A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.

Heart Failure: Systolic and Diastolic Dysfunction

Graduate Depth 253 in the knowledge graph ☐ I know this ☆ Set as goal

8topics build on this

1,397prerequisites beneath it

Cardiac Cycle and Heart Function Cardiac Output and Stroke Volume Regulation +2 more→→Atrial Fibrillation: Atrial Remodeling, Substrate Formation, and Arrhythmia Progression Cardiogenic Pulmonary Edema: Elevated Hydrostatic Pressure, Fluid Accumulation, and Hypoxemia +3 more

Core Idea

Heart failure is impaired myocardial contractility (systolic dysfunction) or relaxation (diastolic dysfunction) causing inadequate cardiac output. Neurohormonal compensation—sympathetic activation, RAAS, natriuretic peptides—initially maintains perfusion but eventually worsens remodeling.

How It's Best Learned

Use ejection fraction (EF) to classify: reduced EF (HFrEF, EF <40%), mildly reduced (HFmrEF, EF 40-49%), preserved (HFpEF, EF ≥50%). Understand diastolic dysfunction as impaired filling despite normal contractility.

Common Misconceptions

Low ejection fraction does not always cause symptoms—many patients are asymptomatic. HFpEF is not simply 'diastolic heart failure'; it involves complex interplay of stiffness, chronotropic incompetence, and vascular dysfunction.

Explainer

Heart failure is best understood by returning to the fundamentals of cardiac output you studied as a prerequisite. Cardiac output equals stroke volume times heart rate. Stroke volume itself depends on three variables: preload (ventricular filling), afterload (resistance the ventricle pumps against), and contractility (the intrinsic force of myocardial contraction). Heart failure occurs when these variables are so disrupted that the heart cannot maintain output sufficient for metabolic demands—or can only do so at the cost of abnormally elevated filling pressures.

Systolic dysfunction (HFrEF) is the classic picture: the ventricle contracts weakly, ejection fraction falls below 40%, and stroke volume drops. This follows directly from your study of myocardial infarction—dead myocardium cannot contract, so ischemic cardiomyopathy is a leading cause. The body's initial compensation is neurohormonal: the sympathetic nervous system increases heart rate and contractility, and the renin-angiotensin-aldosterone system (RAAS) promotes sodium and water retention to increase preload. In the short term, these Frank-Starling compensations maintain output. Over time, however, chronically elevated sympathetic tone causes maladaptive remodeling—the ventricle dilates and becomes more spherical, wall stress increases (by the law of LaPlace, tension = pressure × radius / 2 × wall thickness), and the dilated geometry further impairs ejection efficiency. Compensation becomes the disease.

Diastolic dysfunction (HFpEF) is mechanistically distinct: the ventricle contracts normally (EF ≥ 50%) but is abnormally stiff and cannot relax adequately during diastole. Think of the difference between squeezing a water balloon (systolic) and filling a stiff rubber ball (diastolic). In HFpEF, impaired relaxation means the ventricle requires elevated filling pressures to accept the same stroke volume—those elevated pressures back up into the pulmonary circulation, causing exertional dyspnea and pulmonary edema even with preserved contractility. Hypertension, diabetes, and obesity are major drivers because they all cause concentric left ventricular hypertrophy and increased myocardial stiffness.

The neurohormonal response is a unifying theme across both types. Natriuretic peptides (BNP, NT-proBNP) are secreted by stretched ventricular myocytes as a counter-regulatory signal—they promote vasodilation and natriuresis. Clinically, elevated BNP is the biochemical signature of heart failure regardless of type. The treatment logic for HFrEF follows directly from pathophysiology: ACE inhibitors/ARBs reduce afterload and blunt RAAS; beta-blockers counteract maladaptive sympathetic activation; aldosterone antagonists reduce fibrosis and fluid retention. The remarkable finding is that these agents reduce mortality not just by relieving symptoms but by partially reversing remodeling. For HFpEF, no therapy has yet demonstrated comparable mortality benefit—a reflection of our still-incomplete understanding of its heterogeneous pathophysiology.

Practice Questions 5 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → One-to-One Correspondence → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Making 10 as an Addition Strategy → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Iterated Integrals and Fubini's Theorem → Double Integrals in Cartesian Coordinates → Double Integrals in Polar Coordinates → Double Integrals in Polar Coordinates → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → The Measurement Problem → Interpretations of Quantum Mechanics → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Weak Acid Ionization → Weak Base Ionization → Acid and Base Strength: Ka, Kb, and Ionization → Leaving Groups and Nucleofugality → SN2 Substitution Reactions → SN1 Substitution Reactions → E1 Elimination Reactions → Alcohols and Ethers: Structure, Properties, and Nomenclature → Reactions of Alcohols → Aldehydes and Ketones: Structure and Reactivity → Oxidation Reactions in Organic Chemistry → Oxidation of Alcohols to Aldehydes and Ketones → Aldehyde and Ketone Structure and Nomenclature → Nucleophilic Addition to Aldehydes and Ketones → Carboxylic Acids and Their Derivatives → IUPAC Nomenclature of Carbonyls and Carboxylic Acids → IUPAC Nomenclature of Alkenes → Electrophilic Addition to Alkenes → Aromaticity and Benzene → Electrophilic Aromatic Substitution (EAS) → Nucleophilic Aromatic Substitution (SNAr) → Nucleophilic Acyl Substitution → Amines: Structure, Basicity, and Reactions → Amine Reactivity: Nucleophilicity and Basicity → Amino Acid Structure and Properties → Peptide Bonds and Polypeptide Formation → Protein Primary Structure → Protein Secondary Structure → Protein Tertiary Structure → Enzyme Structure and Function → Transcription: DNA to RNA → RNA Types and Structure → RNA Structure and Intramolecular Base Pairing → RNA Processing and Splicing → Translation: RNA to Protein → Ribosomes: Protein Synthesis Machines → Translation: Initiation and Elongation → Post-Translational Modifications → Proteasomal Degradation and Ubiquitin-Mediated Marking → Cell Cycle Regulation and Checkpoints → Cell Cycle Checkpoints: Ensuring Genome Integrity → Cell Cycle Checkpoints and Cancer Prevention → Mitotic Spindle Checkpoint and Chromosome Segregation → Kinetochore Structure and Function → Mitochondria: Structure and Function → Cellular Respiration Overview → Glycolysis → Pyruvate Oxidation → The Krebs Cycle (Citric Acid Cycle) → Electron Transport Chain → ATP Synthesis and Oxidative Phosphorylation → ATP Hydrolysis and Cellular Free Energy → The Na+/K+-ATPase: Maintaining Ion Gradients → Resting Membrane Potential → Ligand-Gated Ion Channels → Voltage-Gated Sodium Channels → Action Potential Phases → Cardiac Electrophysiology and Action Potentials → Cardiac Pacemaker Activity and the Sinoatrial Node → Atrioventricular Node Conduction and Physiological Delay → Heart Rate Control and Autonomic Modulation → Cardiac Output and Stroke Volume Regulation → Blood Pressure Regulation → Vascular Tone and Resistance Regulation → Capillary Microcirculation and Fluid Exchange → Blood Vessel Structure and Types → Hemodynamics: Pressure, Volume, and Flow Relationships → Vascular Physiology and Hemodynamics → Vascular Resistance and Control → Blood Pressure Regulation: Neural and Hormonal → Hypertension and End-Organ Damage → Left Ventricular Hypertrophy → Cellular Adaptation: Hypertrophy and Hyperplasia → Cell Injury and Adaptation → Cellular Hypertrophy and Hyperplasia in Disease → Vascular Smooth Muscle Remodeling and Arterial Stiffness → Atherosclerosis Development and Progression → Atherosclerotic Plaque Rupture and Thrombosis → Myocardial Infarction and Ischemia-Reperfusion Injury → Heart Failure: Systolic and Diastolic Dysfunction

Longest path: 254 steps · 1397 total prerequisite topics

Prerequisites (4)

Cardiac Cycle and Heart Functionhard Cardiac Output and Stroke Volume Regulationhard Myocardial Infarction and Ischemia-Reperfusion Injurysoft Cardiac Output Control and Regulationsoft

Leads To (5)

Atrial Fibrillation: Atrial Remodeling, Substrate Formation, and Arrhythmia Progressionsoft Cardiogenic Pulmonary Edema: Elevated Hydrostatic Pressure, Fluid Accumulation, and Hypoxemiahard Mitral Regurgitation: Volume Overload, Chamber Remodeling, and Functional Declinesoft Pulmonary Edema: Pathophysiology and Mechanismssoft Right Heart Failure and Cor Pulmonalehard