Staten Island Corner: Coronary CTA

Welcome everyone to a new edition of the EBM blog, which is now renamed Staten Island Corner (Billy and Michelle this is a plea for you two to get involved and add to this).  I am taking over for Zina and will doing this on a monthly basis.  For topics, I welcome any ideas/questions/controversies that people are interested in.

So here it goes:

Chief complaint:  Chest pain.  Sounds pretty familiar.  We see these patients on every shift.  Just observe ED rounds and you will hear:  bed 9 admitted tele ACS, bed 13 admitted tele acs, bed 19 admitted tele (you guessed it… ACS), etc.  We all know the standard algorithm of patients presenting with acute chest pain.  At our hospital and at most hospitals in the US, we follow the rule out MI with serial enzymes path followed by admission to telemetry with the plan for a provocative test in the form of a stress test or cardiac imaging.  Admissions to hospitals are not cheap.  In America, the diagnosis of ED chest pain has been estimated to cost 10-12 BILLION dollars a year.  At a time when our nation’s finances are not in the best of shape (to put it lightly), I believe that it is our responsibility to limit/conserve resources as much as possible while practicing safe and efficient medicine.  However, the flip side of this problem is that law suits are not cheap for the hospital or the doctor and it is not good form to discharge patients home who turn out to have ACS.  Where does this leave us?  Do we admit all patients with any chest pain to avoid missing any cases of ACS?  I am sure we all agree that such a philosophy is unreasonable, boring, bad medicine, stupid, a waste of resources, a waste of our education, not doing anybody any favors, etc, etc, etc.  So now what?  We have all been waiting for the possibility of the perfect test, the test that will solve the chest pain problem.

CORONARY CTA:  Is it the answer we have been waiting for?

So the first question that we should look at is how effective is a coronary CTA when compared to the standard cardiac catheterization?

Paech and Weston conducted a systematic review in 2011 where they attempted to answer that question.  The review included 3,674 patients and excluded patients who have had CABG or PCI, contrast allergy, Afib, and renal insufficiency.  This review defined a positive cardiac cath or coronary CTA as stenosis >50%.  Overall sensitivity was 98.2%, specificity 81.6%, PPV 90.5%, and NPV 99.0%.  As Emergency medicine physicians the statistics that we care about in the particular situation are negative predictive value and sensitivity.  The reason for this is that we want to know if it is safe to send this people home who have a negative CTA.  If a patient has a positive CTA and they are admitted to the hospital and are found to have a negative work up including a negative cath, we can live the consequences of having a patient undergo an unnecessary test to err on the side of caution.  However, the reverse is not true.  We will only adopt a CTA if we can confidently say that the CTA is a suitable substitute for a cardiac cath to rule out significant CAD.  A sensitivity of 98.2% and a NPV of 99.0% are strong numbers and make a good argument for a CTA.

The second question and probably the more important question is can we, as emergency medicine physicians, use a negative CTA in the right group of patients with chest pain as a reason for discharge from the emergency department?

There are three recent relevant studies that I want to discuss here.  Goldstein, Chinnaiyan, Abidov, et al did a study to compare rest-stress myocardial perfusion imaging to coronary CTA.  This study looked at low to intermediate risk patients with chest pain symptoms suspicious for ischemia in the Emergency Department.  Inclusion criteria were TIMI <4, non-diagnositic EKG without signs of ischemia, and acute onset of pain <12 hours.  Exclusion criteria were BMI >39, known CAD, known cardiomyopathy (including EF <45%), elevated cardiac enzymes, abnormal ekg, Afib, contrast allergy, renal insufficiency, contraindication to beta blocker, CT imaging or contrast given within 48 hours.  In the CTA group, patients with <25% stenosis on CT were considered normal and eligible for discharge, 25-75% stenosis had stress-MPI, and >75% had invasive coronary angiography.  In the stress- MPI group, patients with normal study were eligible for discharge and patients with abnormal test for planned for admission/invasive coronary angiography.  Safety was defined as absence of ACS, cardiac death, or revascularization in 6 months in patients with a normal test.  Of patients with normal exams, 2 in the CT group and 1 in the stress MPI group had adverse cardiac events.   There were no significant differences in clinical outcomes in either group and the CT group had a significantly faster time to diagnosis (2.9 hours compared to 6.2 hours).  82.2% of CTA group had normal studies and were therefore eligible for discharge (large amount of people who could therefore avoid admission and all the negatives that come along with admission including cost, time, infection, etc.)

The second study is a study by Hoffmann, Bamberg, Chae, et al that looked at all patients admitted to the hospital with acute onset of chest pain who were eligible for CTA prior to being admitted.  What makes this study a good idea in my opinion is that all physicians involved in the care of the patients were blinded to the results and the CTA did not affect management.  The inclusion criteria were age >18, pain > 5 min within previous 24 hours, NSR and the exclusion criteria were elevated cardiac enzymes, EKG changes significant of ischemia, history of CAD, contrast allergy, and renal insufficiency.  CTA was evaluated for atherosclerotic plaque and stenosis and significant coronary artery stenosis was defined as stenosis > 50%.  If study was indeterminate, it was counted as significant stenosis.  Clinical endpoints were ACS during hospitalization and major adverse cardiac events (MACE) at six months including death, MI, or revascularization.  One downside to this study is that out of 1869 eligible patients, only 368 were able to fulfill eligibility and consent to test.  50.3% had no CAD on CTA, 31.2% had plaque, but no stenosis, and 18.5% had a positive CTA.  None of the patients without plaque had ACS (sensitivity and NPV of 100%).  The absence of significant stenosis had NPV of 98%, but sensitivity of 77% as 7 patients without significant stenosis were determined to have ACS.  The presence of significant stenosis was associated with a 20-fold increase in risk for ACS (OR 22.8), while the presence of plaque had an OR of 1.37.  Therefore, both plaque and significant stenosis are risk factors for ACS independent of TIMI score or cardiovascular risk factors.  50 % of patients had CTA with no evidence of CAD (plaque or stenosis) and were ruled out for ACS (also no MACE at 6 months).

The final study (and probably the most significant) is a recent study done in the NEJM in March 2012 by Litt, Gatsonis, Snyder, et al.  This study compared CTA with traditional rule out criteria.  Inclusion criteria was Age >30 with chest pain that physician determined would need admission or objective testing to rule out ACS, EKG did not reveal acute ischemia, and TIMI between 0-2.  Exclusion criteria was noncardiac chest pain, a coexistent condition that required admission regardless of ACS, normal CTA or ICA within a year, contraindications to CTA, and patients  undergoing PE CTA.  To avoid missing an MI in patients in the CTA group a second troponin was taken 90-180 min after arrival in the ED regardless of findings.  Clinically significant CTA was defined as stenosis > 50%.  None of the patients with a negative CTA (stenosis <50%) died or had an MI within 30 days of presentation.  Patients in the CTA group were more likely to be discharged from the ED (49.6% vs. 22.7%) and also had a shorter length of stay.  This shows that half of chest pain patients in the study (who met inclusion criteria) were eventually discharged from the ED instead of being admitted for traditional “rule out.”  Over the next 30 days after presentation, there was no significant difference in the two groups in cardiac cath, revascularization, repeat ED visit, hospitalization, or cardiology office visit.  This study was powered to show the safety of a CTA strategy giving an upper limit of confidence interval less than 1 % for death or MI 30 days after presentation. 

One of the limitations/downside is the issue of radiation.  However, the radiation exposure in coronary CTAs is less than nuclear myocardial perfusion imaging.  Also the radiation from coronary CTA is much less than the radiation for a PE study.  Another limitation is the need for heart rate to be controlled, hence the requirement for beta block administration which is contraindicated in some patients.  CTA is an anatomic test, not a functional test.  Therefore, stenosis does not necessary equal ACS.  The fear is that this can lead to patients having further studies (cardiac cath) that may not be indicated.  Cardiac cath is not a completely benign procedure and we have all seen or heard of the complications of cath including hematoma, MI, coronary artery rupture, etc.

So where does this leave us.  In my opinion, coronary CTA has the potential to be a practice altering test.  Just imagine how much more common rule out ACS is than rule out PE.  In the near future, we are probably going to be ordering a lot more CT scans.  It is our responsibility to limit the number of CT scans and not order it on all patients with CT scans the same way that we do not admit all patients with chest pain.  However, in the patient that we feel warrants admission for “rule out,” CTA should be strongly considered.  If there are no contraindications to CTA, this test has the potential of significantly decreasing our admissions.

I am sure that some people have strong feelings about this topic and I would like to see what people think:  both pro and con.  This is a very popular topic in Emergency Medicine right now and one that is not going to go away anytime soon.  After deciding to write about this, I heard a section on EMRAP about this and I also got a brochure in the mail to attend a conference in Baltimore that is based solely on Coronary CTA. 

Goldstein JA, Chinnaiyan KM, Abidov A, et al.  The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial.  J Am Coll Cardiol. 2011 Sep 27;58(14):1414-22.

Hoffmann U, Bamberg F, Chae CU, et al.  Coronary computed tomography angiography for early triage of patients with acute chest pain: the ROMICAT (Rule Out Myocardial Infarction using Computer Assisted Tomography) trial.  J Am Coll Cardiol. 2009 May 5;53(18):1642-50.

Litt HI, Gatsonis C, Snyder B, et al.  CT angiography for safe discharge of patients with possible acute coronary syndromes.  N Engl J Med 2012; (Published online at NEJM.org on March 26, 2012)

Malpeso JM, Budoff MJ.  Triaging patients with acute chest pain in the emergency department: implications of the CT-STAT trial.  Expert Rev Cardiovasc Ther. 2012 Feb;10(2):155-7.

Paech DC, Weston AR.  A systematic review of the clinical effectiveness of 64-slice or higher computed tomography angiography as an alternative to invasive coronary angiography in the investigation of suspected coronary artery disease.  BMC Cardiovasc Disord. 2011 Jun 16;11:32.

The following two tabs change content below.

• Bio
• Latest Posts

basile

Latest posts by basile (see all)

• Staten Island Corner: VBG for DKA? - April 9, 2013
• Staten Island Corner: Coumadin Toxicity! - February 25, 2013
• Staten Island Corner: Video vs. Direct Laryngoscopy - January 9, 2013