Tissue characterization after drug-eluting stent implantation using optical coherence tomography.

OBJECTIVE: To validate optical coherence tomography (OCT) imaging for assessment of vascular healing in a preclinical animal model and human autopsy cases and to translate the findings to the assessment of vascular healing after drug-eluting stent implantation in clinical practice. APPROACH AND RESULTS: Drug-eluting and bare metal stents were imaged 28 and 42 days after implantation in atherosclerotic rabbits using OCT and simultaneously evaluated by histology. After coregistration with histology, gray-scale signal intensity (GSI) was measured for identified mature or immature neointimal tissue. Autopsy specimens were imaged with OCT and GSI values correlated with histology. Finally, prospective OCT imaging and GSI measurements were acquired in 10 patients undergoing follow-up 6 months after stenting with drug-eluting stents. Histopathologic and OCT morphometric analysis of implanted stents showed excellent correlation. Neointimal growth and vessel healing at 28 days in the animal model best correlated with human stented arteries at 6 months. In animal and human autopsy specimens, mature neointimal tissue consistently showed higher GSI values. Receiver operating characteristic curve analysis displayed high sensitivity and specificity for detection of mature neointima in animal (96% and 79%, respectively) and human autopsy (89% and 71%, respectively) data. In patients undergoing OCT follow-up 6 months after drug-eluting stent implantation, prospective GSI analysis revealed that a minimum of 27.7% of areas above stent struts represented mature neointima. CONCLUSIONS: Novel GSI analysis of OCT imaging data allows distinction between mature and immature neointimal tissue in animal models, autopsy specimens, and patients undergoing invasive surveillance in simple atherosclerotic lesions.

Morphological assessment of renal arteries after radiofrequency catheter-based sympathetic denervation in a porcine model.

OBJECTIVES: Catheter-based renal artery denervation has been successfully introduced as alternative treatment for patients suffering from drug-resistant essential hypertension. However, the local morphological changes within the vessel wall accompanying this technique remain elusive and we sought to characterize these by utilizing the simplicity radiofrequency catheter approach. METHODS: Following treatment of seven pigs, renal arteries were assigned to either the acute (n  =  6), subacute (10-day follow-up, n  =  6) or control (untreated, n  =  2) group. At follow-up blood analysis, final angiography and optical coherence tomography (OCT)-imaging of the treated arteries were performed and renal arteries and kidneys were processed for histopathology and immunohistochemistry. RESULTS: Radiofrequency-derived energy application to the vessel wall induced transmural tissue coagulation and loss of endothelium resulting in local thrombus formation also detectable by OCT. At 10 days, the luminal surface was almost completely re-endothelialized. Mural wall damage was replaced by fibrotic tissue and the adventitial layer showed strong inflammatory infiltration including vasculogenesis. Remnant autonomic nerve fascicles within the lesion segments of the subacute group displayed enhanced vacuolic degeneration and an impaired neurofilament protein immunostaining pattern. Examination of the kidneys revealed no abnormalities and blood parameters remained within the physiological range. CONCLUSION: Catheter-based application of radiofrequency energy resulted in circumscribed transmural injury within the arterial wall affecting autonomic nerve fascicles delayed to treatment. Acute loss of endothelialization resulted in thrombus formation leaving kidney perfusion apparently unimpaired.