supraventricular tachycardia (svt) - usu...

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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