[Percutaneous aortic valve replacement - pro]

Vascular access site complications after percutaneous transfemoral aortic valve implantation

BACKGROUND AND PURPOSE

Transcatheter aortic valve implantation (TAVI) is a rapidly emerging treatment option for patients with aortic valve stenosis and high surgical risk. Different access routes have been proposed for TAVI including transapical, transsubclavian and transfemoral, with percutaneous transfemoral being the preferred because least invasive and nonsurgical. However, vascular access site complications due to the large-bore delivery catheters remain an important clinical issue, particularly with respect to the elderly patient collective typically considered for TAVI. In the study, the authors analyzed their 4-year TAVI experience with respect to vascular complications and their management in patients undergoing completely percutaneous transfemoral TAVI procedures.

PATIENTS AND METHODS

Since 2006, TAVI was performed in 101 consecutive patients at the West German Heart Center Essen. 33 patients underwent transapical TAVI, eight patients transfemoral TAVI with surgical access or closure, and 60 patients percutaneous transfemoral TAVI using two commercially available prosthetic valve devices.

RESULTS

Completely percutaneous TAVI was technically successful in all but one patient with malpositioning in the aortic arch during valve retrieval. There was no intraprocedural death and 30-day mortality was 12% (7/60). Vascular access site complications occurred in 19 patients (32%), necessitating surgical repair in six of them (10%). Complications included retroperitoneal hematoma (n = 2), iliac or femoral artery dissection (n = 10), (pseudo)aneurysm formation (n = 3), and closure device-induced vessel stenosis/ occlusion (n = 6). Of these, 13 cases could be managed either conservatively (n = 5) or by contralateral endovascular treatment (n = 8).

CONCLUSION

Completely percutaneous TAVI has a high acute success rate with low intraprocedural and 30-day mortality. The patient collective appears to be prone to vascular complications which remain an important limitation of this novel technique. Although conservative or endovascular management is possible in the majority of cases, further technological developments are obliged to reduce the vascular complication rate.

Novel estrogen receptor coregulators and signaling molecules in human diseases

The steroid hormone estrogen and signaling from its receptors are increasingly recognized as critical mediators of a variety of organ-specific biological processes. Recent advances in the identification and functional characterization of novel estrogen receptor interacting proteins clearly show the complexity of hormonal signaling regulation, but may also contribute to our understanding of the roles of estrogen signaling in normal physiology and the pathobiology of human disease.

Conformational constraints on side chains in protein residues increase their information content

Like all other complex biological systems, proteins exhibit properties not seen in free amino acids (i.e., emergent properties). The present investigation arose from the deduction that proteins should offer a good model to approach the reverse phenomenon, namely top-down constraints experienced by protein residues compared to free amino acids. The crystalline structure of profilin Ib, a contractile protein of Acanthamoeba castellanii, was chosen as the object of study and submitted to 2-ns molecular dynamics simulation. The results revealed strong conformational constraints on the side chain of residues compared to the respective free amino acids. A Shannon entropy (SE) analysis of the conformational behavior of the side chains showed in most cases a strong decrease in the SE of the chi1 and chi2 dihedral angles compared to free amino acids. This is equivalent to stating that conformational constraints on the side chain of residues increase their information content and hence recognition specificity compared to free amino acids. In other words, the vastly increased information content of a protein relative to its free monomers is embedded not only in the tertiary structure of the backbone, but also in the conformational behavior of the side chains. The postulated implication is that both backbone and side chains, by virtue of being conformationally constrained, contribute to the recognition specificity of the protein toward other macromolecules and ligands.

Olfactory ensheathing cell phenotype following implantation in the lesioned spinal cord

Although olfactory ensheathing cells (OECs) are used to promote repair in the injured spinal cord, little is known of their phenotype in this environment. In this study, using quantitative reverse transcriptase-polymerase chain reaction RT-PCR, expression of neuregulin-1 mitogen/survival factors and the axonal growth regulator Nogo was quantified in OECs and compared with other non-neuronal cells. Their expression was also compared with OECs which had previously been encapsulated in a porous polymer tube and implanted into the injured spinal cord. Similar to astrocytes and fibroblasts, OECs expressed various neuregulin subtypes including neu differentiation factor, glial growth factor and sensory and motorneuron-derived factor. Implanted OECs upregulated neu differentiation factor and secreted neuregulin, but downregulated expression of all other variants. OECs and oligodendrocytes expressed Nogo-A, -B and -ABC and were immunopositive for Nogo-A protein. The Nogo-A protein in OECs was found to be cytoplasmic rather than nuclear or cell surface associated. Unlike oligodendrocytes, OECs expressed Nogo-66 receptor (NgR) mRNA. Implanted OECs upregulated Nogo-A and -B, but downregulated Nogo-ABC and NgR.