Operator radiation exposure and physical discomfort during a right versus left radial approach for coronary interventions: a randomized evaluation.

OBJECTIVES: This study sought to assess radiation exposure and operator discomfort when using left radial approach (LRA) versus right radial approach (RRA) for coronary diagnostic and percutaneous interventions. BACKGROUND: The transradial approach is increasingly being adopted as the preferred vascular access for coronary interventions. Currently, most are performed using an RRA. This is in part due to the perceived increased operator physical discomforts as well increased radiation exposure with an LRA. METHODS: One hundred patients were randomized to an LRA or RRA. Each operator (n = 5) had an independent randomization process, and patients were stratified according to obesity status. Operator radiation was measured using separate sets of radiation dosimeter badges placed externally on the head and thyroid and internally on the sternum. Operator physical discomfort was surveyed at 2 time points: during vascular access and at the end of the procedure. Moderate to severe physical discomfort was defined as a score of >4. RESULTS: There were no significant differences in baseline and procedural variables between groups. There was a significant increase in external radiation exposure using the RRA versus LRA (head: median: 6.12 [interquartile range (IQR): 2.6 to 16.6] mRems vs. median: 12.0 [IQR: 6.4 to 22.0] mRems, p = 0.02; thyroid: median: 10.10 [IQR: 4.3 to 25] mRems vs. median: 18.70 [IQR: 11.0 to 38] mRems, p = 0.001). More discomfort was reported with the LRA during access (LRA: 22% vs. RRA: 4%; p = 0.017), but not during the procedure (LRA: 10.0% vs. RRA: 4.0%, p = 0.43). This difference was almost entirely noted in obese patients (LRA: 30.0% vs. RRA: 3.7%, p = 0.005). CONCLUSIONS: LRA is as effective as RRA, showing a safer profile with decreased radiation exposure to the operator, at the expense of more operator discomfort only during vascular access and limited to obese patients.

Electrostatic switches that mediate the pH-dependent conformational change of "short" recombinant human pseudocathepsin D.

Human cathepsin D (hCatD) is an aspartic peptidase with a low pH optimum. X-ray crystal structures have been solved for an active, low pH (pH 5.1) form (CatD(lo)) [Baldwin, E. T., Bhat, T. N., Gulnik, S., Hosur, M. V., Sowder, R. C., Cachau, R. E., Collins, J., Silva, A. M., and Erickson, J. W. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 6796-6800] and an inactive, high pH (pH 7.5) form (CatD(hi)) [Lee, A. Y., Gulnik, S. V., and Erickson, J. W. (1998) Nat. Struct. Biol. 5, 866-871]. It has been suggested that ionizable switches involving the carboxylate side chains of E5, E180, and D187 may mediate the reversible interconversion between CatD(hi) and CatD(lo) and that Y10 stabilizes CatD(hi) [Lee, A. Y., Gulnik, S. V., and Erickson, J. W. (1998) Nat. Struct. Biol. 5, 866-871]. To test these hypotheses, we generated single point mutants in "short" recombinant human pseudocathepsin D (srCatD), a model kinetically similar to hCatD [Beyer, B. M., and Dunn, B. M. (1996) J. Biol. Chem. 271, 15590-15596]. E180Q, Y10F, and D187N exhibit significantly higher kcat/Km values (2-, 3-, and 6-fold, respectively) at pH 3.7 and 4.75 compared to srCatD, indicating that these residues are important in stabilizing the CatD(hi). E5Q exhibits a 2-fold lower kcat/Km compared to srCatD at both pH values, indicating the importance of E5 in stabilizing the CatD(lo). Accordingly, full time-course "pH-jump" (pH 5.5-4.75) studies of substrate hydrolysis indicate that E180Q, D187N, and Y10F have shorter kinetic lag phases that represent the change from CatD(hi) to CatD(lo) compared to srCatD and E5Q. Intrinsic tryptophan fluorescence reveals that the variants have a native-like structure over the pH range of our assays. The results indicate that E180 and D187 participate as an electrostatic switch that initiates the conformational change of CatD(lo) to CatD(hi) and Y10 stabilizes CatD(hi) by hydrogen bonding to the catalytic Asp 33. E5 appears to play a less significant role as an ionic switch that stabilizes CatD(lo).