Heart Failure Lecture Notes

Jul 10, 2024

Heart Failure Lecture Notes

Introduction

  • Topic: Heart Failure within Clinical Medicine section
  • Types: Left heart failure, right heart failure, high output failure
  • Reminder: Like, comment, subscribe, and check website for notes, illustrations, courses, and merchandise

Pathophysiology

Types of Heart Failure

  1. Left Heart Failure
    • Most common type
    • Subtypes: Systolic and Diastolic
  2. Right Heart Failure
  3. High Output Failure

Left Heart Failure

Systolic Heart Failure (HFrEF)

  • Cause: Reduction in contractility of LV myocardium
  • Common Causes:
    • Myocardial infarction (MI) -> fibrosis
    • Dilated cardiomyopathy
    • Myocarditis (less common)
  • Mechanism:
    • Contractility ↓, Left ventricular ejection fraction (LVEF) ↓
    • EF < 40% -> Heart Failure with Reduced Ejection Fraction (HFrEF)
    • Cardiac output ↓ due to poor forward flow

Diastolic Heart Failure (HFpEF)

  • Cause: Issues with filling of the heart
  • Common Causes:
    • Chronic hypertension
    • Aortic stenosis
  • Mechanism:
    • Stroke volume = preload + contractility + afterload
    • Afterload ↑ -> blood hard to pump out
    • LV hypertrophy (left ventricular hypertrophy – LVH)
    • LV filling ↓, but LVEF preserved
    • EF > 40% -> Heart Failure with Preserved Ejection Fraction (HFpEF)

Right Heart Failure

Systolic Right Heart Failure

  • Cause:
    • Right ventricular MI
  • Mechanism:
    • Contractility ↓, Right ventricular ejection fraction ↓
    • Low right ventricular cardiac output

Diastolic Right Heart Failure

  • Cause:
    • Pulmonary hypertension (various types)
  • Mechanism:
    • Right ventricular hypertrophy
    • Right ventricular filling ↓, but RV ejection fraction preserved

High Output Heart Failure

  • Cause: Uncommon, includes conditions like sepsis, thiamine deficiency (beriberi), thyrotoxicosis, severe anemia
  • Mechanism:
    • Massive vasodilation -> systemic vascular resistance (SVR) ↓,
    • Compensatory mechanism: cardiac output ↑ but still fails to meet tissue demands
    • Results in low blood pressure, activation of sympathetic nervous system and renin-angiotensin-aldosterone system (RAAS)

Compensatory Mechanisms in Heart Failure

  • Low Cardiac Output:
    • Activates baroreceptors -> Sympathetic nervous system activation
    • Increased heart rate, peripheral vasoconstriction
  • Renin-Angiotensin-Aldosterone System (RAAS):
    • Low cardiac output -> renin release -> angiotensin II formation -> aldosterone and ADH release -> increased preload and afterload
    • Problem: Worsens heart failure by increasing afterload and preload, increasing edema
  • Atrial Natriuretic Peptide (ANP):
    • Counter-regulatory hormone released in response to atrial stretch
    • Goal: Inhibit Angiotensin II, reduce RAAS activity

Complications of Heart Failure

Left Heart Failure

  • Pulmonary Edema: Increased pulmonary capillary wedge pressure (PCWP)
    • Symptoms: Dyspnea, orthopnea, paroxysmal nocturnal dyspnea
  • Severe Complications:
    • Acute decompensated heart failure -> severe pulmonary edema, V/Q mismatch, hypoxia
    • Cardiogenic shock: MI, tachyarrhythmia -> systemic perfusion ↓
      • Symptoms: Cold extremities, pallor, organ malperfusion (brain, heart, kidneys, GIT), lactic acidosis

Right Heart Failure

  • Systemic Congestion: Jugular venous distension (JVD), pitting edema
  • Liver Congestion: Hepatic congestion leading to liver failure
  • Ascites: Increased portal pressure -> fluid leakage into abdomen
  • Cardiogenic Shock: Septal shift causing left ventricular filling ↓ and systemic malperfusion

Diagnosis

Clinical Examination

  • Physical Examination: JVD, pitting edema, crackles on lung auscultation

Imaging & Tests

  • Chest X-ray: Look for cardiomegaly, pulmonary edema, pleural effusions
  • BNP Levels: Helps rule out/exclude heart failure in acute settings (high levels suggest CHF)
  • Echocardiogram: Assess heart function, LV ejection fraction, and wall movements
  • Right Heart Catheterization: Pulmonary capillary wedge pressure > 18 mmHg confirms left heart failure

Treatment

Reduce Sympathetic Nervous System Activity

  • Beta Blockers: Metoprolol, Carvedilol
  • SGLT2 Inhibitors: Empagliflozin

Reduce RAAS Activity

  • ACE Inhibitors
  • Angiotensin Receptor Neprilysin Inhibitor (ARNI): Sacubitril/Valsartan
  • ARB
  • Aldosterone Antagonists: Reduce sodium and water retention

Symptomatic Management

  • Diuretics: Loop and thiazide diuretics for edema
  • Additional Therapies: Hydralazine and Isosorbide dinitrate for African-Americans, Ivabradine (if in normal sinus rhythm and maxed beta-blockers)

Device Therapy

  • Cardiac Resynchronization Therapy (CRT): For LVEF < 35% and LBBB
  • Automatic Implantable Cardioverter Defibrillator (AICD): For LVEF < 35%, preventing VT/VF
  • Left Ventricular Assist Device (LVAD) and Transplant: For advanced heart failure

Acute Management

  • Inotropes: Dobutamine, milrinone for acute decompensation
  • Mechanical Circulatory Support: Intra-aortic balloon pump (IABP), Veno-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO)
  • Non-invasive Ventilation (BiPAP): Helps reduce pulmonary edema and improve cardiac output

Summary Treatment Approach

  1. Initial Management:
  • ACE inhibitor or ARB + beta blocker
  1. Symptom-based Additions:
  • Diuretics for congestion
  • Aldosterone antagonists, SGLT2 inhibitors
  • ARNI for further symptom control
  • Special considerations: Hydralazine + isosorbide dinitrate, ivabradine
  1. Advanced Strategies:
  • CRT or AICD if indicated
  • Inotropes and mechanical support for refractory cardiogenic shock
  1. Final Strategy:
  • LVAD or heart transplant in end-stage cases

Conclusion

  • Summary of key points: Differentiation between types of heart failure, treatment approach, complications, diagnostic strategy