Corresponding Author:
Dr. A. Mohammed Idhrees MBBS, MS MCh, FAIS
Cardiovascular Surgeon
Institute for Cardiac and Aortic Disorders
SRM Institutes for Medical Science (SIMS Hospitals)
Chennai, India – 600 026
Phone: +919962268787
E-Mail:a.m.idhrees@gmail.com
Key Words: FFRCT, Aortic dissection, Aortic aneurysm, Coronary
artery
No. of words: 1115 (including references, abstract, title page)
No. of reference: 9
Conflict of Interest: Nil
Ethic committee clearance: N/A
Coronary artery disease (CAD) is not uncommon among patients who present
with aortic aneurysm of the thoracic or abdominal aorta, as both
diseases share a common aetiology. The prevalence of CAD in patients
with abdominal aortic aneurysm is 31% to 90%, descending thoracic
aortic aneurysm is 51% and ascending aortic aneurysm is 20% (1,2).
Considering the prevalence, it is of crucial importance that CAD has to
be evaluated in these patients prior to intervention.
But there are several questions which are yet to be evidently answered
by the clinicians. What is the optimum investigation of choice to
evaluate the CAD inpatients with aortic aneurysm? Is non-invasive
investigations evaluation suffice for evaluation of CAD? Do we need to
add CT coronary angiogram (CTCA) along with angiogram regularly? If
there is a calcific coronary artery in CTCA, should the patient be
subjected to invasive coronary angiogram (ICA)?
The current European Society of Cardiology (ESC) and the European
Society of Anaesthesiology (ESA) guideline recommend preoperative CAG
only for patients with two or more cardiac risk factors and poor
functional capacity. The American and the Japanese Guidelines are no
different (3-5). It is well documented that perioperative myocardial
infarction has a significant negative impact on both early and late
survival in these patients. Hence most of the aortic surgery units add
CTCA during angiogram. CTCA has a very powerful negative predictive
value but poor positive predictive value and is hobbled by artifacts
like calcification. Such patients are then subjected to ICA. On the
contrary, multiple observational studies have documented that only half
of the suspected CAD patients have an invasively proven obstructive CAD
(5,6).
Noninvasive investigation can be broadly divided into 2 groups -
functional (stress echocardiography, single-photon emission, positron
emission tomography, and stress cardiac MRI) and anatomic (CTCA). It is
evident from above discussion that patients with aortic aneurysm with
suspected CAD will require both functional and anatomical information.
This mandates the patients need to undergo two separate non-invasive
tests or a single invasive test (ICA with fractional flow reserve- FFR)
The newer technology Fractional flow reserve derived from CT
(FFRCT) serves both simultaneously.
FFRCT is a computer-based technology that produces
functional information from a CTCA derived anatomical model.
FFRCT has a better diagnostic ability as compared to
CTCA for identifying stenosis in heavily calcified coronary arteries
(7). Further is a useful adjudicated in intermediate stenosis found on
CTCA.
The technology works on artificial intelligence. The method was
developed by HeartFlow, Inc. and is currently the only FDA- and CE
Mark–cleared FFRCT technology. The software creates a
three-dimensional (3D) anatomic model of the aorta and myocardium. For
each vessel the resting and hyperemic microvascular resistance are
quantified by the software. The computational fluid dynamics is
utilised by the software, and a color-coded, 3D anatomic model with
FFRCT values are generated for every location of the
coronary tree. Functional significance is identified by combing the
FFRCT with the patient-specific anatomic coronary map
value is combined , functionally significant lesions can be identified
(8)
This technology is approved in the U.S. and Europe, and is now
recommended by NICE as an option for patients with stable, recent onset
chest pain(9). The anatomical information coupled with functional
assessment of the coronary artery will act as a gatekeeper, restricting
patients with intermediate or significant stenosis with normal FFRCT
from undergoing ICA. Utilizing this technology, NHS in England would
save £391/ patient and may save a minimum of £9.4 million by 2022 by
avoiding invasive investigation and treatment (9).
Hence FFRCT can be combined with CT angiogram of the aorta. This will
enable the surgeons to assess the CAD and manage appropriately depending
upon the degree of stenosis. This can hopefully reduce the perioperative
mortality in aortic surgery associated with CAD. The advantages would
include (i) patient not subjected to an additional dose of contrast (ii)
Single investigation to assess the functional and anatomical details of
coronary artery (iii) Non-invasive investigation modality as compared to
ICA (iv)Cost effectiveness to the health care system