Cardiac Insufficiency Overview

Heart Failure Pathophysiology

• Definition: Heart failure is a condition where the heart cannot pump enough blood to meet the body's needs. This can lead to reduced cardiac output and potentially inadequate blood flow to the body's organs.
• Morbidity of Heart Disease: Heart disease is a significant cause of morbidity, with heart-related deaths accounting for a considerable portion (approximately 41.52%) of overall deaths— a concerning statistic.
• Contents: This presentation covers heart failure etiology (causes), classification, compensatory responses, alterations in metabolism and function, and pathophysiology.
• Objectives: Students will define cardiac insufficiency and heart failure, understanding their pathogenesis and manifestations. These notes also cover the etiologies, precipitating factors, and classifications of heart failure, along with compensatory responses during cardiac insufficiency. They will also learn the pathophysiological underpinnings of prevention and treatment for heart failure.

Etiology of Cardiac Insufficiency

• Primary Myocardial Dysfunction: This involves problems with the heart muscle's ability to contract and relax in systole and diastole. Causes include myocarditis (inflammation), cardiomyopathy (disease), myocardial necrosis (tissue death), fibrosis (scarring), and myocardial ischemia (lack of blood flow), potentially caused by coronary artery disease or vitamin B1 deficiency.
• Cardiac Overload: Causes include mitral or aortic insufficiency, chronic anemia, and hyperthyroidism. High blood pressure (systemic hypertension) or high blood pressure in the lungs (pulmonary hypertension) also contribute to cardiac overload.
• Restricted Cardiac Filling: Constrictive pericarditis, characterized by inflammation of the pericardium (heart sac), restricts the heart's ability to fill with blood appropriately.

Precipitating Factors

• Infection: Respiratory infections are a key factor.
• Arrhythmias: Irregular heart rhythms (like "horse-running rhythm") can trigger heart failure.
• Pregnancy and Delivery: The physical demands of pregnancy and delivery can put stress on the cardiovascular system.
• Acid-Base/Electrolyte Disturbances: Conditions like acidosis and hyperkalemia are precipitating factors.
• Other: Additional factors may also cause heart failure.

Classification of Heart Failure

• Rapidity of Onset: Acute heart failure occurs rapidly and suddenly, with a sharp drop in cardiac output. Chronic heart failure has a gradual onset, often coupled with compensatory mechanisms and myocardium remodeling.
• Heart Side Involvement: Left heart failure affects the pulmonary circulation, leading to pulmonary congestion. Right heart failure affects the systemic circulation, causing systemic congestion. Whole heart failure implies issues with both circuits.
• Cardiac Output: Low-output heart failure involves an absolute decrease in cardiac output, while high-output heart failure is a relative decrease, often occurring when the body demands high levels of perfusion.
• Systolic/Diastolic Dysfunction: Issues with the heart's pumping (systolic) or filling (diastolic) phases contribute to different types of heart failure.
• Severity: Heart failure severity is graded, from mild with complete compensation to severe where compensation mechanisms fail. The NYHA classification system (New York Heart Association) quantifies severity.

Pathogenesis of Heart Failure

• Depressed Contractility: The heart's ability to contract weakens, leading to reduced cardiac output. Contributing factors include myocardium destruction, impaired myocardial energy metabolism, and problems with excitation-contraction coupling.
• Diastolic Dysfunction: Problems with the heart filling lead to reduced cardiac output. This stems from a delayed repositioning of calcium (Ca2+), an inadequate myosin-actin dissociation, reduced potential energy, and compromised ventricular compliance.
• Asynergic Contraction and Relaxation: Irregular movements between heart muscle contraction and relaxation phases.

Alterations in Metabolism and Function in Cardiac Insufficiency

• Low-output syndrome (forward failure): Decreased cardiac pump function, changes in arterial blood pressure, and blood redistribution affect the body's perfusion. Manifestations include lowered cardiac output, ejection fraction, and cardiac index. Ventricular end-diastolic volume and pressure increase. Heart rate may also increase.
• Venous Congestion Syndrome (backward failure): Right heart failure leading to congestion in the systemic circulation. Manifestations include venous hypertension, water and sodium retention, and systemic circulation congestion. This can lead to edema, hepatomegaly, and gastrointestinal dysfunction. Symptoms might also include jugular venous distention, and, ultimately, ascites.

Pathophysiology Basis of Prevention and Treatment

• Treating Underlying Diseases and Eliminating Precipitating Factors: Identifying and eliminating the root cause of heart failure is crucial for prevention and treatment.
• Regulating Neurohormonal Imbalance and Myocardial Remodeling: Controlling the body's hormonal response and correcting any myocardium damages are vital.
• Reducing Cardiac Volume Load and Pressure Load: Reducing the workload on the heart to improve its efficiency.
• Improving Myocardial Systolic and Diastolic Function: Promoting the heart muscle's pumping and filling capabilities.
• Correcting Water-Electrolyte and Acid-Base Balance: Ensuring proper fluid and electrolyte balance.