Inverse association between the existence of coronary artery disease and progression of abdominal aortic aneurysm

The effect of exercise training intervention for patients with abdominal aortic aneurysm on cardiovascular and cardiorespiratory variables: an updated meta-analysis of randomized controlled trials

OBJECTIVE

The purpose of this meta-analysis was to evaluate the effect of exercise training intervention in patients with abdominal aortic aneurysm (AAA).

METHODS

Eight randomized controlled trials (RCTs) that recruited 588 AAA patients were extracted using 4 databases (PubMed, Embase, Wanfang Data, and Cochrane Library). Physiological and biochemistry parameters that included in this study are high-sensitivity C-reactive protein (hs-CRP), respiratory peak oxygen uptake rate (VO2peak), triglyceride (TG), total cholesterol (TC), anaerobic threshold (AT), the diameter of AAA, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), and matrix metalloproteinase-9 (MMP-9). Standard mean difference (SMD) was used to assess the between group effect.

RESULTS

This meta-analysis was synthesized with findings from RCTs and found that hs-CRP (SMD, - 0.56 mg/dL; 95% CI: - 0.90 to 0.22; P = 0.001), VO2peak (SMD, 0.4 mL/kg/min; 95% CI, 0.21 to 0.60; P < 0.001), TG (SMD, - 0.39 mg/dL; 95% CI: - 0.02 to 0.77; P = 0.04), and AT (SMD, 0.75 mL/kg/min; 95% CI, 0.54 to 0.96; P < 0.001) were significantly improved in the exercise groups, while the size of AAA (SMD, - 0.15; 95% CI: - 0.36 to 0.06; P = 0.15), TC (SMD, 0.16 mg/dL; 95% CI: - 0.10 to 0.42; P = 0.23), HDL/LDL ratio (SMD, - 0.06; 95% CI: - 0.32 to 0.20; P = 0.64), HDL (SMD, - 0.09; 95% CI: - 0.39 to 0.20; P = 0.54), LDL (SMD, 0.08; 95% CI: - 0.21 to 0.38; P = 0.59), and MMP-9 (SMD, - 0.23 mg/dL; 95% CI: - 0.53 to 0.06; P = 0.12) did not differ in the exercise groups compared with the controls.

CONCLUSION

Exercise intervention improved some of the CVD risk factors but not all, hs-CRP, VO2peak and AT were significantly improved after exercise intervention, while, changes of MMP-9, the size of AAA, and the overall lipids profile were not. Exercise intervention provides an additional solution for improving cardiorespiratory capacity and health status among AAA patients, and might lead to a delay of AAA progression.

Associations of Genes for Killer Cell Immunoglobulin-like Receptors and Their Human Leukocyte Antigen-A/B/C Ligands with Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an immune-mediated disease with a genetic component. The multifactorial pathophysiology is not clear and there is still no pharmacotherapy to slow the growth of aneurysms. The signal integration of cell-surface KIRs (killer cell immunoglobulin-like receptors) with HLA (ligands, human leukocyte class I antigen molecules) modulates the activity of natural killer immune cells. The genetic diversity of the KIR/HLA system is associated with the risk of immune disorders. This study was a multivariate analysis of the association between genetic variants of KIRs, HLA ligands, clinical data and AAA formation. Genotyping was performed by single polymerase chain reaction with sequence-specific primers using commercial assays. Patients with HLA-A-Bw4 have a larger aneurysm by an average of 4 mm (p = 0.008). We observed a relationship between aneurysm diameter and BMI in patients with AAA and co-existing CAD; its shape was determined by the presence of HLA-A-Bw4. There was also a nearly 10% difference in KIR3DL1 allele frequency between the study and control groups. High expression of the cell surface receptor KIR3DL1 may protect, to some extent, against AAA. The presence of HLA-A-Bw4 may affect the rate of aneurysm growth and represents a potential regional pathogenetic risk of autoimmune injury to the aneurysmal aorta.

Comprehensive Cardiac Rehabilitation as a Therapeutic Strategy for Abdominal Aortic Aneurysm

Abdominal aortic aneurysms (AAA) are referred to as “time bombs”. The only way to prevent AAA rupture is elective repair beforehand using surgical replacement or an endovascular procedure. Non-surgical strategies to prevent AAA expansion are under intense investigation. At each AAA stage, that is, occurrence, expansion, and rupture, the mechanisms and risk factors are different, as discussed in this review. Based on the mechanism and risk factors for AAA expansion, the most effective strategy against AAA expansion need to be identified, but so far none has. Exercise is known to be essential for preventing atherosclerosis related to the coexistence of AAA and CAD, but some doctors are hesitant to prescribe exercise programs to AAA patients given that BP elevation during exercise can cause AAA expansion or rupture. In our retrospective study and prospective study on the safety and effectiveness of exercise for AAA patients, the protective role of mild-moderate exercise against expansion of small AAA was clearly shown. The stability of AAA on exercise might be related to reduced inflammatory activity in the aortic wall, stabilized elevation in BP during exercise, increased aortic blood flow, upregulation of transforming growth factor-β1, moderated BMI and/or fat, or improved endothelial function. Until a revolutionary drug emerges that can regress AAA, cardiac rehabilitation remains the best strategy for preventing AAA expansion and rupture.

Coronary artery disease and abdominal aortic aneurysm growth

To determine whether coronary artery disease (CAD) is associated with abdominal aortic aneurysm (AAA) growth, we performed a meta-analysis of currently available studies. Databases including MEDLINE and EMBASE were searched through October 2015 using PubMed and OVID. Search terms included enlargement, expansion, growth, or progression; rate or rates; and abdominal aortic aneurysm. Studies considered for inclusion met the following criteria: the design was unrestricted; the study population was AAA patients with and without CAD; and outcomes included data regarding AAA growth. For each study, growth rates in both the CAD and non-CAD groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Of 664 potentially relevant publications screened initially, we identified 20 eligible studies including data on a total of 7238 AAA patients. A pooled analysis of all 20 studies demonstrated a statistically significant association of CAD with slower AAA growth rates (i.e. a significantly negative association of CAD with AAA growth) in the fixed-effect model (SMD, −0.06 [–0.0592]; 95% CI, −0.12 [–0.1157] to −0.00 [–0.0027]; p = 0.04). There was minimal between-study heterogeneity ( p = 0.16) and a statistically non-significant association of CAD with slower AAA growth rates (i.e. a non-significantly negative association of CAD with AAA growth) in the pooled result from random-effects modeling (SMD, −0.06; 95% CI, −0.13 to 0.01; p = 0.12). In conclusion, CAD may be negatively associated with AAA growth.

Inverse Correlation Between Calcium Accumulation and the Expansion Rate of Abdominal Aortic Aneurysms

BACKGROUND

When the maximal diameter of an abdominal aortic aneurysm (AAA) exceeds a threshold, the likelihood of catastrophic rupture increases markedly. Therefore, surveillance at optimal intervals should be offered to patients with AAA. However, other than AAA diameter, there is no useful marker or index for predicting the expansion rate of an AAA or determining the optimal intervals for surveillance. The aim of this study was to evaluate the usefulness of calcium accumulation in the AAA for predicting its expansion rate.

METHODS AND RESULTS

We performed a retrospective cohort study in 414 patients with infrarenal AAA who visited The University of Tokyo Hospital. The maximal diameter and extent of calcification of each AAA were evaluated by multidetector-row computed tomography imaging. There was an inverse correlation between the extent of calcification and the subsequent AAA expansion. A lower extent of calcification in the AAA as well as the AAA diameter and absence of coronary artery disease correlated with an accelerated expansion of the AAA.

CONCLUSIONS

In AAA, a lower extent of calcification correlated with accelerated expansion. The calcification index of an AAA can be a useful predictor of its expansion rate. The study findings also support the theory that the mechanisms for progression in atherosclerosis with calcification and external expansion of an aneurysm are distinct.

Diabetes and Abdominal Aortic Aneurysm Growth

We performed a systematic literature search and a meta-analysis to assess the association between diabetes mellitus (DM) and abdominal aortic aneurysm (AAA) growth. Databases including MEDLINE and EMBASE were searched through June 2015 using PubMed and OVID. For each study, data regarding AAA growth rates in both the DM and the non-DM groups were used to generate standardized mean differences (SMDs) and 95% confidence intervals (CIs). Our search identified 19 relevant studies including data on 9777 patients with AAA. Pooled analyses demonstrated a statistically significant slower growth rates in DM patients than in non-DM patients (unadjusted SMD, −0.32; 95% CI, −0.40 to −0.24; P < .00001; adjusted SMD, −0.29; 95% CI, −0.417 to −0.18; P < .00001). Despite possible publication bias in favor of DM based on funnel plot asymmetry, even adjustment of the asymmetry did not alter the beneficial effect of DM. In conclusion, on the basis of a meta-analysis of data on a total of 9777 patients (19 studies) identified through a systematic literature search, we confirmed the association of DM with slower growth rates of AAA.

Abdominal aortic aneurysm screening for high-risk cardiac patients in the emergency department

Background: The prevalence of abdominal aortic aneurysm (AAA) is 1-2 percent in the general population, and is as high as 6 percent in groups with risk factors. Objectives: The aim of this study was to determine the prevalence of AAA amongst high-risk cardiac patients in the emergency department (ED). Methods: A prospective study was conducted to evaluate the prevalence of AAA in a high-risk population presenting to the ED. Inclusion criteria included male gender, Caucasian race, age over 50 years, history of smoking, and presentation to the ED with chest pain requiring admission. Patients enrolled in the study were screened for AAA by ultrasound (US) scan. Study subjects were excluded if there was inadequate imaging. Results: One hundred and nine patients were recruited into the study. Nineteen patients were excluded by the ED US Director secondary to inadequate imaging. Of the remaining 90 patients, eight patients were found to have AAA (n = 8; 8.9%; CI 3.9 - 16.8%). Of the eight patients with an AAA, four had diagnosed cardiovascular disease during their hospital admission. There was no statistically significant difference in secondary risk factors such as hypertension, diabetes, dyslipidemia or previous history of coronary artery disease between those with AAA and those without AAA. Conclusions: This study found that in a single ED, the prevalence of AAA in high-risk cardiac patients admitted to rule out acute coronary syndrome who could be adequately visualized with ultrasound was over 8 percent. With such a high prevalence, this population could be a potential screening group.

Coronary atherosclerotic lesions in patients with a ruptured abdominal aortic aneurysm

In this study, the coronary findings in 185 autopsy cases with a ruptured abdominal aortic aneurysm (AAA) from the Tokyo Medical Examiner's Office were examined and compared with those in 1,056 patients undergoing AAA repair at the University of Tokyo Hospital or Sakakibara Heart Institute (Tokyo, Japan). The number of cases with any significant coronary stenosis was significantly greater in the autopsy cases with a ruptured AAA than in the patients undergoing emergency repair of a ruptured AAA, suggesting that the low prevalence of CAD observed in patients undergoing emergency repair of a ruptured AAA was due to the survival bias before reaching hospital. In addition, we also found that significant coronary left main trunk stenosis was more frequent in CAD cases with a ruptured AAA than in those with an unruptured AAA, findings that suggest novel clinical implications. Large-scale prospective studies are warranted to confirm our findings and to clarify the pathophysiological relationship between coronary atherosclerosis and AAA status.

Predictors of mortality after emergency or elective repair of abdominal aortic aneurysm in a Japanese population

In Japan, there has been virtually no study in a population large enough to definitively demonstrate a relationship between the preoperative clinical features and postoperative outcomes in patients undergoing abdominal aortic aneurysm (AAA) repair. The aim of this study was to determine the preoperative variables that significantly predict postoperative mortality after emergency or elective repair in Japanese patients with infrarenal AAA. In this retrospective cohort study, we assessed significant predictors of postoperative mortality in 1055 consecutive patients undergoing emergency (n = 186) or elective repair (n = 869) of an infrarenal AAA at the University of Tokyo Hospital or Sakakibara Heart Institute (Tokyo, Japan). Using logistic regression analysis, anemia (hemoglobin <9 g/dl), shock (systolic blood pressure <80 mmHg), and hypocholesterolemia (total cholesterol <120 mg/dl) were found to be independent preoperative predictors of 30-day mortality after emergency repair for ruptured AAA. The hazard ratio (HR) (95 % confidence interval) for these three predictors was 5.96 (1.70-20.84), 8.48 (1.47-49.02), and 7.31 (1.96-27.35), respectively. In the elective repair cases, no significant preoperative predictor of postoperative mortality could be identified either within or beyond 30 days of surgery. Hypocholesterolemia, anemia, and shock were found to be independent preoperative predictors of a postoperative high mortality rate in Japanese patients undergoing emergency repair for ruptured infrarenal AAA.