April 5th, 2013

Thrombi on Riata ICD Leads: Another Piece in the Puzzle of Riata Management

St. Jude Riata family ICD leads are subject to an FDA class I recall due to insulation failure, cable extrusions, and a high rate of electrical failures. Sometimes the extruded cables have been related to electrical malfunction but at other times no discernable abnormalities other than a “cosmetic” defect in lead appearance has been noted. Opinion on best management of Riata leads with extruded conductors and normal electrical function is divided, with arguments both in favor and against early lead extraction.

In the Journal of Cardiovascular Electropysiology, my colleagues and I report 5 cases of conductor-extrusion-associated thrombi on Riata leads in our cohort of 87 Riata patients (5.7%).  Until now, the primary hazard associated with externalized conductor cables has been electrical failure, however, the significant number of patients that we found to have readily visualized thrombus suggests that externalized cables may result in a different sort of risk. Flow over externalized cables and exposed conductors may be associated with turbulence that predisposes to thrombus initiation.

Our data highlight several challenges when evaluating Riata ICD leads with conductor extrusions: Large thrombi carry a risk of pulmonary embolism, endocarditis, and tricuspid valve obstruction. The strategy of capping ICD leads with externalized conductors leaves the nidus for thrombus formation in the vascular system. Additionally, the thrombus may increase in size, complicating later efforts at extraction, and large thrombi adherent to externalized conductors may embolize. Conversely, this risk may increase with extraction. We also found that anticoagulation was not very effective except in one case with a small thrombus.

Based on these data, we recommend that evaluation for large thrombi be performed before transvenous lead removal of Riata leads and in all patients with visible externalized conductors. We are currently performing screening echocardiography for ICD-lead-associated thrombi for such patients. Screening guides consideration for hybrid surgical extraction when large or calcified thrombi are present, which poses increased procedural risk to a transvenous-only approach. Early extraction of Riata leads with externalized conductors may be considered in experienced centers to avoid the potential for large organized thrombus formation, regardless of electrical lead performance.

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