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.

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.

The most probable diagnosis for this child would be rheumatic fever due to a previous history of rheumatic fever, evidence of streptococcal disease from a throat swab, a raised ASO titre and a positive streptococcal antigen test or a leukocytosis.Acute Rheumatic Fever:ARF occurs because of an abnormal immune response to a streptococcal antigenic component. It has a latent period of 1–3 weeks and is more common in the lower socio-economic classes. It peaks at around 5–15 years of age and affects the blood vessels, joints, nervous system and subcutaneous tissues. It is characterised as an autoimmune disease, and there is a risk of rheumatic fever occurring after infection in 3% of the population. The recurrence is greater in younger children and increases with each attack. Duckett-Jones criteria:The diagnostic criteria for acute rheumatic fever.Major: – Pancarditis- Chorea (Sydenham’s) – Polyarthritis (flitting)- Erythema marginatum- Subcutaneous nodulesMinor criteria include the presence of arthralgia, fever, prolonged PR interval, raised ESR, raised CRP.Note that:To make the diagnosis of rheumatic fever: Two major and/or one major with two minor criteria are required. Evidence of a recent streptococcal infection with a raised ASO titre or an antiribonuclease B level is sufficient. Exceptions to this rule are mentioned below:- Chorea alone is diagnostic.- Insidious or late-onset carditis with no other explanation.- Rheumatic recurrence: The presence of one major and one minor criterion with a prior streptococcal disease that is recurring.Consequences of pericarditis include heart block, pericardial effusion, tachycardia, cardiomegaly, pericardial friction rub, congestive cardiac failure, valvular disease and a Carey–Coombes apical mid-diastolic rumbling murmur.New heart murmurs are often audible, including those of mitral regurgitation and aortic regurgitation. Skin nodules affect the perivascular tissues and are non-specific lesions resulting from fibroid degeneration.Management:Medication includes aspirin for the acute phase, non-steroidal anti-inflammatory drugs for arthritis, prednisolone for severe carditis, and high-dose penicillin for immediate management with antibiotic prophylaxis in the long term. Antibiotics may include penicillin V, erythromycin or benzylpenicillin. Diazepam and haloperidol may be required to control the chorea.

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.

Kawasaki disease is an acute febrile illness of early childhood characterized by vasculitis of the medium-sized arteries. Diagnostic criteria include fever of at least 5 days duration along with 4 or 5 of the principal clinical features – extremity changes, polymorphous rash, oropharyngeal changes, conjunctival injection and unilateral nonpurulent cervical lymphadenopathy.

Coarctation of the aorta is one of the serious forms of congenital heart diseases characterized by a congenitally narrowed down proximal thoracic aorta. This narrowing is usually located distal to the origin of the left subclavian artery. Coarctation can occur in isolation but can accompany other cardiac lesions, including a bicuspid aortic valve. When the coarctation is located just above the left subclavian artery, raised blood pressure can be noted in the right arm. The most common type of murmur found in coarctation of the aorta is a diastolic murmur of aortic regurgitation due to the presence of a bicuspid aortic valve. Exercise augmented cardiac output is only affected in cases where coarctation of the aorta leads to heart failure. Hypertension persists even after the surgical repair and needs to be closely monitored.

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

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.

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.

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.