Assay of serial cardiac markers, combined with subsequent provocative testing for patients not found to have an MI, remains the preferred strategy in patients at risk for acute coronary syndrome (ACS), but this approach requires at least a six-hour ED stay and hospital admission in most cases. Some experts have pointed to coronary CT angiography as a replacement for traditional risk stratification methods. (J Am Coll Cardiol 2011;58:1414.) AHA guidelines on chest pain evaluation include it as an option, but no evidence proves its superiority to traditional care.
CT Angiography for Safe Discharge of Patients with Possible Acute Coronary Syndromes
Litt HI, Gatsonis C, et alNew Engl J Med2012;366(15):1393
The authors hypothesized that the 30-day rate of adverse cardiac events (MI, death) in ED chest pain patients with a negative coronary CT angiogram would be less than one percent. Patients were eligible for the study if their treating physician felt that objective testing was required to evaluate suspected ACS and if they met low-risk criteria: no ischemic EKG findings and an initial thrombolysis in myocardial infarction (TIMI) score of 0–2. A total of 1,370 subjects were randomized, with 908 assigned to undergo coronary CT angiography while the others received traditional care.
Patients were followed for 30 days to assess clinical outcomes, and the authors collected data on lengths of stay, other cardiac testing, and resource utilization. No patient with a negative coronary CT angiogram (640 patients) had an MI or died after 30 days, meeting the primary outcome measure of less than one percent of major cardiac events.
None of the patients in either arm of the study died, and only one percent of the control group patients had an MI within 30 days, meaning all patients in the study met the authors' criteria for low risk, regardless of the result of their coronary CT angiogram. None of the secondary outcome measures demonstrated any significant difference across groups, although there was a trend toward increased use of cardiac catheterization and of revascularization in the coronary CT angiography group. Overall, the rate of medication use among these patients appears to reflect their low-risk status: less than 25 percent were on aspirin and less than 13 percent were on statins at 30-day follow-up.
The major positive finding promulgated by the authors of this study in promoting coronary CT angiography use was a significant increase in the rate of ED discharge versus hospital or observation unit admission, and a corresponding decrease in total hospital length of stay. The median length of stay in the coronary CT angiography group was 18 hours overall, decreasing to 12 hours in the subset of patients with a negative coronary CT angiogram and to as low as seven hours in the group of patients discharged from the ED. The median total length of stay in the traditional care group was 24 hours.
The results of this study are extremely important, though not for the reasons implied by the authors. It seems clear from the data presented that their entry criteria defined a group of chest pain patients that can be safely discharged from the ED without any further testing at all: no ischemic EKG changes, TIMI score of 2 or less, and no coexisting condition requiring admission or precluding coronary CT angiography, such as renal impairment. Ordering a coronary CT angiogram did not add anything to the risk stratification of these patients; their rate of events would indicate they were already very low risk.
The AHA guidelines agree that chest pain patients are low risk once acute MI or high-risk ACS is excluded by troponin assays, and say the patient should be discharged with a prescription for aspirin and a referral for outpatient stress testing within 72 hours. (Circulation 2011;123:e426.) Admitting or catheterizing such patients is a waste of resources, and CT scanning serves only to irradiate the patient, expose him to contrast, and increase the rates of invasive angiography and revascularization without any decrease in adverse outcomes or increase in optimal medical therapy.
The claims of decreased length of stay and increased rate of ED discharge are a bit dubious; seven hours should have been enough time to exclude MI by serial troponin assays, and the decision to discharge was being made by unblinded clinicians whose investigator colleagues receive grant support from CT manufacturers. I would estimate, in fact, that the approximately $500 spent on each of the 794 coronary CT angiograms performed in this trial could have bought about five years' worth of aspirin and antilipid therapy for each study participant, which can be predicted to have a far more salutary effect.
Coronary CT angiography, admission, and prolonged observation are not indicated in low-risk chest pain patients in the ED. Perhaps coronary CT angiography will find a use in higher-risk patients as an alternative to cardiac catheterization rather than as an alternative to tried-and-true methods of risk stratification.
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