Except Tetralogy of Fallot, the others are acyanotic heart diseases. The cyanotic spells and loss of consciousness are due to spasm of the infundibular septum, which acutely worsens the right ventricular outflow tract obstruction. The given murmur is due to a ventricular septal defect.

Normal QT interval in a 6 months old baby is < 0.44 seconds. A duration exceeding this value is referred to as QT interval prolongation, which is associated with some important congenital syndromes that include Brugada syndrome which is characterized by vasovagal syncope and sudden cardiac death, Jervell and Lange-Nielsen syndrome which is associated with congenital deafness, Andersen syndrome which is marked by bone deformities, and Timothy syndrome with associated heart disease and immunodeficiency. Romano-Ward syndrome is the commonest cause of congenital QT prolongation with no associated extra-cardiac manifestations. Lown-Ganong-Levine syndrome is characterized by a shortened PR interval and a normal QRS duration.

The most common congenital cyanotic heart disease and the most common cause of blue baby syndrome, Tetralogy of Fallot shows four cardiac malformations occurring together. These are ventricular septal defect (VSD), pulmonary stenosis (right ventricular outflow obstruction), overriding aorta (degree of which is variable), and right ventricular hypertrophy. The primary determinant of severity of disease is the degree of pulmonary stenosis. Tetralogy of Fallot is seen in 3-6 per 10,000 births and is responsible for 5-7% congenital heart defects, with slightly higher incidence in males. It has also been associated with chromosome 22 deletions and DiGeorge syndrome. It gives rise to right-to-left shunt leading to poor oxygenation of blood. Primary symptom is low oxygen saturation in the blood with or without cyanosis at birth of within first year of life. Affected children ay develop acute severe cyanosis or ‘tet spells’ (sudden, marked increase in cyanosis, with syncope, and may result in hypoxic brain injury and death). Other symptoms include heart murmur, failure to gain weight, poor development, clubbing, dyspnoea on exertion and polycythaemia. Chest X-ray reveals characteristic coeur-en-sabot (boot-shaped) appearance of the heart. Treatment consists of immediate care for cyanotic spells and Blalock–Taussig shunt (BT shunt) followed by corrective surgery.

The murmur of tricuspid valve regurgitation is typically a high-pitched, blowing, holosystolic, plateau, nonradiating murmur best heard at the lower left sternal border. The intensity is variable, but tends to increase during inspiration (Carvallo’s sign), with passive leg raising, after a post-extrasystole pause, and following amyl nitrite inhalation. The intensity of the murmur tends to correlate positively with the severity of regurgitation. Right ventricular enlargement may displace the location of the murmur leftward. Right ventricular failure may abolish respiratory variation. When tricuspid regurgitation is caused by pulmonary hypertension, a pulmonic ejection click may be audible. Severe tricuspid regurgitation is commonly accompanied by a third heart sound emanating from the right ventricle and best heard at the lower left sternal border. Severe tricuspid regurgitation typically produces an accentuated jugular cv wave and may produce hepatic congestion with a pulsatile liver.The auscultatory findings associated with ventricular septal defect are variable, depending on a variety of morphologic and hemodynamic considerations. The systolic murmur associated with a Roger’s-type ventricular septal defect (regurgitant jet flows directly into the right ventricular outflow tract) in patients with low pulmonary vascular resistance is a low to medium pitched, holosystolic murmur with midsystolic accentuation. The intensity of the murmur is typically grade 3 or higher.Patent ductus arteriosus produces a continuous murmur in patients with normal pulmonary vascular resistance.

A 3-dimensional transoesophageal echocardiography (3D TEE) provides direct visualization of the entire PFO anatomy and surrounding structures. It allows more accurate diagnosis.

The murmur and thrill indicate a right outflow tract murmur, coupled with the right ventricular heave suggests right ventricular hypertrophy. The VSD would not have been amenable to surgery due to the child’s size/weight and so instead would have been palliated with a PA band. As the child grows, this band progressively restricts pulmonary blood flow until the left to right shunt has reversed. Then it is time for the band to be removed and the VSD to be closed.Pulmonary atresia is a cyanotic condition, which may be palliated with an arterial duct stent. This answer is incorrect as the stent placement would not require a midline sternotomy and would give a continuous machinery type murmur. Pulmonary stenosis with PDA ligation is incorrect. The murmur, thrill, and heave all match a pulmonary stenosis but in the absence of an additional shunt lesion the child would not be cyanosed.

Blalock-Thomas-Taussig shunt is a surgical procedure done to increase pulmonary blood flow in cases like pulmonary atresia and results in a continuous murmur.The type of murmur which is heard during the systole and remains continuous till the second heart sound is known as a continuous murmur. This murmur is often intense and considered rough. It can also be accompanied by quivering. There are numerous causes of a continuous murmur that differ depending on the location and components of this murmur. It is caused by the shunting of blood from a high-pressure circulation to a low-pressure circulation. Pathological causes of a continuous murmur include patent ductus arteriosus, aortopulmonary window, AV malformation, coarctation of aorta, any acquired trauma, and iatrogenic cause like interventional or surgical procedures.

ASD is an acyanotic congenital heart disease, characterized by the failure of the interatrial septum to form completely, which results in the mixing of left and right-sided blood. There are various types of ASD, some of them are ostium primum septal defect and patent foramen ovale. Clinical findings associated with ASD are a systolic ejection murmur, fixed splitting of second heart sound, prolonged PR interval, both left and right axis deviation (primum and secundum ASD, respectively). The most common finding is an incomplete right bundle branch block.

The most probable diagnosis for the patient in question is atrioventricular nodal re-entrant tachycardia (AVNRT).The presenting features of the patient are suggestive of supraventricular tachycardia (SVT). The most common form of SVT in children over 8 years old is atrioventricular nodal re-entrant tachycardia. It occurs as a result of an additional electrical circuit in or near the AV node itself.Other options:- Atrial Flutter: is a form of re-entry tachycardia within the atria which then becomes unsynchronised with the ventricles, which is not the case here. Furthermore, it is most common in babies and children with congenital heart disease.- Atrial tachycardia: is a condition where an area of atrium takes over the pacemaker activity of the heart. However, it is relatively uncommon.- Atrioventricular re-entrant tachycardia (AVRT): occurs due to an accessory electrical pathway between the atria and ventricles forming a re-entry circuit. This is the most common cause of SVT in children < 8 years old. One of the specific diagnoses of AVRT is Wolff-Parkinson-White syndrome. However, WPW syndrome is much rarer than AVNRT.- Premature atrial contractions (PACs): are very common in normal, healthy children and adolescents. Occasionally, they can give rise to the feeling of a 'skipped beat'. Fortunately, they are rarely associated with any significant underlying pathology or need to be treated.

Administration of IV prostaglandin/PGE1 (e.g., alprostadil) is indicated in ductal-dependent CHDs until surgery can be performedMechanism: prostaglandin prevents the ductus arteriosus from closing → creates intentional shunt to allow mixing of deoxygenated with oxygenated blood.

The heart is the first organ to form and become functional, emphasizing the importance of transport of material to and from the developing infant. It originates about day 18 or 19 from the mesoderm and begins beating and pumping blood about day 21 or 22. It forms from the cardiogenic region near the head and is visible as a prominent heart bulge on the surface of the embryo. Originally, it consists of a pair of strands called cardiogenic cords that quickly form a hollow lumen and are referred to as endocardial tubes. These then fuse into a single heart tube and differentiate into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22. The primitive heart begins to form an S shape within the pericardium between days 23 and 28. The internal septa begin to form about day 28, separating the heart into the atria and ventricles, although the foramen ovale persists until shortly after birth. Between weeks five and eight, the atrioventricular valves form. The semilunar valves form between weeks five and nine.

Coarctation of the aorta is one of the serious forms of congenital heart diseases Occurring in about 1 in 2,500 births. It is characterized by a congenitally narrowed proximal thoracic aorta. Coarctation can occur in isolation but can accompany other cardiac lesions, including a bicuspid aortic valve in 70% of the cases and berry aneurysms in 10% of the cases. Coarctation of the aorta is commonly found in association with Turner’s syndrome, Edward’s syndrome, and Patau syndrome.

Tetralogy of Fallot usually is diagnosed after a baby is born, often after the infant has an episode of turning blue during crying or feeding (a tet spell). A loud heart murmur is usually present.An atrial septal defect is present at birth, but many babies do not have any signs or symptoms.Coarctation of the aorta is usually diagnosed after the baby is born. How early in life the defect is diagnosed usually depends on how mild or severe the symptoms are. New-born screening using pulse oximetry during the first few days of life may or may not detect coarctation of the aorta.In babies with a more serious condition, early signs usually include:pale skinirritabilityheavy sweatingdifficulty breathingBabies born with pulmonary atresia will show symptoms at birth or very soon afterwards. They may be cyanotic. However, it is not uncommon for a heart murmur to be absent right at birth.

Infective endocarditis (IE) is an acute infective pathology of the endocardium secondary to some underlying cardiac pathology like VSD and TOF. Most commonly, it is bacterial in origin, caused by staphylococcus aureus in the majority of cases. Clinical features include fever, arthralgias, weight loss, anorexia, new-onset, or changing existing murmur. Skin manifestations include Osler’s nodes, Janeway lesions, splinter haemorrhages, and clubbing. Roth spots are conjunctival haemorrhages found in IE. Beau’s lines are not found in IE.

Congenital LQTS arises from mutations in genes that code for ion channels within myocytes.These mutations all cause ventricular action potentials to be prolonged, resulting in a lengthened QT interval on ECG. The congenital long-QT syndrome (LQTS) is a life-threatening cardiac arrhythmia syndrome that represents a leading cause of sudden death in the young. LQTS is typically characterized by a prolongation of the QT interval on the ECG and by the occurrence of syncope or cardiac arrest, mainly precipitated by emotional or physical stress.LQTS type 1Most common type of congenital LQTSDefect: loss of function mutation on the KCNQ1 gene located on chromosome 11p → defective slow delayed rectifier voltage-gated potassium channelSubtypesJervell and Lange-Nielsen syndrome Associated with congenital deafnessAutosomal recessiveAssociated with ventricular tachyarrhythmiasRomano-Ward syndrome No associated deafnessAutosomal dominantAssociated with ventricular tachyarrhythmias

The most probable diagnosis based on the clinical presentation is myocarditis secondary to Coxsackie virus infection.Myocarditis is an important cause of acquired heart failure. The other infective causes of myocarditis are influenza and adenoviruses, and bacterial causes as seen with Borrelia burgdorferi (Lyme disease). Rheumatic fever is unlikely if the ASO titres are within normal limits. While pancarditis may occur as part of Kawasaki disease| the patient is unlikely to present in failure.

The most probable diagnosis for the clinical scenario provided is coarctation of the aorta. It contributes to about 4% of all congenital heart disease and is more prominent in males than females.It is associated with trisomy 13 and 18, Turner syndrome, valproate toxicity as well as ventricular septal defects, persistent ductus arteriosus, mitral valve abnormalities and berry aneurysms of the circle of Willis. Other associated cardiac abnormalities include a bicuspid aortic valve (50%), mitral valve disease, aortic regurgitation (20%) and subaortic stenosis. Ninety-eight per cent of coarctations occur at the level of the pulmonary artery after the subclavian artery. It is for this reason that, on observation, the proximal blood pressure varies compared with the distal blood pressure. The blood pressure in the right arm is often higher than that in the left arm. Clinically, these children present with hypertension, prominent carotid pulses, radio-femoral delay, left ventricular hypertrophy and an ejection systolic murmur maximum over the posterior left interscapular area. An apical click over the aortic valve may be heard. Coarctation of the aorta may be simple (post-ductal), or complex (pre-ductal or with a septal defect), and may be associated with aortic stenosis, transposition of the great arteries or a bicuspid aortic valve. The ECG and chest radiograph may be normal. However, as the child enters the first decade, evidence of cardiomegaly, congestive heart failure, post-stenotic dilatation with a dilated subclavian artery and rib notching may be noticed. The ECG may show right ventricular hypertrophy, left ventricular hypertrophy in infancy and right axis deviation. Complications of coarctation of the aorta include left ventricular failure, cerebral haemorrhage, aortic dissection, renal vascular stenosis and infective endocarditis. This condition may result in death due to an aortic aneurysm or rupture in the third or fourth decade of life. It may also cause premature ischaemic heart disease as a result of hypertension. If left untreated, 20% of individuals die before 20 years of age and 80% before 50 years of age. Treatment options include surgical balloon dilatation or the grafting of a subclavian flap, and should surgical correction not normalise the blood pressure, further medical management is required.

Key Observations:

1. Cyanosis and Low Oxygen Saturation:
   • Central cyanosis indicates mixing of oxygenated and deoxygenated blood.
   • The aortic oxygen saturation is low (76%), indicating a significant amount of deoxygenated blood entering systemic circulation.
2. Pressure Analysis:
   • The right ventricle pressure is significantly elevated (110/6 mmHg), suggesting an obstructive lesion like pulmonary stenosis or an increased volume load due to a shunt.
   • The pulmonary artery pressure is low (20/5 mmHg) despite the high right ventricular pressure, suggesting an obstruction to flow from the right ventricle to the pulmonary artery, consistent with pulmonary stenosis.
3. Oxygen Saturation Analysis:
   • There is a notable drop in oxygen saturation from the left ventricle (87%) to the aorta (76%), indicating a mixture of oxygenated and deoxygenated blood in the systemic circulation, suggestive of a right-to-left shunt.

Differential Diagnosis:

1. Pulmonary Stenosis:
   • Supported by elevated right ventricular pressure and low pulmonary artery pressure.
2. Ventricular Septal Defect (VSD):
   • Would typically cause left-to-right shunting, leading to increased pulmonary blood flow and higher oxygen saturation in the right ventricle and pulmonary artery, which is not observed here.
3. Over-riding Aorta:
   • Seen in conditions like Tetralogy of Fallot where the aorta receives blood from both the right and left ventricles, leading to mixed oxygen saturation.
4. Right-to-Left Shunt:
   • The data indicates a right-to-left shunt, with low oxygen saturation in the aorta, suggesting that deoxygenated blood is bypassing the lungs and entering systemic circulation.
5. Aortic Stenosis:
   • Typically presents with high left ventricular pressure and a pressure gradient between the left ventricle and the aorta, which is not observed here.

Conclusion:

Given the data, the most likely abnormalities present in this patient are Pulmonary Stenosis, Right-to-Left Shunt, and Over-riding Aorta. These findings are consistent with a condition like Tetralogy of Fallot, where all these features are present.

PDA is particularly common in premature babies and it is managed by indomethacin administration. However, if PDA is not the only defect, prostaglandin E1 can be administered in order to keep the ductus open until the surgery takes place.

The most possible diagnosis is SVT. The boy is suffering from hemodynamic instability, as indicated by his cold extremities. DC cardioversion is the treatment of choice.

Key observations in the results:

1. Oxygen Saturation Step-Up:
   • There is a significant step-up in oxygen saturation from the right ventricle (72%) to the pulmonary artery (86%). This suggests the presence of left-to-right shunting of blood.
2. Pressure Differences:
   • The pressure in the pulmonary artery is elevated (53/13 mmHg), indicating pulmonary hypertension.

Differential Diagnosis:

1. Patent Ductus Arteriosus (PDA):
   • PDA can cause increased pulmonary blood flow, leading to a step-up in oxygen saturation in the pulmonary artery. The pulmonary artery pressures can also be elevated due to increased blood flow.
2. Primary Pulmonary Hypertension:
   • Typically presents with elevated pulmonary pressures but does not usually show a step-up in oxygen saturation.
3. Pulmonary Stenosis:
   • Would result in elevated right ventricular pressure but would not explain the step-up in oxygen saturation.
4. Septum Primum Atrial Septal Defect (ASD):
   • Would result in a step-up in oxygen saturation from the right atrium to the right ventricle, not between the right ventricle and pulmonary artery.
5. Tetralogy of Fallot:
   • Characterized by right ventricular outflow tract obstruction, VSD, right ventricular hypertrophy, and an overriding aorta. Oxygen saturation levels would typically be lower in the systemic circulation.

Tetralogy of Fallot (TOF), a congenital heart defect, includes the following: right ventricular hypertrophy, ventricular septal defect, abnormal position of the aorta and pulmonary valve stenosis. The O2 saturation in patients with TOF is typically lower than normal and the condition usually becomes symptomatic early in life. A feature of the disease with high diagnostic significance is squatting or crouching of the infant as a compensatory mechanism to increase the peripheral vascular resistance.

Heart murmurs are common in healthy infants, children, and adolescents. Although most are not pathologic, a murmur may be the sole manifestation of serious heart disease. Historical elements that suggest pathology include family history of sudden cardiac death or congenital heart disease, in utero exposure to certain medications or alcohol, maternal diabetes mellitus, history of rheumatic fever or Kawasaki disease, and certain genetic disorders. Physical examination should focus on vital signs| age-appropriate exercise capacity| respiratory or gastrointestinal manifestations of congestive heart failure| and a thorough cardiovascular examination, including features of the murmur, assessment of peripheral perfusion, and auscultation over the heart valves. Red flags that increase the likelihood of a pathologic murmur include a holosystolic or diastolic murmur, grade 3 or higher murmur, harsh quality, an abnormal S2, maximal murmur intensity at the upper left sternal border, a systolic click, or increased intensity when the patient stands. Electrocardiography and chest radiography rarely assist in the diagnosis.

DiGeorge syndrome is one of the most common microdeletion syndromes, resulting from 22q11 deletion. 10% of the cases can be inherited in an autosomal dominant fashion, while 90% are sporadic. The syndrome is characterized by a deficiency of both T and B-cell lines along with hearing loss, 20-fold increased lifetime chances of developing schizophrenia, renal abnormalities, congenital heart defects, and a borderline or low IQ. Distinctive facial features include micrognathia, long face, short philtrum, cleft palate, and small teeth.

Ebstein’s anomaly is characterised by apical displacement and adherence of the septal and posterior leaflets of the tricuspid valve to the underlying myocardium, thereby displacing the functional tricuspid orifice apically and dividing the right ventricle into two portions. The main haemodynamic abnormality leading to symptoms is tricuspid valve incompetence. The clinical spectrum is broad| patients may be asymptomatic or experience right-sided heart failure, cyanosis, arrhythmias and sudden cardiac death (SCD). Many Ebstein’s anomaly patients have an interatrial communication (secundum atrial septal defect (ASD II) or patent foramen ovale). Other structural anomalies may also be present, including a bicuspid aortic valve (BAV), ventricular septal defect (VSD), and pulmonary stenosis. The morphology of the tricuspid valve in Ebstein anomaly, and consequently the clinical presentation, is highly variable. The tricuspid valve leaflets demonstrate variable degrees of failed delamination (separation of the valve tissue from the myocardium) with fibrous attachments to the right ventricular endocardium.The displacement of annular attachments of septal and posterior (inferior) leaflets into the right ventricle toward the apex and right ventricular outflow tract is the hallmark finding of Ebstein anomaly.

Infective endocarditis occurs when microorganisms enter the bloodstream and infect damaged endocardium or endothelial tissue. It most commonly involves the heart valves (either native or prosthetic), but it may also occur at the site of a septal defect, on the chordae tendineae, or on the mural endocardium. The prototypic lesion is at the site of the infection| the vegetation is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells. Endocarditis is classified as acute or subacute, which applies to the features and the progression of infection until diagnosis.The oral cavity, the skin, and the upper respiratory tract are the primary portals for Streptococcus viridans| Staphylococcus species| and Haemophilus aphrophilus, Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae (HACEK) organisms. Streptococcal and staphylococcal organisms are responsible for more than 80% of cases of bacterial IE.Streptococcus viridans accounts for approximately 50-60% of cases of subacute disease.While S aureus infection is the most common cause of IE, including Prosthetic valve endocarditis, acute IE, and IV Drug Abusers IE

The most common congenital cyanotic heart disease and the most common cause of blue baby syndrome, Tetralogy of Fallot shows four cardiac malformations occurring together. These are ventricular septal defect (VSD), pulmonary stenosis (right ventricular outflow obstruction), overriding aorta (degree of which is variable), and right ventricular hypertrophy. The primary determinant of severity of disease is the degree of pulmonary stenosis. Tetralogy of Fallot is seen in 3-6 per 10,000 births and is responsible for 5-7% congenital heart defects, with slightly higher incidence in males. It has also been associated with chromosome 22 deletions and DiGeorge syndrome. It gives rise to right-to-left shunt leading to poor oxygenation of blood. Primary symptom is low oxygen saturation in the blood with or without cyanosis at birth of within first year of life. Affected children ay develop acute severe cyanosis or ‘tet spells’ (sudden, marked increase in cyanosis, with syncope, and may result in hypoxic brain injury and death). Other symptoms include heart murmur, failure to gain weight, poor development, clubbing, dyspnoea on exertion and polycythaemia. Chest X-ray reveals characteristic coeur-en-sabot (boot-shaped) appearance of the heart. Treatment consists of immediate care for cyanotic spells and Blalock–Taussig shunt (BT shunt) followed by corrective surgery.

The most probable diagnosis in this patient would be pulmonary stenosis. Pulmonary Stenosis:Pulmonary valve murmurs are heard in the upper left sternal edge, associated with a thrill but no desaturation in the absence of an additional shunt. The ECG changes suggest right ventricular hypertrophy. Pulmonary stenosis is often well tolerated in childhood unless severe. These should be monitored with serial echocardiography, and balloon pulmonary valvoplasty should be considered once the pressure gradient reaches 64 mmHg.Other options:- Atrial septal defect: While atrial septal defects are associated with right ventricular outflow tract murmurs, they would not cause a thrill.- Patent ductus arteriosus: PDA murmurs can be audible in the left upper sternal edge, but would normally be audible in the left infraclavicular area and be continuous rather than ejection systolic. This left to right shunt would not cause desaturation but does cause left-sided volume loading and hence left-sided ECG changes.- Tetralogy of Fallot: Ventricular septal defect, overriding aorta, subpulmonary stenosis, and right ventricular hypertrophy. This would often cause a ULSE murmur with a thrill and RVH on ECG. However, this degree of obstruction would cause shunting from right to left, and this child would be desaturated.- Ventricular septal defect: Isolated ventricular septal defects cause pansystolic murmurs at the left lower sternal edge. They would have left-sided ECG changes and normal saturations (in the absence of pulmonary hypertension).

On electrocardiography (ECG), characteristic changes in patients with hypercalcemia include:Tall T wavesReduced QTProlonged and depressed STArrhythmiaOther electrolyte disturbances:Hypokalaemia:Flat T wavesST depressionU waveAtrial and ventricular ectopicsVF and VTHyperkalaemia:Tall T wavesST- changesReduced QT intervalIncreased PR intervalSmaller or absent P wavesWidened QRS, broadening to VFHypocalcaemia:Prolonged QTProlonged STFlat or absent T wavesU waves

Torsade de pointes is an uncommon and distinctive form of polymorphic ventricular tachycardia (VT) characterized by a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line.Conditions associated with torsade include the following:Electrolyte abnormalities – Hypokalaemia, hypomagnesemia, hypocalcaemiaEndocrine disorders – Hypothyroidism, hyperparathyroidism, pheochromocytoma, hyperaldosteronism, hypoglycaemiaCardiac conditions – Myocardial ischemia, myocardial infarction, myocarditis, bradyarrhythmia, complete atrioventricular (AV) block, takotsubo cardiomyopathyIntracranial disorders – Subarachnoid haemorrhage, thalamic hematoma, cerebrovascular accident, encephalitis, head injuryNutritional disorders – Anorexia nervosa, starvation, liquid protein diets, gastroplasty and ileojejunal bypass, celiac diseaseRisk factors for torsade include the following:Congenital long QT syndromeFemale genderAcquired long QT syndrome (causes of which include medications and electrolyte disorders such as hypokalaemia and hypomagnesemia)BradycardiaBaseline electrocardiographic abnormalitiesRenal or liver failure