Clinical question: Does an early invasive strategy for acute coronary syndrome improve short-term outcomes?
Bottom line: According to this real-world observational study, an early invasive strategy—coronary angiogram within 72 hours of presentation—is associated with lower risks of short-term cardiac death and rehospitalization for myocardial infarction (MI). However, this inference may not be valid because of a lack of key clinical information that may have influenced the data. (LOE = 2b-)
Reference: Hansen KW, Sorensen R, Madsen M, et al. Effectiveness of an early versus a conservative invasive treatment strategy in acute coronary syndromes. Ann Intern Med. 2015;163(10):737-746.
Study design: Cohort (retrospective)
Funding source: Foundation
Setting: Inpatient (any location) with outpatient follow-up
Synopsis: Using data from a Danish national registry, these investigators included patients aged 30 years to 90 years who were hospitalized with a first episode of unstable angina or acute MI. Patients were identified as having had an early invasive strategy (diagnostic coronary angiogram within 72 hours of hospitalization) or a conservative invasive strategy (coronary angiogram after 72 hours or no angiogram). The primary outcome was cardiac death or rehospitalization for MI within 60 days.
The investigators used propensity score matching to balance the baseline characteristics of the 2 groups in the initial cohort of 54,000 patients, resulting in 9852 matched patient-pairs. Notably, 42% of the conservative-strategy patients in the propensity-matched cohort received no cardiac catheterization. Overall, treatment with an early invasive strategy was associated with lower risks of cardiac death (5.9% vs 7.6%; number needed to treat [NNT] = 59; P < .001), all-cause death (7.3% vs 10.6%; NNT = 30; P < .001), and rehospitalization for MI (3.4% vs 5%; NNT = 63; P < .001).
However, as an accompanying editorial suggests, the causal inference is not necessarily valid. Given the use of an administrative database, the investigators lacked important clinical information, including indications for the angiograms performed, troponin levels, ejection fractions, and electrocardiogram findings. Without these key data, it is difficult to say whether they were comparing apples to apples, even after propensity score matching. Additionally, the study really just measures the timing of the initial angiogram without taking into account procedures done later that may have affected outcomes. As such, the validity of this study is questionable and, although the results agree with previous randomized clinical trial outcomes, it neither strengthens nor weakens what is already known.
Dr. Kulkarni is an assistant professor of hospital medicine at Northwestern University in Chicago.