27 Patho

Disorders of Cardiac Function, Heart Failure, and Circulatory Shock

Introduction

This chapter covers the major disorders affecting cardiac function, including pericardial diseases, heart failure, and various forms of circulatory shock. Understanding these conditions is essential for recognizing their impact on cardiovascular health and systemic physiology.

Structure and Functions of the Pericardium

Definition and Anatomy

• Pericardium: A double-layered serous membrane that surrounds and protects the heart.

• Contains a small amount of fluid to reduce friction during heart movements.

Functions

• Protection: Isolates the heart from other thoracic structures.

• Position Maintenance: Keeps the heart in its anatomical position within the thorax.

• Prevents Overfilling: Limits excessive distension of the heart chambers.

• Coupling Distensibility: Ensures both ventricles fill equally during diastole.

Pericardial Disorders

Types of Pericardial Disorders

• Pericardial Effusion: Accumulation of fluid in the pericardial cavity.

• Cardiac Tamponade: Compression of the heart due to rapid or slow accumulation of fluid, pus, or blood in the pericardial sac.

• Pericarditis: Acute inflammatory process of the pericardium; can be acute, chronic, or constrictive.

• Constrictive Pericarditis: Development of calcified scar tissue between the visceral and parietal layers, fixing cardiac output and reserve.

Clinical Manifestations

• Ascites, pedal edema, dyspnea on exertion, fatigue, and Kussmaul sign (distended jugular veins during inspiration).

• Diagnosis: Based on clinical manifestations, ECG, chest radiography, and echocardiography.

• Pericardial friction rub may be present.

• Etiologies include infectious pathogens and autoimmune disorders.

Cardiac Tamponade

Pathophysiology and Effects

• Results from pericardial effusion leading to restricted movement of the heart muscle.

• Inhibits ventricular contraction and reduces stroke volume (SV).

• Conduction system remains intact, but cardiac output is severely compromised.

Coronary Circulation

Major Coronary Arteries

• Left Main Coronary Artery

• Left Anterior Descending Artery

• Circumflex Branch

• Right Coronary Artery

• Posterior Descending Artery

These arteries supply oxygenated blood to the myocardium and are critical for heart function.

Additional info:

• Pericardial disorders can lead to life-threatening complications such as cardiac tamponade, which requires immediate medical intervention.

• Coronary artery disease is a major cause of myocardial infarction and arrhythmias, which are covered in detail in subsequent sections of the chapter.