2007 Abstracts: Atheroembolization During Percutaneous Renal Artery Revascularization

Background: Liberation and distal passage of atheroemboli during renal artery angioplasty and stenting (RA-PTAS) has been postulated as a cause for the inferior renal function results when compared to those of open surgical revascularization. Distal embolic protection (DEP) has been advocated as a means to improve RA-PTAS outcomes, but the frequency of embolization and the characteristics of the embolic material are unknown. To further characterize procedure-associated atheroembolism, we analyzed recovered atheroembolic debris and clinical data from patients undergoing RA-PTAS with DEP.
Methods: RA-PTAS procedures were performed with DEP using a commercially available temporary balloon occlusion and aspiration catheter system. Patients treated between July 2005 and August 2006 were examined. Following RA-PTAS but prior to deflation of the distal occlusion balloon, blood was aspirated from the static column of blood proximal to the balloon and submitted for embolic particle analysis. Fragments <60µm were counted using a Coulter Counter after filtration of cellular elements, while larger fragments were counted microscopically. Angiograms, demographics and laboratory data were reviewed. Glomerular filtration rate (eGFR) was estimated pre-RA-PTAS and 3-8 weeks post-intervention using the abbreviated Modification of Diet in Renal Disease formula. Associations between clinical factors and liberated debris were examined using Spearman rank correlation coefficients, changes in renal function were examined using paired t-tests.
Results: Twenty RA-PTAS procedures were performed with DEP in 11 female and 9 male patients with renal artery stenosis and a mean age of 71.6 years. Procedures included 18 primary RA-PTAS, one RA-PTAS ipsilateral to a previous renal endarterectomy, and one angioplasty without stenting ipsilateral to a previous RA-PTAS. Mean pre-intervention stenosis was 69±13.3% and complete protection balloon occlusion was achieved in 19/20 patients. 4/20 renal arteries were predilated with DEP prior to stent insertion. Embolic debris was grossly visible at the time of specimen collection in 2/20 patients but microscopically evident in all patients. In 18 patients with both pre- and post-intervention renal function measurements, mean±SD pre- and post-intervention serum creatinines (SCr) were 1.64±0.57 vs. 1.49±0.62 mg/dL (mean±SD post- minus pre-intervention difference: -0.16±0.25; P=0.02); pre- and post-intervention eGFRs were 45.0±17.4 vs. 51.1±17.8 mL/min/1.73m² (mean±SD change: 6.1±8.1; P=0.01). Mean total embolic count was 2389±1502 (Table 1), and 96% of fragments were <100µm in diameter. No significant associations were observed between quantity of embolic particles and preoperative use of antiplatelet agents or statin medications. Correlation analyses demonstrated positive trends between increasing collected debris and impaired renal function response (rank correlation with SCr difference: +0.45, P=0.06; rank correlation with eGFR difference: -0.40, P=0.10).

Conclusion: These results demonstrate the liberation of thousands of atheroembolic particles during RA-PTAS. A marginally significant correlation between increasing quantity of embolic debris and diminished renal function response was observed, suggesting that active, "embolization-prone" lesions may be associated with suboptimal clinical results following RA-PTAS. Further investigation is ongoing to establish the relationship between atheroembolism, end organ functional impairment, and clinical responses.