Low-dose unfractionated heparin administration during intravascular ultrasound studies is safe even shortly after endomyocardial biopsy in cardiac transplant patients

Background: Full therapeutic heparin doses ranging from 5000-10,000 units or weight based (70-100 units/kg) have been recommended during percutaneous coronary interventions. However, there are currently no data available in regards to the appropriate dosing of unfractionated heparin during intravascular ultrasound (IVUS) studies without therapeutic coronary interventions. The goal of this study was to evaluate the safety of low dose unfractionated heparin during IVUS studies, shortly after endomyocardial biopsy in cardiac transplant patients. Methods: At the University of Arizona Medical Center, transplant patients routinely undergo diagnostic IVUS studies for the detection of early cardiac allograft vasculopathy (CAV) shortly after endomyocardial biopsy. A low-dose heparin (2000 to 3000 Units) is given before coronary wire and IVUS catheter advancement without checking activated clotting time. We evaluated the occurrence of any thromboembolic event or any other adverse outcomes in this population. Results: A total of 108 cardiac transplant patients, who had underwent routine IVUS studies between 2004-2008 were identified retrospectively. The average heparin dose used was 2528 ± 501 units. The left anterior descending artery was studied in 93% of cases. There was no thromboembolic event. Only one catheter-induced coronary dissection occurred treated with percutaneous coronary intervention. An endomyocardial biopsy was performed 10-15 minutes before the administration of low-dose heparin. There were no other major adverse cardiac events in this population during the procedure. Conclusion: This is the first study showing the safety of low-dose heparin use during diagnostic IVUS studies in cardiac transplant patients, even shortly after endomyocardial biopsy.