Adherence to dual anti-platelet therapy after acute coronary syndrome and its impact on patient outcome
Authors: Sulzgruber P , Sinkovec H , Kazem N , Hofer F , Hammer A , Koller L , Todorovic M , Katsch F , Gall W , Duftschmid G , Heinze G , Niessner A 
Published: November 2020

Abstract

Background
Secondary prevention after acute coronary syndrome (ACS) mirrors a key position in the reduction of morbidity and mortality in this highly vulnerable patient population. Especially dual anti-platelet therapy (DAPT) – including aspirin plus a P2Y12 inhibitor – proved to be one of the most beneficial therapeutic approaches for the reduction of re-events and stent thrombosis. However, profound epidemiological measures on adherence to DAPT intake after ACS remain scare, but seem of major importance in terms of preventing fatal cardiac adverse events. Therefore, we aimed to investigate adherence to DAPT after ACS and its impact on patient outcome from an Austrian nationwide perspective.

Methods
Within this population-based national observation all patients presenting with ACS between 04/2011 and 8/2015 in Austria were enrolled. Patient characteristics and co-morbidities were assessed via the Austrian national health insurance system and elucidated according to ICD10 definitions. Adherence to DAPT was investigated according to handing in prescriptions for aspirin and P2Y12 inhibitors at local pharmacies. Patients were followed prospectively until the primary study endpoint (=mortality) was reached. Cox Regression hazard analysis was used to investigate the impact of non-adherence to DAPT on patient outcome and was adjusted for a comprehensive subset of confounders within the multivariate model.

Results
During the observation period a total of 22.331 patients (median age: 65 years [55–75]; male: 69.7% [n=15.176]) met the inclusion criteria. Patients presenting with the indication for oral anticoagulation (n=2165; 9.7%), individuals that died during the index event (n=151; 0.7%), patients that presented with a re-ACS (n=396; 1.7%) or those who were lost during follow-up (n=96; 0.4%) were not included within the final analysis. Of alarming importance 70.7% (n=15.792) of all patients presenting with ACS did not take DAPT as recommended by current guidelines. The highest rate of drug interruption/end of therapy was observed within the first month after the index event with almost 50% of all cases. During patient follow-up until 14 months after the index event 513 individuals died. Non-adherence to DAPT proved a strong an independent association with mortality with an adjusted hazard ratio of 1.25 (95% CI: 1.09–1.41; p&lt;0.001). (see Figure 1)

Conclusion
The present nationwide investigation highlighted an overall low adherence to DAPT after ACS, with the highest interruption/end of therapy rate within the first month after the index event. Since the intake of DAPT after ACS was associated with a 20% risk reduction for fatal cardiovascular events during the observation period, awareness in terms of drug-adherence and intensified patient follow-up should be promoted, in order to prevent fatal atherothrombotic events.
Figure 1. Cumulative Mortality

Funding Acknowledgement
Type of funding source: None