Congestive Heart Failure in Infants and Children

Dr A.N PatnaikAdditional professor of

Pediatrics,NIMS,Hyderabad.

ObjectivesUnderstand the path physiology of heart failure because it serves as the rationale for management and drug therapy.

Highlight on the different way of classification of heart failure in infants and children.

Stress on management of acute/ chronic heart failure in neonates, infants and children

Background

In children, cardiac failure is most often caused by congenital heart disease and cardiomyopathy. These causes are significantly different from those usually responsible for the condition in adults, which include coronary artery disease and hypertension.Literature review: Pub Med, the Cochrane Library, BMJ Clinical Evidence, National Guideline Clearinghouse and EMLc - There is a large amount of research published on the management of heart failure in adults but a fewer studies in children and those which do exist are often small, retrospective and use a diverse range of measures to assess efficacy. The management of cardiac failure in children has largely evolved based on clinical experience and the application of adult data, supported by the more limited pediatric literature.

Anatomy of Heart.

Burdon of Heart Failure in Children.

In adults, cardiac failure usually involves failure of the left ventricle, with the most common causes in developed nations being coronary artery disease; hypertension induced ‐cardiac stress, arrhythmias and valvular disease. In developing nations, it has been reported that other causes are frequently implicated, including rheumatic heart disease (20.1%) and cardiomyopathy (16.8%).In children for developed countries, the causes of cardiac failure :congenital malformations, such as left to right shunts(the function of both the right and the left ventricles will be affected ‐ ‐and these children suffer from high output cardiac failure),cardiomyopathy , anthracycline ‐toxicity. In developing nations, many cases are caused or exacerbated by anemia, often secondary to malaria , malnutrition and hypocalcaemia and vitamin D deficiency. Heart failure in post surgical or cardiac procedures (61.4%) compared to adults with heart failure (0.28%).Congenital heart disease occurs in around 8 per 1000 live births; many of these children receive early surgical intervention and the yearly incidence of heart failure as a result of congenital defects is between 1 and 2 per 1000 live births . Hence cardiomyopathy contributes to a .lot

Definition of CHF

Congestive heart failure (CHF) occurs when the heart can no longer meet the metabolic demands of the body at normal physiologic venous pressures either in lungs or systemic veins or both.

Compensatory Mechanisms of CHF

Typically, the heart can respond to increased demands

by means of one of the following:

Increasing the heart rate, which is controlled by neural and humoral input

Increasing the contractility of the ventricles, secondary to both circulating

catecholamine's and autonomic input

Augmenting the preload, medicated by constriction of the venous capacitance vessels

and the renal preservation of intravascular volume

Compensatory Mechanisms of CHF

Contributary Factors of CHF

Systolic dysfunction is characterized by diminished ventricular contractility resulting in an impaired ability to increase the stroke volume to meet systemic demands.

Factors such as anatomic stresses (eg, coarctation of the aorta) that contribute to an increased afterload (end-systolic wall stress) and those resulting from neurohormonal factors that increase systemic vascular resistance also lead to increased systolic dysfunction

Contributary Factors of CHF Diastolic dysfunction results from decreased

ventricular compliance, necessitating an increase in venous pressure to maintain adequate ventricular filling.

Causes of primary diastolic dysfunction include an anatomic obstruction that prevents ventricular filling (eg, pulmonary venous obstruction), a primary reduction in ventricular compliance (eg,cardiomyopathy), external compression (eg, pericardial effusion).

Path physiology in AHFDuring acute CHF, the sympathetic nervous system and renin-angiotensin system act to

maintain flow and pressure to the vital organs.

Increased Neurohormonal activity results in increased myocardial contractility, selective

peripheral vasoconstriction, salt and fluid retention, and blood pressure maintenance.

As a chronic state of failure ensues, these same mechanisms cause adverse effects.

The myocardial oxygen demand that exceeds the supply increases because of an increase in the

heart rate, in contractility, and in wall stress.

Alterations in calcium homeostasis and changes in contractile proteins occur, resulting in a

hypertrophic response of the myocytes.

Neurohormonal factors may lead to direct cardio toxicity and necrosis.

Path physiology in CHF

In chronic heart failure, myocardial cells die from energy starvation, from cytotoxic

mechanisms leading to necrosis.

Necrosis stimulates fibroblast proliferation, which results in the replacement

of myocardial cells with collagen.

The loss of myocytes leads to cardiac dilation and an increased after load and wall

tension, which results in further systolic dysfunction.

In addition, the loss of mitochondrial mass leads to increased energy starvation.

Signs /Symptoms of CHF

Tachycardia Venous congestion

Right-sided Left-sided Hepatomegaly Tachypnea Ascites Nasal flaring or gruntingPleural effusion Retractions Edema Pulmonary edema Jugular venous distension

Low cardiac output Fatigue or low energy Pallor Sweating Cool extremities Poor growth Dizziness Altered consciousness Syncope

Signs /Symptoms of CHF

CHF with normal cardiac output is called compensated CHF.

CHF with inadequate cardiac output is considered decompensa

Ross Classification of Cardiac Failure in children

Physical Examination

Ross score was 7 Diaphoresis of head/body =2 Frequent tachypnea=2 Retraction=1 RR<50/min=0 HR<160/min=0 Hepatomegaly >3cm =2

His weight and length are in 10th centile for age.BP= 90/45mmHg.Cardiomegaly ,normal intensity of sounds, no audible murmurs

NYHA Classification of CHF

This system relates symptoms to everyday activities and the patient's quality of life. Patient Symptoms: Class IAsymptomatic; no limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, or dyspnea (shortness of breath ).Class II Symptoms with moderate exertion; slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in fatigue, palpitation, or dyspnea. Class III Symptoms with minimal exertion; marked limitation of physical activity. Comfortable at rest, but less than ordinary activity causes fatigue, palpitation, or dyspnea.Symptoms at rest; unable to carry out any physical activity without discomfort. Symptoms of cardiac insufficiency at rest. If any physical activity is undertaken, discomfort is increased. Class IV Symptom at rest.

Causes of Heart failureFinding Causes

Cardiac rhythm disordersCardiac rhythm disorders CHB,SVT,SNDCHB,SVT,SND

Volume overloadVolume overload Structural heart disease (e.g., VSD, PDA, AR, Structural heart disease (e.g., VSD, PDA, AR, MR) ,Anemia, SepsisMR) ,Anemia, Sepsis

Pressure overloadPressure overload Structural heart disease (e.g., AS, PS, COA ) Structural heart disease (e.g., AS, PS, COA )

HypertensionHypertension

Systolic ventricular dysfunction or failureSystolic ventricular dysfunction or failure MyocarditisMyocarditisDilated cardiomyopathyDilated cardiomyopathyMalnutritionMalnutritionIschemiaIschemia

Diastolic ventricular dysfunction or failureDiastolic ventricular dysfunction or failure Hypertrophic cardiomyopathyHypertrophic cardiomyopathyRestrictive cardiomyopathyRestrictive cardiomyopathy

Pericardial or cardiac tamponadePericardial or cardiac tamponade

Work-up in CHFWork-up in CHF

Thorough history taking and physical examination, including an assessment of the upper- and lower-extremity blood pressuresLaboratory testing : CBC Electrolyte levels Calcium level, BUN level, creatinine level

Chest/Heart X-ray: Increase C/T ratio (except TAPVR with obstruction) Pulmonary blood flow and congestion

A 12-lead ECG: Hypertrophy of ventricles Arrhythmia.

Echocardiography Etiology of CHF Assess systolic and diastolic functions

Pulse oximetry, and a hyperoxia of arterial test in newborns distinguishing intracardiac mixing malformations from pulmonary disease in the setting of hypoxia.

Blood gas abnormalities Respiratory alkalosis (mild forms of CHF) Metabolic acidosis (low cardiac output or ductal-dependent lesions

Left ventricular/LA enlargementPulmonary venous congestion grade I

Echocardiograghy Segmental Approach-to establish pathology.

Treatment of CHFTreatment of CHF

The management of CHF is difficult and sometimes dangerous without knowledge of the underlying cause.

The goals of medical therapy for CHF include reducing the preload, enhancing cardiac contractility, reducing the after load, improving oxygen delivery, and enhancing nutrition.

Preload reduction can be achieved with oral or intravenous diuretics (e.g., furosemide, thiazides, metolazone). Venous dilators (e.g., nitroglycerin) can be administrated.

Contractility can be supported with intravenous agents (e.g., dopamine) or mixed agents (e.g., dobutamine, inamrinone, milrinone). Digoxin appears to have some benefit in CHF,

After load reduction is obtained orally by administration of angiotensin-converting enzyme (ACE) inhibitors or intravenously by administration of other agents such as hydralazine, nitroprusside, and alprostadil.

Pharmaceutical Agents used in the Treatment of CHF

Preload reduction Furosemide 1 mg/kg/dose qid (PO or IV)

Hydrochlorothiazide 2 mg/kg/d bid-qid

Metolazone 0.2 mg/kg/dose bid (PO)

InotropicDigoxin Preterm infants: 0.005 mg/kg/d PO bid or 75% of this dose IV

<10 y: 0.010 mg/kg/d PO bid or 75% of this dose IV

>10 y: 0.005 mg/kg/d PO qd or 75% of this dose IV

Dopamine 5-28 mcg/kg/min IV

Dobutamine 5-28 mcg/kg/min IV

Milrinone 0.5-1 mcg/kg/min IV Load: 50 mcg/kg IV slowly over 15 min

Pharmaceutical Agents used in the Treatment of CHF

Afterload reduction

Captopril 0.1-0.5 mg/kg/d PO tid

Enalapril 0.1 mg/kg/d PO qd/bid

Nitroprusside 0.5-10 mcg/kg/min IV monitor cyanide

Acute CHF in the neonate or infantCardiac lesions that may appear early and that should be considered include coarctation or interruption of the aortic arch, total anomalous pulmonary venous return, hypoblastic left-heart syndrome. More chronic conditions to consider in young infants with CHF include a large VSD.

PGE1 infusion is indicated when ductal-dependent cardiac lesions are diagnosed or when they cannot be ruled out in a timely fashion. Absent femoral pulses or the inability to increase the systemic arterial PaO2 to above 150 mm Hg with a fraction of inspired oxygen (FiO2) of 1 suggests a ductal-dependent lesion, and treatment with PGE1 is mandatory.

Nonstructural cardiac problems that occur during this stage include tachyarrhythmia's (usually supraventricular tachyarrhythmia [SVT]) and complete heart block. Pharmacologic or electrical cardio version is needed in any patient with a tachyarrhythmia who presents with CHF.

Acute CHF in the older child

In older children with acute CHF, admission to ICU for diuresis with IV furosemide and

IV dopamine infusion at a rate of 5-10 mcg/kg/min are appropriate until stabilization is

achieved.

Older children may require the placement of a central venous catheter to monitor venous

pressure and cardiac output during stabilization.

Chronic or stable CHFFor more severe CHF, diuretic therapy with oral furosemide may be increased to 2 mg/kg/dose

PO tid, or a second agent, such as hydrochlorothiazide can be added.

After load reduction is indicated in patients who have large Lt-Rt shunt, left-sided regurgitant

lesions or poor systolic function .

In any patient taking more than 1 mg/kg of oral furosemide bid without ACE inhibitors,

spironolactone should be added for its potassium-sparing effect. Alternatively, their serum

potassium levels should be monitored, and appropriate supplementation should be provided

Chronic stable CHFThe selective beta1-blocker metoprolol and the nonselective beta1- and beta2-blocker

carvedilol, used primarily in adults have generally shown encouraging results in select patients

with cardiomyopathy and mild or moderate chronic CHF in children.

Carvedilol has been shown to decrease pulmonary artery mean and wedge pressures, decrease

cardiac nor epinephrine levels, and increase peripheral vasodilatation by means of alpha1-

blockade. For these reasons, in part, increased use of carvedilol has progressed in recent years,

particularly in cardiomyopathy.

An increased ejection fraction has been demonstrated in children and adults using both drugs.

Adults using these beta blockers have demonstrated an increased stroke volume during exercise,

along with a decreased heart rate and LV chamber size.

Chronic or stable CHF In a patient who is haemodynamically stable, outpatient management can be initiated by

using several agents.

In mild forms of CHF, Digoxin and low-dose furosemide may be initiated.

The dose of Digoxin is almost never increased, either for effect or according to Digoxin

levels, which are notoriously unreliable. However, the dose may be decreased in the presence

of signs of toxicity. The suspicion of Digoxin toxicity should increase if an infant is

uninterested in feedings, gags, or vomits frequently. These symptoms are typically due to an

overdose or renal failure.

Management of Chronic CHFNutrition is crucial in the management of chronic CHF. Particularly during infancy, CHF

increases the metabolic demands while making feeding itself more difficult. Enhanced caloric

content feedings and, in some cases, nasogastric feedings may be necessary to maintain the

patient's growth.

Anemia aggravates CHF by increasing the demands for cardiac output, and often, careful

attention to iron stores or the administration of red cell transfusions results in a significant

improvement the oxygen-carrying capacity of the blood.

The success of medical therapy of CHF in infants and small children is judged according to the

child's growth. The failure to gain weight in the setting of marked CHF signifies that the current

regimen is not sufficient. A failure to thrive is an indication for increased medical management

or surgical repair.