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HEART FAILURE - Complete Exam Notes

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DEFINITION

Heart failure = Heart cannot pump blood fast enough to meet the body's metabolic demands, OR it can only do so at an elevated filling pressure (meaning it needs to be overfilled just to push out a normal amount of blood).

• It is a complex syndrome arising from any structural or functional cardiac disorder.
• The older term "Congestive Heart Failure (CHF)" should be avoided because NOT all patients have volume overload (e.g., acute HF may have no edema initially). The preferred term is simply "Heart Failure."
• It is the common end-stage of many forms of chronic heart disease.
• It is the most common reason for hospitalization in adults >65 years of age.
• Heart failure usually develops insidiously from cumulative effects of chronic work overload (valve disease, hypertension) or ischemic heart disease.
• Acute hemodynamic stresses (fluid overload, sudden valvular dysfunction, MI) can cause sudden heart failure.

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EPIDEMIOLOGY

• Heart failure is the major cause of morbidity and mortality worldwide.
• Prevalence increases significantly with age.
• Blacks have the highest risk, followed by Hispanics, Whites, and Chinese Americans.
• Majority of patients die from progressive heart failure or sudden cardiac death.

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PATHOPHYSIOLOGY

The Three Pillars of Cardiac Output

Cardiac Index = Cardiac Output / Body Surface Area (BMI in some texts) Normal = 2.5 - 4.0 L/min/m²

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What Happens in the Failing Heart?

• Damages the heart muscle (loss of cardiac myocytes), OR
• Disturbs the myocardium's ability to generate force

1. Tachycardia - Heart beats faster to increase total output
2. Increased myocardial contractility - Via catecholamine release
3. Activation of neurohumoral systems - RAAS, sympathetic nervous system, vasopressin, endothelin

• Pathological peripheral vasoconstriction - increases afterload, making it harder for the heart to pump
• Sodium and water retention - increases preload beyond helpful levels, causing congestion
• Cardiac remodeling - the heart enlarges and changes shape, becoming less efficient

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Flowchart of Mechanism of Heart Failure (Flowchart 1.8)

LEFT VENTRICULAR FAILURE              RIGHT VENTRICULAR FAILURE
(IHD, Valvular disease,               (Cor pulmonale, Right-sided
Myocarditis, Restrictive              valvular disease, Pulm HTN)
pericarditis)
            \                              /
             -----> REDUCED CARDIAC OUTPUT <----
                           |
                    COMPENSATORY MECHANISMS
                    /                        \
     NEUROHUMORAL ACTIVATION         CARDIAC COMPENSATORY
            |                         MECHANISMS
    -Sympathetic NS                         |
    -RAAS (Renin-Angiotensin-         - Tachycardia + increased
     Aldosterone System)               myocardial contractility
    -Vasopressin                             |
    -Endothelin                      - Compensatory Hypertrophy
            |                          and Dilatation
    Sodium + Water Retention          (Heart enlarges in size to
            |                         pump more blood = "zyada
    Increased Intravascular            tez pump karna padta hai,
    Volume                             isliye size barhti hai")
            |
    Vasoconstriction
            |
    Increased BP + Cardiac Workload
            |
    FURTHER STRESS ON MYOCARDIUM
            |
    CONGESTIVE HEART FAILURE

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GENETIC BASIS OF HEART FAILURE (Cardiomyopathy Genes)

Selected Inherited Disorders That Progress to Heart Failure:

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CARDIAC REMODELING (Ventricular Remodeling)

• Left ventricular remodeling is the process by which mechanical, neurohormonal, and possibly genetic factors alter ventricular size, shape, and function.
• Occurs in: myocardial infarction, hypertension, cardiomyopathy, valvular heart disease.

1. Hypertrophy - increase in myocyte size
2. Loss of myocytes - apoptosis and necrosis
3. Increased interstitial fibrosis - scarring of the heart muscle

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TYPES OF HEART FAILURE

A. Based on Output

1. Low-Output Heart Failure (most common type)

• Characterized by decreased cardiac output (CO) AND decreased left ventricular ejection fraction (EF < 40%)
• This is a pumping problem - the heart muscle is weak and thin
• Causes: coronary artery disease, hypertension, valvular heart disease
• Memory: "Weak pump - can't squeeze properly"

• Characterized by elevated left AND right ventricular end-diastolic pressures with normal EF (>50%)
• This is a filling problem - the heart is stiff and can't relax to let blood in
• Causes: LV hypertrophy, Aortic Stenosis (AS), Systemic Hypertension (HTN), HOCM, Restrictive cardiomyopathy
• Memory: "Stiff pump - can't fill properly"
• NOTE: Heart Failure with Mid-Range EF (HFmrEF) = EF 41-49%

2. High-Output Heart Failure

• The heart pumps a lot of blood, but the body's metabolic demand is so insanely high that even an increased output isn't enough.
• Cardiac output > 8 L/min OR Cardiac Index > 3.9 L/min/m²
• Causes: Hyperthyroidism, Anemia, Pregnancy, Arteriovenous fistulae, Beriberi, Paget's disease
• Memory: "The demand exceeds even a hyperdynamic heart"

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B. Systolic vs. Diastolic Dysfunction (Important Distinction)

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C. Acute vs. Chronic Heart Failure

• Sudden development of heart failure
• Causes sudden reduction in cardiac output + systemic hypotension
• WITHOUT peripheral edema (no time to develop it)
• Examples: Acute MI, Rupture of a cardiac valve
• Can be: de novo (brand new) OR acute decompensation of chronic HF ("acute-on-chronic HF")

• Gradual development
• Systemic arterial pressure is well maintained
• Edema develops over time
• Examples: Dilated cardiomyopathy, multivalvular disease

• Impaired cardiac function, but compensatory/adaptive changes have prevented overt heart failure from developing.
• Can be precipitated (pushed into decompensated HF) by minor insults like infection or new-onset atrial fibrillation.

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D. Left-sided, Right-sided, and Biventricular Heart Failure

• Left side of heart: Left atrium + Left ventricle + Mitral valve + Aortic valve
• Right side of heart: Right atrium + Right ventricle + Tricuspid valve + Pulmonary valve

Left-Sided (Left Ventricular) Heart Failure:

1. Reduction in left ventricular output
2. Increase in left atrial and pulmonary venous pressure

• Acute rise in left atrial pressure (e.g., MI) → Pulmonary edema (fluid floods the lungs)
• Gradual rise in left atrial pressure (e.g., mitral stenosis, aortic stenosis) → Reflex pulmonary vasoconstriction → Prevents pulmonary edema but increases pulmonary vascular resistance → Leads to pulmonary hypertension → This impairs right ventricular function too

Right-Sided (Right Ventricular) Heart Failure:

1. Reduction in right ventricular output
2. Increase in right atrial and systemic venous pressure (causing peripheral edema, hepatomegaly, JVP rise)

• Chronic lung disease (Cor pulmonale)
• Multiple pulmonary embolism
• Pulmonary valvular stenosis

Biventricular Heart Failure:

• Failure of BOTH left and right ventricles
• Causes: Dilated cardiomyopathy, Ischemic heart disease (affects both ventricles)
• Mechanism: Left heart disease → chronic elevation of left atrial pressure → pulmonary HTN → impairs right ventricle → right heart fails too

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E. Forward vs. Backward Heart Failure

• Decreased cardiac output → inadequate perfusion of organs → poor tissue perfusion
• Reduced renal perfusion → activates RAAS → excessive sodium absorption by renal tubules
• Memory: "The pump can't push forward enough - organs suffer" (failure of the ventricle to empty properly)

• Normal cardiac output, but severe salt and water retention
• Venous congestion in pulmonary and systemic circulation
• Memory: "Blood backs up behind the failing side"

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CAUSES OF HEART FAILURE (Table 1.83)

Reduced EF (<40% HFrEF):

• Myocardial infarction, myocardial ischemia

• Regurgitant valvular disease (mitral/aortic regurgitation)
• Left-to-right shunts: VSD, PDA, ASD

• Hypertension
• Obstructive valvular disease (mitral/tricuspid stenosis)
• Endomyocardial fibrosis

• Cor pulmonale, pulmonary vascular disorders

Preserved EF (>50% HFpEF):

• Pathologic hypertrophy, aging, restrictive cardiomyopathy

High-Output States:

• Metabolic: Thyrotoxicosis
• Nutritional: Beriberi (thiamine deficiency)
• Hematological: Chronic anemia

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PRECIPITATING FACTORS FOR HEART FAILURE (Box 1.49)

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EXACERBATING FACTORS IN DETAIL (Important Long Questions)

1. Chronic Anemia:

• Associated with high cardiac output (CO) when hemoglobin drops significantly.
• Mechanism: Low Hb → decreased oxygen-carrying capacity → tissues signal vasodilation → vasodilatory metabolites released → arteriolar vasodilation → low SVR (Systemic Vascular Resistance) → compensatory tachycardia and high CO
• Even severe anemia rarely causes high-output HF in the absence of specific cardiac abnormalities.

2. Ischemia (Myocardial Infarction):

• Following ischemia, there is disproportionate elongation and thinning of infarcted regions of the LV.
• Overall chamber enlargement = Cardiac Remodeling
• Infarcts in the anterior wall and apex of LV cause the most severe hemodynamic impairment.

3. Persistent Arrhythmias:

• Cause: LV systolic dysfunction → condition called Arrhythmia-Induced Cardiomyopathy
• Most common precipitants:
  • Supraventricular tachycardia - in children
  • Atrial fibrillation - in adults
• Timely recognition + early treatment can prevent progression to HF.

4. Thyrotoxicosis (Hyperthyroidism):

• 1% develop thyrotoxic cardiomyopathy - a fatal form of dilated cardiomyopathy with severe LV dysfunction.
• Mechanism (multiple pathways):
  1. Beta-adrenergic overactivity → persistent tachycardia
  2. Thyroid hormones stimulate erythropoietin synthesis → increases blood volume → increases CO
  3. Thyroid hormones stimulate juxtaglomerular apparatus → more renin + aldosterone → sodium and water retention → increased effective blood volume
  4. Molecular level: Hyperthyroidism increases expression of positive regulated genes and decreases expression of negative regulated genes → enhances diastolic dysfunction, inotropism, and chronotropism → increases cardiac output further
• This creates a persistently hyperdynamic state until the heart decompensates.

5. Dietary Factors:

• Prolonged deficiency → Wet Beriberi (cardiovascular form)
• Mechanism: Impaired myocardial energy metabolism + dysautonomia
• Result: High-output cardiac failure

• Causes endemic cardiomyopathy = Keshan Disease

• Cobalt cardiomyopathy in chronic beer consumers
• Features: Severe HF, hypotension, cyanosis, pericardial effusion, low voltage ECG, elevated liver enzymes, lactic acidosis

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CLINICAL MANIFESTATIONS OF HEART FAILURE

Symptoms:

1. Exertional dyspnea - breathlessness on exertion (earliest symptom)
2. Orthopnea - breathlessness while lying flat (relieved by sitting up). Mechanism: When lying flat, venous return increases, fluid redistributes from legs to lungs. Patients sleep on multiple pillows. Graded by number of pillows needed.
3. Bendopnea - breathlessness when bending forward (e.g., putting on shoes). Newer symptom, indicates high filling pressures.
4. Paroxysmal Nocturnal Dyspnea (PND) - sudden breathlessness at night, patient wakes up gasping. Mechanism: Fluid redistribution during sleep + reduced adrenergic tone + reduced hypoxic ventilatory response during sleep.

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EXAM QUICK-SUMMARY TABLE

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