MIAMI BEACH — Coronary CT angiography might improve detection of significant coronary risk in an emergency department and help physicians decide which chest pain patients can be discharged, according to a presentation at a symposium on emergency radiology sponsored by Baptist Health South Florida.
“In low-risk patients, we need a test with a high negative predictive value. Essentially we are screening for [those patients] we can send home. Many people think coronary CTA is that test,” Dr. Ella A. Kazerooni said.
Nonspecific chest pain is the second most common reason that people seek emergency department care, but only about 10%–15% of those patients have an acute coronary syndrome. “On the other hand, 2%–5% with acute coronary syndromes are mistakenly sent home. Often they do not meet risk criteria. And later they are admitted with a severe MI, or they die at home,” said Dr. Kazerooni, professor and director of the division of cardiothoracic radiology at the University of Michigan, Ann Arbor.
An estimated 5 million to 8 million Americans present to an emergency department with nonspecific chest pain each year, she said. The approximate cost for taking care of these patients is $10 billion.
Identification of which low-risk patients will progress to an acute coronary event has proved difficult, Dr. Kazerooni said. Other researchers performed a meta-analysis to determine potential risk factors (JAMA 1998;280:1256–63), but most likelihood ratios were not robust enough “to say 'send them home,'” said Dr. Kazerooni.
A total of 240 patients (12%) had a confirmed cardiac etiology among those presenting with chest pain during a 1-month study at the University of Michigan emergency department chest pain center. This finding supports what is in the literature, Dr. Kazerooni said. Annually, the mean length of stay is 21 hours, and the total room cost alone for this group of patients is close to $4 million.
“If you can do something to expedite triage, you can diagnose them earlier, at a lower cost, and use those rooms for other patients,” Dr. Kazerooni said.
What is the role of coronary CT angiography in the emergency department? Immediate coronary CT angiography can safely triage low-risk acute chest pain patients home if they have negative ECG/enzymes for ischemia/infarction, Dr. Kazerooni said. “Also, it can provide a significant reduction in length of stay and cost of care.”
In another study, 31 patients who presented to an emergency department with at least 30 minutes of chest pain had coronary CT angiography performed (Circ. J. 2005;69:1047–51). These patients “were already going to the cath lab, so it was not a low-risk population,” Dr. Kazerooni said. A total of 93% of the patients were men, and 71% had acute coronary syndrome. “Remember I told you in general 12%–15% of patients [have acute coronary syndrome] in other studies, so this was biased.” This was essentially a feasibility study that demonstrated coronary CT angiography can be performed in an emergency department, she added.
Some of the best data on coronary CT angiography in the emergency department came from another study that found 75% of 69 patients had no significant CT findings, Dr. Kazerooni said (Am. J. Roentgenol. 2005;185:553–40). About half the participants were men. Outside of the study, 45 patients would not have had a chest CT. A total of 19% patients had significant CT findings that explained their chest pain. There were two false negative CT findings because the images suffered from motion artifact, she said.
The 16-slice ECG-gated multidetector CT had a negative predictive value of 96% in this study. “They concluded this was a pilot study demonstrating feasibility, and that the greatest potential is for exclusion of significant coronary disease,” Dr. Kazerooni said.
A prospective, blinded study of 103 patients, 60% of whom were men, found CT angiography had a negative predictive value of 100% (Circulation 2006:114:2251–60).
Despite its impressive negative predictive value, the safety of screening nonspecific chest pain patients in the emergency department with coronary CT angiography still needs to be established, Dr. Kazerooni said.
The high negative predictive value of normal coronary CTangiograms like this one, in a 52-year-old woman presenting with chest pain, can expedite diagnosis. Courtesy Dr. Ella A. Kazerooni