Pediatric Cardiology Course Notes 2010-2011

Course Overview and Anatomical Foundations of Pediatric Cardiology

This pediatric cardiology course, taught by Dr. John Senga L. for the 2010-2011 academic year, provides an exhaustive review of cardiologic pathologies in children. The course structure follows a specific progression starting with a segmental anatomical review and moving through functional signs, clinical examinations, and paraclinical tests. The primary pathologies discussed include both non-cyanotic and cyanotic congenital heart diseases, Acute Rheumatic Fever (RAA), and cardiac decompensation.

Anatomical assessment in pediatric cardiology must be evaluated at every level or "stage." The segmental anatomy of the right heart involves the flow from the venae cavae to the Right Atrium (OD), then to the Right Ventricle (VD), and finally into the Pulmonary Artery (AP). The left heart involves flow from the pulmonary veins to the Left Atrium (OG), then to the Left Ventricle (VG), and out through the Aorta (Ao). Evaluation of cardiac anomalies must account for obstacles to flow or anomalies in venous return (e.g., anomalies of the venae cavae) at each stage of this anatomy.

Clinical and Functional Signs in Pediatric Patients

Clinical identification of cardiac issues in children relies on specific functional signs. These include shortness of breath or dyspnea, recurrent respiratory infections, insufficient weight gain, and profuse sweating. Cyanosis is a critical marker, defined specifically as occurring when reduced hemoglobin ($Hb$) is greater than or equal to $5\,g/dl$ or when oxygen saturation is less than $80\%$.

Additional physical signs involve thoracic deformation, chest pain, and malaise during exertion. Heart sounds may exhibit anomalies such as murmurs (souffle) or a gallop rhythm. Peripheral pulses must be meticulously evaluated at the carotid, humeral, and femoral sites. Extremity anomalies, such as digital clubbing (hippocratism), are also significant indicators of chronic cardiac or respiratory distress.

Indispensable Paraclinical Examinations

A comprehensive diagnostic workup includes biological tests such as the Hemogram, inflammatory tests, troponin, and CPK levels. Thoracic Radiography (Rx Thorax) and various forms of electrocardiography—including standard ECG, Holter-ECG, Holter-Tensional, R-Test, and exercise stress tests—are fundamental. Echocardiography combined with color Doppler provides definitive structural imaging.

For complex cases, more advanced modalities are employed: diagnostic or interventional cardiac catheterization and angiography, ventilation-perfusion scintigraphy, Magnetic Resonance Imaging (MRI), and multidetector spiral CT scanners. Specialized studies such as endocavitary electrophysiology and isotopic studies are also utilized to determine specific functional or electrical cardiac anomalies.

Atrial Septal Defect (Communication Inter-Auriculaire - CIA)

The CIA accounts for approximately $8\%$ of all congenital heart diseases. It has a marked female predominance with a ratio of $2:1$. Prenatal diagnosis is noted as difficult and delicate. This defect can be part of the Holt-Oram Syndrome, which associates CIA with limb anomalies linked to a genetic localization on the 12th chromosome ($12q24$).

There are several anatomical types of CIA:

1. CIA Secundum: Located at the center of the septum in the region of the foramen ovale.
2. CIA Sinus Venosus: Located between the right pulmonary vein and the vena cava.
3. CIA Ostium Primum: Located in the lower part of the septum, often as part of an Atrioventricular Canal defect.
4. Unroofed Coronary Sinus: A rare defect located on the roof of the coronary sinus.

Physiologically, a CIA causes a left-to-right shunt dependent on the size of the defect and the compliance ratio between the two ventricles. After birth, if the compliance of the Right Ventricle (VD) is better than the Left Ventricle (VG), the shunt is left-to-right. Before birth, the shunt is right-to-left because pulmonary resistance ($RP$) is greater than systemic resistance ($RS$). While rare, Pulmonary Arterial Hypertension (HTAP) can complicate CIA, leading to shunt inversion known as Eisenmenger Syndrome. Bacterial endocarditis typically does not occur on a simple CIA. However, the dilation of the Right Atrium (OD) can cause arrhythmias like flutter, ectopic tachycardia, atrial extrasystoles, and, in adults, atrial fibrillation.

Clinically, CIA is often asymptomatic and discovered incidentally. Patients may rarely experience exertional dyspnea. Growth disorders only occur if associated with genetic or chromosomal anomalies. Physical signs include a functional pulmonary stenosis murmur ($2/6$ intensity) at the upper left sternal border and a fixed splitting of the second heart sound (B2) at the pulmonary foyer. Imaging may show Right Atrial (OD) dilation and Pulmonary Artery (AP) convexity. Treatment involves surgery under extracorporeal circulation (CEC) via sternotomy at puberty, or catheterization to place a prosthesis between ages $5$ and $6$. In a normal child, the ratio of pulmonary flow to systemic flow ($QP/QS$) is $1$.

Ventricular Septal Defect (Communication Interventriculaire - CIV)

CIV is the most common congenital heart disease, representing $25\text{-}30\%$ of cases. Prenatal diagnosis is possible. It is frequently associated with syndromes like fetal alcohol syndrome, Trisomy 21, and the microdeletion $22q1.1$. The pathology creates a left-to-right shunt (assuming no fixed HTAP), leading to pulmonary, Left Atrial (OG), and Left Ventricular (VG) overload. Small CIVs may undergo spontaneous closure.

Types of CIV include perimembranous, muscular (trabeculated), admission (sub-aortic), and sub-pulmonary (supracristal). The shunt magnitude depends on the defect size, the ratio of vascular resistances, and the presence of sub-pulmonary obstacles. Large, non-restrictive CIVs result in pressure equalization between ventricles, while restrictive CIVs maintain a high pressure difference between the VG and VD. Roger's Disease refers to a small CIV without functional signs that only requires monitoring. There is a risk of Osler's endocarditis. The combination of CIV and aortic insufficiency is known as the Laubry & Pezzy Syndrome.

Clinical signs include symptoms of cardiac decompensation: dyspnea, recurrent respiratory infections, poor weight gain, and profuse sweating. A physical exam reveals an intense systolic murmur at the left sternal border radiating in a "wagon wheel" pattern. Interestingly, the larger the CIV, the quieter the murmur may be. An apical diastolic murmur might indicate functional mitral stenosis due to OG/VG overload. Rx Thorax shows an increased cardiothoracic index (ICT), pulmonary hypervascularity, and convex arcs. ECG indicates hypertrophy of the Left Ventricle (HVG) and Left Atrium (HAG); Sokolow calculations ($Vs + SaV2$) exceeding $36$ suggest HVG, and values below $40$ for other metrics can indicate HAG. Treatment includes medical management with ACE inhibitors (IEC) and diuretics, surgery (complete repair or AP cerclage), or catheterization for rare cases.

Patent Ductus Arteriosus (Persistance du Canal Artériel - PCA)

PCA has a prevalence of $7\text{-}10\%$ in congenital heart disease, occurring in approximately $8$ out of $10,000$ newborns, with a female predominance of $2\text{-}3:1$. It is classical in cases of rubella embryopathy. The ductus arteriosus is a vascular channel connecting the Aorta to the Pulmonary Artery, essential for intrauterine life. Post-birth closure occurs in $88\%$ of infants by the 8th hour, triggered by the clamping of the umbilical cord (increasing systemic pressure) and the arrival of oxygen, which causes vasoconstriction of the ductal cells.

Physiopathology depends on the ductus size and the $RP/RS$ ratio. Symptoms include dyspnea, recurrent infections, sweating, and poor weight gain. A characteristic continuous "machinery" murmur is heard, with telesystolic reinforcement. Pulses are described as bounding or hyperpulsatile, with femoral pulses often appearing more ample than those in the upper limbs. Paraclinical signs include ICT increase and HAG/HVG on ECG. Treatment varies from medical (IEC, diuretics) to surgical, catheterization, or video-thoracoscopy.

In premature infants, a permeable Ductus Arteriosus can lead to severe complications: intraventricular or intrapulmonary hemorrhages in the first hours; necrotizing enterocolitis, renal failure, or aggravation of hyaline membrane disease (MMH) in the first days; and bronchopulmonary dysplasia in the first weeks. Medical treatment involves Indomethacin (which carries renal toxicity) or IV Ibuprofen ($10\,mg/kg$ then $5\,mg/kg/j$ for $2$ days). Surgical complications may include accidental ligation of the aorta, coarctation, or residual shunts.

Atrioventricular Canal (Canal Atrio-Ventriculaire - CAV)

The CAV is embryologically a structure between the primitive atrium and ventricle. As a pathology, it presents in two forms: Complete (CAVc) and Partial (CAVp). CAVc is the most frequent heart disease associated with Trisomy 21 ($50\%$ association).

1. CAVc ($20\%$ of cases): Includes CIA primum, admission CIV, and a mitral cleft, often with a single AV valve.
2. CAVp ($80\%$ of cases): Includes CIA primum and a mitral cleft.

Physiopathology involves facultative shunts ($VD \rightarrow OG$), mandatory shunts ($VD \rightarrow VG$ or $OG$), and homologous regurgitations ($VG \rightarrow OG$ or $VD \rightarrow OD$). Half of affected children die before age $1$. Symptoms include early cardiac failure, dyspnea, and pulmonary edema. Murmurs are often discrete, but heart sounds B1 and B2 are strong. ECG is characteristic: sinus rhythm, left anterior hemiblock (HAG), right anterior hemiblock (HAD), prolonged P-R interval, and a QRS axis at $-90^\circ \pm 30^\circ$ ("axis at the ceiling"). Treatment is medical (IEC, diuretics, nutritional support) and early surgery before obstructive pulmonary vascular disease develops. Digitalis is of little importance here. Note on cardiac output: $Output = Stroke Volume (VES) \times Heart Rate (FC)$; where $VES$ is determined by pre-load, contractility, and post-load.

Consequences of Left-to-Right Shunts and Coarctation of the Aorta

Left-to-Right (G-D) shunts result in additional blood flow to the pulmonary circulation. This leads to pulmonary hyperflow, media hypertrophy, and intima hyperplasia of the arterioles. This cascade increases the risk of HTAP, heart failure, and infections like bronchopneumonia, eventually progressing to obstructive pulmonary arteriolar disease.

Coarctation of the Aorta (CoAo) represents a Left Ventricular ejection obstacle, accounting for $6\%$ of heart diseases. It usually occurs at the aortic isthmus near the ductus arteriosus but can occur in the thoracic or abdominal aorta. It is often associated with bicuspid aortic valves, Turner Syndrome ($20\%$), perimembranous CIV, and Shone Syndrome (parachute mitral valve).

Clinically, CoAo is identified by a difference in pulse palpation between upper and lower extremities and left-sided heart failure. A systolic murmur is audible under the left scapula and in the back. Hypertension (HTA) is common; a blood pressure difference of $20\,mmHg$ between the right arm and legs is diagnostic. Rx Thorax may show rib erosions due to collateral circulation. Treatment is surgical (Crafoord operation or resection-anastomosis) or stent placement. Medical treatment is generally illusory for this condition.

Cyanotic Congenital Heart Diseases: Tetralogy of Fallot and TGV

Cyanotic diseases involve a right-to-left shunt, making them refractory to oxygen therapy. Tetralogy of Fallot is the most frequent cyanotic heart disease ($6\%$ of heart diseases) and is a conotruncal anomaly. It associates four features: a CIV (due to anterior malalignment of the conal septum), pulmonary stenosis, Right Ventricular Hypertrophy (HVD), and an overriding aorta (Aorte à cheval). If the pulmonary artery is completely blocked, it is termed Pulmonary Atresia with Operating Septum (APSO) or Intact Septum (APSI).

Clinical features of Fallot include cyanosis proportional to stenosis, exacerbated by crying or effort. Patients exhibit anoxic spells (which can lead to convulsions), squatting (to increase systemic resistance), and digital clubbing. A systolic stenosis murmur is present. Urgent treatment for anoxic spells involves volume replacement, Diazepam for tonic phases, and Propranolol (Avlocardyl/Inderal) for hypotonic phases. Surgery can be palliative (Blalock-Taussig shunt) or reparative.

Transposition of the Great Vessels (TGV) involves simple ventriculo-arterial discordance, accounting for $5\%$ of heart diseases, with a male Steiner predominance. The two circulations run in parallel. Survival depends on shunts (CIA or PCA) to allow mixing. Shunts usually flow $G \rightarrow D$ at the CIA and $D \rightarrow G$ at the PCA. Clinical signs include intense, refractory cyanosis immediately after birth with normal respiration (absent acidosis). Rx Thorax shows an "egg on a string" (ovoïde) heart shape. Treatment includes Prostaglandins (Pg) to keep the ductus open, Rashkind procedure (atrial septostomy), or restorative surgeries like the Switch (Arterial Switch), Rastelli, Mustard, or Senning procedures.

Anomalous Pulmonary Venous Returns (RVPAT and RVPAP) and Heart Position

Abnormal heart positions include:

• Situs Solitus: Normal position.
• Situs Inversus: Mirror image of normal with inverted viscera (liver, spleen).
• Levocardia: Heart point to the left (normal).
• Dextrocardia: Heart point to the right.
• Dextroposition: Entire heart shifted right.

Anomalous Pulmonary Venous Returns involve drainage of pulmonary veins (VP) to the right side of the heart.

• Total (RVPAT): Exclusive to neonates; requires emergency surgery or death occurs in $2\text{-}3$ weeks. Physiopathology: All venous blood drains to the OD. For survival, a right-to-left interatrial shunt is required. High venous stasis occurs. Rx Thorax shows a "figure-8" (snowmen) heart.
• Partial (RVPAP): Less severe, resembling a CIA. The most frequent involves the Left Superior Pulmonary Vein draining to the Innominate Vein (TVI) or Left Superior Vena Cava (VCSG).

Types of RVPAT include:

• Type I (Supracardiac): VP to TVI (Ia) or Azygos (Ib).
• Type II (Intracardiac): VP to Coronary Sinus (IIa) or directly to OD (IIb).
• Type III (Infracardiac): VP to Canal of Aranthius (IIIa) or VCI (IIIb).
• Type IV: Mixed forms.

Acute Rheumatic Fever (Rhumatisme Articulaire Aigu - RAA)

RAA is an autoimmune and inflammatory disease secondary to an infection by Group A Lancefield Beta-hemolytic Streptococcus. According to the WHO, $500$ people develop RAA annually, $60\%$ of whom develop cardiac damage. It is a leading cause of valvulopathy worldwide, with $15\,million$ currently living with rheumatic carditis.

Diagnosis uses the modified Jones Criteria:

• Major Criteria: Carditis, Polyarthritis, Chorea, Erythema Marginatum, Subcutaneous Nodules.
• Minor Criteria: Fever, polyarthralgia, elevated inflammatory markers (VS, CRP, Fibrinogen), history of scarlet fever, and ECG anomalies.
• Evidence of Strep infection is required: Throat swab, ASLO (>200\,Todds\,units), Antistreptodormase, or Antihyaluronidase.

Diagnostic confirmation requires $2$ major criteria OR $1$ major and $2$ minor. Polyarthritis is typically migratory, asymmetric, and affects large joints. Carditis primarily attacks the valves, with the mitral valve being the most frequent, followed by the aortic valve. Insufficiency is more common than stenosis. Sydenham's Chorea (St. Vitus Dance) involves CNS inflammation and presents with involuntary movements, speech difficulties, and lack of coordination. Erythemas include Erythema Marginatum of Besnier (pink macules on the trunk). Aschoff's subcutaneous nodules are small ($0.1\text{-}1\,cm$), firm, and found on extensor surfaces. The pathophysiology is based on molecular mimicry between Strep protein M (especially serotypes $1, 3, 5, 6, 18, 19,$ and $24$) and human tissues. Treatments include prophylactic antibiotics (primary, secondary, or tertiary), anti-inflammatories (NSAIDs or steroids), and valvuloplasty or replacement.

Management of Heart Failure (Décompensation Cardiaque)

Heart failure management is categorized by severity:

1. Early Heart Failure (tachypnea on effort, weight conserved):

• Digoxine: $150\text{ to }250\,\mu g/m^2$ twice daily.
• Lasix: $1\,mg/kg$ every other day.
• Potassium Gluconate: $1\,ml/kg$ every other day (adapted to ionogram).

1. Confirmed Heart Failure (permanent tachypnea, hepatomegaly, weight difficulty):

• Right failure: Digoxine ($150\text{-}250\,\mu g/m^2$ 2x/j), Lasix ($1\,mg/kg$ daily), and Aldactone ($30\text{-}75\,mg/m^2/j$).
• Left failure (VG failure or large G-D shunt): Digoxine ($150\text{-}250\,\mu g/m^2$ 2x/j), Lasix ($1\,mg/kg$), Enalapril ($30\text{-}75\,mcg/m^2/j$—avoid if obstruction exists), and fractionated enriched feeding.

1. Severe Heart Failure (respiratory distress, low output signs):

• Hospitalization.
• Lasix: $2\,mg/kg$.
• Enalapril: $30\text{-}75\,mcg/m^2/j$.
• Digoxine: $150\text{-}250\,\mu g/m^2$ three times daily.
• Beta-blockers: Carvedilol, Bisoprolol, Metoprolol.
• Oxygen or artificial ventilation.
• Maintain hemoglobin ($Hg$) > 10\,g/dl (or $15\,g/dl$ if G-D shunt is present).