Heart Failure

Definition

  • Heart failure is described as a syndrome of inadequate cardiac output to maintain end organ perfusion.   It could be due systolic or diastolic dysfunction. Patients with left to right shunts develop congestive heart failure (CHF) because of excessive volume overload to the lungs with a normal cardiac function.

Compensatory Mechanisms

  • Catecholamine surge by the sympathetic nervous system that leads to tachycardia and increased myocardial contractility to increase the cardiac output.  
  • Salt and water retention through activation of the renin-angiotensin-aldosterone system (RAAS) to increase the intravascular volume and enhance the end organ perfusion.  

 

Table showing two classification systems of heart failure in children and adults
Ross Classification of Heart Failure in Children

 

Class I

Asymptomatic

Class II

Mild tachypnea or diaphoresis with feeding in infants, dyspnea on exertion in older children

Class III

Marked tachypnea or diaphoresis with feeding in infants, marked dyspnea on exertion in older children

Class IV

Symptoms such as tachypnea, retractions, grunting or diaphoresis at rest

 

 

NYHA Classification of Heart Failure in Adults

 

Class I

Symptoms are only present at exertion that would limit normal individuals

Class II

Symptoms are present at ordinary levels of exertion

Class III

Symptoms are present at less than ordinary levels of exertion

Class IV

Symptoms at rest

 

Etiology

Table showing mechanisms of heart failure in neonates/infants

Underlying mechanism

Examples

Pressure overload

Critical aortic stenosis (AS), Coarctation of aorta/interrupted aortic arch

Volume overload

Left to right shunts such as VSD, AVSD, PDA, truncus arteriosus, aortic pulmonary (AP) window

Valvular dysfunction

AV valve insufficiency after AVSD repair, semilunar valve insufficiency, truncal valve regurgitation, TOF with absent pulmonary valve

Myocardial dysfunction

Ischemia, anomalous left coronary artery from the pulmonary artery (ALCAPA)

Cardiomyopathy

Primary and secondary myocarditis

Post-op ventricular dysfunction

 

 

Table showing etiologies of heart failure in children/adolescents

Underlying mechanism

Examples

Left heart failure

MR, AR, progressive AS

Right heart failure

Ebstein's anomaly, Eisenmenger syndrome

Cardiomyopathy (primary)

Dilated, hypertrophic, restrictive

Cardiomyopathy (secondary)

Myocarditis

Chronic arrhythmia

SVT

Toxins

Anthracyclines, radiation

Metabolic disorders

Glycogen storage diseases

Clinical features

  1. Neonates/infants:
    • Respiratory distress, tachypnea and tachycardia
    • Diaphoresis with feeding and poor weight gain
    • Deceased urine output
    • Hepatomegaly
  2. Children/adolescents:
    • Dyspnea on exertion, tachypnea and tachycardia
    • Hepatomegaly and edema of extremities
    • Cough
    • Pallor

Diagnosis

  1. Blood work:
    • CBC (may show anemia) and thrombocytosis in case of Kawasaki disease
    • CMP (look for elevated LFT's and BUN/Cr, may have elevated Na and low K secondary to activation of RAAS)
    • Troponin I (only useful if concerned about acute ischemic injury)
    • CK-MB (non-specific marker of cardiac injury)
    • BNP/NTproBNP (see discussion below)
    • Lactate (if concerned about low cardiac output)
  2. Imaging:
    • CXR (cardiomegaly, pulmonary edema)
    • Echocardiogram (evaluate cardiac structure/function and coronary arteries)
    • Cardiac MRI (done in cases of myocarditis/cardiomyopathies for risk stratification)

Utility of biomarkers in CHF

The ideal biomarker would have the following properties:

  1. Specific for the myocardium
  2. Is released in quantities sufficient to be detected by an assay with sufficient sensitivity and specificity to distinguish between healthy and disease states
  3. A relationship can be determined between the serum level of the biomarker and the clinical severity of the disease state
  4. Can provide diagnostic and prognostic information

 

  • The prototype biomarker is Brain Natriuretic Peptide (BNP)
  • BNP and its inactive processed product, N-terminal-pro-BNP (NTproBNP), are released from ventricular myocardium in response to increased myocardial fiber stretch
  • BNP and NTproBNP have different biochemical properties, are measured by different assays
  • NTproBNP has a longer half-life in plasma than BNP; therefore, NTproBNP levels are generally higher than BNP and display less variability

Management of CHF

1. Diuretics:

  • Reduce symptoms of volume overload such as dyspnea, orthopnea, peripheral edema, hepatomegaly
  • Loop diuretics (furosemide, bumetanide) are typically used as first-line agents, with thiazide diuretics (chlorothiazide, metolazone) added for refractory fluid retention
  • Frequent monitoring of serum electrolytes is necessary, particularly if diuretics are used in combination with ACE inhibitors and/or digoxin 
Table showing the commonly used diuretics in pediatric CHF

Drug

Class

Action

Furosemide

Loop diuretic

Inhibits Na/K/Cl transport in ascending loop of Henle

Bumetanide

Loop diuretic

Inhibits Na/K/Cl transport in ascending loop of Henle

Hydrochlorothiazide

Thiazide

Inhibits Na/Cl transport in distal tubule

Metolazone

Thiazide

Inhibits Na/Cl transport in distal tubule

2. ACE inhibitors/Angiotensin Receptor Blockers (ARBs):

  • Afterload reduction of the left ventricle through systemic vasodilation has been a basic therapeutic premise of heart failure
  • ACE inhibitors effect systemic vasodilation through blockade of ACE which converts angiotensin I into angiotensin II
  • ARBs produce similar effects by blocking the angiotensin receptors

3. Beta-Blockers:

  • Beta-blockers are widely used in chronic heart failure
  • Beta-blockers improve left ventricular function, heart failure symptoms, and survival in adults
  • Potential mechanisms of include up regulation of beta-adrenergic receptors, decreased stimulation of other neuro-hormonal systems, antiarrhythmic effects, coronary vasodilation, negative chronotropic effects, antioxidant effects, and improved myocardial energetics

4. Aldosterone receptor antagonists:

  • The aldosterone receptor antagonists such as spironolactone prevent aldosterone from exerting adverse compensatory downstream mechanisms that are activated in chronic heart failure, many of which involve sodium and extracellular fluid retention
  • Evidence also indicates that chronic aldosterone receptor stimulation leads to adverse remodeling such as myocardial scarring/fibrosis, ventricular dilation, and ventricular dysfunction
  • Spironolactone is generally well tolerated in children, although hyperkalemia is a common side effect necessitating careful monitoring of serum electrolytes
  • Gynecomastia can occur in males (up to 10%) and may be irreversible

5. Digoxin:

  • Digoxin is a cardiac glycoside, which exerts positive inotropic effects on the heart by increasing sarcoplasmic calcium concentrations by inhibition of the sodium-potassium ATPase pump of the myocardial cellular membrane
  • Digoxin also counteracts the adverse neuro-hormonal milieu of chronic heart failure by increasing vagal tone and sympatholytic effects, decreasing plasma norepinephrine levels, and possibly antagonism of aldosterone
  • Digoxin is currently indicated for chronic heart failure in adults for patients who remain symptomatic despite adherence to guideline-directed medical therapy

6. Inotropes:

  • Inotropes are frequently used in the inpatient setting to improve ventricular function or augment cardiac output in patients with exacerbations of chronic heart failure
  • At present, there are no oral agents with inotropic properties, apart from digoxin, available in the United States
  • In some situations, continuous inotropic therapy may be used as part of a palliative care strategy or as a bridge to more definitive treatment such as ventricular assist device or heart transplantation

7. Interventional catheterization:

  • These procedures may be used for myocardial biopsy and to evaluate the cardiac hemodynamics  
  • Interventional balloon valvuloplasty may be needed for critical aortic or pulmonary stenosis

8. Surgery:

  • It is often the definitive treatment of heart failure if it is secondary to structural heart diseases