DISCUSSION
Transcatheter ASD closure is a well-established procedure. However,
closure of ASD in the elderly population is to be performed with caution
as many patients may have a masked restrictive left ventricular
physiology, which is not detectable using routine echocardiographic
parameters 11. In the presence of a restrictive left
ventricular physiology, more left atrial blood is shunted across the ASD
to the right atrium and there is a decreased amount of blood flowing
into the restrictive left ventricle, a physiology very much akin to a
“Lutembacher’s Syndrome” 12. This often leads to
symptoms of heart failure due to an increase in pulmonary blood flow and
a decrease in cardiac output, which is a strong indication to close off
the interatrial septal communication. Patients with old age, chronic
obstructive airway diseases, diabetes mellitus, hypertension and
ischemic heart disease are particularly at risk of developing
restrictive left ventricular physiology 13.
Echocardiogram depicting severely dilated atriums should raise the
suspicion of a restrictive left ventricular physiology even though
conventional echocardiographic diastolic measurements do not suggest so.
During balloon occlusion of the ASD, all pulmonary venous blood is
forced into the left ventricle, causing an abrupt volume loading of the
restrictive left ventricle leading to an increase in left ventricular
end-diastolic pressure and acute pulmonary edema. Nevertheless, this
does not preclude ASD closure. Previous attempt to condition the left
ventricle by diuresing the patients 2-3 weeks prior to the closure has
yielded variable results. Creating a fenestration at the atrial septal
occluder with as a pop-off to offload the left ventricle is generally a
more accepted way of treatment 13-14. Self-created
fenestration usually closes off spontaneously. Its purpose is to buy
time for the left ventricle to remodel while the fenestration closes
gradually over time. To date, there is generally no consensus as the
degree of elevation of left ventricular end-diastolic pressure that
warrants the creation of fenestration or the size of the fenestration.
However, our center has a low threshold of creating a small fenestration
in patients with severely dilated atriums and the fenestration is deemed
adequate if the left ventricular end-diastolic pressure post-closure is
less than 20mmHg.
Often, elderly patients with ASD also present with atrial fibrillation.
Currently, there is no consensus as to how this group of patients should
be treated. Generally, there is 2 mainstays of treatment - rhythm or
rate control. One may attempt electrophysiological ablation to revert
the patient to sinus rhythm prior to the closure of ASD16, or close the ASD and treat the atrial fibrillation
medically. In the presence of atrial fibrillation combined with a
CHA2DS2-VASc score of
more than 1, there is a need for thromboprophylaxis 5.
Although anticoagulant therapy has been preferred choice for
thromboembolic stroke, the increased risk of bleeding especially in the
elderly population may be a factor for LAA closure. In addition, since
atrial septal closure is indicated, there is a role in closing the left
atrial appendage in the same setting. In the absence of an ASD,
consideration is made to weigh the risks and benefits of LAA occlusion,
especially procedural related complications such as the risk of cardiac
tamponade and injury to the adjacent structures during trans-septal
puncture. In patients with existing ASD, a trans-septal puncture is not
necessary and hence the procedure is much simplified. Transcatheter ASD
closure utilizes similar equipment, sheath and approach as LAA closure.
The procedure time is slightly increased if both procedures are carried
out together. Our series demonstrated a high rate of success in LAA
closure. If the transesophageal echocardiogram immediately after the
procedure shows total occlusion of the LAA, ASD closure can be performed
right away. If there is any doubt to the LAA closure, there is always
the option of deferring the ASD closure to a later date. Performing both
procedures in the same setting brings about significant cost advantage
and improved patient experience.
A recent report recommended performing these two procedures simultaneous
in patients with enlarged atriums without atrial fibrillation17. We are of the opinion that many amongst those in
sinus rhythm may continue to remain so for an extended period. Patients
with paroxysmal or newly onset atrial fibrillation may be treated via
transcatheter ablation. Indiscriminately closing the LAA during ASD
closure increases procedural cost and may even increase the patient’s
risk for procedure-related complications 17-18. We,
therefore opined that such a simultaneous approach should be
patient-specific rather than universal. In our case, we selected only
patients with chronic atrial fibrillation. In this group of patients,
LAA closure may be indicated even though patients do not have
contraindications for oral anticoagulants. Our study offers the prospect
of a novel indication for LAA closure in patients who are suitable
candidates for transcatheter ASD closure with chronic atrial
fibrillation. The presence of chronic atrial fibrillation can be an
indication for left atrial appendage closure regardless of what the
CHADS2,
CHA2DS2-VASc and
HAS-BLED scores may be.