supraventricular tachycardia (svt) - usu...
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Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)
MUHAMMAD ALIMUHAMMAD ALIMUHAMMAD ALIMUHAMMAD ALI
Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)Supraventricular Tachycardia (SVT)
• SVT is characterized by rapid heart rates, usually 200 to
300 beats/minute, with a QRS complex of normal
duration
Cardiovascular emergency in infant and children
The incidence: 1/25,000-1/250
Early detection and prompt treatment important
• Congestive heart failure
• Circulatory arrest
Mechanism of SVT
• Mechanism of SVT
– Automaticity– Automaticity
– Reentry
Mechanism of SVT
• Automaticity– Acceleration of phase 4– Source:
• Atrium• AV junction• His bundle• Ventricle• Pulmonary vein• SVC
– Cause• Metabolic disorder• Hypoxia• Hypokalemia• Hypo magnesemia• acidosis
Mechanism of SVT
• Reentry
– Condition
• Two pathway make closed closed circuit
• Block in 1 pathway
• Antegrad in normal conduction�retrograd in block pathway
Mechanism of SVT
• The episodes usually start and end abruptly
• Wolff-Parkinson-White (WPW) syndrome is
responsible for about 50% of SVT in neonates
• Structural heart diseases (such as Ebstein's • Structural heart diseases (such as Ebstein's
Anomaly, Tricuspid Atresia, and cardiac tumors)
are less frequent causes of SVT in neonates
• Viral myocarditis and thyrotoxicosis also have
been associated with SVT
Short episodes of tachycardia usually do not harm the patient
Newborns with sustained SVT become restless and Newborns with sustained SVT become restless and
tachypneic with feeding difficulties and eventually develop
signs of CHF and circulatory shock within 12 to 24 hours
after onset
Although rare, SVT diagnosed in utero may present with
severe CHF at birth and has a high mortality rate, requiring
prenatal treatment
TreatmentTreatmentTreatmentTreatment
• Adenosine is the treatment of choice, followed by digitalization
• Adenosine is given in a rapid intravenous bolus, starting at 50 µg/kg, every 1 to 2 minutes (maximum, 250 µg/kg)
• If the patient is unresponsive to adenosine and is in CHF, cardioversion may be performed, followed by digitalization and diuretics
• In SVT of short duration without signs of CHF, digoxin alone is used
• An ice bag applied to the face has been effective in some neonates
• Vagal stimulatory maneuvers rarely are effective in neonates
• Transesophageal atrial overdrive stimulation may prove effective
• Verapamil and propranolol are not the drugs of choice
• Verapamil and propranolol are not the drugs of choice
• Tried only when other measures fail, and may produce extreme bradycardia and hypotension in a newborn; one should administer these drugs in a step-by-step dosage, monitor the infant carefully, and be prepared to resuscitate
Short-Term management
of SVT
Delacretaz. NEJM 2006;354:1039-51
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