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Information pooled in a meta-analysis of 18 data sets may allow clinicians to fine-tune the ultrasonographic surveillance of small abdominal aortic aneurysms, according to a report in JAMA.
"By pooling results from 18 studies, we quantified AAA growth rates and the AAA rupture risk as a function of aortic diameter. Our intent was to provide an objective basis for selecting surveillance intervals for patients with small AAAs," said Simon G. Thompson, D.Sc., of the cardiovascular epidemiology unit, department of public health and primary care, University of Cambridge (England), and his associates.
Their findings suggest that the overall number and frequency of surveillance scans can be reduced, at least for men. However, the picture is still unclear for women, and more research is required before specific recommendations can be made, the investigators said.
The researchers reviewed the literature for data sets with 100 or more patients who had repeated ultrasound measurements of their AAAs over time. This yielded 18 data sets with 15,471 subjects with AAA diameters between 3.0 and 5.4 cm.
The 13,728 men and 1,743 women were followed for an average of 1-8 years. There were "relatively few" AAA ruptures: 178 among men and 50 among women. Among men, a 3-cm AAA took a mean of 7.4 years to have a 10% chance of reaching 5.5 cm, a 4-cm AAA took a mean of 3.2 years to have a 10% chance of reaching 5.5 cm, and a 5-cm AAA took a mean of 0.7 years to have a 10% chance of reaching 5.5 cm. Similarly, rupture rates among men approximately doubled for every 0.5-cm increase in AAA diameter. For AAAs with diameters of 3.0-4.5 cm, the average time to reach a rupture risk of 1% was at least 2 years.
Based on the lower 95% confidence limits, the risk of rupture in men would be less than 1% if surveillance intervals were extended to 3 years for AAAs measuring 3.0-3.9 cm, to 2 years for those measuring 4.0-4.4 cm, and to 1 year for those measuring 4.5-5.4 cm.
"For a U.S. patient with a 3.0-cm AAA detected by screening, this would reduce the average number of surveillance scans from approximately 15 to 7" (JAMA 2013;309:806-13).
However, if the lower 95% prediction limits of the estimates were applied (to acknowledge that the population in each study might have different growth and rupture rates), the risk of rupture in men would be less than 1% if surveillance intervals were extended to 2 years for AAAs measuring 3.0-3.9 cm, to 1 year for those measuring 4.0-4.9 cm, and to 6 months for those measuring 5.0-5.4 cm. This would result in a lesser average reduction in the number of surveillance scans from 15 to 10.
The rate of rupture was four times higher for women than for men, even though the rate of AAA growth was similar. "The clinical implication is that a lower AAA diameter threshold for surgery should be adopted for women, a recommendation already made by the joint council of the American Association for Vascular Surgery and the Society for Vascular Surgery," the researchers wrote.
A threshold of 4.5 cm rather than 5.5 cm might be more appropriate for women, but this decision must be weighed against the evidence that women have operative mortality and a poorer outcome at hospital discharge.
This study was supported by the U.K. National Institute for Health Research. The authors had no conflicts.
This meta-analysis derived from a literature sample of more than 15,000 patients largely confirms the empirically determined recommendations in the SVS practice guidelines for care of patients with AAA published in 2009.
| Dr. Larry Kraiss |
One strategy outlined by Dr. Thompson et al. in the meta-analysis proposes surveillance at 2-year intervals for AAA 3.0-3.9 cm, 1-year intervals for AAA 4.0-4.9 cm, and 6-month intervals for AAA 5.0-5.4 cm. The SVS practice guidelines recommend 3-year intervals for AAA 3.0-3.4 cm, 1-year interval for AAA 3.5-4.4 cm, and 6-month intervals for AAA 4.5-5.4 cm. The authors also acknowledge that their findings have questionable applicability to women with small AAA.
Of course, vascular surgeons treat individuals who may or may not behave like the average patient from this group of 15,000. Patients with small AAA have varying levels of anxiety and co-morbidities that must be accounted for when making decisions when to re-image the known small AAA. This account of the report does not mention whether there were subgroups of patients whose AAA grew more rapidly and might merit more frequent surveillance. Active smokers and those with COPD are often seen as having more rapid rates of AAA growth.
The report offers vascular surgeons additional evidence to reassure their patients that commonly practiced surveillance intervals are not too long and that the likelihood that a given AAA will dramatically increase its chances of rupture over the recommended interval is low. This report should not be used by payers to trump the vascular surgeon’s clinical judgment.
Dr. Larry Kraiss is Professor and Chief of Vascular Surgery, University of Utah, Salt Lake City, and is an associate medical editor for Vascular Specialist.
This meta-analysis derived from a literature sample of more than 15,000 patients largely confirms the empirically determined recommendations in the SVS practice guidelines for care of patients with AAA published in 2009.
| Dr. Larry Kraiss |
One strategy outlined by Dr. Thompson et al. in the meta-analysis proposes surveillance at 2-year intervals for AAA 3.0-3.9 cm, 1-year intervals for AAA 4.0-4.9 cm, and 6-month intervals for AAA 5.0-5.4 cm. The SVS practice guidelines recommend 3-year intervals for AAA 3.0-3.4 cm, 1-year interval for AAA 3.5-4.4 cm, and 6-month intervals for AAA 4.5-5.4 cm. The authors also acknowledge that their findings have questionable applicability to women with small AAA.
Of course, vascular surgeons treat individuals who may or may not behave like the average patient from this group of 15,000. Patients with small AAA have varying levels of anxiety and co-morbidities that must be accounted for when making decisions when to re-image the known small AAA. This account of the report does not mention whether there were subgroups of patients whose AAA grew more rapidly and might merit more frequent surveillance. Active smokers and those with COPD are often seen as having more rapid rates of AAA growth.
The report offers vascular surgeons additional evidence to reassure their patients that commonly practiced surveillance intervals are not too long and that the likelihood that a given AAA will dramatically increase its chances of rupture over the recommended interval is low. This report should not be used by payers to trump the vascular surgeon’s clinical judgment.
Dr. Larry Kraiss is Professor and Chief of Vascular Surgery, University of Utah, Salt Lake City, and is an associate medical editor for Vascular Specialist.
This meta-analysis derived from a literature sample of more than 15,000 patients largely confirms the empirically determined recommendations in the SVS practice guidelines for care of patients with AAA published in 2009.
| Dr. Larry Kraiss |
One strategy outlined by Dr. Thompson et al. in the meta-analysis proposes surveillance at 2-year intervals for AAA 3.0-3.9 cm, 1-year intervals for AAA 4.0-4.9 cm, and 6-month intervals for AAA 5.0-5.4 cm. The SVS practice guidelines recommend 3-year intervals for AAA 3.0-3.4 cm, 1-year interval for AAA 3.5-4.4 cm, and 6-month intervals for AAA 4.5-5.4 cm. The authors also acknowledge that their findings have questionable applicability to women with small AAA.
Of course, vascular surgeons treat individuals who may or may not behave like the average patient from this group of 15,000. Patients with small AAA have varying levels of anxiety and co-morbidities that must be accounted for when making decisions when to re-image the known small AAA. This account of the report does not mention whether there were subgroups of patients whose AAA grew more rapidly and might merit more frequent surveillance. Active smokers and those with COPD are often seen as having more rapid rates of AAA growth.
The report offers vascular surgeons additional evidence to reassure their patients that commonly practiced surveillance intervals are not too long and that the likelihood that a given AAA will dramatically increase its chances of rupture over the recommended interval is low. This report should not be used by payers to trump the vascular surgeon’s clinical judgment.
Dr. Larry Kraiss is Professor and Chief of Vascular Surgery, University of Utah, Salt Lake City, and is an associate medical editor for Vascular Specialist.
Information pooled in a meta-analysis of 18 data sets may allow clinicians to fine-tune the ultrasonographic surveillance of small abdominal aortic aneurysms, according to a report in JAMA.
"By pooling results from 18 studies, we quantified AAA growth rates and the AAA rupture risk as a function of aortic diameter. Our intent was to provide an objective basis for selecting surveillance intervals for patients with small AAAs," said Simon G. Thompson, D.Sc., of the cardiovascular epidemiology unit, department of public health and primary care, University of Cambridge (England), and his associates.
Their findings suggest that the overall number and frequency of surveillance scans can be reduced, at least for men. However, the picture is still unclear for women, and more research is required before specific recommendations can be made, the investigators said.
The researchers reviewed the literature for data sets with 100 or more patients who had repeated ultrasound measurements of their AAAs over time. This yielded 18 data sets with 15,471 subjects with AAA diameters between 3.0 and 5.4 cm.
The 13,728 men and 1,743 women were followed for an average of 1-8 years. There were "relatively few" AAA ruptures: 178 among men and 50 among women. Among men, a 3-cm AAA took a mean of 7.4 years to have a 10% chance of reaching 5.5 cm, a 4-cm AAA took a mean of 3.2 years to have a 10% chance of reaching 5.5 cm, and a 5-cm AAA took a mean of 0.7 years to have a 10% chance of reaching 5.5 cm. Similarly, rupture rates among men approximately doubled for every 0.5-cm increase in AAA diameter. For AAAs with diameters of 3.0-4.5 cm, the average time to reach a rupture risk of 1% was at least 2 years.
Based on the lower 95% confidence limits, the risk of rupture in men would be less than 1% if surveillance intervals were extended to 3 years for AAAs measuring 3.0-3.9 cm, to 2 years for those measuring 4.0-4.4 cm, and to 1 year for those measuring 4.5-5.4 cm.
"For a U.S. patient with a 3.0-cm AAA detected by screening, this would reduce the average number of surveillance scans from approximately 15 to 7" (JAMA 2013;309:806-13).
However, if the lower 95% prediction limits of the estimates were applied (to acknowledge that the population in each study might have different growth and rupture rates), the risk of rupture in men would be less than 1% if surveillance intervals were extended to 2 years for AAAs measuring 3.0-3.9 cm, to 1 year for those measuring 4.0-4.9 cm, and to 6 months for those measuring 5.0-5.4 cm. This would result in a lesser average reduction in the number of surveillance scans from 15 to 10.
The rate of rupture was four times higher for women than for men, even though the rate of AAA growth was similar. "The clinical implication is that a lower AAA diameter threshold for surgery should be adopted for women, a recommendation already made by the joint council of the American Association for Vascular Surgery and the Society for Vascular Surgery," the researchers wrote.
A threshold of 4.5 cm rather than 5.5 cm might be more appropriate for women, but this decision must be weighed against the evidence that women have operative mortality and a poorer outcome at hospital discharge.
This study was supported by the U.K. National Institute for Health Research. The authors had no conflicts.
Information pooled in a meta-analysis of 18 data sets may allow clinicians to fine-tune the ultrasonographic surveillance of small abdominal aortic aneurysms, according to a report in JAMA.
"By pooling results from 18 studies, we quantified AAA growth rates and the AAA rupture risk as a function of aortic diameter. Our intent was to provide an objective basis for selecting surveillance intervals for patients with small AAAs," said Simon G. Thompson, D.Sc., of the cardiovascular epidemiology unit, department of public health and primary care, University of Cambridge (England), and his associates.
Their findings suggest that the overall number and frequency of surveillance scans can be reduced, at least for men. However, the picture is still unclear for women, and more research is required before specific recommendations can be made, the investigators said.
The researchers reviewed the literature for data sets with 100 or more patients who had repeated ultrasound measurements of their AAAs over time. This yielded 18 data sets with 15,471 subjects with AAA diameters between 3.0 and 5.4 cm.
The 13,728 men and 1,743 women were followed for an average of 1-8 years. There were "relatively few" AAA ruptures: 178 among men and 50 among women. Among men, a 3-cm AAA took a mean of 7.4 years to have a 10% chance of reaching 5.5 cm, a 4-cm AAA took a mean of 3.2 years to have a 10% chance of reaching 5.5 cm, and a 5-cm AAA took a mean of 0.7 years to have a 10% chance of reaching 5.5 cm. Similarly, rupture rates among men approximately doubled for every 0.5-cm increase in AAA diameter. For AAAs with diameters of 3.0-4.5 cm, the average time to reach a rupture risk of 1% was at least 2 years.
Based on the lower 95% confidence limits, the risk of rupture in men would be less than 1% if surveillance intervals were extended to 3 years for AAAs measuring 3.0-3.9 cm, to 2 years for those measuring 4.0-4.4 cm, and to 1 year for those measuring 4.5-5.4 cm.
"For a U.S. patient with a 3.0-cm AAA detected by screening, this would reduce the average number of surveillance scans from approximately 15 to 7" (JAMA 2013;309:806-13).
However, if the lower 95% prediction limits of the estimates were applied (to acknowledge that the population in each study might have different growth and rupture rates), the risk of rupture in men would be less than 1% if surveillance intervals were extended to 2 years for AAAs measuring 3.0-3.9 cm, to 1 year for those measuring 4.0-4.9 cm, and to 6 months for those measuring 5.0-5.4 cm. This would result in a lesser average reduction in the number of surveillance scans from 15 to 10.
The rate of rupture was four times higher for women than for men, even though the rate of AAA growth was similar. "The clinical implication is that a lower AAA diameter threshold for surgery should be adopted for women, a recommendation already made by the joint council of the American Association for Vascular Surgery and the Society for Vascular Surgery," the researchers wrote.
A threshold of 4.5 cm rather than 5.5 cm might be more appropriate for women, but this decision must be weighed against the evidence that women have operative mortality and a poorer outcome at hospital discharge.
This study was supported by the U.K. National Institute for Health Research. The authors had no conflicts.
Major Finding: The risk of AAA rupture in men would be less than 1% if surveillance intervals were extended to 3 years for AAAs measuring 3.0-3.9 cm, to 2 years for those measuring 4.0-4.4 cm, and to 1 year for those measuring 4.5-5.4 cm.
Data Source: A meta-analysis of 18 studies each involving at least 100 patients who had AAAs of 3.0-5.4 cm in diameter and who had serial ultrasound measurements of the lesions for an average of 1-8 years.
Disclosures: This study was supported by the U.K. National Institute for Health Research’s Health Technology Assessment Programme. The authors reported that they had no relevant financial conflicts, although individual members had participated in aneurysm clinical trials.
