Paediatrics JC123: Heart Failure And Cyanosis In Children: Acyanotic And Cyanotic Congenital Heart Disease Flashcards
Concept of Heart failure
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
- Dysfunction of heart
- Pump dysfunction
- more common cause of heart failure in adult: IHD —> impaired contractile function of LV - ***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
Symptoms / Signs of Heart failure
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
- 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) - Compensatory mechanisms
- **Tachycardia
- **Cardiomegaly - Diminished CO (unusual, only when decompensated)
- Cool extremities
- Prolonged capillary refill
- Decreased pulse volume
***Causes of Neonatal Heart failure
Neonates (4 categories):
1. ***LV outflow tract obstruction (MUST exclude)
- Coarctation / Interruption of aorta
- Critical aortic stenosis
- Aortic atresia (in Hypoplastic left heart syndrome)
- Myocardial dysfunction
- Transient myocardial ischaemia (babies born with perinatal asphyxia —> hypoxaemia, metabolic acidosis —> transient MI)
- Myocarditis
- Cardiomyopathies (usually present in older children) - 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) - Extra-cardiac causes
- Systemic disturbance causing ventricular dysfunction
—> Sepsis
—> Asphyxia
—> HypoCa
- Anaemia (cause high output cardiac failure)
Coarctation / Interruption of aorta
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
Critical aortic stenosis
Thickened + Fused aortic cusps
- ***LV pressure overload + ↓ CO
Aortic atresia (in Hypoplastic left heart syndrome)
- 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
P/E in children
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
***Causes of Infants Heart failure (2-3 months)
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
VSD
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)
AVSD
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
PDA (Persistent Arterial Duct)
Ductus usually close 10 to 15 hours after delivery, complete within 2-3 weeks (UpToDate)
Aorta —> Pulmonary artery —> Congestion —> LA dilation —> LV dilation
ASD
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)
Causes of Older children Heart failure
- Myocardial disease (i.e. Acquired)
- Myocarditis (∵ viral infections)
- Cardiomyopathy (primary, secondary) (∵ mutation of sarcomeric proteins e.g. actin, myosin, troponin) - Unoperated structural heart defects
- Certain repaired / palliated congenital heart defects (∵ Ventricular dysfunction +/- Valvular insufficiency)
Management of Paediatric Heart failure
- Identification of cause + precipitating factors (e.g. infection, metabolic disturbance e.g. thyrotoxicosis, anaemia)
- Tackling of precipitating factors
- General supportive management (e.g. optimisation of ***nutrition, ↑ caloric intake)
-
**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 - Treatment of underlying cause
- **Surgical / **Catheter intervention - 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))
Management of Severe LV outflow obstruction
- ***PGE1, PGE2 for initial stabilisation (maintain DA patency in Coarctation / Interruption to ensure enough systemic bloodflow)
- Corrective surgery / Catheter intervention
- tackle stenosis / reanastomose aortic arch
Management of Large L to R shunts
Surgical closure of VSD + PDA
- Patch repair
- Catheter-delivered device
- Ductal ligation of PDA
Cyanotic congenital heart disease
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
- ***Respiratory tract disease
- Airway obstruction
- Pulmonary parenchymal disease (congenital pneumonia, meconium aspiration syndrome)
- Diaphragmatic hernia - CNS (less common)
- Hypoventilation (∵ Brain damage / Drugs e.g. narcotics) - Congenital methaemoglobinaemia (rare)
Differentiate Cardiac / Respiratory causes of Cyanosis
- Factors predisposing to respiratory disease
- maternal infections —> **congenital pneumonia
- **meconium-stained liquor (meconium aspiration syndrome) - ***Respiratory distress
- Tachypnea
- Insucking of chest wall
- Presence of nostril flaring
- Grunting - CXR
- Respiratory causes: Abnormalities of lung parenchyma
- Cardiac causes: ***Oligemic lung field (∵ ↓ pulmonary bloodflow) -
**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)
Cardiac causes of Central cyanosis
Pathophysiology:
1. Systemic venous blood bypass lung back to systemic circulation
- **R to L shunts
- **Transposition haemodynamics
- Reduced pulmonary flow for gas exchange (in the majority)
- **Pulmonary outflow obstruction
- **Pulmonary atresia - ***Common-mixing conditions (oxygenated mixed with deoxygenated blood —> systemic oxygen desaturation)
- Atrial, Ventricular, Arterial levels
***Categories of Cyanotic congenital heart disease
- ***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 - ***Transposition of Great arteries
- ***Common-mixing conditions (oxygenated mixed with deoxygenated blood —> systemic oxygen desaturation)
- Arterial: Truncus arteriosus
- Ventricular: Univentricular hearts
- Atrial: Total anomalous pulmonary venous return - Ebstein anomaly
- R to L shunts: ***Tetralogy of Fallot
- ***Large VSD (no pansystolic murmur heard (SpC OG))
- ***Pulmonary outflow obstruction (ejection systolic murmur)
- ∵ infundibular stenosis
- associated with Pulmonary stenosis, Branch pulmonary arterial stenosis - ***RVH
- ***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)
- R to L shunts: Tetralogy of Fallot with Pulmonary atresia (PA with VSD)
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
- Unifocalisation of aortopulmonary collaterals (i.e. Collaterals growing from descending aorta)
- 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
- R to L shunts: Pulmonary atresia with Intact ventricular septum
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
- Transposition of Great arteries
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!
- ***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)
- Common-mixing conditions: Truncus arteriosus
- 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)
- Common-mixing conditions: Univentricular hearts
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
- Common-mixing conditions: Total anomalous pulmonary venous return
Mixing at atrial level
- Supracardiac
- Pulmonary veins —> SVC —> RA - Cardiac
- Pulmonary veins —> RA - Infracardiac
- Pulmonary veins —> join together —> descending vein —> Portal vein —> RA
LA can only receive blood from **Patent foramen ovale / **ASD
- Ebstein anomaly
**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)
SpC Revision: Functional murmur (Flow murmur)
- Soft
- Ejection systolic (Never diastolic)
- No thrills
- No cardiac signs / symptoms
Chest pain
- Cardiac causes
- LVOT obstruction (AS, HCM, Cardiomyopathy
- Coronary arteries (Kawasaki)
- Pericarditis
- Arrhythmia (Ectopics, SVT)
- MVP - Other causes (e.g. Costochondritis)
Palpitations
Subjective sensation of cardiac contractions
1. Benign
2. Arrhythmia
3. Hyperdynamic circulation
- Anaemia
- Thyrotoxicosis
- Emotional
Distinguish Fast vs Slow palpitations
SpC Paed: Paediatric hypertension
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
Common presentations of cardiac problems (SpC Paed E-learning: Common Cardiac Problems)
- Heart murmur
- Heart failure
- Cyanosis
- Chest pain
- Palpitations
- Syncope
History taking in Cardiac problems
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)
Febrile cardiac illness
- Kawasaki disease
- Infective endocarditis
- Pericarditis
ECG abnormalities
- WPW
- AVRT / AVNRT
- 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
Short QT syndrome
Normal population: Prevalence of QTc 340ms <=0.5%
Suspect SQTS:
- QTc <330 in male, <340 in female
ECG:
- Tall + peaked T wave
