Aspirin Sensitivity Wanes Early during Left Ventricular Assist Device Support

Abstract

Aspirin (ASA) therapy is recommended in left ventricular assist device (LVAD) patients to prevent thromboembolic complications. Up to 30% of LVAD patients may demonstrate ASA resistance, which has been related to thrombotic complications. However, it is unknown whether individual patients exhibit temporal alterations in ASA sensitivity during LVAD support. This project evaluated changes in ASA platelet inhibition over the first 6 months of LVAD support. We hypothesized that ASA platelet inhibition would wane after the initial post-implant period. Patients who underwent placement of Heartware or Heartmate III LVAD at our institution and had serial ASA platelet sensitivity assays were included for analysis. ASA responsiveness was determined by VerifyNow assay with results expressed in aspirin reactivity units (ARU). ASA platelet resistance was defined by ARU greater than 550. ASA responsiveness was assessed post-implant after 5 days, 3 months, and 6 months. Out of 28 patients included for analysis only 7% were ASA-resistant at baseline. However, 32% of patients were ASA-resistant at 3 months and 28% at 6 months. (Figure 1). ASA-resistance was significantly more prevalent at 3-months (OR 6.1, p=0.03) with a trend toward increased prevalence at 6 months (OR 4.1, p=0.1) compared to early post-implant. ASA dose was increased in 4% and 14.3% of ASA-resistant patients at 3 and 6 months, respectively. ASA responsiveness not only varies between patients, but can significantly change within individual LVAD patients over time. Over the first 3 months, the odds of ASA-resistance increased 6-fold and remained relatively constant at 6 months despite aspirin dose adjustment. Serial assessment of ASA responsiveness may help better identify LVAD patients at risk for thrombotic or bleeding complications. Further study is required into the both the clinical implications and the mechanism of waning aspirin sensitivity in LVAD patients.