Risk Factors and Prognosis for Clot Formation on Cardiac Device Leads

Background Clot formation on cardiac device leads is poorly understood. We sought to determine how often clot is seen on device leads by transthoracic echo (TTE), identify risk factors, and to describe the natural history of this phenomenon. Methods We reviewed 71,888 echocardiographic studies performed at the University of California, San Francisco from 2005 to 2011. We searched for cases where clot was found adhered to a device lead with no diagnosis of endocarditis. For every case, three age‐matched controls with a device but no clot were selected from the echo database. Results We found 15 cases with clot adhered to a device lead among 1,086 patients with devices who had TTE (1.4%). In univariate analysis, females had more than four times greater odds of having a clot on their device lead and patients with a history of atrial fibrillation (AF) had an eight times greater odds. Percentage mode switch was also associated with clot formation. Only AF was still associated with clot formation after multivariate analysis. Follow‐up data were available for nine of 15 patients. All nine patients had intensification of their anticoagulant/antiplatelet regimen following clot discovery. Complete resolution or shrinkage of clot was observed in eight of nine patients. The one case with no change was a patient who continued taking only aspirin (higher dose) after clot discovery. None of the nine patients had embolic phenomenon. Conclusion Patients with AF are at higher risk for clot formation on device leads. After clot detection, treatment with anticoagulants usually results in resolution of the clot without embolic phenomenon.