Carotid Atherosclerosis Before and After Cardiac Rehab
Carotid Atherosclerosis Before and After Cardiac Rehab
Our goal was to investigate the potential changes in carotid atherosclerosis in subjects who had enrolled in a randomized controlled trial of six month CCR post-TIA. We showed: 1) there were no significant changes in IMT, TPA, TPV and VWV in group A and B, and there were no significant differences in US measurements between groups A and B before or after therapy, 2) there were no significant correlations between baseline US measurements and the change in risk factors and, 3) there were no statistically significant differences in the change in US measurements between subjects with an improved and unchanged TC/HDL ratio.
First, we observed no significant changes in carotid ultrasound measurements of atherosclerosis in either groups A or B after 6 months of therapy. We note that a previous study in a small group of 30 patients showed a significantly decreased TPV in high risk stroke subjects who administered 3-months intensive atorvastatin therapy as compared to those who received placebo. Another dietary intervention study also showed significant 2-year changes in 3DUS VWV a larger group of 140 subjects. The fact that there were no significant changes in IMT, TPV or VWV here suggests that an extended period of CCR or perhaps a larger sample size is required to detect differences in carotid atherosclerosis measurements. Previous work that showed significant improvements in serum and other stroke risk factors after 6 months CCR (although not controlled) also suggests that improvements in carotid atherosclerosis may require a longer time-frame or perhaps a larger sample size to detect.
As might be expected, we observed significant and modestly strong correlations between the 1D, 2D and 3D carotid ultrasound measurements. These results were similar to previous findings in different patient populations and suggest that changes in IMT and TPA explain some of the variability in carotid TPV and VWW. This is not unexpected because TPV is in essence a 3D TPA measurement and VWV is essentially a 3D IMT + plaque measurement. It is also worth noting that there were significant linear correlations for male and female measurements when considered independently. These findings strengthen the conclusions derived from previous work where a significant but weak correlation for TPV and VWV was observed in females.
Total cholesterol (TC) to high-density lipoprotein (HDL) cholesterol ratios are commonly used for evaluating the risk of stroke and can be used as predictors of peripheral arterial disease. For the small number of subjects with improved TC:HDL ratio (n = 24), regardless of treatment group, there were no significant differences and this suggests that a larger sample size may be needed to show significant improvement in US measurements after 6 months therapy.
It is important to note the rationale for including carotid ultrasound imaging in this randomized controlled trial. While a previous study of the effects of CCR evaluated risk factors and plasma lipid biomarkers and showed modest effects, carotid US measurements of atherosclerosis were included here to try to determine the direct effects of CCR on carotid artery media hypertrophy, intima thickening and atherosclerotic plaque. Carotid US measurements provide a robust, rapid and relatively inexpensive way to generate non-invasive measurements of the direct determinants of stroke and TIA risk.
We must acknowledge a number of study limitations. First, this was a small pilot study, involving only subjects who consented to US monitoring (39 in total) and of these, there were subjects with incomplete imaging data, mainly due to insufficient image quality to complete quantitative analysis for some of the US data. As previously described, subjects were also provided a choice between two exercise treatments. We think that this choice of treatment may have had an effect on outcomes, including results obtained from carotid ultrasound measurements. Among the different ultrasound measurements, we believe that VWV would be a strong candidate in monitoring atherosclerotic disease over time in individuals performing CCR. It offers a wide dynamic range and it provides information about the arterial wall thickness as well as any plaque that may be present in the area of interest around the bifurcation of the carotid artery. Future studies may be required with a larger number of subjects or perhaps a longer follow-up study to measure and follow stroke risk factors and 3DUS measurements. Further studies can be performed to evaluate how patients who have not yet experienced a stroke but are at high risk would respond to comprehensive cardiac rehabilitation. We would hypothesize an improved quality of life and risk factors, including those related to carotid atherosclerosis decreasing the likelihood of a stroke.
Discussion
Our goal was to investigate the potential changes in carotid atherosclerosis in subjects who had enrolled in a randomized controlled trial of six month CCR post-TIA. We showed: 1) there were no significant changes in IMT, TPA, TPV and VWV in group A and B, and there were no significant differences in US measurements between groups A and B before or after therapy, 2) there were no significant correlations between baseline US measurements and the change in risk factors and, 3) there were no statistically significant differences in the change in US measurements between subjects with an improved and unchanged TC/HDL ratio.
First, we observed no significant changes in carotid ultrasound measurements of atherosclerosis in either groups A or B after 6 months of therapy. We note that a previous study in a small group of 30 patients showed a significantly decreased TPV in high risk stroke subjects who administered 3-months intensive atorvastatin therapy as compared to those who received placebo. Another dietary intervention study also showed significant 2-year changes in 3DUS VWV a larger group of 140 subjects. The fact that there were no significant changes in IMT, TPV or VWV here suggests that an extended period of CCR or perhaps a larger sample size is required to detect differences in carotid atherosclerosis measurements. Previous work that showed significant improvements in serum and other stroke risk factors after 6 months CCR (although not controlled) also suggests that improvements in carotid atherosclerosis may require a longer time-frame or perhaps a larger sample size to detect.
As might be expected, we observed significant and modestly strong correlations between the 1D, 2D and 3D carotid ultrasound measurements. These results were similar to previous findings in different patient populations and suggest that changes in IMT and TPA explain some of the variability in carotid TPV and VWW. This is not unexpected because TPV is in essence a 3D TPA measurement and VWV is essentially a 3D IMT + plaque measurement. It is also worth noting that there were significant linear correlations for male and female measurements when considered independently. These findings strengthen the conclusions derived from previous work where a significant but weak correlation for TPV and VWV was observed in females.
Total cholesterol (TC) to high-density lipoprotein (HDL) cholesterol ratios are commonly used for evaluating the risk of stroke and can be used as predictors of peripheral arterial disease. For the small number of subjects with improved TC:HDL ratio (n = 24), regardless of treatment group, there were no significant differences and this suggests that a larger sample size may be needed to show significant improvement in US measurements after 6 months therapy.
It is important to note the rationale for including carotid ultrasound imaging in this randomized controlled trial. While a previous study of the effects of CCR evaluated risk factors and plasma lipid biomarkers and showed modest effects, carotid US measurements of atherosclerosis were included here to try to determine the direct effects of CCR on carotid artery media hypertrophy, intima thickening and atherosclerotic plaque. Carotid US measurements provide a robust, rapid and relatively inexpensive way to generate non-invasive measurements of the direct determinants of stroke and TIA risk.
We must acknowledge a number of study limitations. First, this was a small pilot study, involving only subjects who consented to US monitoring (39 in total) and of these, there were subjects with incomplete imaging data, mainly due to insufficient image quality to complete quantitative analysis for some of the US data. As previously described, subjects were also provided a choice between two exercise treatments. We think that this choice of treatment may have had an effect on outcomes, including results obtained from carotid ultrasound measurements. Among the different ultrasound measurements, we believe that VWV would be a strong candidate in monitoring atherosclerotic disease over time in individuals performing CCR. It offers a wide dynamic range and it provides information about the arterial wall thickness as well as any plaque that may be present in the area of interest around the bifurcation of the carotid artery. Future studies may be required with a larger number of subjects or perhaps a longer follow-up study to measure and follow stroke risk factors and 3DUS measurements. Further studies can be performed to evaluate how patients who have not yet experienced a stroke but are at high risk would respond to comprehensive cardiac rehabilitation. We would hypothesize an improved quality of life and risk factors, including those related to carotid atherosclerosis decreasing the likelihood of a stroke.