Category: Radiology

CT Coronary Angiography Proves People WIth CAD Die Sooner

This is a neat study that followed up 23,854 patients from a multicenter CTCA registry – the CONFIRM registry – over three years to evaluate their long term prognostic risk.  And – amazingly enough – the patients who had no coronary artery disease identified on their CTCA had an annualized rate of 0.28% of death from all causes.  Which seems pretty impressive, and it’s better than the people who had non-obstructive and various types of obstructive CAD on their CTCA.

But then, the hazard ratios for patients who had 3-vessel and left main disease on their CTCA was still only as high as six times more likely than the no CAD cohort – which is a lot higher in relative terms, but still not very high in absolute terms – and there were a lot of other comorbidities in these patients that would contribute to their all-cause mortality from non-cardiac causes.  So, yes, not having CAD – as well as being a generally healthy person – helps you live longer.

The question still remains where CTCA fits into an Emergency Department evaluation for chest pain.  We are seeing more and more research now that primary PCI for asymptomatic lesions isn’t any survival benefit over medical management – so identifying these lesions and admitting these patients to cardiology for intervention isn’t going to be in our future.  Considering over 55% of their cohort had either non-obstructive or obstructive disease found, now you’re going to be on the hook for making outpatient CAD risk-modification decisions after cardiology declines them.

Whether CTCA is used should be a standardized, institution-wide decision, because I don’t think anyone wants to take the weight of sorting through all this evidence and risk/benefit ratios as a lone wolf.

“Age- and Sex-Related Differences in All-Cause Mortality Risk Based on Coronary Computer Tomography Angiography Findings”
www.ncbi.nlm.nih.gov/pubmed/21835321

CT Use Is Increasing(ly Justified?)

Retrospective cohort analysis based off the NHAMCS dataset, with all the inherent limitations within.

We have a 330% increase in the use of CT in the Emergency Department – up from 3.2% in 1996 to 13.9%  in 2007.  This increase is pretty stable across all age groups (including a rate of up to nearly 5% now in patients under 18 years of age).  The interesting part of the paper that’s something we didn’t already know, is their data regarding the adjusted rate of hospitalization or transfer after receiving CT.  In 1996, 26% of patients receiving a CT were admitted to the hospital, while now only 12% of patients receiving CT are admitted to the hospital.

The problem is, I’ve seen news organizations running with the conclusion: CT rates might be higher, but since the relative risk of hospitalization is lower after a CT, therefore, it must be preventing hospitalizations.  But, you can’t draw any such conclusion from the data – particularly considering hospitalizations have climbed over that same period.

We just aren’t seeing any data that links the increase in CT use to improved outcomes.  Increased CT usage certainly has its place as the standard of care in many instances, but there’s no silver lining to this 330% increase.

“National Trends in Use of Computer Tomography in the Emergency Department.”
www.ncbi.nlm.nih.gov/pubmed/21115875

CT Is No Longer Adequate To Clear C-Spine

The insanity never stops.  It’s a good thing MRI is becoming increasingly available, because the more papers like this are published in major journals, the more we’re going to be stuck following every possible outcome to it’s bitterest end with the strongest microscope we have.

There a lots of problems with using this paper to change practice – of their 9152 patients undergoing CT for trauma, 741 had persistent midline tenderness leading towards MRI.  Of those 741, only 174 were enrolled for a variety of reasons.  And this study doesn’t tell us enough useful information to help distinguish the characteristics of the 78 patients in whom an injury was detected to help us differentiate them from the patients in whom no injury was detected.

But the fact remains, they identified serious injuries on MRI in patients who had negative CTs – and not just obtunded, intubated, polytrauma patients like in the other studies.

Just one more thing to worry about.

“Cervical Spine Magnetic Resonance Imaging in Alert, Neurologically Intact Trauma Patients With Persistent Midline Tenderness and Negative Computed Tomography Results”
http://www.ncbi.nlm.nih.gov/pubmed/21820209

The Slow Death of the Lumbar Puncture

As modern CT scanners become more sensitive, the ability of scanners to discriminate smaller and small abnormalities – such as spontaneous aneurysmal subarachnoid hemorrhage – continues to increase.  This BMJ paper makes another case for forgoing lumbar puncture in patients with a negative CT scan.

Specifically, they say that all the SAH in their cohort was picked up by a 3rd generation scanner as long as the scan was performed within six hours of headache onset.  Unfortunately, this is another one of those studies that uses follow-up as a proxy for the gold standard evaluation – only half of their enrolled cohort underwent lumbar puncture.  They followed up their patients for six months, but survival at six months doesn’t rule out pathology, it only rules out death from that specific pathology, and only if an autopsy was performed.

But, CT scan is starting to get close to the point where the false negatives of CT are equivalent to the false positives of the lumbar puncture – and I would imagine the costs and harms to the patient begin to approach equivalence.  It definitely changes the equation for your patients when you come back with a negative CT scan and your patient wants to know what the chances are they really need this lumbar puncture.

“Sensitivity of Computer Tomography Performed Within Six Hours of Headache For Diagnosis of Subarachnoid Haemorrhage: Prospective Cohort Study”
www.ncbi.nlm.nih.gov/pubmed/21768192

CTCA Studies Are Not Externally Valid

This is a multicenter study from Canada that looked at the diagnostic accuracy of computed tomographic coronary angiography using invasive coronary angiography as the gold standard – and they found that it’s not bad.  Specifically, they found it was not bad at one of their four centers used in the study, and terrible at three of the four centers used in the study.  In a patient population with a pretest probability of CAD less than 50%, the AUC for CTCA was 0.951 at center 1, and 0.597 at centers 2, 3, and 4 combined.

So, clearly, the most important factor affecting the results of your CTCA is your institution’s skill at performing and interpreting the test.  Which, if you take it one step further, means that unless your institution is a CTCA center of excellence like the ones pumping out the CTCA studies, you can’t apply their results to your practice.  Specificity stays reasonable, but you lose a lot of sensitivity – and when the CTCA for low-risk rapid rule-out is predicated on the high NPV, you can’t afford to lose sensitivity.

“Ontario Multidetector Computed Tomographic Coronary Angiography Study”
www.ncbi.nlm.nih.gov/pubmed/21403014

The Diagnose-a-Tron of the Future: FDG-PET

Imagine, if necessary, a case you see every hour in the ED – a child with a fever.  Wave a magic wand in triage, find the source of the fever, and let the doctor pick up the decision-making process advance from there.

This scenario is, of course, totally farfetched – after all, you still need a certain number of HPI and ROS elements before you wave the magic wand to bill at a higher level of service.

But, the principle – this is a fascinating article regarding the workup of “fever of unknown origin” in adults.  These 81 patients had fevers for 3 weeks without a satisfactory explanation, and their cases were retrospectively reviewed following referral to FDG-PET scans.  Essentially, any time this FDG-PET scan localized to an area of high uptake, it provided significant helpful localizing information regarding the underlying disease process.  Examples of diagnoses it identified were infectious endocarditis, tuberculosis, pyogenic spondylitis, graft infections, Takayasu arteritis, and a host of other fascinatingly difficult diseases to identify.

The main diagnostic drawback is that it is mostly only structurally/anatomically specific, not necessarily disease specific, so there is a lot to do in terms of clinical correlation with imaging findings.  And then there is the small issue where it’s a nuclear medicine study requiring 5 hours of fasting and an injection of the FDG tracer 1 hour before the study is performed.  But, someday a decade out, the next generations of these devices might be more clinician-friendly….

“FDG-PET for the diagnosis of fever of unknown origin: a Japanese multi-center study.”
www.ncbi.nlm.nih.gov/pubmed/21344168

Send Children With Negative CTs Home

We should all love PECARN.  I love PECARN (Pediatric Emergency Care Applied Research Network) – and not just because I helped set it up as a research assistant peon before medical school.  I love it because it takes multicenter enrollment cohorts to conduct adequately powered research in a population that is rarely affected by serious morbidity and mortality.

Of 13,543 children with GCS 14 or 15 and a normal CT scan, none needed neurosurgical intervention in their follow-up period.  A small handful of these patients had a repeat CT or MRI for some reason, and between 10-25% of the hospitalized patients and 2-10% of the discharged patients had an abnormal result on repeat imaging.  None led to any intervention…which then, of course, begs the question whether it was appropriate to perform a test that did not result in meaningful change in management.  But, there’s not enough patients in this group to draw conclusions as to whether repeat scans should or should not be performed.

My only caveat – when you take an over-utilized test in which nearly all patients are certainly fine and will continue to be fine, you actually dilute its external validity to the patient population that really matters.  However, even in a higher-risk patient population in which CTs are used far more conservatively, the clinically relevant answer is still going to be same – the only reasonable practice is still going to be to discharge these patients home.

“Do children with blunt head trauma and normal cranial tomography scan results require hospitalization for neurologic observation?”
www.ncbi.nlm.nih.gov/pubmed/21683474

CCTA Only Predicts Revascularizations

This is an interesting systematic review of coronary computer tomography angiography that, I think, shows mostly that the endpoints for cardiology studies need to be re-evaluated.  The conclusion that circulates in the new has been that positive CCTA was highly predictive of coronary events – patients with >1 segment of >50% stenosis on CCTA had an 11.9% annualized rate of coronary “events” when compared to the 1.1% annualized rate of patients without any >50% stenosis.  This generates the 10.74 hazard ratio that has been circulating through the press releases trumpeting the predictive value of CCTA.

Unfortunately, this predictive value is a self-fulfilling prophecy because 62% of their “events” were revascularizations.  If you subtract out the portion that went for revascularization, the remaining all-cause mortality, cardiovascular death, nonfatal MI, UA requiring hospitalization, that’s 5% annualized rate.  Still higher than folks without any coronary stenoses at all, but you have to wonder – could we have predicted the population with a 5% cardiovascular morbidity risk without a CCTA?  Does the management decision to perform revascularization confer upon this population a cardiovascular morbidity/mortality benefit?  We are seeing a lot more in the literature showing that medical management is as advantageous as stenting, so, again, I’m not sure what the role of CCTA is – particularly from the Emergency Department.

“Meta-analysis and systematic review of the long-term predictive value of assessment of coronary atherosclerosis by contrast-enhanced coronary computed tomography angiography.”
http://www.ncbi.nlm.nih.gov/pubmed/21658564

Sensitivity of CT Angiography for Aneurysms

Not exactly the article I was expecting when I pulled it, but mildly interesting nonetheless.  The real applicability of this article is towards those folks who say the LP for SAH is outdated, and we should just proceed with CTA to identify the culprit aneurysm.

As opponents say, many aneurysms identified by CTA are asymptomatic and unrelated to the acute headache in the Emergency Department, and, without the LP, you don’t know their clinical relevance.  This study lets them also say that CTA doesn’t even necessarily perform well enough at this task to warrant use – it will miss 5% of aneurysms and overcall 3.8%.

However, it must be said, this meta-analysis uses data from a number of old studies that have older CT scanners that were very poor at detecting <4mm aneurysms.  Once you get to 16 and 64 row CT, your sensitivity is closer to 98-99% – and then you have to fall back to the asymptomatic/clinical relevance argument.

“Diagnosing cerebral aneurysms by computed tomographic angiography: meta-analysis”
http://www.ncbi.nlm.nih.gov/pubmed/21391230

CT Coronary Angiography Screening Is Not Beneficial

Disclaimer: I despise CCTA for low-risk chest pain in the ED.  It leads to additional unnecessary testing, interventions, and harms that outweigh the risk of coronary events in its target population.  Our liability-sensitive practice has us evaluating an ever-increasing cohort of low- and (mostly) zero-risk young chest pain patients, and this is purported to be a test of choice for identifying a zero-zero risk population.
But there are just far too many false positives that have coronary artery disease of uncertain clinical significance.
This is a Korean study that compared 1000 matched controls that did not undergo CCTA with 1000 who did.  215 asymptomatic patients had positive CCTA – defined as any atherosclerotic plaque.  52 had >50% stenosis and 21 had >75% stenosis.
Their control cohort and their CCTA cohort were very similar – and 55-59% low risk, 34-29% intermediate, and 10% high risk based on NCEP risk stratification.
And their control group had a grand total of 1 cardiac event within their 18 month follow-up period, as did a single person in their positive CCTA group.  However, the CCTA group ended up with more additional testing and cardiac revascularization procedures during their follow-up time frames – with no change in outcomes.
Now, these are asymptomatic patients chosen for screening – not the same as our chest pain patients in the ED – but it’s another call for caution regarding overtesting and overtreating.