Paul D. Hayes

Endovascular stenting versus open surgery for thoracic aortic disease : Systematic review and meta-analysis of perioperative results

BACKGROUND Endovascular stenting has emerged as an alternative to open repair in patients requiring surgery for thoracic aortic pathology. A number of comparative series have been published but, to date, there has been no meta-analysis comparing outcomes following stenting as opposed to open surgery. METHODS Electronic abstract databases and conference proceedings were searched to identify relevant series. Pooled odds ratios were calculated using random effects models for perioperative mortality, neurological injury, and major reintervention. RESULTS The search identified 17 eligible series, totaling 1109 patients (538 stenting). Stenting was associated with a significant reduction in mortality (pooled odds ratio 0.36; 95% CI 0.228-0.578; P < .0001) and major neurological injury (pooled odds ratio 0.39; 95% CI 0.25-0.62; P = .0001). There was no difference in the major reintervention rate (pooled odds ratio 0.91; 95% CI 0.610-1.619). There was a reduction in hospital and critical care stay although there was evidence of heterogeneity and bias with respect to these outcomes. Subgroup analyses suggested that endovascular repair reduced mortality (pooled odds ratio 0.25; 95% CI 0.09-0.66) and neurological morbidity (pooled odds ratio 0.28; 95% CI 0.13-0.61) in stable patients undergoing repair of thoracic aortic aneurysms. There was no effect on mortality in patients with thoracic aortic trauma but neurological injury was reduced (pooled odds ratio 0.17; 95% CI 0.03-1.03). Endovascular repair did not confer any apparent benefit over open surgery in patients with thoracic aortic rupture. CONCLUSION Endovascular thoracic aortic repair reduces perioperative mortality and neurological morbidity in patients with descending thoracic aortic aneurysms. There may be less benefit in other thoracic aortic conditions.

Effect of CO2 on dynamic cerebral autoregulation measurement

Arterial pCO2 is known to influence cerebral autoregulation but its effect on the dynamic relationship between mean arterial blood pressure (ABP) and mean cerebral blood flow velocity (CBFV), obtained from spontaneous fluctuations in ABP, has not been established. In 16 normal subjects, ABP was measured non-invasively (Finapres), CBFV was estimated with Doppler ultrasound in the middle cerebral artery, and end-tidal CO2 (EtCO2) was measured with an infrared capnograph. Recordings were made before, during and after breathing a mixture of 5% CO2 in air. The coherence function, amplitude and phase frequency responses, and impulse and step responses for the effects of ABP on CBFV were calculated by spectral analysis of beat-to-beat changes in mean ABP and CBFV before (mean CO2 5.55 +/- 0.38 kPa), during (6.43 +/- 0.31 kPa) and after 5% CO2 (5.43 +/- 0.26 kPa). During 5% CO2, the coherence function and the amplitude frequency response were significantly increased for frequencies below 0.05 Hz and the phase was reduced for the frequency range 0.02-0.1 Hz. The impulse and step responses indicated that 5% CO2 reduces the efficiency of the autoregulatory mechanism. A 20.7% average increase in CBFV induced by a 14.4% increase in EtCO2 was found to be mediated by a 25.9% reduction in critical closing pressure, while the change in resistance area product was non-significant.

Neurological complications after left subclavian artery coverage during thoracic endovascular aortic repair: a systematic review and meta-analysis.

INTRODUCTION Recent studies suggest an increased risk of neurologic complications after coverage of the left subclavian artery (LSA) during thoracic endovascular aortic repair (TEVAR). The preventative role of preoperative revascularization of the LSA using carotid-subclavian bypass or transposition remains controversial. We assessed this increased risk and the role of revascularization by undertaking a systematic review and meta-analysis of the literature. METHODS In the absence of any randomized controlled trials, the Pubmed and Embase databases were searched to identify all series reporting TEVAR without LSA coverage compared with LSA coverage with and without revascularization. The incidence of neurologic complications, namely cerebrovascular accident (CVA) and spinal cord ischemia (SCI), were recorded for each group. Pooled odds ratios (POR) were then calculated for postoperative CVA and SCI. RESULTS Compared with patients without LSA coverage, the risk of CVA was increased both in patients with LSA coverage alone (4.7% vs 2.7%; POR, 2.28; 95% confidence interval [CI], 1.28-4.09; P = .005) and in those with LSA coverage after revascularization (4.1% vs 2.6%; POR, 3.18; 95% CI, 1.17-8.65; P = .02). The risk of SCI was also increased in patients requiring LSA coverage (2.8% vs 2.3%; POR, 2.39; 95% CI, 1.30-4.39; P = .005) but not for LSA coverage after revascularization (0.8% vs 2.7%; POR, 1.69; 95% CI, 0.56-5.15; P = .35). CONCLUSION The risk of neurologic complications is increased after coverage of the LSA during TEVAR. Preemptive revascularization offers no protection against CVA, perhaps indicating a heterogeneous etiology. Revascularization may reduce the risk of SCI, although limited data tempers this conclusion. Improved or perhaps compulsory reporting to registries of a minimum data set may help further assess the exact etiology of these complications and identify a higher-risk subset of patients in whom revascularization might prove protective.

Multivariate dynamic analysis of cerebral blood flow regulation in humans

The contributions of beat-to-beat changes in mean arterial blood pressure (MABP) and breath-by-breath fluctuations in end-tidal CO/sub 2/ (EtCO/sub 2/) as determinants of the spontaneous variability of cerebral blood flow velocity (CBFV) were studied in 16 normal subjects at rest. The two input variables (MABP and EtCO/sub 2/) had significant cross-correlations with CBFV but not between them. Transfer functions were estimated as the multivariate least mean square finite impulse response causal filters. MABP showed a very significant effect in explaining CBFV variability (p<10/sup -11/, Fishers aggregated-p test) and the model mean square error was significantly reduced (p<0.001) by also including the contribution EtCO/sub 2/. The estimated mean CBFV step response to MABP displayed the characteristic return to baseline caused by the cerebral autoregulatory response. The corresponding response to EtCO/sub 2/ showed a gradual rise taking approximately 10 s to reach a plateau of 2.5%/mmHg. This study demonstrated that spontaneous fluctuations in EtCO/sub 2/ can help to explain the CBFV variability at rest if appropriate signal processing techniques are employed to address the limited power and bandwidth of the breath-by-breath EtCO/sub 2/ signal.

The role of risk and benefit perception in informed consent for surgery.

Background. Informed consent relies on patients’ ability to understand risk information. Evidence suggests that people may extract the gist of any risk information to make medical decisions. Existing evidence also suggests that there is an inverse relationship between the perception of risk and the perception of benefit. Method. Seventy-one patients on the waiting list for carotid endarterectomy (CEA) were surveyed regarding their understanding and recall of the risk and benefit to health of undergoing CEA. Patients were surveyed 1 month after their initial consultation, and a subgroup was surveyed again on the day before their operation. Results. Patients’ estimates of their baseline risk of stroke without surgery were significantly different from what they had been told by the surgeon. Patients’ estimates of stroke risk due to surgery ranged from 0% to 65% (actual local risk 2%). Patients also had unreasonable expectations about the benefit of the operation for their health. Estimates of stroke risk correlated positively with the degree of expected benefit from the operation (r = 0.29, P = 0.05). When resurveyed the day before the operation, patients’ perceptions of both risk and benefit had increased significantly. The risk perception data from some patients appeared to contradict some of the predictions of the fuzzy-trace theory. Conclusions. Most patients failed to understand the risks and benefits associated with CEA. Some patients’ estimates of stroke risk were actually greater than the perceived potential benefit of surgery in terms of risk reduction. The data also suggested a positive correlation between the degree of perceived benefit and the degree of perceived risk.

Assessment of the Thigh Cuff Technique for Measurement of Dynamic Cerebral Autoregulation

BACKGROUND AND PURPOSE Dynamic methods of measuring cerebral autoregulation have become an accepted alternative to static evaluation. This article aims to describe a set of data collected from healthy volunteers by a dynamic method, the purpose being to qualify and quantify expected results for those who may be designing a study using this technique. METHODS Cerebral blood flow velocity (CBFV) (measured by transcranial Doppler) and arterial blood pressure (Finapres) were recorded in 16 normal subjects before, during, and after the induction of a blood pressure drop (release of bilateral thigh cuffs). This procedure was repeated 6 times for each subject. A mathematical model was applied to the data to generate an autoregulatory index (ARI) with values between 0 and 9. RESULTS The ARI values for this sample population follow a normal distribution, with a mean+/-SD of 4.98+/-1.06 (n=15). Analysis of the cumulative mean ARI values of all subjects showed an exponential-type convergence of ARI toward the sample mean as the number of test iterations increased. The population average blood pressure drop on thigh cuff release was 26.4+/-7.1 mm Hg (n=16), occurring in 4.6+/-1. 7 seconds. The corresponding population average drop for CBFV was 15. 6+/-5.8 cm/s, taking 2.5+/-1.0 seconds. No significant trend was noted in the measurements as the number of test iterations increased. The correlation between the predicted and actual CBFV, having a mean value of 0.76+/-0.19, showed evidence of a nonlinear relationship to ARI values. Significant correlation was also found between ARI and (1) arterial blood pressure before cuff release and (2) the magnitude of the drop in CBFV on cuff release. CONCLUSIONS The distribution of ARI values is not significantly different from normal. At least 3 iterations of the test procedure should be performed and averaged to obtain the mean ARI for each subject. There is no significant evidence of physiological accommodation as the number of test iterations increases. The effects of mean blood pressure and the magnitude of the change in CBFV should be considered as possible covariates when ARI data are analyzed.

Remote Ischemic Preconditioning for Renal and Cardiac Protection during Endovascular Aneurysm Repair: A Randomized Controlled Trial

Purpose: To report a randomized clinical trial designed to determine if remote ischemic preconditioning (IP) has the ability to reduce renal and cardiac damage following endovascular aneurysm repair (EVAR). Methods: Forty patients (all men; mean age 76±7 years) with abdominal aortic aneurysms averaging 6.3±0.8 cm in diameter were enrolled in the trial from November 2006 to January 2008. Eighteen patients (mean age 74 years, range 72–81) were randomized to preconditioning and completed the full remote IP protocol; there were no withdrawals. Twenty-two patients (mean age 76 years, range 66–80) were assigned to the control group. Remote IP was induced using sequential lower limb ischemia. Serum and urinary markers of renal and cardiac injury were compared between the groups. Results: Urinary retinol binding protein (RBP) levels increased 10-fold from a median of 235 µmol/L to 2356 µmol/L at 24 hours (p=0.0001). There was a lower increase in the preconditioned group, from 167 µmol/L to 413 µmol/L at 24 hours (p=0.04). The median urinary albumin:creatinine ratio was significantly lower in the preconditioned group at 24 hours (5 versus 8.8, p=0.06). There were no differences in the rates of renal impairment or major adverse cardiac events. Conclusion: Remote preconditioning reduces urinary biomarkers of renal injury in patients undergoing elective EVAR. This small pilot trial was unable to detect an effect on clinical endpoints; further trials are warranted.

Multicenter Nellix EndoVascular Aneurysm Sealing system experience in aneurysm sac sealing

OBJECTIVE Despite improvements in endograft devices, operator technique, and patient selection, endovascular repair has not achieved the long-term durability of open surgical aneurysm repair. Persistent or recurrent aneurysm sac flow from failed proximal sealing, component failure, or branch vessel flow underpins a significant rate of reintervention after endovascular repair. The Nellix device (Endologix, Irvine, Calif) employs a unique design with deployment of polymer-filled EndoBags surrounding the endograft flow lumens, sealing the aneurysm sac space and potentially reducing complications from persistent sac flow. This retrospective analysis represents the initial experience in consecutive patients treated with the device in real-world practice. METHODS This study was performed at six clinical centers in Europe and one in New Zealand during the initial period after commercialization of the Nellix device. Patients underwent evaluation with computed tomography and other imaging modalities following local standards of care. Patients were selected for treatment with Nellix and treated by each institution according to its endovascular repair protocol. Clinical and imaging end points included technical success (successful device deployment and absence of any endoleak at completion angiography), freedom from all-cause and aneurysm-related mortality, endoleak by type, limb occlusion, aneurysm rupture, and reintervention. RESULTS During a 17-month period, 171 patients with abdominal aortic aneurysms were treated with the Nellix device and observed for a median of 5 months (range, 0-14 months). The 153 male and 18 female patients with mean age of 74 ± 7 years had aneurysms 61 ± 9 mm in diameter with an average infrarenal neck length of 28 ± 15 mm and infrarenal angulation of 37 ± 22 degrees. Technical success was achieved in all but two patients (99%); one patient had a type Ib endoleak and another had a type II endoleak. Through the last available follow-up, type Ia endoleak was observed in five patients (3%), type Ib endoleak in four patients (2%), and type II endoleak in four patients (2%). There were eight limb occlusions (5%), among which seven were evident at the 1-month follow-up visit. Aneurysm-related reinterventions were performed in 15 patients (9%). There were no aneurysm ruptures or open surgical conversions. CONCLUSIONS This first multicenter postmarket report of the Nellix device for infrarenal abdominal aortic aneurysm repair demonstrates satisfactory results during the initial learning phase of this new technology. The rate of aneurysm exclusion was high, and frequency of complications was low. More definitive conclusions on the value of this novel device await the results of the ongoing Nellix EVAS FORWARD Global Registry and the EVAS FORWARD investigational device exemption trial.

Endovascular vs open repair of acute abdominal aortic aneurysms--a systematic review and meta-analysis.

OBJECTIVE To compare the results of emergency open repair of acute (ruptured or symptomatic intact) abdominal aortic aneurysms with that of endovascular repair. METHODS A systematic literature search was performed to identify series that reported comparative outcomes. PubMed, Embase, the randomized controlled trial (RCT) register, and all relevant major journals were searched independently by two researchers. The outcome measures were 30-day mortality, intensive care unit (ICU) stay, hospital stay, blood loss, and operative time. RESULTS Twenty-three studies were identified. Of these, only one was a randomized controlled trial, which is now halted. The total number of patients in the pooled data was 7040 (730 emergency endovascular aneurysm repair [eEVAR]). Emergency EVAR was associated with a significant reduction in mortality (pooled odds ratio 0.624; 95% confidence interval [CI] 0.518 to 0.752; P < .0001). The eEVAR groups ICU stay was reduced by 4 days (pooled effect size estimate -0.70; 95% CI -1.05 to -0.35; P < .0001) and hospital stay with eEVAR was reduced by 8.6 days (pooled effect size estimate -0.33; 95% CI -0.50 to -0.16; P = .0001). In addition, eEVAR was also associated with a significant reduction in blood loss (pooled effect size estimate -1.88 liters; 95% CI -2.49 to -1.27; P < .0001) and reduced procedure time (pooled effect size estimate -0.65; 95% CI -0.95 to -0.36; P < .0001). CONCLUSION This meta-analysis suggests benefits to the selected group of patients undergoing this minimally invasive procedure. There is a reduction in the high mortality, prolonged intensive care requirement and total hospital stay, which are historically associated with open repair. It also indicates that most patients are fit enough to undergo computerized tomography (CT) scanning in acute settings. However, because of heterogeneity and bias in the outcomes these results should be interpreted with caution.

Utility of high resolution MR imaging to assess carotid plaque morphology: A comparison of acute symptomatic, recently symptomatic and asymptomatic patients with carotid artery disease

OBJECTIVES Compare carotid plaque morphology of acute symptomatic, recently symptomatic and asymptomatic patients (groups 1, 2 and 3 respectively) with carotid artery disease using high resolution magnetic resonance imaging (MRI), to identify high-risk plaque characteristics best associated with risk of recurrent thrombo-embolic events. METHODS 60 patients underwent multi-contrast imaging of their internal carotid arteries. Different plaque components were manually delineated on acquired axial images to assess the difference in prevalence of plaque hemorrhage, fibrous cap (FC) rupture and FC thickness among the three groups. RESULTS 55% acute symptomatic patients had plaque hemorrhage vs. 35% for recently symptomatic group and 5% for asymptomatic group (p-value: group 1 vs. 3: 0.001, group 2 vs. 3: 0.04). Type 1 hemorrhage was more common in acute symptomatic patients than recently symptomatic patients (40% vs. 5%, p=0.01). Type 2 hemorrhage was more common in recently symptomatic vs. acute symptomatic patients (15% vs. 30%). FC rupture was observed in 50% of patients in group 1 vs. 35% of group 2 patients (p=0.02) but none in group 3. The mean minimum FC thickness was same in acute and recently symptomatic groups (600+/-200microm), compared to 800+/-200microm for asymptomatic patients (p-value: 0.03 and 0.007 respectively). Good correlation was present among the three MR readers (intra-class correlation coefficient=0.71). CONCLUSION High resolution MRI can differentiate plaque components associated with increased risk of thrombo-embolic events.