tacchyarrythmias approach in children

1. Tachyarrhythmias
&
Ventricular arrythmias

2. Introduction
An arrythmia is defined as an abnormality in heart rate or rhythm.
5% of the emergency hospital admissions in the pediatrics are attributed to symptomatic
arrhythmias.
The frequency and clinical features of arrhythmias in children are relatively infrequent and
differs from that in adults.
Tachycardias, are defined as a heart rate beyond the upper limit of normal for the patient’s age
and bradycardia is defined as a heart rate slower than the lower limit of normal age, as The
normal heart rate range varies with age.
Tachyarrhythmias, are tachycardia with an irregular heart rate.

3. Classification of tachyarrhythmias
Tachycardias or tachyarrhythmias can be classified according to-
a) anatomic level of origin as supraventricular or ventricular, and
b) functional mechanism reentry, automaticity or triggered activity.

4. 1. Increased Automaticity
Normally, sinus node automaticity is higher than other cardiac tissues with impulses at a rate
varying between 60 to 200/min.
If another automatic focus develops in the atrium that fires at a rate faster than sinus rate, then
it would result in ectopic atrial tachycardia (EAT).
If there are multiple automatic foci, then the resulting tachycardia is called as multifocal atrial
tachycardia (MAT).
If an automatic focus develops in the junctional tissue (near His bundle), it would cause
‘junctional ectopic tachycardia’ (JET) and a similar focus in the ventricle will result in
automatic VT.

5. 2. Re-entrant Mechanism
Here, an abnormal electrical circuit is formed where some portion conducts fast and
the other portion conducts slowly.
This is the most common cause of pediatric tachycardias.
When an impulse encounters this circuit, it travels along both slow and fast
pathways.
By the time the impulse passes through the slow pathway, the fast pathway is
repolarized and is ready to conduct the impulse retrogradely.
The wave then returns down the slow pathway setting up a closed circuit that is self-
sustaining.
The tachycardias caused by this mechanism and the associated re-entrant circuits.
e.g:- Atrial flutter and fibrillation.

7. 3. Triggered Activity
This occurs during the repolarization phase of the cardiac cycle.
If the trigger occurs in phase 3 of ventricular depolarization, it is called early after
depolarization.
If the trigger occurs in phase 4, it is called delayed after-depolarization.
Long QT syndrome and digoxin toxicity related tachycardias are associated with this.

8. Tachyarrhythmias can also be broadly categorized into :-
a) narrow complex and
b) wide complex.
The duration of the QRS depends on the patient's age and history of cardiovascular surgery.
 Any Wide complex tachycardias should be assumed to be VT until proven otherwise.
 Many situations when a wide complex tachycardia is supraventricular in origin. (shown later)

9. Type Conduction pathway PR interval QRS interval Delta wave?
Wolff-Parkinson-White
syndrome
Bundle of Kent (atria to
ventricles)
short long yes
Lown-Ganong-Levine
syndrome
"James bundle" (atria
to bundle of His)
short normal no
Mahaim-type Mahaim fibers normal long no
Preexcitation syndromes
 Certain preexcitation syndromes can also have broad complex QRS.

10. • Most wide complex tachycardias except for ventricular fibrillation are relatively regular
tachycardias.
• In irregular wide complex tachycardia present, the possibility of atrial origin should be strongly
considered.
• QRS complex in ventricular tachycardia often has a right or left bundle branch morphology.
• In general, a tachycardia originating in the left ventricle produces a right bundle branch block
pattern, whereas a tachycardia originating in the right ventricle results in a left bundle branch
block pattern.
• A left bundle branch block pattern of aberrancy is much more common in neonates, while a
right bundle branch block pattern is more common in children and adolescents.
• Ventricular tachycardia was found in 3% of neonates and 15% of older children (Gross-
Wortmann, 2010).

11. Premature ventricular contractions
A PVC is a premature QRS complex that does not have the same morphology
as the sinus complex and is not preceded by a P wave.
PVCs may not have a broad QRS complex (Especially in infants), but they
have a morphology different than that of the sinus QRS.
Based on morphology of QRS PVCs are classified as –
a) Uniform (monomorphic or unifocal) - if all PVCs have similar
morphology, they originate from a single focus,
b) Multiform (polymorphic or multifocal) - if they have more than one
morphology, they originate from different foci.

14. Interrelationship with normal QRS
1. Ventricular bigeminy or coupling: Each abnormal QRS complex regularly alternates with a
normal QRS complex. i.e. every other beat is a PVC.
2. Ventricular trigeminy: Each abnormal QRS complex regularly follows two normal QRS
complexes. i.e. every third beat is a PVC.
3. Couplets: A ventricular couplet is defined as two PVCs in a row.
4. Triplets: Three abnormal QRS complexes appear in sequence.
NOTE:- Three or more successive PVCs arbitrarily are termed ventricular tachycardia.

15. ECG : PVCs
 Premature Ventricular Complexes on the Electrocardiogram
a) Premature QRS complex in relation to the expected impulse of the basic
rhythm.
b) Abnormal QRS complex in duration and morphology. It is accompanied by
ST-segment and T wave changes.
c) The premature ventricular complex is not preceded by a P wave.
d) Full compensatory pause: after the PVCs a delay occurs until the appearance
of basic rhythm.

16. Coupling interval- is the distance between the PVC and the preceding QRS complex.
The compensatory pause is marked in blue.
Isolated Premature Ventricular Complexes marked by the arrow on an EKG in sinus rhythm.

17. The compensatory pause of PVC are of two types :-
 Complete compensatory pause
This occurs when the sum of the coupling interval and the compensatory pause is equal to twice
the sinus cycle length. It is characteristic of a ventricular ectopic which fails to conduct
retrogradely to the atria, hence leaving the sinus node undisturbed.
(A) Late PVC, which results in a full compensatory pause; presumably, retrograde discharge of the sinus node did
not occur.
(A)

18. (A)Early PVC, which results in a retrogradely conducted P wave (P′) with a less than full compensatory pause. The
first postectopic beat is a ventricular escape beat (E).
(B)Early PVC with a retrogradely conducted P wave (P′) with a less than full compensatory pause. A ventricular
fusion beat (F) resumes the cardiac cycle.
 Incomplete compensatory pause
If there is retrograde conduction of p wave sinus node is discharged early by the
ectopic depolarization. The sum of the coupling interval and the compensatory
pause is less than twice the sinus cycle length.
(A) (B)

19. Coupling Interval
1. Fixed coupling :- PVCs appear at a constant interval after the QRS complex of the previous
cardiac cycle. Due to ventricular reentry within the Purkinje system. Most PVCs in children
have a fixed coupling interval.
2. Varying coupling :- When coupling intervals vary by more than 80 msec, the PVCs may
result from parasystole. Due to impulse-forming focus in the ventricle that is independent of
the sinus node-generated impulse and is protected from depolarization (entrance block) by
sinus impulses.

20. Significance of PVCs
40% of otherwise normal children may have PVCs seen on Holter monitoring (24-hour ambulatory
ECGs).
Occasional PVCs are benign in children, particularly if they are uniform and disappear or become less
frequent with exercise.
PVCs are more significant in the following cases:
a. They are associated with underlying heart disease (preoperative or postoperative status, MVP,
cardiomyopathy).
b. There is a history of syncope or a family history of sudden death.
c. They are precipitated by or become more frequent with activity.
d. They are multiform, particularly couplets.
e. There are runs of PVCs with symptoms.
f. There are incessant or frequent episodes of paroxysmal VT (more likely myocardial tumours).
Ventricular parasystole does not appear to have any consequences in children.

21. ECG, echocardiography studies, and 24-hour Holter monitoring suffice asymptomatic child
with PVC.
Treatment is needed in following cases:-
a) Arrhythmias that are potentially related to exercise
b) All children with symptomatic ventricular arrhythmias and those with complex PVCs
(multiform PVCs, ventricular couplets, un-sustained VT)

22. Accelerated idioventricular rhythm
Its benign in children.
Results when the rate of an ectopic ventricular pacemaker exceeds that of the sinus node. Often
associated with increased vagal tone and decreased sympathetic tone.
The ventricular rate approximates the patient’s sinus rate, within ±10% to 15% of the sinus rate
(isochronicity).
The ventricular rate is usually 120 beats/min or less in children (and 140–180 beats/min in
newborns). The rate helps differentiate AVR from VT (with a rate >120 bpm).
The rate of AIVR distinguishes it from others rhythms of similar morphology.
a) Ventricular Escape Rhythm -Rates < 50 bpm or sinus discharge rate.
b) Ventricular Tachycardia- Rates > 120 bpm.

23. Ventricular Tachycardia
Description :-
1. VT is a series of at least 3 PVCs (premature ventricular contractions) with a heart rate of
120 to 200 beats/min. QRS complexes are wide and bizarre. T wave points in opposite
direction.
2. These are the Most common cause of wide complex tachycardia (80%).
3. VT arises distal to bifurcation of His bundle or vent muscle or both.
4. VT may be classified in following ways:-
a. The onset may be paroxysmal (sudden) or non-paroxysmal.
b. By duration,
c. By morphology,

24. Classification of VT
Based on Morphology
1. Monomorphic VT
2. Polymorphic VT
3. Bidirectional VT
4. Torsades De Pointes (Polymorphic
with QT prolongation)
5. Right Ventricular Outflow Tract
Tachycardia
6. Fascicular Tachycardia
7. Ventricular Flutter
8. Ventricular Fibrillation
Based on Duration
1. A Salvo VT - 4-6 PVC beats in a row
2. Sustained - Duration > 30 seconds or
requiring intervention due to
hemodynamic compromise.
3. Non-sustained - Three or more
consecutive ventricular complexes
terminating spontaneously in < 30
seconds.

25.  Torsade de pointes (meaning “twisting of the points”)
It is characterized by a paroxysm of VT with – progressive changes in the amplitude and polarity
of QRS complexes separated by a narrow transition QRS complex. It is a distinct form of
polymorphic VT, occurring in patients with marked QT prolongation.
 Can lead to sudden cardiac death.

27.  Differentiating VT from SVT with aberrant conduction is sometimes difficult.
 However, in children, almost all wide QRS tachycardias are VT. They should be treated as such until
proven otherwise.
A) Orthodromic reciprocating tachycardia (ORT)
with bundle branch block (BBB),
B) Antidromic tachycardia using an accessory
AV connection (ART),
C) Primary atrial tachycardia with BBB,
D) Atrioventricular nodal reentry tachycardia
(AVNRT) with a bystander accessory
connection (AC),
E) Tachycardia using a Mahaim fiber, or
F) Ventricular tachycardia.
Situations when a wide complex tachycardia
is supraventricular in origin.

28. Causes
1. In patients with structural heart diseases such as tetralogy of Fallot (TOF), aortic stenosis,
hypertrophic or dilated cardiomyopathy, or MVP.
2. Postoperative CHDs (e.g., TOF, dextro-transposition of the great arteries, or double-
outlet RV).
3. Myocarditis, cardiomyopathies, Chaga’s disease (trypanosomiasis in South America),
myocardial tumors, myocardial ischemia, and infarction
4. Pulmonary hypertension
5. Inherited electric cardiac diseases such as long QT syndrome, Brugada, and
catecholaminergic VT.

29. 6. Metabolic causes include hypoxia, acidosis, hyper-kalemia, hypo-kalemia, and
hypomagnesemia.
7. Mechanical irritation from an intraventricular catheter.
8. Pharmacologic and chemical causes include catecholamine infusion, digitalis toxicity,
cocaine, and organophosphate insecticides.
9. Most antiarrhythmic drugs (especially classes IA, IC, and III) are also proarrhythmic.
10. VT may occur in healthy children who have structurally and functionally normal hearts.

30. Significance
1. VT may cause of sudden cardiac death.
2. Prompt recognition and initiation of treatment (e.g. electrical cardioversion) is required in all
cases of VT.
3. Presenting symptoms may be dizziness, syncope, palpitation, or chest pain. The family
history may be positive for ventricular arrhythmia or sudden death.
4. With a fast heart rate, cardiac output may decrease notably and the rhythm may deteriorate to
ventricular fibrillation (VF) in which effective cardiac output does not occur.
5. Chronic low rate VT may lead to a tachycardia-mediated cardiomyopathy.
6. Polymorphic VTs are more significant than monomorphic ones.

31. 7. Those associated with abnormal cardiac structure (pre and postoperative) or function are more
significant than those seen in patients with structurally and functionally normal hearts.
8. VTs associated with certain forms of cardiomyopathy (arrhythmogenic RV dysplasia,
hypertrophic or dilated cardiomyopathy) and genetic electrical heart diseases (LQTS ) can be
a cause of sudden death.
9. Patients with Long QT are at increased risk of sudden cardiac death, specifically related to
their propensity to develop torsade's de pointes.

33. Evaluation of ventricular arrhythmias
I. (FIRST) Its important to evaluate for malignant causes of arrhythmias.
Thorough evaluation of the ECG and echo
Exclude presence of following disorders
a) LQTS,
b) Short QT syndrome,
c) Brugada syndrome,
d) CPVT,
e) ARVC,
f) cardiomyopathy,
if identified, specific management is initiated

34. II. (Second) Important to distinguish the following characteristics:-
a) degree of symptoms;
b) grade of ventricular arrhythmias (uniform/multiple morphology
and PVCs/non- sustained VT/sustained VT);
c) presumed VT site of origin (RVOT, idiopathic left ventricular
VT, and others); and
d) presence or absence of hemodynamic effects of the arrhythmia.
e) The age of the patient.
Younger children cannot cooperate with SAECG (Signal-averaged electrocardiography) and
exercise testing; use of general anaesthesia to acquire cardiac MRI in younger children should
discourage (except in very specific situations).

35. HISTORY
• Symptoms range from non-specific discomfort to rare cases of syncope.
• Some symptoms presentation can be age dependent e.g.- Palpitations are mostly described in
older children, but aborted sudden death, heart failure, and syncope have no difference in
frequency across age groups.
Note - The absence prodrome before a significant symptom such as syncope is concerning for a
more malignant form of ventricular arrhythmia.
• The patient's emotional state before tachycardia - to determine the likelihood of anxiety as the
cause of symptoms.
• H/O Precipitating factors tachycardia - Fever, anemia, and exercise.
• Exercise-related syncope should be thoroughly investigated, with a high index of suspicion for
ventricular arrhythmias related to a channelopathy or structural heart disease.

36.  Recent medications, e.g.- cough or cold preparations, toxic exposures;
 Drugs of abuse; unregulated dietary substances, e.g.- ephedra; and caffeine-containing
beverages can cause tachycardia.
 Heart disease/heart surgery - A history of heart disease or heart surgery increases the risk of
atrial and ventricular tachyarrhythmias and post-pericardiotomy syndrome.
 A complete family history is necessary, as some patients with inherited channelopathies can
present with undifferentiated VT.
Family history of sudden cardiac death or deafness may raise clinical suspicion for genetic
disorders such as long QT syndrome and hypertrophic cardiomyopathy that may cause sudden
onset of ventricular tachycardia.
•

37. PHYSICAL EXAM
 Physical examination is often unrevealing in these patients, especially with a structurally
normal heart.
In physical examination we focus on:-
I. General appearance (hemodynamic status),
Initial general assessment of hemodynamic stability is very important and cardiovascular collapse
should be treated immediately.
II. Vital signs (tachycardia recognized),
III. Respiratory exam (retractions, increased work of breathing, crackles, wheezing),
IV. Cardiac exam (heart sounds, dyspnea, liver size, peripheral perfusion, cyanosis, rate/rhythm,
murmurs-underlying heart defect),
V. Level of consciousness.
Note:- Headache and diaphoresis are associated with pheochromocytoma. A widened pulse
pressure and thyromegaly may indicate hyperthyroidism.

38. INVESTIGATIONS
Routine tests –
a) CBC
b) Serum Electrolytes (Mg/Ca)
c) RBS
d) Blood gas
e) TFT
f) Cardiac troponin levels (troponin-I and -T) may be elevated in myocarditis.
However, myocardial enzymes (CK, CK-MB) levels are generally not helpful as
they are rarely abnormal.
g) CXR
Cardiac investigations-
a) 12 lead ECG
b) Holter monitoring – frequency of PVC
c) Exercise testing- for elucidating adrenergic- sensitive ventricular arrhythmias.
d) Cardiac echo.
e) Electrophysiological studies

39.  Electrophysiological studies -indicated for:
(1)Those with high-density PVCs and symptoms suspicious for tachyarrhythmia,
(2) Those with underlying heart disease, especially those in postoperative status, with
potentially life-threatening inducible sustained VT,
(3) To target the VT focus or reentry circuit for ablation,
(4) To check for the effectiveness of orally administered antiarrhythmic therapy.

40. ECG
 Unless there is hemodynamic compromise; the important initial step is to record a 12 lead ECG and
rhythm strip during tachycardia
 Features suggestive of VT
i. Absence of typical RBBB or LBBB morphology.
ii. Extreme axis deviation (“northwest axis”) - QRS is positive in aVR and negative in I + aVF.
iii. AV dissociation (P and QRS complexes at different rates).
iv. Capture beats - occur when the sinoatrial node transiently ‘captures’ the ventricles, in the
midst of Very broad complexes (>160ms).
v. AV dissociation, to produce a QRS complex of normal duration.
vi. Fusion beats - occur when a sinus and ventricular beat coincide to produce a hybrid complex
of intermediate morphology.

41. AV dissociation (P and QRS complexes at
different rates).
Capture beats — occur when the
sinoatrial node transiently ‘captures’ the
ventricles, in the midst of AV dissociation,
to produce a QRS complex of normal
duration.
Fusion beats - occur when a sinus and
ventricular beat coincide to produce a
hybrid complex of intermediate
morphology.

42. vii. Positive or negative concordance throughout the chest leads, i.e. leads V1-6 show
entirely positive (R) or entirely negative (QS) complexes, with no RS complexes seen.
viii.Brugada’s sign – The distance from the onset of the QRS complex to lowest point of
the S-wave is > 100ms.
vii. Josephson’s sign – Notching near the lowest point of the S-wave.
viii.RSR’ complexes with a taller “left rabbit ear”. This is the most specific finding in
favour of VT. This is in contrast to RBBB, where the right rabbit ear is taller.
Brugada’s sign (red callipers) and Josephson’s sign (blue arrow)

43. Evaluation algorithm

44. MANAGEMENT
 Assessment for shock and the determination of rhythm are two key decision points in the
evaluation of children with tachycardia.
Children can tolerate a wide range of heart rate, may appear quite comfortable with heart rates
exceeding 240/min.
The behavior and management of tachyarrhythmias depends on the mechanism of arrhythmia.
Tachyarrhythmia can occur by three mechanisms:-
1. Increased automaticity
2. Re entrant mechanism
3. Triggered activity

45. Treatment algorithm

46. Management of VT –
a) Initial/acute therapy
b) Chronic therapy

47. Initial/acute therapy
Symptomatic VT
A. Patient is unconscious or cardiovascular instability with clinical evidence of low cardiac output
synchronized DC cardioversion (0.5–1 joule/kg).
B. If the patient is conscious (rarely) with clinical evidence of low cardiac output
an IV bolus of lidocaine (1 mg/kg per dose over 1–2 minutes) - f/b - IV drip of lidocaine (20–50
μg/kg per minute) may be effective.
Note:- Lidocaine or procainamide is often initiated after cardioversion in an attempt to suppress
re-initiation of the tachycardia.
Cardiopulmonary resuscitation as necessary.

48. Patients with drug-refractory VT (particularly in postoperative patients) - IV amiodarone is
used.
The mechanism of action of amiodarone appears to be by reducing transmural heterogeneity of
repolarization in the ventricular muscle.
IV injection of magnesium sulfate is reportedly an effective and safe treatment for torsades de
pointes in adults (2 g in an IV bolus).
A trial of adenosine may be helpful in some patients with structurally normal hearts.
VT with RBBB and superior axis (LV septal origin) may be calcium channel dependent and
respond to a slow IV push of verapamil.
Treat reversible conditions.

50. Initial approach to the child with tachycardia
HF: heart failure; SVT: supraventricular tachycardia; VT: ventricular tachycardia.
Δ Causes of SVT include structural heart disease, WPW, and drugs (eg:- sympathomimetics).

51. Pediatric tachycardia algorithm (with a pulse and poor perfusion): 2010 PALS guidelines

53. Chronic therapy
Conservative management safe for those asymptomatic patients with repetitive nonsustained VT in
absence of evidence of ventricular dysfunction.
Antiarrhythmic drug treatment: Complete pharmacologic suppression may not be achieved without
serious complications. Therefore, controlling the rate to an asymptomatic level may be adequate.
A combination of 24-hour Holter monitoring and treadmill exercise testing is the best noninvasive means
of evaluating drug effectiveness.
Virtually all classes of antiarrhythmic agents can be used
Beta-blockers may be very effective for patients who have no underlying heart disease and those who
have exercise-provokable monomorphic VT.
In patients with reduced LV function, digitalis and an afterload reducer may be beneficial (to improve LV
function).

54. Patients with LQTS are treated with beta-blockers- alleviate symptoms in 75% to 80% of
patients. An implantable cardioverter-defibrillator (ICD) is sometimes recommended as initial
therapy.
Catheter ablation is most successful in patients with structurally normal hearts with focal origin
of VT.
Implantable cardioverter defibrillators

55. Benign VT
Benign ventricular arrhythmias occur in patients without known heart disease and do not require
treatment and have Excellent long term prognosis.
Two forms of VT are thought to be benign variants –
a) Right ventricular outflow tract tachycardia (RVOT VT) -left bundle branch block morphology,
inferior QRS axis on ECG, seen in 50% of patients with benign VT,
b) Right bundle branch block VT (RBBB VT) or Idiopathic left VT or Belhassen’s tachycardia -
RBBB morphology and superior QRS axis on ECG.
These tachycardias tend to be responsive to verapamil. RVOT Beta-blockers are sufficient for
the treatment.
RF ablation is curative.
It is important to recognize underlying precipitating causes of VT-such as long QT syndrome.

58. Ventricular Fibrillation
Rare in the pediatric population.
Bizarre QRS complexes of varying sizes and configurations
Arrhythmia is maintained by multiple reentrant circuits because portions of the myocardium are
depolarizing constantly.
Causes- VF usually is a degeneration of VT and is terminal arrhythmia because it results in ineffective
circulation. Immediate resuscitation must be provided.
Management-
a) Acute –
- CPR (100%O2)
- Defibrillation- 2, 4, and 6 joule/kg
- identify and treat underlying causes - metabolic environment
- One of the following antiarrhythmic agents may be used:
(1) Amiodarone 5 mg/kg bolus, IV or IO
(2) Lidocaine 1 mg/kg IV, or IO, or ET
(3) Magnesium sulfate 25 to 50 mg/kg IV or IO (not to exceed 2 g) for torsades de pointes or
hypomagnesemia

60. Long QT Syndrome
Long QT syndrome is a genetically transmitted cardiac arrhythmia caused by ion channel
protein abnormalities.
It is characterized by a prolonged QT interval on the ECG and ventricular arrhythmias, usually
torsade's de pointes, that may result in sudden death.
Prognosis – poor
Four variants of LQTS –
a) Jervell and Lange-Nielsen syndrome (AR inheritance) - associated with congenital
deafness, syncopal spells, and a family history of sudden death,
b) Romano-Ward syndrome (AD inheritance) - all of the above features without deafness,
c) Sporadic form of Romano-Ward syndrome - a negative family history of the syndrome.

61. d) Anderson-Tawil syndrome or LQT7 - QU interval, rather than QT interval, is prolonged,
along with muscle weakness (periodic paralysis), ventricular arrhythmias, and
developmental abnormalities.
e) Timothy syndrome - associated with webbed fingers and toes with long QT measurement.
 Acquired prolongation of the QT interval - caused by a number of drugs, electrolyte
disturbances, and other underlying medical conditions.
Diagnosis
 Schwartz et al incorporated clinical , family history and electrocardiogram (ECG) findings in a
probability-based diagnostic criteria for long QT syndrome.
 the scoring of the probability of LQTS is as follows.
a) ≤1 point = Low probability of LQTS
b) 2 to 3 points = Intermediate probability of LQTS
c) ≥4 points = High probability LQTS

62. SCHWARTZ DIAGNOSTIC CRITERIA FOR LONG
QT SYNDROME

63. Accurate measurement of the QTc interval
1. Lead II is preferred to measure the QT interval as q wave is usually present in this lead, but precordial leads
(V1, V3, or V5) provide better definition of T waves and may also be used.
2. QTc interval (heart rate–corrected QT) is calculated by using Bazett’s formula. Used only for the steady state.
3. Sinus arrhythmia creates problems in measuring an accurate and reliable QTc interval because the QTc
interval varies with the R-R interval. So the longest QTc interval after the shortest R-R interval be used.
4. In patients with prolonged QRS duration (as seen in bundle branch block), the QT interval may be prolonged
secondary to long QRS.
In such cases, the JT interval may be a more sensitive predictor of repolarization abnormalities than the QTc
interval. The JT interval is measured from the J point (the junction of the S wave and the ST segment) to the end
of the T wave.

64. According to Bazett’s formula
The normal QTc interval (mean ± standard deviation) is 0.40 (±0.014) seconds.
a) Children 6 month and older - the upper limit of 0.44 seconds.
b) In newborn and small infants – the upper limit of QTc 0.47 second in 1st week of life and 0.45
second in the 1st 6 months of life.

65. Management of Long QT Syndrome
T/t based on known risk factors.
Known risk factors for sudden death include:
(1) Bradycardia for age (from sinus bradycardia, junctional escape rhythm, or second-degree AV block)
(2) An extremely long QTc interval (>0.55 second)
(3) Symptoms at presentation (syncope, seizure, cardiac arrest)
(4) Young age at presentation (<1 month)
(5) Documented torsades de pointes or VF
Physicians should be aware of the conditions and medications that prolong the QT interval.
Catecholamines and sympathomimetic drugs should also be avoided if possible because they can potentially trigger
torsades de pointes in patients with LQTS.
No competitive sports policy applies.
Avoid Alarm clocks and bedside telephones.
Compliance very important.

66. Management of long qt syndrome
Management of patients with LQTS consists of life-style modification, β-blockers, left cardiac
sympathetic denervation (LCSD), and implantable cardioverter-defibrillator (ICD)
implantation.
a) β-blockers - present therapy of choice in moderate doses. Effective in preventing cardiac
events in approximately 70% of Patients but can lead to bradycardia.
• Started in –
i. Any patients who scores 4 or greater on the Schwartz diagnostic criteria.
ii. Asymptomatic patients with congenital LQTS in the following circumstances –
(1)newborns and infants,
(2)patients with sensorineuronal hearing loss,
(3)affected siblings with LQTS and sudden cardiac death,
(4)extremely long QTc (>0.60 sec) or T-wave alternans, and
(5)to prevent family or patient anxiety.

67. b) Implantation of cardiac pacemakers (with continuous ventricular or dual chamber pacing) -
as arrhythmogenic bradycardia may result from high doses of betablockers.
• So a maximally dose of beta-blockers (e.g., atenolol 50–200 mg/day, metoprolol to 50 to 200
mg/day, propranolol 60–120 mg/day) can be used because the pacemaker is expected to prevent
bradycardia from occurring.
• not provide complete protection (sudden death occurring in 16% of patients) as lacks
defibrillation capability.
• ICD that can defibrillate as well as pace.
c) Left cardiac sympathetic denervation: Because of the availability of other options, such as
pacing and ICD, this procedure is rarely performed.
d) ICD: Implantation of an ICD appears to be the most effective therapy for high-risk patients.

68. Treatment of Acquired Long QT Syndrome
Done with –
a) IV magnesium,
b) discontinuation of any precipitating drug, and
c) correction of any metabolic abnormalities (e.g., hypokalemia or hypomagnesemia).

70. Brugada Syndrome
Inherited arrhythmogenic disorder with a high risk of sudden cardiac death occurring during
sleep, resulting from ventricular tachyarrhythmias, appears to be inherited as an autosomal
dominant pattern.
SCN5 defect.
This syndrome has also been demonstrated in children and infants. No male preponderance is
observed in children, raising a possibility of high level of androgen in the occurrence of the
fatal event.

71. Short QT Syndrome
A familial short QT interval has been reported to be a cause of sudden death. Short QT
syndrome is characterized by a very short QTc (≤300 msec).
Symptoms of palpitation, dizziness or syncope, and family history of sudden death.
Cause of death VF - Often during sleep.
Autosomal dominant inheritance.
the use of an antiarrhythmic agent, particularly quinidine (which prolongs the QT interval)
has been suggested.
An ICD may become standard practice.

73. Take home message
40% of children with PVCs are otherwise normal with no complaints.
Broad complex tachycardias of ventricular origin until proven otherwise.
Long QT syndrome is a familial cause of sudden cardiac death and
compliance is important for survival.
RVOT VT and LVOT VT are benign variants of VT.

74. Thank you