Stress CMR Reduces Revascularization, Hospital Readmission, and Recurrent Cardiac Testing in Intermediate-Risk Patients With Acute Chest Pain: A Single-Center Randomized Trial
What is the impact of stress cardiac magnetic resonance (CMR) imaging in an observation unit setting compared with inpatient care on revascularization, hospital readmission, and recurrent cardiac testing among intermediate-risk patients with suspected acute coronary syndromes (ACS)?
The investigators conducted a randomized, single-center trial of 105 intermediate-risk patients with suspected, but not definite ACS. They were randomized 1:1 to usual care, which consisted of inpatient admission, or observation unit care combined with stress CMR. The primary endpoint was the composite of coronary revascularization, hospital readmission, and recurrent cardiac testing within 90 days. The secondary endpoint was length of stay from randomization to discharge from index visit. The primary safety endpoint was ACS within 90 days.
The study population was largely middle aged (median 56 years), gender balanced (54% male), and had relatively low prevalence of prior coronary artery disease (20%). Hypertension (78%), diabetes (30%), and hyperlipidemia (69%) were all highly prevalent. The primary outcome occurred more frequently among those randomized to usual care (38%), compared to those randomized to CMR (13%) (hazard ratio, 3.4; p = 0.0006). Notably, revascularization was far more frequent among those randomized to usual care (15% vs. 2%, p = 0.03). Hospital readmission and recurrent cardiac testing followed similar patterns (23% vs. 8%, p = 0.03 and 17% vs. 4%, p = 0.03, respectively). Median length of stay was decreased from 26 hours to 21 hours in the stress CMR arm (p < 0.0001). Nearly all patients in the usual care group underwent cardiac testing (91%), and all patients assigned to CMR underwent stress testing (96% with CMR imaging, 4% with stress echocardiography). Among those assigned to usual care, the great majority (62%) underwent stress echocardiography. No patients underwent stress nuclear imaging in either arm. There were no deaths in either arm or adverse events related to stress testing. ACS after discharge occurred in three subjects assigned to usual care, and none in those assigned to CMR (p = 0.24).
The authors concluded that patients with suspected ACS and intermediate risk can be safely managed in the observation unit setting when stress CMR is used for risk stratification. This approach leads to improved clinical outcomes compared to inpatient admission (usual care).
This study adds to prior work done by this group showing that stress CMR, combined with observation unit care, leads to lower costs compared to hospital admission among intermediate-risk patients with suspected ACS (Miller CD, et al., JACC Cardiovasc Imaging 2011;4:862-70), and supports a growing body of evidence that stress CMR is a safe, effective, and cost-efficient means of risk stratification of patients with suspected ACS. The primary limitations of this study are several. First, this study was conducted at a single center with very high-quality stress CMR imaging. Stress CMR remains unavailable at the vast majority of hospitals, and may be of variable quality and safety at others. Second, among subjects assigned to usual care, the majority underwent stress echocardiography. It is unclear whether results would be different if a more sensitive test were used such as if nuclear imaging had been used instead. Third, no core labs were used. It is unclear whether core lab imaging for stress echocardiography would have improved the outcomes among the usual care group. Finally, observation unit staff were aware that patients were participating in this study, while inpatient staff were blinded to patient participation. This may have led to more cautious behavior among providers caring for observation unit patients, magnifying a difference which may have been smaller or nonexistent outside of the trial setting.
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