quarta-feira, agosto 22, 2007

A opinião de outros colegas (Mayo Clinic)

Coronary computed tomographic angiography and
exercise electrocardiography: a great match or
unequal partners?
Thomas C. Gerber1*, Birgit Kantor2, and Panithaya Chareonthaitawee2
1Division of Cardiovascular Diseases and Department of Radiology, Mayo Clinic, 4500
European Heart Journal (2007) 28, 1787–1789

Trecho: Que ajuda para traduzir? copie e cole o texto no Google Tradutor

There are two fundamentally different approaches to assess
CAD, functional and anatomical. From a functional perspective,
a haemodynamically significant coronary stenosis
renders coronary blood flow inadequate to meet the metabolic
requirements of the dependent myocardium at rest
or during stress, or both. This condition is referred to as
reduced coronary flow reserve. However, which morphological
features on anatomic imaging such as SCA or CCTA are
associated with a trans-stenotic gradient is controversial.
There is general consensus that coronary artery stenoses
exceeding 70–75% of the reference diameter are likely to
be haemodynamically significant and may warrant coronary
revascularization. However, in the presence of ‘borderline
coronary stenoses (50–60% diameter in locations other
than the left main coronary artery)’, choosing coronary
revascularization as a therapeutic strategy is supported by
evidence only if there is ‘demonstrable ischemia on noninvasive
testing’.6,12 The reason for this stipulation in the
ACCF/AHA guidelines is that luminal diameter stenoses
between 50 and 70% may not reduce coronary flow reserve
as consistently as stenoses of 70%.13,14 Correlative clinical
studies between invasive, selective angiography and exercise
ECG have therefore been divided on the use of 50 or
70% luminal narrowing to define significant stenosis.4
While studies comparing CCTA with SCA have generally
considered 50% diameter stenoses as ‘significant’,3 this criterion
may not be ideally suited for comparing anatomical
and functional testing for the detection of CAD. The discordance
in diagnostic accuracy between functional testing and
CCTA results in the current study and others15–17 is therefore
not unexpected.
Is there a role for complementary non-invasive functional
and anatomical assessment? Preliminary studies of integrated
hybrid imaging combining CCTA and myocardial perfusion
imaging for the assessment of CAD have
demonstrated promising results,18 but the potential benefits
must be weighed against the substantial radiation
exposure.19 Prospective studies, such as the Study of Myocardial
Perfusion and Coronary Anatomy Imaging Roles in
CAD (SPARC) registry,20 that are designed to determine the
prognostic value, cost-effectiveness, and associated risks
of CCTA, hybrid imaging, single-photon emission tomography,
and positron emission tomography, are ongoing and
1788 Editorial
will hopefully help define their role and value in the diagnostic
work-up of patients suspected of having CAD.

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