Paediatrics JC123: Heart Failure And Cyanosis In Children: Acyanotic And Cyanotic Congenital Heart Disease

Question 1

Concept of Heart failure

Answer 1

Consider 2 components
1. Pump function
2. Demand of body

Heart failure:
- Pathophysiologic state in which the heart **fails to pump blood at a rate to **meet the demand of body
- Reason: ***Imbalance between function of heart + demand on heart for body, either:
—> Heart cannot pump efficiently
—> Demand on heart too large even though pump is functioning but cannot maintain adequate output

1. Dysfunction of heart
   - Pump dysfunction
   - more common cause of heart failure in adult: IHD —> impaired contractile function of LV
2. ***Cardiac overload
   - ∵ Pressure / Volume overload (excessive demand on heart despite good pump function)
   - more common cause of heart failure in children (>90%)

NB:
- 大人: Poor cardiac function —> Congestive / Forward heart failure —> Pressure / Volume overload
- 小朋友: Pressure / Volume too large —> Even adequate cardiac function —> Overload the heart

Question 2

Symptoms / Signs of Heart failure

Answer 2

Symptoms (History taking):
1. **SOB (esp. on exertion e.g. feeding)
2. **Poor feeding (require longer time to finish feed)
3. **Excessive sweating (esp. on exertion e.g. feeding)
4. **Failure to thrive
5. Recurrent chest infection
6. Exercise incapacity in older children

Signs (P/E):
1. ***Pulmonary venous congestion
- Tachypnea
- Subcostal insucking
- Wheezing in infants

2. Systemic venous congestion
   - **Hepatomegaly
   - **Distension of neck veins (not obvious in small children)
   - Peripheral edema (rare in the absence of cardiac dysfunction, ∵ volume / pressure overload rather than cardiac dysfunction —> CVP not elevated)
3. Compensatory mechanisms
   - **Tachycardia
   - **Cardiomegaly
4. Diminished CO (unusual, only when decompensated)
   - Cool extremities
   - Prolonged capillary refill
   - Decreased pulse volume

Question 3

***Causes of Neonatal Heart failure

Answer 3

Neonates (4 categories):
1. ***LV outflow tract obstruction (MUST exclude)
- Coarctation / Interruption of aorta
- Critical aortic stenosis
- Aortic atresia (in Hypoplastic left heart syndrome)

2. Myocardial dysfunction
   - Transient myocardial ischaemia (babies born with perinatal asphyxia —> hypoxaemia, metabolic acidosis —> transient MI)
   - Myocarditis
   - Cardiomyopathies (usually present in older children)
3. Abnormalities of HR / rhythm
   - Supraventricular tachycardia (more common, ∵ accessory pathway (e.g. WPW))
   - Complete heart block (bradycardia, important to assess whether mother has SLE ∵ Anti-Ro, Anti-La Ab cross placenta —> cause destruction of conduction tissue)
4. Extra-cardiac causes
   - Systemic disturbance causing ventricular dysfunction
   —> Sepsis
   —> Asphyxia
   —> HypoCa
   - Anaemia (cause high output cardiac failure)

Question 4

Coarctation / Interruption of aorta

Answer 4

Coarctation of aorta:
Segment of aorta near **insertion of PDA narrowed
1. ↓ Perfusion of gut, kidney, lower limbs
2. **LV pressure overload
3. if PDA is patent (in neonates) —> lower limbs supplied by blood in pulmonary artery —> progressive closure of PDA after birth —> severe ↓ of flow to descending aorta —> gut, kidney, lower limbs
—> ***Prostaglandin E1, E2 (life saving)
—> Maintain PDA patency (reopen stenosed / closed PDA)

Interrupted aortic arch (in extreme coarctation):
- Ascending aorta同Descending aorta斷開
- Descending aorta totally dependent on PDA from Pulmonary artery

Question 5

Critical aortic stenosis

Answer 5

Thickened + Fused aortic cusps
- ***LV pressure overload + ↓ CO

Question 6

Aortic atresia (in Hypoplastic left heart syndrome)

Answer 6

• Extreme case of LV outflow obstruction
• Atresia of Aortic valve (usually coupled with Mitral atresia + LV Hypoplasia)
• Pulmonary venous blood —> Patent **Foramen ovale —> RA —> RV —> Pulmonary trunk —> Lungs + Aorta (through **persistent PDA)
• ***Right heart supporting both pulmonary + systemic circulation

Question 7

P/E in children

Answer 7

Importance of **Pulse examination
- Upper + **Femoral pulse in particular
- ***Pulse volume
- Discrepancies between Upper / Lower limb pulses —> Coarctation of aorta, Interrupted aortic arch
- Diminished Upper + Lower limb pulses —> Aortic atresia, Hypoplastic left heart syndrome

Question 8

***Causes of Infants Heart failure (2-3 months)

Answer 8

Large L-to-R shunts (***Volume overload)
1. VSD
2. AVSD
3. Persistent DA

Pathophysiology:
Later onset of symptoms (as compared to LV outflow obstructive lesions)
—> ∵ Pulmonary vascular resistance ↓ from birth to adult level (~6-8 weeks)
—> ↓ Pulmonary arterial pressure + ↑ Bloodflow from L to R through septal defects
—> **↑ Pulmonary blood flow
—> ↑ Pulmonary venous return
—> **Volume overloading of LA + LV (except ASD (also L to R shunt))
—> Symptom of heart failure

Signs of CXR:
1. Cardiomegaly
2. Pulmonary plethora

Question 9

VSD

Answer 9

Pressure difference:
- LV —> RV —> Pulmonary circulation —> Pulmonary arterial congestion —> LA dilation —> ***LV dilation

Signs:
1. **Displaced cardiac apex / Cardiomegaly (strong LV impulse)
2. **Respiratory distress (∵ flooding of lung)

Question 10

AVSD

Answer 10

Entire AV septum (Central canal) devoid of partition
1. LA —> RA
2. LV —> RV
—> Pulmonary arteries
3. Only 1 single common AV valve that guard orifice between Atrium and Ventricle

AVSD particularly common in ***Down syndrome

Question 11

PDA (Persistent Arterial Duct)

Answer 11

Ductus usually close 10 to 15 hours after delivery, complete within 2-3 weeks (UpToDate)

Aorta —> Pulmonary artery —> Congestion —> LA dilation —> LV dilation

Question 12

ASD

Answer 12

Shunting from LA —> RA
—> ↑ flow through Tricuspid valve during diastole
—> Volume overload of **RA + **RV (vs other L to R shunt)

Uncommon cause of heart failure in infancy / childhood (compared to L to R shunt)

Signs:
1. Left Parasternal heave (RV dilation)

Question 13

Causes of Older children Heart failure

Answer 13

1. Myocardial disease (i.e. Acquired)
   - Myocarditis (∵ viral infections)
   - Cardiomyopathy (primary, secondary) (∵ mutation of sarcomeric proteins e.g. actin, myosin, troponin)
2. Unoperated structural heart defects
3. Certain repaired / palliated congenital heart defects (∵ Ventricular dysfunction +/- Valvular insufficiency)

Question 14

Management of Paediatric Heart failure

Answer 14

1. Identification of cause + precipitating factors (e.g. infection, metabolic disturbance e.g. thyrotoxicosis, anaemia)
2. Tackling of precipitating factors
3. General supportive management (e.g. optimisation of ***nutrition, ↑ caloric intake)
4. **Medical therapy of heart failure
   - ACEI (↓ afterload) (2nd line (SpC Paed))
   - Carvediol (used in dilated cardiomyopathy)
   - **Diuretics (↓ preload, fluid retention ∵ activation of RAAS system)
   - Digoxin
5. Treatment of underlying cause
   - **Surgical / **Catheter intervention
6. Mechanical circulatory support / Heart transplantation
   - **Extracorporeal membrane oxygenation (for transient cardiac support while wait for myocardium recovers)
   - **Ventricular assist device
   —> all are temporary measures —> ultimate: Heart transplantation

(NOT give O2, since O2 will dilate pulmonary vessels causing more L-R shunt! (SpC Paed))

Question 15

Management of Severe LV outflow obstruction

Answer 15

1. ***PGE1, PGE2 for initial stabilisation (maintain DA patency in Coarctation / Interruption to ensure enough systemic bloodflow)
2. Corrective surgery / Catheter intervention
   - tackle stenosis / reanastomose aortic arch

Question 16

Management of Large L to R shunts

Answer 16

Surgical closure of VSD + PDA
- Patch repair
- Catheter-delivered device
- Ductal ligation of PDA

Question 17

Cyanotic congenital heart disease

Answer 17

Cyanosis:
- Central vs Peripheral

• Apparent in infants / children with 3-5 g/dL of DeoxyHb (note the confounding influence of anaemia / polycythaemia)
• “Traumatic” cyanosis —> difficult labour —> venous congestion (mimic cyanosis)
• Need to confirm with ***Pulse oximetry (SaO2)

Cause of Central cyanosis:
1. ***Cyanotic congenital heart disease

2. ***Respiratory tract disease
   - Airway obstruction
   - Pulmonary parenchymal disease (congenital pneumonia, meconium aspiration syndrome)
   - Diaphragmatic hernia
3. CNS (less common)
   - Hypoventilation (∵ Brain damage / Drugs e.g. narcotics)
4. Congenital methaemoglobinaemia (rare)

Question 18

Differentiate Cardiac / Respiratory causes of Cyanosis

Answer 18

1. Factors predisposing to respiratory disease
   - maternal infections —> **congenital pneumonia
   - **meconium-stained liquor (meconium aspiration syndrome)
2. ***Respiratory distress
   - Tachypnea
   - Insucking of chest wall
   - Presence of nostril flaring
   - Grunting
3. CXR
   - Respiratory causes: Abnormalities of lung parenchyma
   - Cardiac causes: ***Oligemic lung field (∵ ↓ pulmonary bloodflow)
4. **Hyperoxic test / **Nitrogen washout test (no longer used —> now replaced by echocardiogram)
   - >90% O2 for >10 min
   —> Normal: PaO2 >50 kPa
   —> Lung disease: PaO2 >15 kPa (PaO2泵得起)
   —> Cyanotic heart disease: PaO2 remains unchanged / slight ↑ (<1.5 kPa) (PaO2泵唔起)

Question 19

Cardiac causes of Central cyanosis

Answer 19

Pathophysiology:
1. Systemic venous blood bypass lung back to systemic circulation
- **R to L shunts
- **Transposition haemodynamics

2. Reduced pulmonary flow for gas exchange (in the majority)
   - **Pulmonary outflow obstruction
   - **Pulmonary atresia
3. ***Common-mixing conditions (oxygenated mixed with deoxygenated blood —> systemic oxygen desaturation)
   - Atrial, Ventricular, Arterial levels

Question 20

***Categories of Cyanotic congenital heart disease

Answer 20

1. ***R to L shunts with RV outflow obstruction
   - Tetralogy of Fallot
   - Tetralogy of Fallot with Pulmonary atresia (PA with VSD)
   - Pulmonary atresia with Intact ventricular septum
2. ***Transposition of Great arteries
3. ***Common-mixing conditions (oxygenated mixed with deoxygenated blood —> systemic oxygen desaturation)
   - Arterial: Truncus arteriosus
   - Ventricular: Univentricular hearts
   - Atrial: Total anomalous pulmonary venous return
4. Ebstein anomaly

Question 21

1. R to L shunts: ***Tetralogy of Fallot

Answer 21

1. ***Large VSD (no pansystolic murmur heard (SpC OG))
2. ***Pulmonary outflow obstruction (ejection systolic murmur)
   - ∵ infundibular stenosis
   - associated with Pulmonary stenosis, Branch pulmonary arterial stenosis
3. ***RVH
4. ***Overriding aorta
   - override ventricular septum (receives blood from RV + LV)
   - deoxygenated blood goes from VSD —> overriding aorta —> deoxygenated aorta —> Central cyanosis

CXR:
1. Oligemic lung fields (∵ ↓ pulmonary vascular markings)
2. Boot-shaped heart (∵ RVH —> uptilting of cardiac apex)

***Hypercyanotic spell (medical emergency)
- intermittent episodes of severe desaturation
—> spasm of muscles that guard RV outflow
—> even less blood to lungs / more to aorta
—> intensive O2 desaturation
—> may lose consciousness / convulsion

Management:
Total surgical correction at ~6-12 months
- Patch closure of VSD
- Resection of muscles guarding RV outflow
- Patch enlarge RV outflow (may need to cut pulmonary valve if stenosis / hypoplasia)

Question 22

1. R to L shunts: Tetralogy of Fallot with Pulmonary atresia (PA with VSD)

Answer 22

Pulmonary outflow obstruction —> Pulmonary atresia

Pulmonary bloodflow supplied by ***PDA
—> closure of PDA
—> baby even more cyanotic

**Ductal-dependent **pulmonary circulation (vs Ductal-dependent systemic circulation)
—> Prostaglandin E1, E2 very important

Management:
1. Systemic-pulmonary arterial shunt (e.g. modified Blalock-Taussig shunt)
- ***Subclavian artery to Pulmonary artery
- replace function of PDA

2. Unifocalisation of aortopulmonary collaterals (i.e. Collaterals growing from descending aorta)
3. Total surgical repair in early childhood (2-3 yo)
   - implantation of artificial valve conduit from RV to pulmonary artery
   - closure of VSD
   —> children can become completely acyanotic now

Question 23

1. R to L shunts: Pulmonary atresia with Intact ventricular septum

Answer 23

Pulmonary Valve atresia / Muscular atresia
- blood through patent Foramen ovale (i.e. ASD) (from RA —> LA —> LV —> Aorta —> ***PDA —> pulmonary circulation)

• Duct-dependent pulmonary circulation —> PDA important!

Management:
1. **PGE1, PGE2 for initial stabilisation
2. **Surgical systemic-to-pulmonary arterial shunt
3. Catheter / Surgical opening of **atretic pulmonary outflow
- Radiofrequency-assisted **pulmonary valvotomy

Question 24

2. Transposition of Great arteries

Answer 24

RV to Aorta, LV to Pulmonary trunk
- ***Parallel systemic + pulmonary circulation (not in series)
- High pulmonary blood flow —> Heart failure

2 site of potential mixing:
1. **PDA
2. **Patent Foramen ovale (ASD)
—> need to maintain these 2 openings

Management:
Temporary
1. **PGE1, PGE2
2. **Balloon atrial septostomy (tear open atrial septum)

Surgical
3. **Arterial switch operation (anatomic correction, **surgery of choice)
- rmb Coronary arteries also need transposition!

4. ***Venous switch operation (physiologic correction, obsolete) (Mustard, Senning operations)
   - IVC to LA
   - PV to RA
   - problem:
   —> at risk of atrial arrhythmia
   —> RV now act as systemic ventricle (deteriorate in function, after 40 may suffer from RV dysfunction, Tricuspid regurgitation TR)

Question 25

3. Common-mixing conditions: Truncus arteriosus

Answer 25

• No division of Aorta and Pulmonary artery
• VSD
• High pulmonary blood flow

S/S:
1. Cyanosis (usually mild ∵ high pulmonary blood flow to get oxygen)
2. Heart failure (predominant, ∵ pulmonary vascular resistance ↓ after birth —> high pulmonary blood flow —> pulmonary arterial congestion —> volume overload of LV)

Question 26

3. Common-mixing conditions: Univentricular hearts

Answer 26

Large single functional ventricle

2 types:
1. 2 arteries
2. 1 single large aorta with Pulmonary atresia

Staged management:
1. Shunt insertion if pulmonary outflow obstruction is severe
2. **Fontan-type procedure (when older)
- direct shunt IVC + SVC blood to lungs (bypass RV)
- the single ventricle now only support aorta
- problem: high CVP —> **congested liver, gut —> ***liver cirrhosis, protein-losing enteropathy

Question 27

3. Common-mixing conditions: Total anomalous pulmonary venous return

Answer 27

Mixing at atrial level

1. Supracardiac
   - Pulmonary veins —> SVC —> RA
2. Cardiac
   - Pulmonary veins —> RA
3. Infracardiac
   - Pulmonary veins —> join together —> descending vein —> Portal vein —> RA

LA can only receive blood from **Patent foramen ovale / **ASD

Question 28

4. Ebstein anomaly

Answer 28

**Downward displacement of Tricuspid valve
—> Tricuspid regurgitation from RV to RA
—> **Atrialisation of RV (thinning of myocardial wall)

Reason of cyanosis:
- ASD
—> TR
—> blood from RV back to RA
—> RA —> LA —> LV

CXR:
1. **Giant RA (∵ **severe TR + ***atrialisation of RV)

Question 29

SpC Revision: Functional murmur (Flow murmur)

Answer 29

• Soft
• Ejection systolic (Never diastolic)
• No thrills
• No cardiac signs / symptoms

Question 30

Chest pain

Answer 30

1. Cardiac causes
   - LVOT obstruction (AS, HCM, Cardiomyopathy
   - Coronary arteries (Kawasaki)
   - Pericarditis
   - Arrhythmia (Ectopics, SVT)
   - MVP
2. Other causes (e.g. Costochondritis)

Question 31

Palpitations

Answer 31

Subjective sensation of cardiac contractions
1. Benign
2. Arrhythmia
3. Hyperdynamic circulation
- Anaemia
- Thyrotoxicosis
- Emotional

Distinguish Fast vs Slow palpitations

Question 32

SpC Paed: Paediatric hypertension

Answer 32

Children <13 yo:
- Based on BP percentiles for ***sex, age, height
- Normal: SBP, DBP <90th percentile
- Elevated BP (Pre-HT): SBP / DBP 90-95th percentile
- Stage 1 HT: SBP / DBP >=95th percentile
- Stage 2 HT: SBP / DBP >=95th percentile + 12mmHg

Adolescents >=13 yo:
- Definition same as adult

Question 33

Common presentations of cardiac problems (SpC Paed E-learning: Common Cardiac Problems)

Answer 33

1. Heart murmur
2. Heart failure
3. Cyanosis
4. Chest pain
5. Palpitations
6. Syncope

Question 34

History taking in Cardiac problems

Answer 34

Chest pain:
- Very low risk: Localised, A few seconds, Pin-prick like
- High risk: History of heart disease, Kawasaki disease, Related to exercise, Associated syncope

Syncope:
- Very low risk: Typical Vasovagal
- High risk (i.e. Cardiac syncope): History of heart disease, Related to exercise, FH of SCD, Triggered by emotion / loud noise, Associated chest pain, Seizure, Sudden onset, No prodromal, Injuries

Palpitations:
- Ask patient to finger tap the rhythm
- Heavy, forceful beats
- Rapid / Slow
- Regular / Irregular
- Pauses
- Intermittent / Persistent
- Associated symptoms: dizziness, syncope, chest pain, SOB, N+V, pallor, sweating, cyanosis

Non-specific symptoms:
- Myocarditis
- Pericarditis
- Pericardial effusion
—> Tiredness, Vomiting, Epigastric discomfort (∵ acute liver congestion)

Question 35

Febrile cardiac illness

Answer 35

1. Kawasaki disease
2. Infective endocarditis
3. Pericarditis

Question 36

ECG abnormalities

Answer 36

1. WPW
2. AVRT / AVNRT
3. Inherited ventricular arrhythmias (Autosomal dominant)
   - Long QT syndrome
   - Short QT syndrome
   - Catecholaminergic polymorphic VT
   - Brugada syndrome (ST elevation + T inversion in V1-3, RBBB (persistent / intermittent))

Measurement of QT interval:
- Use Lead 2, V5, V6
- Bazett’s formula: QTc = QT / √RR interval
- <=0.45 in male, <=0.46 in female

Question 37

Short QT syndrome

Answer 37

Normal population: Prevalence of QTc 340ms <=0.5%

Suspect SQTS:
- QTc <330 in male, <340 in female

ECG:
- Tall + peaked T wave