The benefit and utility of high-sensitivity cardiac troponin in the diagnosis of myocardial infarction (MI) in patients with renal impairment is unclear. Here, we describe the implementation of high-sensitivity cardiac troponin testing on the diagnosis, management, and outcomes of MI in patients with and without renal impairment. Consecutive patients with suspected acute coronary syndrome enrolled in a stepped-wedge, cluster-randomised controlled trial were included in this pre-specified secondary analysis. Renal impairment was defined as an eGFR <60mL/min/1.73m2. The index diagnosis and primary outcome of type 1/4b MI or cardiovascular death at one year were compared in patients with and without renal impairment following implementation of a high-sensitivity cardiac troponin I assay with 99th centile sex-specific diagnostic thresholds. Serum creatinine concentrations were available in 46,927 (97%) patients (61±17years; 47% women), of whom 9,080 (19%) had renal impairment. Cardiac troponins were >99th centile in 46% and 16% of patients with and without renal impairment. Implementation increased the diagnosis of type 1 MI from 12.4% to 17.8%, and from 7.5% to 9.4% in patients with and without renal impairment (P<0.001 [both]). Patients with renal impairment and type 1 MI were less likely to undergo coronary revascularisation (26% versus 53%; P<0.001) or receive dual anti-platelets (40% versus 68%;P<0.001) than those without renal impairment, and this did not change post-implementation. In patients with cardiac troponins >99th centile, the primary outcome occurred twice as often in those with renal impairment compared to those without (24% versus 12%, HR 1.53, 95%CI 1.31 to 1.78). Implementation increased the identification of myocardial injury and infarction but failed to address disparities in management and outcomes between those with and without renal impairment.