August 09, 2013
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Stress CMR in observation unit associated with more efficient treatment of possible ACS

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In a single-center trial, managing intermediate-risk patients with possible ACS using stress cardiac magnetic resonance imaging in an observation unit setting was associated with reduced coronary artery revascularization, hospital readmissions and additional testing.

Researchers investigated whether the use of stress cardiac magnetic resonance (CMR) imaging in the observation unit to evaluate intermediate-risk patients with possible ACS could be a better strategy than inpatient care.

“We hypothesized that an observation unit CMR care strategy would provide a highly accurate, noninvasive, comprehensive assessment during the index visit, thereby allowing some patients to safely avoid revascularization while reducing hospital readmissions and recurrent cardiac testing,” Chadwick D. Miller, MD, MS, and colleagues wrote.

The randomized, controlled trial included 105 participants (median age, 56 years; 54% men; 20% with preexisting CHD) from the ED at Wake Forest Medical Baptist Center. All presented with symptoms suggestive of ACS and were classified as intermediate risk. Half (n=53) were received the usual care provided by cardiologists or internists while the other half (n=52) underwent stress CMR imaging (1.5-T Siemens Magnetom Avanto system) in the observation unit. The data were then used by caregivers in the observation unit to decide whether to discharge the patient or obtain a cardiology consultation.

The primary composite endpoint was coronary artery revascularization, hospital readmission and recurrent cardiac testing after 90 days. Hospital admission was avoided in 85% of participants who had stress CMR imaging in the observation unit. Coronary artery revascularization, hospital readmission or recurrent cardiac testing occurred in 38% of the usual-care group vs. 13% of the stress CMR imaging group (HR=3.4; 95% CI, 1.4-8). All components of the primary outcome were also lower in the stress CMR imaging group: coronary artery revascularization, 15% vs. 2% (P=.03); hospital readmission, 23% vs. 8% (P=.03); and recurrent cardiac testing, 17% vs. 4% (P=.03).

The secondary endpoint was length of stay from randomization to discharge. Median length of stay was 26 hours (interquartile range: 23 hours to 45 hours) in the usual-care group vs. 21 hours (interquartile range: 15 hours to 25 hours) in the stress CMR imaging group (P<.001).

No participants who received stress CMR imaging experienced ACS after discharge, compared with of participants who received usual care.

“In this context, an observation unit CMR pathway whereby nearly all participants underwent stress CMR as the first objective cardiac test appears to approve efficiency and did not incur any safety events through 90 days,” Miller and colleagues wrote.

A limitation of the study, they wrote, is that they did not adjudicate whether revascularization was appropriate in each case, and thus cannot draw any conclusions about whether the reduction in revascularizations was appropriate. The researchers will conduct longer follow-up and recommended evaluation across multiple centers.

Disclosure: The study was supported in part by Siemens. See the full study for a list of the researchers’ relevant financial disclosures.