Characteristic ECG findings include:
A large P wave, some studies suggest that a
large P wave correlates with decreased oxygen saturation, severe symptoms
and increased risk of death with or without pre-excitation.
Eighty-seven to ninety-seven per cent
(87-97%) of patients initially present in normal sinus rhythm.
PR interval is prolonged in 16-42% of cases.
Right axis deviation is common in frontal
Complete or incomplete right bundle branch
block is seen in 77-94% of cases.
QRS morphology is abnormal with slurring,
notching and low voltage due to paucity of right ventricular tissue and
displacement of the left ventricle by a large right atrium.
Absent Q wave in V6 due to ventricular
displacement secondary to a dilated right atrium.
Pre-excitation in 6-26% of patients in (WPW).
WPW is seen in other types of congenital heart disease but of all of the
WPW cases with congenital heart disease, one-third of them have
WPW is usually of type B (RV free wall bypass
tract). This will present as a positive delta wave in lead V6 giving the
appearance of left bundle branch block.
Pre-excitation may not be easy to spot
because of large P waves and delayed conduction in atrium causing
prolonged PR interval and therefore attention should be paid to the delta
wave rather than a short PR interval.
24-Hour Holter monitor is valuable in
assessing arrhythmias not spotted on a 12-lead ECG.
Exercise testing is usually done for
assessing function severity but is also helpful with exercise induced
Before echocardiography, diagnosis was done
by obtaining RV electrical recording with right atrial pressure tracing
during cardiac catheterization. However, cardiac catheterization is risky
as it may lead to arrhythmia and therefore should be done cautiously.
In reciprocating a tachycardia the RP
distance on surface ECG is prolonged due to delayed atrial conduction in
almost all patients. Almost all bypass pathways are on the right side
(free wall or septa), however, it is to the left side with corrected TGA
in situs inversus with Ebsteinís malformation. Most supraventricular
tachycardias are orthodromic. Electrophysiology study is indicated in
patients with Ebsteinís malformation and arrhythmias.
Sudden death is encountered in 3-10% of
patients and this is thought to be secondary to SVT leading to ventricular
tachycardia or fast conduction of atrial fibrillation or flutter.
Ebsteinís malformation cause 6% of all cases of sudden death with
congenital heart disease which is a large percentage for such a rare
Sudden death percentage increases after
tricuspid valve annuloplasty.