Figure 1.
Study time-line.
Figure 2.
Implanted casts and cuffs produce a unique echogenic signature and their length can be precisely measured by ultrasound.
Casts or cuffs were implanted around the right common carotid artery as described in Methods. (a) Representative sagittal and transverse B-mode ultrasound images of RCCA with cast or cuff 2 weeks post-surgery. Device length was measured from sagittal B-mode images or directly with microcalipers following fixation and the analyzed by (b) linear regression or (c) Bland-Altman Analysis. (b) Dotted lines indicate 95% confidence intervals. Correlation coefficient = 0.85; n = 20. (c) dotted lines: 95% limits of agreement. Bias, indicated by solid line, was calculated as -0.18 mm+/−0.27 SD.
Figure 3.
Plaque length is accurately measured by ultrasound.
(a) Representative sagittal B-mode images of RCCA from one animal prior to surgery (0) and 3, 6 and 9 weeks after cast placement. Plaque length is indicated with arrows. (b) Whole mount of the carotid artery in (a) at study termination. (c) Linear regression of ultrasound vs microcaliper measurements of plaque length (n = 6 cuffs, 10 casts). Dotted lines indicate 95% confidence intervals. Correlation coefficient = 0.92, n = 16. (d) Bland Altman analysis of plaque length as measured by microcaliper and UBM. Dotted lines represent 95% limits of agreement. Bias, indicated by solid line, was calculated as −0.27 mm+/−0.22 SD.
Figure 4.
Percent stenosis calculated from UBM parameters correlates with histological measurements.
(a) Transverse B-mode image of RCCA 2 and 9 weeks after surgery. Upper Images, Adventitia is marked “A”, plaque “P”, “Medial layer M”. Lower, images are identical, but the inner elastic lamina is outlined with dotted white line, lumen with a red dotted line. Trichrome-stained transverse sections of the same 9 wk artery; internal elastic lamina (IEL) and lumen are outlined in white and red, respectively. (b) IMT measurements of casted and cuffed animals after 2 and 9 weeks of surgery. n.s. Not significant. (c) Linear regression analysis of percent stenosis estimated by UBM and histology. See Materials and Methods for calculations of percent stenosis. Dotted lines indicate 95% confidence intervals; correlation coefficient = 0.75, n = 10 casts. (d) Comparison of UBM and histology measurements using Bland-Altman analysis. Dotted lines indicate 95% limits of agreement. Bias is indicated by solid line, was calculated as −4.76 mm±13.3 SD.
Table 1.
Changes in Lumen and IEL area upon carotid constriction.
Figure 5.
Plaques Progress More Rapidly in Casted vs Cuffed Animals.
The rate of plaque growth was determined by performing individual linear regression analysis of plaque length or stenosis over time for each animal. The slopes (rates) were compared by unpaired t-test. (a) Rate of plaque growth in length (b) Rate of plaque growth in terms of stenosis. Data are mean±SEM, n = 7 cuffs, 10 casts “*” indicates p<0.05. (See Fig. S2 for source data.)
Figure 6.
Pre-plaque PW-Doppler parameters correlate with plaque length at 9 weeks.
(a) Representative PW-Doppler tracing of a proximal RCCA before and after surgery. Note the dramatic decrease in velocity. Measurements of vmax, time in systole (ts) and tT (total time) are indicated. (b) vmax and ts/tT were calculated from pre-surgery tracings and 2 and 9 weeks after device placement. Data (mean±SEM, n = 7 cuffs, 10 casts), were analyzed by 2 way ANOVA. There was a highly significant effect of device on vmax and ts/tT ratio (p<0.005), but no significant difference between cast and cuffs on either parameter. “*” p<0.05 compared to pre-surgery. (c) Using 39 animals fitted with casts, 2 week ts/tT and vmax values were calculated and plotted against plaque length at 9 weeks and the correlation determined by linear regression. ts/tT positively correlated with plaque length (p<0.0005, r = 0.66) between, vmax and plaque length were negatively correlated (p<0.0005, r = 0.59). Dotted lines indicate 95% confidence interval.
Table 2.
Sensitivity and Specificity of PW-Doppler parameters ts/tT and vmax as predictors of plaque formation.