Pre-excitation syndromes in children

Posted by e-Medical PPT Saturday, March 10, 2012
What are “Pre-excitation syndromes”?
A group of ECG and Electrophysiological abnormalities in which
The atrial impulses are conducted partly or completely, PREMATURELY, to the ventricles via a mechanism other than the normal AV-node *
Associated with a wide array of tachycardias with both normal QRS and prolonged QRS durations

Origin of the Accessory pathways ?
In early stages of cardiac development, there is direct physical and electrical contact between the atrial and ventricular myocardium
….disrupted by susequent in-growth of the AV sulcus tissue and formation of the annulus fibrosus
Defects in this annulus results in accessory pathhways

Most of these connections are of ventricular myocardial origin, rather than of atrial issue origin
May be found anywhere across the tricuspid or mitral valve annulus – whether endocardial or epicardial
Most common pathways in children are Left Free Wall followed by Posteroseptal and Right Free Wall ; Midseptal and Anteroseptal are least common *

Accessory Pathway mediated SVTs account for > 70% of all SVTs in children who have not undergone surgical repair of CHDs *

WPW Syndrome
Characteristic appearance on surface ECG during Sinus Rhythm:
Short PR interval
Slurred initial QRS ( ‘Delta wave’ ) resulting in broadening of the QRS complex , without widening the duration from beginning of P to end of QRS
The most common cardiac pre-excitation syndrome.
Overall incidence in a population study of Olmstead County, Minnesota : 3.96/100,000 persons/year. (*Munger et al. Circ 1993)
Exact cause unknown.
Most cases sporadic.
Bimodal age distribution – 1st year, then young adulthood.
3% of Probands have an affected 1st-deg relative.
Familial occurrence reported – autosomal dominant inheritance.
Recent report – Chr 7q3 in a family with WPW / HCM / HB.
Tuberin and Hamartin gene mutations in WPW + Tuberous Sclerosis
Myo Binding Prot / cardiac troponin gene mutations in WPW + HCM

Risk of sudden death from rapid Ventricular response to Atrial Fibrillation
Per se, WPW refers to patients with pre-excitation in ECG + symptomatic episodes of tachycardia – “Manifest Pathways”
Asymptomatic patients with pre-excitation pattern are simply described as having “VPE pattern”
Patients with Accessory Pathways, but no pre-excitation are described as having “Concealed Pathways”. Pathways may become manifest during episodes of tachycardia...

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