Value of the Triple Rule Out CTA
Isabel B. Oliva, MD
TRIPLE RULE OUT CHEST CTA
INTRODUCTION
• Chest pain is the most common presenting
symptom in the Emergency Department.
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• In the US approximately 6 million patients
present annually to the ED complaining of chest
pain.
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Isabel Oliva
Oliva,, MD
Assistant Professor
Cardiothoracic Imaging
Dept of Diagnostic Radiology
Yale School of Medicine
• Annual cost of chest pain in the Emergency
department exceeds $10 billion.
ACUTE CORONARY SYNDROME
ACUTE CORONARY SYNDROME
• Most of the patients presenting with chest pain to
the ED do not have ACS (10(10-20%).
• On the other hand,, 22--8% of ppatients with ACS are
misdiagnosed and inappropriately discharged
home resulting in a doubling mortality.
• Most of patients in whom diagnosis of ACS is
missed tend to be younger and to have an atypical
presentation with a nonnon-diagnostic ECG.
• A typical presentation of ACS includes typical
chest pain, ischemic changes in the ECG, and
elevated biochemical markers.
• Patients with clear evidence of ACS should be
admitted and are likely to proceed to cardiac
catheterization and intervention; these patients
will not benefit from triple rule out chest CTA.
ACUTE CORONARY SYNDROME
PULMONARY EMBOLISM
• Young patients presenting with chest pain with
low risk of coronary disease and no clinical
suspicion for PE or aortic dissection should be
evaluated by dedicated coronary CTA, instead of
triple rule out chest CTA.
• Chest CTA is currently the standard method used
to evaluate patients with suspected pulmonary
embolism.
• Patients with clear risk factors for pulmonary
embolism and no clinical suspicion or risk factors
for ACS should be evaluated with chest CTA
using the standard PE protocol.
TRIPLE RULE OUT
• Hypertensive patients presenting with chest pain
radiating to the back and unequal blood pressure
in the upper extremities should be evaluated with
chest CTA with a protocol dedicated for aortic
dissection, not triple rulerule-out.
• Crucial patient selection is essential before
proceeding with triple rule out (TRO) CTA.
• Indicated in patients with atypical chest pain with
reasonable pre
pre--test likelihood of ACS and aortic
dissection and pulmonary embolism.
• Low
Low-- to intermediateintermediate-risk patients with atypical
chest pain, nonspecific or normal ECG changes,
and normal initial biochemical markers
TRO - PATIENT SELECTION
TRO - TECHNIQUE
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AORTIC DISSECTION
• Patients who likely will not benefit from TRO CT
– Irregular cardiac rhythm ((atrial
atrial fibrilation
fibrilation,, multiple
PVCs))
– Unable to breath hold for more than 1010-15 seconds
– High HR and contra
contra--indication for beta blocking
– High likelihood of CAD
• History of MI
• Prior coronary stent placement
• Calcium score > 1000
• Technology
– At least 64 detectors MDCT
– ECG gating
– Tube current modulation
• Expertise
– Radiologist trained in cardiac imaging (coronary CTA)
– Need of a radiologist on site to monitor the study
TRO - IV CONTRAST DOSE
• IV contrast load
– Peak of contrast opacification in the aorta occurs 111112 sec later than peak opacification of the main
pulmonary artery
– Need an extended bolus of IV contrast to achieve
adequate concomitant opacification of the systemic
and pulmonary circulations --- minimum of 130 cc
– Limitations may occur due to borderline impaired
renal function, patient’s age, or co
co--morbidities
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TRO - QUALITY CONTROL
• Diagnostic quality
• Radiation exposure
• IV contrast load
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Total effective dose = 32.79 mS v
TRO - DIAGNOSTIC QUALITY
• Diagnostic quality
– Coronary artery opacification strongly correlates with
rate
t off IV contrast
t t injection
i j ti andd iodine
i di concentration
t ti
– Cardiac motion artifact --- ECG leads placement
– Streak artifact from SVC opacification
TRO - IV CONTRAST DOSE
• IV contrast load
– Peak of contrast opacification in the aorta occurs 111112 sec later than p
peak opacification
p
of the main
pulmonary artery
– Need an extended bolus of IV contrast to achieve
adequate concomitant opacification of the systemic
and pulmonary circulations
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TRO - RADIATION EXPOSURE
• Radiation exposure
– Reduced the FOV by excluding lung apices
– Prospective ECG gating reduces radiation exposure
BUT needs a very regular HR
– Retrospective gating allows padding and does not
depend as much on the stability of the cardiac cycle
BUT radiation exposure is much higher
CONCLUSION
• Triple rule out ECG gated chest CTA is helpful in
differentiating between the most life threatening
causes of chest pain in emergency department in
carefully selected patients.
CONCLUSION
• Most of patients who present with chest pain to
the emergency department and require a chest
CTA benefit from dedicated coronary CTA or
chest CTA with pulmonary embolism/aortic
dissection protocol rather than triple rulerule-out
protocol.
REFERENCES
• Gruettner et al. European Journal of Radiology 2011 [[Epub
Epub ahead of
print]
331--41
• Curi et al. Journal of Nuclear Cardiology 2011, vol. 18, no. 2, 331
• Madder et al. Journal of cardiovascular computed tomography 2011, vol
165--171
5, issue 3, 165
45:64--71
• Sommer et al. Invest Radiol 2010; 45:64
• Hein et al. EurRad 2009; 19:1148
19:1148--55
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