The devices used were self-expanding, double-disc VSD occluders
(Lifetech Scientific Co, Ltd of Shenzhen, China). There are two
types of occluders, symmetric and asymmetric, that differ in their
LV dish style. On the LV side of the asymmetric device, the aortic
end of the disc is 1 mm wider than the waist, so as to avoid impinging
upon the aortic valve. The other side is 5 – 6 mm wider than
the waist and has a platinum marker to guide device orientation.
The symmetric device has a LV disc that is 2 mm larger than the
waist. The right ventricular disc is 2 mm larger than the waist in
both types of occluders (Figure 2). The size of the occluders is
based on the waist diameter, which ranged from 6 to 14 mm in
1-mm increments (Table 1).
Under general anaesthesia, patients received a probe placed below
the xiphoid process to guide the whole procedure. The size of the
occluder was determined on the basis of the maximal measured diameter
by TTE plus 1 – 2 mm. An incision of 2 – 3 cm in length was made
in the lower sternum to expose the right ventricle, and heparin (1 mg/kg)
was then administered. The location of the puncture was determined
by protruding the right ventricle towards the VSD guided by TTE. The
right ventricular-free wall was punctured using a trocar, and then a
floppy guide wire was inserted and advanced to cross the VSD into
the left ventricle under TTE guidance (Figure 3). An appropriately
sized delivery sheath was advanced along the wire into the left
ventricle (Figure 4), and TTE subcostal views were used to make
sure the wire and sheath were directed through the VSD into the
left ventricle. The VSD occluder was screwed into the delivery
cable, and the device was loaded and introduced into the delivery
sheath and then advanced to the tip of the sheath. Before release,
TTE subcostal views were used to evaluate the device position