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.

Congenital heart diseases such as complete atrioventricular septal defects are most likely to cause large left to right shunts leading to faltering growth due to chronic severe hypoxia, pulmonary oedema, and feeding problems. Isolated atrial septal defects or ventricular septal defects result in relatively smaller shunts. Pulmonary stenosis and bicuspid aortic valve do not cause chronic systemic hypoxia. People with these conditions are often asymptomatic and only show some symptoms with intense physical activity.

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.

Marfan syndrome is a disorder that affects the connective tissue found throughout the body, Marfan syndrome can affect many systems, often causing abnormalities in the heart, blood vessels, eyes, bones, and joints. The two primary features of Marfan syndrome are vision problems caused by a dislocated lens (ectopia lentis) in one or both eyes and aortic root disease, leading to aneurysmal dilatation, aortic regurgitation and dissection is the main cause of morbidity and mortality in Marfan syndrome.

Hyperkalaemia presents with high voltage (peaked) T waves on ECG. Other features on ECG include smaller p-waves and wider QRS complexes.

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.

Atrial septal defects may also occur in association with a variety of other congenital heart defects, or in new-borns that are relatively small or premature. The following conditions are associated with an atrial septal defect:Ebstein’s anomalyFoetal alcohol syndromeHolt-Oram syndromeDown syndromeEllis van Creveld syndromeLutembacher’s syndrome Ostium primum defects occur frequently in individuals with Down syndrome or Ellis van-Creveld syndrome.Holt-Oram syndrome characterized by an autosomal dominant pattern of inheritance and deformities of the upper limbs (most often, absent or hypoplastic radii) has been attributed to a single gene defect in TBX5Fragile X syndrome is characterized by moderate intellectual disability in affected males and mild intellectual disability in affected females. The physical features in affected males are variable and may not be obvious until puberty. These symptoms can include a large head, long face, prominent forehead and chin, protruding ears, loose joints and large testes. Other symptoms can include flat feet, frequent ear infections, low muscle tone, a long narrow face, high arched palate, dental problems, crossed eyes (strabismus) and heart problems including mitral valve prolapse.

Auscultatory findings of VSD vary with the size of the defect. Small VSDs typically produce murmurs ranging from a grade 1 to 2/6 high-pitched, short systolic murmur (due to tiny defects that actually close during late systole) to a grade 3 to 4/6 holosystolic murmur (with or without thrill) at the lower left sternal border| this murmur is usually audible within the first few days of life (see table Heart Murmur Intensity). The precordium is not hyperactive, and the 2nd heart sound (S2) is normally split and has normal intensity.Moderate to large VSDs produce a holosystolic murmur that is present by age 2 to 3 wk| S2 is usually narrowly split with an accentuated pulmonary component. An apical diastolic rumble (due to increased flow through the mitral valve) and findings of heart failure (e.g., tachypnoea, dyspnoea with feeding, failure to thrive, gallop, crackles, hepatomegaly) may be present. In moderate, high-flow VSDs, the murmur is often very loud and accompanied by a thrill (grade 4 or 5 murmur). With large defects allowing equalization of left ventricular and right ventricular pressures, the systolic murmur is often attenuated.

Wolff-Parkinson-White (WPW) syndrome is a pre-excitation syndrome characterised by re-entry tachycardia that most commonly presents as a recurrent supraventricular tachycardia. ECG will show a short PR interval and a prolonged QRS complex.

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 (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.

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

The most probable diagnosis for this patient would be Coarctation of Aorta (CoA).Infants with CoA present within the first few weeks of life with signs suggestive of congestive cardiac failure and general circulatory shock. In these patients, the aorta is supplied by the right ventricle, via the ductus arteriosus. Pathophysiology:When the left ventricle supplies the aorta via the aortic isthmus, children are usually asymptomatic or may present with occasional complaints of leg pain. Associated cardiac anomalies are uncommon but for a bicuspid aortic valve, which is present in approximately 50% of cases. Good collateral circulation usually develops in these patients, which in the long term, causes notching of ribs. Clinical Presentation:Clinically, there may be hypertension in the upper limbs (or higher BP readings than in the lower limbs), and leg pulses are absent, or weak and delayed. A systolic click and aortic ejection systolic murmur are heard, caused by the bicuspid aortic valve. Management:The primary medical management is to treat hypertension. After stabilization, the patient can undergo definitive surgical repair. Transcatheter balloon angioplasty of the coarctation is controversial, but ballooning +/- stenting of re-coarctation following surgery is commonly performed.Systemic hypertension may occur following repair, even in the absence of re-coarctation necessitating the re-initiation/continuation of antihypertensive therapy in these patients.

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 best answer is Henoch-Schönlein Purpura (HSP). This patient has a characteristic rash and the labs are consistent with this diagnosis.

The T wave represents ventricular repolarization. Other options:- P wave:Depolarization that spreads from the SA node throughout the atria. The wave lasts 0.08 to 0.1 seconds (80-100 ms).The isoelectric period after the P wave represents the time in which the impulse is travelling within the AV node.- P-R interval:Time from the onset of the P wave to the beginning of the QRS complex. The wave ranges from 0.12 to 0.20 seconds in duration.Represents the time between the onset of atrial depolarization and the onset of ventricular depolarization- QRS complex:It represents ventricular depolarization. The duration of the QRS complex is normally 0.06 to 0.1 seconds.- ST-segment:The isoelectric period following the QRS. It represents the period in which the entire ventricle is depolarized and roughly corresponds to the plateau phase of the ventricular action potential- U wave: It is a small positive wave which may follow the T wave. It represents the last remnants of ventricular repolarization.- Q-T intervalIt represents the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential.The interval ranges from 0.2 to 0.4 seconds depending upon heart rate.At high heart rates, ventricular action potentials shorten in duration, which decreases the Q-T interval. Therefore the Q-T interval is expressed as a corrected Q-T (QTc) by taking the Q-T interval and dividing it by the square root of the R-R interval (interval between ventricular depolarizations). This allows an assessment of the Q-T interval that is independent of heart rate.The normal corrected Q-Tc interval is less than 0.44 seconds.

Pulmonary arterial hypertension (PH) is noted in 9 to 35 % of patient with a secundum type ASD. The haemodynamic definition of PH is a mean pulmonary arterial pressure (mPAP) of ≥25 mmHg at rest by means of right heart catheterization. In ASD, The findings on physical examination depend on the degree of left-to-right shunt and its hemodynamic consequences, which, in turn, depends on the size of the defect, the diastolic properties of both ventricles, and the relative resistance of the pulmonary and systemic circulations.Blood flow across the atrial septal defect (ASD) does not cause a murmur at the site of the shunt because no substantial pressure gradient exists between the atria. However, ASD with moderate-to-large left-to-right shunts results in increased right ventricular stroke volume across the pulmonary outflow tract creating a crescendo-decrescendo systolic ejection murmur. This murmur is heard in the second intercostal space at the upper left sternal border.Patients with large left-to-right shunts often have a rumbling mid-diastolic murmur at the lower left sternal border because of increased flow across the tricuspid valve.ASD is an acyanotic lesion. Thus, the patient should be normally saturated. In the rare case of severe pulmonary arterial hypertension, atrial shunt reversal (Eisenmenger syndrome) may occur, leading to cyanosis and clubbing

Several types of right-sided aortic arch exist, the most common ones being right-sided aortic arch with aberrant left subclavian artery and the mirror-image type. The variant with aberrant left subclavian artery is associated with congenital heart disease in only a small minority of affected people. The mirror-image type of right aortic arch is very strongly associated with congenital heart disease, in most cases tetralogy of Fallot. A right-sided aortic arch does not cause symptoms on itself, and the overwhelming majority of people with the right-sided arch have no other symptoms. However when it is accompanied by other vascular abnormalities, it may form a vascular ring, causing symptoms due to compression of the trachea and/or oesophagus.

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 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).

A ventricular septal defect (VSD) is a common form of congenital heart defects and is characterised by the presence of a hole in the wall that separates the right from the left ventricle. Medium or large defects can cause many complications. One of these complication is Eisenmenger syndrome, characterised by reversal of the shunt (from left-to-right shunt into a right-to-left) ,cyanosis and pulmonary hypertension.

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.

Tooth extraction or any surgical procedure may introduce bacteria into the blood stream. The most commonly involved organisms include Staphylococcus aureus and Streptococcus viridans. Once in the blood, these organisms have a very high tendency of attaching to the walls of the heart and causing inflammation known as endocarditis.

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.

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

Cyanotic congenital heart disease (CCHD) is a common cause of neonatal morbidity and mortality. They can be classified as CCHD due to:- Right-to-left shunt, associated with the decreased pulmonary flow, e.g., tetralogy of Fallot (TOF), pulmonary atresia, right-sided hypoplastic heart,- Right-to-left shunt, associated with the decreased aortic flow, e.g., left-sided hypoplastic heart, interrupted arch, severe coarctation| – Bidirectional shunt, e.g., TGA, DORV, TA, etc. Eisenmenger syndrome is not a neonatal CCHD| rather it develops later in young adulthood secondary to various CHD.

Infective endocarditis (IE) is defined as an infection of the endocardial surface of the heart.Fever, possibly low-grade and intermittent, is present in 90% of patients with IE. Heart murmurs are heard in approximately 85% of patients.One or more classic signs of IE are found in as many as 50% of patients. They include the following:- Petechiae: Common, but nonspecific, finding- Subungual (splinter) haemorrhages: Dark-red, linear lesions in the nail beds -Osler nodes: Tender subcutaneous nodules usually found on the distal pads of the digits- Janeway lesions: Nontender maculae on the palms and soles- Roth spots: Retinal haemorrhages with small, clear centres| rareSigns of neurologic disease, which occur in as many as 40% of patients, include the following:- Embolic stroke with focal neurologic deficits: The most common neurologic sign- Intracerebral haemorrhage- Multiple microabscessesOther signs of IE include the following:- Splenomegaly- Stiff neck- Delirium- Paralysis, hemiparesis, aphasia- Conjunctival haemorrhage- Pallor- Gallops- Rales- Cardiac arrhythmia- Pericardial rub- Pleural friction rub