CT Scans Cause Delays in Care When Performed Prior to Primary PCI

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Performing computed tomography (CT) imaging in the emergency department (ED) prior to primary percutaneous coronary intervention (PCI) in patients with suspected ST-segment elevation myocardial infarction (STEMI) leads to longer door-to-balloon (D2B) times and rarely results in changes in patient management, according to findings published online April 26, 2012, ahead of print in the American Journal of Cardiology.

Researchers led by James M. McCabe, MD, of Brigham and Women’s Hospital (Boston, MA), performed a retrospective analysis of 410 STEMI patients admitted to EDs of 2 San Francisco institutions (1 tertiary care hospital, 1 urban trauma center) from October 2008 through April 2011. Overall, 11% (n = 45) received a CT scan in the ED prior to planned primary PCI.

Longer D2B Times, Little Gain

After activation of the cardiac cath lab, a greater number of patients who underwent CT scanning were not taken directly to cardiac catheterization compared with those who did not have a CT (31% vs. 15%; P = 0.002). However, only 4% (n = 2) of CT scans led to a change in clinical management. In both cases, these were head CT scans that showed significant strokes, leading to cancelation of cardiac catheterization.

Patients who underwent CT scans prior to catheterization had longer system delays and higher mortality compared with those who did not receive CT scans in the ED (table 1).

Table 1. In-hospital Outcomes

 

CT Scan
(n = 45)

No CT Scan
(n = 365)

P Value

Door-to-Activation Time, min

51

19

0.001

Door-to-Balloon Time, min

166

75

< 0.001

Door-to-Balloon Time < 90 min

19%

63%

< 0.001

Initiation of Dialysis

9%

1%

< 0.001

Mortality

20%

7.8%

0.006


On multivariable analysis, CT scanning in the ED before primary PCI remained an independent predictor of longer door-to-activation times (110% longer; 95% CI 40-205; P = 0.001) and longer D2B times (100% longer; 95% CI 60-160; P < 0.001). After propensity matching, CT scans were no longer a predictor of mortality (OR 1.4; 95% CI 0.4-4.6; P = 0.5).  

According to the study authors, the initial mortality difference was most likely caused by higher comorbidities among patients who received CT scanning. Compared with patients who did not receive a CT scan, those who did were less likely to have typical ischemic symptoms (33% vs. 58%; P = 0.001), and more likely to have cardiac arrest (36% vs. 15%; P = 0.001) and be intubated (31% vs. 12%; P = 0.001).

The study authors concluded that “CT scanning before primary PCI rarely changed management and was associated with significant delays in door-to-balloon times. More judicious use of CT scanning should be considered.”

In the study, CT scanning was performed to rule out multiple potential complications:

  • Intracranial process (42%)
  • Aortic dissection (40%)
  • Trauma-related injury (9%)
  • Pulmonary embolus (7%)
  • Acute abdominal process (2%)

The authors note that these fall under 2 main rationales: helping to identify an alternate diagnosis, eg, aortic dissection or pulmonary embolism, and excluding suspected contraindications to PCI, eg, intracranial hemorrhage. However, “the consequences of not learning of conditions that seriously complicate primary PCI (such as intracerebral bleeds) will typically have far greater repercussions,” than alternative causes for chest pain and ST elevation. Therefore, they note, “the threshold for CT scanning to exclude hemorrhage compared to that of ruling out alternative diagnoses should reasonably be lower.”

Mortality a Realistic Concern

Dr. McCabe and colleagues also acknowledged that while CT scans in the ED were not associated with mortality after propensity matching, “longer door-to-balloon times might affect long-term mortality and morbidity.”

Matthew J. Budoff, MD, of Harbor-UCLA Medical Center (Torrance, CA), expressed surprise at the findings. “It seemed high to me. To be honest, I did not expect 11% of patients getting a CT scan before getting to the cath lab,” he told TCTMD in a telephone interview. “That’s not our experience at all. I would say ours’ is less than 1%. We expedite these patients to the cath lab the minute an EKG shows a STEMI.”

He added that the lack of statistical significance behind the mortality association was probably due to small sample size. “I would expect that ultimately if you did a larger trial, [CT scans before primary PCI] would be associated with worse mortality,” Dr. Budoff said. “We know door-to-balloon is the primary determinant of outcomes, and [CT scans] worsened it. The trend was there, and we all know what that trend means.”

The John Ritter Syndrome

Dr. Budoff theorized that the 11% rate of CT scanning was most likely not the average for each physician in the study, but instead focused around a few who ordered CT scans more than the rest. “It doesn’t seem to be possible that it’s a perfectly uniform 11% across all providers,” he said. “I have a feeling it’s more selective, like some doctor who got burned or sued for not doing a chest X-ray, like with John Ritter [the actor who died after suffering an aortic dissection], and now they feel obligated to double check everybody. It’s that kind of defensive medicine that ultimately I think will kill people.”

There are some circumstances where performing a CT scan is called for in a suspected STEMI patient, Dr. Budoff noted. “If the chest X-ray shows a widened mediastinum, a CT scan is appropriate before rushing them to the cath lab [or] for ruling out a hemorrhagic stroke,” he said. “But that’s a rare diagnosis, and rare diagnoses are going to be found rarely. We can’t delay everybody for a rare eventuality.”

Overall, Dr. Budoff said the study findings call for increased doctor education, and suggested that clinicians “need to rely more on good clinical judgment and a chest X-ray, and less on advanced imaging unless it’s absolutely necessary, because as this study shows, the yield is astronomically small. For the most part, a STEMI is a STEMI, and unless they have a very weird presentation, they need to get to the cath lab as soon as possible.”

 


Source:
Armstrong EJ, Kulkarni AR, Hoffmayer KS, et al. Delaying primary percutaneous coronary intervention for computed tomographic scans in the emergency department. Am J Cardiol. 2012;Epub ahead of print.

 

Disclosures:

  • The paper contains no statement regarding conflicts of interest.
  • Dr. Budoff reports no relevant conflicts of interest.

 

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