Assessment of acute chest pain by computed tomography angiography

The current work-up of patients with acute chest pain and a possible acute
coronary syndrome (ACS) is difficult, inefficient and errors are common. On a
daily basis physicians are forced to make a decision whether or not to admit a
patient with chest complaints, based on clinical insight, a rough estimation of
risk, but without evidence that an ACS is absent. Because of the potentially
catastrophic consequences of premature discharge physicians tend to be
conservative and practice a low threshold for admitting patients for
observation and noninvasive testing. The majority of patients admitted do not
have an ACS, while a small but significant number (3-5%) of patient sent home
end up having a myocardial infarction.
Noninvasive imaging has developed into an accepted technique in stable chest
pain patients, and may also be useful in patients with acute chest complaints
as it images several relevant cardiac aspects: coronary obstruction,
atherosclerotic plaque, myocardial hypoperfusion and non-cardiac thoracic
emergencies.

We hypothesize that early CT imaging allows better and faster triage (without
the need for prolonged observation) of patients with acute chest pain: early
discharge of the majority without significant coronary or other
life-threatening conditions and earlier coronary intervention of those with
significant disease before repeated blood tests or stress tests indicate to do
so.
A number of investigators have studies the potential value of CT in patients
with acute chest pain. Despite promising, preliminary results, particularly to
exclude ACS, in these low-risk patients, without ECG changes or elevated
cardiac markers, results were negatively affected by non-interpretable scans
and low rates of ACS. However manu unresolved issues remain: which patients
benefit most (or not at all), how will CT perform in a Dutch/European setting,
can we reduce the rate of nondiagnostic tests with current state-of-the-art
technology, how will CT perform in intermediate-high risk patients, can CT
avoid catheterization in patients with minimally elevated biomarkers, how does
mycardial enhancement imaging add, in how many patients can CT replace
noninvasive testing.
Invasive coronary lumenography identifies coronary stenosis but is unable to
investigate the vessel wall. Intra-coronary imaging can be helpful to
investigate the coronary vessel wall, to detect plaque, plaque disruption or
thrombus. Optical coherence tomography (OCT) is a light-based intravascular
imaging technique with a very high spatial resolution and can provide direct
visual evidence of plaque disruption as the cause of an acute coronary
syndrome. OCT images can be used to investigate the ability of MSCT to identify
vulnerable or culprit plaques.

The ultimate goal is to develop a system that allows better triage of patients
with acute chest pain to earlier identify of patients who need intervention and
salvage more heart muscle, and at the same time reduce unnecessary hospital
admission and testing in patients without a symptomatic coronary artery
disease. Based on these results, we will be able to design a randomized trial,
in a (sub)population that is expected to benfit most from early, noninvasive
coronary imaging, using parameters that best differentiate patients with or
without an ACS, to investigate the diagnostic and economic consequences of a
CT-guided or standard approach to patients with suspected acute coronary
syndrome.

This is a prospective, observational study. After the necessary, standard
procedures have been completed, consenting study participants will undergo a
non-invasive coronary angiography by contrast-enhanced, ECG-synchronized
computed tomography, to assess: a) coronary atherosclerosis; b) coronary
obstruction; c) myocardial hypoenhancement; d) alternative causes of acute
chest pain. After a preparational scan to determine the position of the heart
within the chest, a low-dose, non-enhanced scan will be performed to assess the
coronary calcium burden. In case of a high heart rate (>80/min), and in the
absence of contraindications, a betablocker will be administrated. After iv
contrast injection (80ml) the CT coronary angiogram is acquired. If important
(non-coronary) pathology is detected the blinding will be broken and the
attending physician will be notified. After the CT scan the patient will
continue the clinical workup for possible ACS. Depending on the results
patients will either undergo cardiac catheterization or be observed with
additional blood tests and a noninvasive stress test. A single bloodsample will
be taken and stored, which may be used for measurement of biomarkers.
If patients at high risk (based on presentation and test results) need to
undergo catheterization, then OCT will be performed as well during this
procedure, which will provide evidence for plaque rupture as the cause of the
acute coronary syndrome.
At 6 months patients will receive a questionaire by mail, to assess whether
cardiovascular events occurred after initial evaluation.

The CT examination is relatively short, well tolerated by most, without
significant extension of the patients stay at the ER. Iodine containing
contrast medium potentially affects the kidney function, although significant
dysfunction is rare in patients with a normal baseline kidney function.
Allergic reactions can occur but severe symptoms are rare. Roentgen exposure
(2-5 mSv, annual background radiation 3.6 mSv) will be minimized, but a very
small risk of significant disease remains. Betablockers used in a small number
of patients without contraindications is generally regarded as safe, but may
cause hypotension or bradycardia (which is the reason for giving it).
Optical coherence tomography, performed in ±50 patients, will prolong the
catheterization by 10-15 minutes, and may result in vessel wall damage in very
rare cases. Current OCT technology is well tolerated.
After 6 months patients will be requested to fill out and return a
questionnaire.
The investigated patient group will also be one benefiting from the study
results in the future. In case of CT evidence other relevant (non-coronary)
findings the blinding will be broken, and the patient may benefit from earlier
diagnosis and treatment.