Discussion:
In patients with a porcelain ascending aorta, cardiac surgery is
challenging. The manipulation of the thoracic aorta during cardiac
surgery, such as cross-clamping, incisions or cannulations, increases
the risk of perioperative embolic stroke in these patients(3) and more importantly
damage or incisions to porcelain aorta are not repairable and can risk
patients live on table. As an alternative to hypothermic fibrillatory
arrest, deep hypothermic total circulatory arrest techniques are most
commonly used for mitral valve surgery(4). As an alternative
to conventional mitral valve surgery, beating heart mitral valve surgery
without cross-clamping the aorta has been successfully performed with
acceptable clinical outcomes(5-7).
Arterial perfusion via the common femoral artery is a classic approach
to cardiac surgery in patients with calcification of the ascending
aorta. In spite of its ease of use, this method carries the risk of
embolization by atherosclerotic plaque or thrombus from the thoracic and
abdominal aortas due to retrograde perfusion(8). However, Grossi et
al (9). demonstrated
that retrograde perfusion had no significant impact on stroke incidence
in patients <50 years of age, (as in our patient 40 year old
with low risk of atherosclerosis) but had a significant effect on
neurological events in high-risk patients with aortic disease.
Nevertheless, several reports have described positive results of
axillary artery cannulation, which has become increasingly popular(10-12).
Axillary artery perfusion is associated with a lower risk of cerebral
atheroembolism because it is less affected by atherosclerosis than the
femoral artery. It can be used for selective antegrade cerebral
perfusion to avoid cannulation in patients with severe atheroma of the
brachiocephalic artery. The axillary vessels also have abundant
collaterals, which reduces the risk of severe distal
ischemia-reperfusion injury or embolization following cannulation(13).
Patients with severe porcelain aortas may benefit from cannulation of
the brachiocephalic artery. It is possible to avoid the difficulties
associated with a second incision (axillary artery cannulation) or the
problems associated with retrograde perfusion (femoral artery
cannulation) by utilizing the brachiocephalic artery(14). Transapical
aortic cannulation is an alternative method of central cannulation but
its clinical impact in patients with porcelain aorta is unclear(15).
One of the most feared complications of mitral valve replacement in a
beating heart is air embolism. A patient’s position (head down), strict
application of routine de-airing maneuvers, intraoperative use of
transesophageal echocardiography for the detection of bubbles, and a
competent aortic valve reduce the risk of air embolism(16).
Conclusion: It is critical to diagnose patients with porcelain
aorta preoperatively so that appropriate surgical methods can be
prepared. Furthermore, peripheral arteries assessment is mandatory to
select excellent site for cannulation. Although severe calcification of
the ascending aorta can easily be detected on a chest X-ray film or by
cine angiography, these modalities are not able to determine whether
there is nearly or completely circumferential calcification. It is
possible to demonstrate calcification in the aorta with a simple chest
CT, but it does not provide a satisfactory assessment of the
three-dimensional distribution of calcification. Furthermore,
multidetector-row CT images with maximum intensity projections and
volume-rendered images can be used to evaluate calcification in three
dimensions A beating heart mitral valve surgery without aortic cross
clamp can be performed safely as long as all precautions are taken to
prevent the most feared complication: an air embolism and adequate
arterial cannulation.