratory Service.

Lecture Outline and Objectives

1. Heart Failure:
   • List features of left heart failure.
   • List features of right heart failure.
2. Congenital Heart Disease:
   • List disorders causing left-to-right shunts.
   • List disorders causing right-to-left shunts.
   • List obstructive lesions.
3. Ischemic Heart Disease:
   • Define angina pectoris.
   • Define myocardial infarction and pathogenesis thereof.
   • Define chronic ischemic heart disease.
   • Describe the morphology of myocardial infarction.
   • List the complications of ischemic heart disease.

Heart Failure

• Definition: Heart failure (also termed congestive heart failure, CHF) is a common, usually progressive condition characterized by the heart's inability to provide adequate perfusion to meet the metabolic demands of peripheral tissues or only does so at elevated filling pressures.
• Characteristics:
  • Forward Failure: Variable degrees of decreased cardiac output and tissue perfusion.
  • Backward Failure: Pooling of blood in the venous capacitance system.
• Note: It is the common end stage of many forms of chronic heart disease.

Left Heart Failure

• Definition: Left heart dysfunction resulting in insufficient delivery of blood to vital organs.
• Causes:
  1. Ischemic heart disease.
  2. Hypertension.
  3. Aortic and mitral valvular diseases.
  4. Primary myocardial diseases.
• Clinical and Morphologic Effects:
  • Consequences include passive congestion in the pulmonary circulation, stasis of blood in left-sided chambers, and inadequate perfusion leading to organ dysfunction.

Clinical Features of Left Heart Failure

• Symptoms:
  • Paroxysmal Nocturnal Dyspnea.
  • Orthopnea.
  • Exertional Dyspnea.
  • Fatigue.
  • Tachycardia.
  • Restlessness and confusion.
  • Cyanosis.
• Pulmonary Congestion Indicators:
  • Elevated Pulmonary Capillary Wedge Pressure.
  • Cough and crackles.
  • Wheezes.
  • Blood-tinged sputum.
  • Tachypnea.

Types of Left Heart Failure

1. Systolic Failure:
   • Definition: Insufficient ejection fraction (pump failure).
   • Causes: Myocyte damage or derangement.
2. Diastolic Failure:
   • Definition: Abnormally stiff ventricle, unable to relax during diastole.
   • Causes: Hypertension, diabetes mellitus, etc.

Morphology of Left Heart Failure

• Macroscopic Findings:
  • Heart: Left ventricle (LV) dilated and hypertrophied; left atrium (LA) dilated.
  • Lungs: Enlarged with increased weight (congested).
• Microscopic Findings:
  • Heart: Nonspecific myocyte hypertrophy and variable degrees of interstitial fibrosis.
  • Lungs: Perivascular and interstitial edema; accumulation of edema fluid in alveolar spaces; hemosiderin-laden macrophages (heart failure cells).

Right Heart Failure

• Definition: Right heart dysfunction resulting in impaired ability to perfuse the lungs at normal central venous pressures.
• Causes:
  1. Left heart failure.
  2. Primary pulmonary disorders (e.g., cor pulmonale).

Clinical Features of Right Heart Failure

• Symptoms:
  • Fatigue.
  • Ascites.
  • Peripheral venous pressure changes.
  • Enlarged liver and spleen (cor pulmonale).
  • Distended jugular veins.
  • GI distress (anorexia, complaints).
  • Weight gain and dependent edema.

Morphology of Right Heart Failure

• Macroscopic Findings:
  • Heart: Hypertrophy and dilation of the right atrium (RA) and right ventricle (RV).
  • Liver: Increased size and weight (congestive hepatomegaly with nutmeg appearance).
  • Spleen: Increased size and weight (congestive splenomegaly).
  • Effusions and ascites in pleural, pericardial, and peritoneal spaces.

Congenital Heart Disease

• Definition: Abnormalities of the heart or great vessels present at birth, often due to faulty embryogenesis during gestational weeks 3 to 8.
• Aetiology/Pathogenesis:
  1. Environmental exposures (e.g., congenital rubella infection, teratogens).
  2. Genetic factors (e.g., trisomies, DiGeorge syndrome).
  3. Nutritional factors.
• Clinical Features: Major functional abnormalities include:
  1. Left-to-right shunts.
  2. Right-to-left shunts.
  3. Obstruction.

Congenital Heart Disease: Left-to-Right Shunt

• Description: Most common congenital heart disease, characterized by increased pulmonary blood flow without cyanosis, leading to chronically elevated volume and pressure in the pulmonary circulation.
• Types of Disorders:
  1. Atrial Septal Defect (ASD): Abnormal openings in the atrial septum due to incomplete tissue formation.
  2. Ventricular Septal Defect (VSD): Incomplete closure of the ventricular septum, typically single.
  3. Patent Ductus Arteriosus (PDA): Normally allows blood flow from the pulmonary artery to the aorta; may remain open in conditions like hypoxia or other congenital defects.

Congenital Heart Disease: Right-to-Left Shunt

• Description: Causes cyanosis early in postnatal life.
• Types of Congenital Heart Diseases:
  1. Tetralogy of Fallot: Characterized by four features:
     • VSD
     • Subpulmonary stenosis
     • Overriding aorta
     • Right ventricular hypertrophy.
  2. Transposition of the Great Arteries: Characterized by ventriculoarterial discordance.
  3. Tricuspid Atresia: Complete occlusion of the tricuspid valve orifice.
  4. Persistent truncus arteriosus.
  5. Total anomalous pulmonary venous connection.

Congenital Heart Disease: Obstructive Lesions

• Description: Congenital blockage to blood flow which can occur at the level of heart valves or a great vessel.
• Types:
  1. Coarctation of the Aorta: A narrowing of the aorta.
  2. Pulmonary Stenosis and Atresia.
  3. Aortic Stenosis and Atresia.

Coarctation of the Aorta**

• Description: Constriction of the aorta, occurring twice as frequently in males. Two classic forms:
  1. Infantile form: Often symptomatic in early childhood with tubular hypoplasia proximal to a PDA.
  2. Adult form: Characterized by discrete ridge-like infolding opposite the closed ductus arteriosus.

Ischemic Heart Disease

• Definition: Myocardial ischemia, an imbalance between myocardial supply (perfusion) and cardiac oxygen demand.
• Causes:
  • Coronary artery disease (CAD) due to obstructive atherosclerotic lesions.
  • Other causes: coronary emboli, vessel inflammation, vascular spasm.
• Clinical Presentations:
  1. Angina pectoris.
  2. Myocardial infarction (heart attack).
  3. Chronic ischemic heart disease.
  4. Sudden cardiac death.

Pathogenesis of Ischemic Heart Disease

• Insufficient coronary perfusion due to:
  • Chronic vascular occlusion.
  • Acute changes, thrombosis, and vasospasm.
• Entities:
  1. Angina pectoris.
  2. Myocardial infarction.

Angina Pectoris

• Definition: Transient myocardial ischemia without myocyte necrosis.
• Symptoms: Recurrent, paroxysmal chest discomfort.
• Patterns:
  1. Stable Angina: Precipitated by physical activity or stress.
  2. Prinzmetal Angina: Due to coronary vasospasm, occurs at rest.
  3. Unstable Angina: Increasingly frequent and prolonged episodes.

Myocardial Infarction

• Definition: Myonecrosis caused by prolonged ischemia.
• Clinical Features:
  • Symptoms include prolonged chest pain, weak pulse, sweating, nausea, dyspnea, and specific alterations found in ECGs and blood tests.
• Morphological Changes:
  • Sequence of ischemic coagulative necrosis visible over time, leading to distinct appearances of infarcts.
  • Progression from reddish-blue discoloration to yellow-tan soft areas, followed by scarring over weeks.

Microscopic Changes in Myocardial Infarction

• Detectable changes from 6 to 12 hours post-infarction.
• Include acute inflammation (peaking at days 1 to 3), macrophages removing necrotic myocytes (days 3 to 7), and subsequent replacement by granulation tissue and fibrous tissue.

Complications of Myocardial Infarction

• Include:
  1. Contractile dysfunction.
  2. Arrhythmias.
  3. Myocardial rupture.
  4. Ventricular aneurysm.
  5. Pericarditis.
  6. Infarct expansion.
  7. Mural thrombus.
  8. Papillary muscle dysfunction.
  9. Progressive heart failure (chronic ischemic heart disease).

Chronic Ischemic Heart Disease

• Also known as ischemic cardiomyopathy.
• Definition: Accumulated ischemic myocardial damage that may lead to inadequate responses, signaling progressive congestive heart failure.
• Causes:
  • Can result from previous myocardial infarction or severe obstructive coronary artery disease without infarction.
• Morphology:
  • Macroscopy: Includes cardiomegaly, left ventricular hypertrophy, and signs of stenotic coronary atherosclerosis.
  • Microscopy: Features myocardial hypertrophy, diffuse subendocardial vacuolization, and interstitial fibrosis.

References

• Cotran, R., Kumar, V. and Robbins, S., 2015. Pathologic Basis Of Disease. 9th ed. Philadelphia, PA: Saunders Elsevier.