OBJECTIVES: Reliable identification of adverse events is cumbersome and requires inspection of a large number of patient records. We evaluated whether focusing the search of adverse events to patients with poorer than expected outcome could help targeting adverse event detection to patients most likely to have encountered them. METHODS: Patients admitted to the Kuopio University Hospital for coronary revascularization (bypass grafting or percutaneous intervention) are asked, for monitoring of treatment effectiveness, to fill in the 15D health-related quality of life (HRQoL) questionnaire at baseline and 12 months after the intervention. The 15D score represents overall HRQoL on a 0-1 scale. A score change of ≥ ±0.015 has been reported to be clinically significant. Accordingly, patients were categorized to those with a clinically significant improvement (change ≥ 0.015), or a clinically significant deterioration (change ≥ - 0.015) in HRQoL and their patient records were reviewed for possible adverse events and complications. RESULTS: Of the altogether 217 patients, 81 showed clinically significant improvement and 64 clinically significant deterioration. Of those with a deteriorated 15D score, a significantly larger proportion had encountered a major complication (27% vs. 9%, p=0.004) or a post-intervention infection (16% vs. 5 %, p=0.030) than patients with an improved score. Patients with a negative treatment outcome also tended to have more cardiovascular complications (19% vs. 9%, p=0.068) and more often minor complications (16% vs. 7%, p=0.118). The association between adverse events and clinically significant deterioration of the HRQoL score remained after adjusting for comorbidities. CONCLUSIONS: Poor effectiveness of treatment, as judged by a patient-reported outcome such as HRQoL, can be a consequence of adverse events. Using routinely collected patient reported data may target the search for adverse events to the right patients. Enhanced identification of adverse events enables efficient learning from them and creates prospects for improved health care processes