Coronary CT Angiograms Show Diagnostic Promise

By Michael Smith
WASHINGTON, 30 may 2008 -- In patients with potential acute coronary syndromes, a negative CT angiogram means they can be sent home safely, a researcher said here.That finding comes from a study of patients considered to be at low risk for heart attack who were treated in a hospital emergency department for chest pain, Anne Marie Chang, M.D., of the University of Pennsylvania, reported at the Society for Academic Emergency Medicine meeting.Dr. Chang and colleagues assigned the patients to either an immediate coronary computerized tomographic angiography or to CT angiography after a nine- to 12-hour observation period that included tests for coronary biomarkers, Dr. Chang said.
The bottom line, Dr. Chang said, is that patients whose coronary [CT angiography] is negative are not at risk for cardiovascular death or MI.
"We have shown in our clinical practice," she said, "that if they have a negative [CT angiogram], you should be able to safely send patients home."
The procedure has "excellent performance characteristics" when it's compared to standard coronary angiography, as well as to exercise or pharmacological stress tests.
But it remained unclear if doctors can use the method to stratify low-risk patients, Dr. Chang reported, where low-risk is defined as a Thrombolysis in Myocardial Infarction (TIMI) score of less than two.
To try to answer the question, she and colleagues conducted a prospective evaluation of 568 consecutive patients, with 285 in the immediate CT angiography arm and 283 in the observation-first arm.
Patients with negative tests were sent home. The main outcome was cardiovascular death or myocardial infarction within 30 days, Dr. Chang said.
All told, 476 patients (84%) had a negative coronary CT angiogram and were sent home.
During the 30-day follow-up period, none of them died of a cardiovascular event or had a nonfatal MI, she said, implying that the negative scan is sufficient to rule out any danger.
The study was one of two evaluating aspects of coronary CT angiography presented by Dr. Chang.
The other was a retrospective look at four strategies for evaluating low-risk patients after a doctor determined they should be admitted and tested to rule out acute coronary syndrome.
The four strategies were:
Immediate coronary CT angiography in the emergency room for 98 patients, without serial cardiac biomarkers.
Coronary CT angiography and clinical decision unit evaluation with serial cardiac biomarkers for 102 patients.
Clinical decision unit evaluation with serial cardiac biomarkers and stress testing, for 154 patients.
Usual care, defined as admission with serial cardiac biomarkers and hospitalist-directed evaluation, for 289 patients.
The outcomes were actual cost of care, length of stay, diagnosis of coronary disease, and cardiovascular death or MI within 30 days, Dr. Chang said.
Analysis found that the median cost for immediate CT angiography was $1,240 compared with $2,318 for clinical decision unit evaluation with CT angiography, $4,024 for clinical decision unit evaluation and stress testing, and $2, 913 for usual care. The differences were significant at P<0.01, Dr. Chang reported.
Length of stay was 8.1 hours for immediate CT angiography, compared with 20.9 hours for clinical decision unit evaluation with CT angiography, 26.2 for clinical decision unit evaluation and stress testing, and 30.2 for usual care. The differences were, again, significant at P<0.01.
The rate of diagnosis of coronary disease was similar in all four arms, ranging from 5.1% to 6.6%.
However, there were no cardiovascular deaths or MIs within 30 days in the immediate CT angiography arm, compared with 0% and 3.2% for clinical decision unit evaluation with CT angiography, 0.7% and 2.3% for clinical decision unit evaluation and stress testing, and 3.1% and 12.2% for usual care. The differences were significant at P=0.04 for cardiovascular death and P<0.01 for MI.
The cohorts for the two studies overlapped, Dr. Chang said, with some of the patients in the prospective analysis also used in the cost-benefit analysis.
The retrospective study had support from Siemens. There was no external support for the prospective study. Dr. Chang said she had no potential conflicts.
Primary source: Society for Academic Emergency Medicine meetingSource reference:Chang AM, et al "Coronary computerized tomography for rapid discharge of low risk patients with potential acute coronary syndromes" SAEM Meeting 2008; Abstract 11. Additional source: Society for Academic Emergency Medicine meetingSource reference: Chang AM, et al "Actual financial comparison of four strategies to evaluate patients with potential acute coronary syndromes" SAEM Meeting 2008; Abstract 12.