Tips and tricks for antegrade recanalization of chronic total occlusions using the CrossBoss catheter

OBJECTIVES

To provide new strategies and techniques for the successful recanalization of chronic total occlusions (CTOs) with the sole use of the CrossBoss catheter. In addition, some common CTO scenarios are illustrated in detail.

BACKGROUND

CTOs are one of the most challenging complex coronary lesion subsets to intervene upon. Even with the innovation of specialized catheters, the success rate of antegrade recanalization remains low.

METHODS

Between June and December 2013, a retrospective analysis of 50 consecutive patients who presented with a planned percutaneous intervention (PCI) of a CTO was performed. In all patients, the CrossBoss catheter was used. No additional reentry devices were necessary. Procedural success was defined as <20% residual stenosis and TIMI-3 distal blood flow of the treated vessel at the end of the procedure.

RESULTS

The majority of the patients were male (72%), with an average age of 68 years. Thirty percent of patients presented with prior CTO-PCI failure. The average fluoroscopy time was 45.9 minutes and the average amount of contrast use was 273.8 mL. No patient suffered a coronary perforation from the CrossBoss catheter.

CONCLUSIONS

With increased experience using the CrossBoss catheter, the antegrade success rate of CTOs can be improved. Some tips include identifying the likely course of the artery with the aid of retrograde injection, proper guidewire selection and manipulation, and redirecting the CrossBoss catheter if there is substantial deviation from the original path.

The utility of extension catheters in transradial percutaneous coronary intervention

OBJECTIVES

To evaluate the use of extension catheters in transradial intervention of complex coronary lesions.

BACKGROUND

Complex percutaneous coronary intervention (PCI) via transradial approach remains a challenge for many interventionalists, primarily due to the difficulty in obtaining adequate guide catheter support.

METHODS

A retrospective case series identified 54 patients who presented for PCI of complex coronary lesions. A lesion was defined as complex if it contained severe calcification, proximal tortuosity, chronic total occlusion, or was located distal to a previously implanted stent. After identifying the complex lesions, a conversion to femoral approach was considered, but an attempt via the transradial approach with the use of an extension catheter was chosen as the initial strategy. Specific cases highlighting this approach are illustrated in detail.

RESULTS

The average age of the patients was 72 years old, with male predominance (55%). The success rate of completing the transradial intervention with the help of an extension catheter was 96%. Stent delivery failed due to severe tortuosity and calcification in only 2 cases. The coronary artery involved was either the left anterior descending (n = 25), the left circumflex (n = 10), the right coronary artery (n = 14), or a saphenous vein graft (n = 5). There were no coronary dissections evident from use of the extension catheter.

CONCLUSION

In the treatment of complex coronary lesions via the transradial approach, the use of an extension catheter may assist in improving successful intervention and decrease the frequency of crossover to a femoral approach.

Study of the binding environment of alpha-factor in its G protein-coupled receptor using fluorescence spectroscopy

Mating in Saccharomyces cerevisiae is induced by the interaction of alpha-factor (W1H2W3L4Q5L6K7P8G9Q10P11M12Y13) with its cognate G protein-coupled receptor (Ste2p). Fifteen fluorescently labeled analogs of alpha-factor in which the 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) group was placed at the alphaN-terminus and in side-chains at positions 1, 3, 4, 6, 7, 12 and 13 were synthesized and assayed for biological activity and receptor affinity. Eleven of the analogs retained 6-60% of the biological activity of the alpha-factor, as judged using a growth arrest assay. The binding affinities depended on the position of NBD attachment in the peptide and the distance of the tag from the backbone. Derivatization of the positions 3 and 7 side-chains with the NBD group resulted in analogs with affinities of 17-35% compared with that of alpha-factor. None of the other NBD-containing agonists had sufficient receptor affinity or strong enough emission for fluorescence analysis. The position 3 and 7 analogs were investigated using fluorescence spectroscopy and collisional quenching by KI in the presence of Ste2p in yeast membranes. The results showed that the lambda max of NBD in the position 7 side-chain shifted markedly to the blue (510 nm) when separated by 4 or 6 bonds from the peptide backbone and that this probe was shielded from quenching by KI. In contrast, separation by 3, 5, 10 or more bonds resulted in lambda max ( approximately 540 nm) and collisional quenching constants consistent with increasing degrees of exposure. The NBD group in the position 3 side-chain was also found to be blue shifted (lambda max=520 nm) and shielded from solvent. These results indicate that the position 7 side-chain is likely interacting with a pocket formed by extracellular domains of Ste2p, whereas the side-chain of Trp3 is in a hydrophobic pocket possibly within the transmembrane region of the receptor.