Impaired Cerebrovascular Reactivity Predicts Recurrent Symptoms in Patients with Carotid Artery Occlusion: A Hypercapnia BOLD fMRI Study.

BACKGROUND AND PURPOSE: A key factor in predicting recurrent ischemic episodes in patients with carotid artery occlusion is the presence of hemodynamic impairment. There is, however, no consensus on how to best assess this risk in terms of imaging modalities or thresholds used. Here we investigated whether a predefined threshold of hemispheric asymmetry in hypercapnia fMRI predicts recurrent symptoms in patients with carotid artery occlusion. MATERIALS AND METHODS: We studied 23 patients (2 women) with a mean age of 67.5 ± 9 years. Patients were assessed for recurrent ischemic events until lost to follow-up, study end, death, or recurrent ischemic event. Hypercapnia fMRI was used to assess the cerebrovascular reserve and quantify the percentage signal change in GM in the MCA territory and the hemispheric asymmetry index. Kaplan-Meier survival analysis and log-rank tests were performed to assess differences between patients with normal or abnormal hemispheric indices. RESULTS: The median follow-up was 20 months. During this period, 8 patients experienced recurrent events, and 15 did not. The percentage signal change in GM in the MCA territory was significantly decreased in those patients with recurrent events compared with those without (2.39 ± 0.22 versus 2.70 ± 0.42, P = .032). The normal hemispheric index predicted event-free survival during follow-up (median, 20 months) for both the combined outcome (recurrent events and/or death, log-rank, P = .034) and recurrent retinal or ipsilateral ischemic events only (log-rank, P = .012). CONCLUSIONS: The hemispheric asymmetry index derived from hypercapnia fMRI showed hemodynamic impairment in more than half of the studied patients with carotid occlusion, and those patients showed a higher risk of recurrent ischemic symptoms.

Carotid endarterectomy improves cerebrovascular reserve capacity preferentially in patients with preoperative impairment as indicated by asymmetric BOLD response to hypercapnia.

PURPOSE: In patients with symptomatic carotid artery disease the predominant mechanism causing ischaemic injury is considered to be thromboembolic, however compromise of cerebral haemodynamics is considered to be a significant factor. Removal of the embolic source is accepted as the major benefit from carotid endarterectomy (CEA), however improvement in cerebral haemodynamics may be another beneficial outcome as suggested by transcranial doppler (TCD). Blood oxygen level-dependent (BOLD) hypercapnia functional magnetic resonance imaging (fMRI) can be used to map the cerebrovascular reserve (CVR). The aim of this study was to assess the effects of carotid surgery on cerebral haemodynamics in patients with carotid artery disease using a hypercapnia BOLD fMRI and assessment of hemispheric asymmetry. MATERIALS AND METHODS: Seventeen patients with symptomatic internal carotid artery stenosis were scanned using a clinical 1.5T MR scanner. Scanning was done immediately prior to and between 4 and 8 weeks after CEA. 10% carbon dioxide was administered to achieve transient episodes of hypercapnia. The data was analyzed using FMRIB Software Library (FSL) software to derive percentage signal change (PSC) for the grey matter of the middle cerebral artery (MCA-GM) territory for both hemispheres. MCA-GM PSC was furthermore normalized to the contralateral hemisphere to derive an Hemispheric Asymmetry Index (hAI) for all patients pre- and postoperatively. RESULTS: Ipsilateral GM CVR improved significantly following CEA (2.47% preoperatively vs. 2.73% postoperatively, p=0.038). There was no change in CVR in the contralateral grey and white matter MCA territories (p=0.27, p=0.1). Also, the hAI was significantly more shifted to the ipsilateral hemisphere after CEA (preoperative hAI -0.56, vs. -3.90 postoperatively, p=0.02). Patients with an impaired hAI preoperatively were found to show the greatest improvement in PSC and hAI following CEA (p=0.007). CONCLUSIONS: CEA resulted in improved CVR in patients with carotid artery disease as shown by the absolute and hemispheric asymmetry of BOLD response to hypercapnia.. These findings show that benefits from recanalisation may go beyond removal of the embolic source, by improving the cerebrovascular reserve. Moreover, hypercapnia BOLD fMRI may be a useful clinical tool in predicting this therapeutic potential in patients with severe carotid artery disease.

A randomised trial of endovascular and open surgery for ruptured abdominal aortic aneurysm - results of a pilot study and lessons learned for future studies.

INTRODUCTION: EVAR has the potential to improve outcome after ruptured abdominal aortic aneurysm (AAA). Published series have been based upon selected populations. METHODS: An interim analysis of a single centre prospective randomised controlled trial comparing endovascular aneurysm repair (EVAR) with open aneurysm repair (OAR) in patients with ruptured AAA was performed. Patients who had a ruptured AAA and who were considered fit for open repair were randomised to EVAR or OAR after consent had been obtained. Those in the EVAR group had pre-operative spiral computed tomographic angiography (CTA). The primary endpoint was operative (30-day) mortality and secondary endpoints were moderate or severe operative complications, hospital stay and time between diagnosis and operation. A power study calculation required 100 patients to be recruited. RESULTS: Between September 2002 and December 2004, 103 patients were admitted with suspected ruptured AAA. Only 32 patients were recruited to the study. Of these, four patients died before receiving surgical treatment. On an intention to treat basis the 30-day mortality rate was 53% in the EVAR group and 53% in the OAR group. Moderate or severe operative complications occurred in 77% in the EVAR group and in 80% in the OAR group. Median total hospital stay in the EVAR group was 10 days (inter-quartile range 6-28) and 12 days (4-52) in the OAR group. Median time between diagnosis and operation was 75 minutes (64-126) in the EVAR group and 100 minutes (48-138) in the OAR group. CONCLUSIONS: Despite the relative high operative mortality in the EVAR group, these preliminary results show that it is possible to recruit patients to a randomised trial of OAR and EVAR in patients with ruptured AAA. CT scanning does not delay treatment.

A UK multi-centre experience with a second-generation endovascular stent-graft: results from the Zenith Users Group.

BACKGROUND: Endovascular aneurysm repair has been criticised for high rates of technical failure and secondary intervention. Second generation stent-grafts have been developed in an attempt to reduce these problems. The results of a UK multi-centre experience with a second generation device (Zenith) are presented. METHODS: Data were collected retrospectively from five experienced UK vascular centres in patients undergoing endovascular aneurysm repair with the Zenith stent-graft. RESULTS: A total of 269 patients underwent attempted aneurysm repair with the Zenith device. Median aneurysm diameter was 65 (interquartile range 52-78) mm. There were no conversions to open repair. Peri-operative mortality was 4.1% (11/269). On the initial post-operative scan, 94.1% of aneurysms were successfully excluded. During a median follow-up of 363 (interquartile range 154-720) days there were 19 secondary interventions and two aneurysm ruptures. CONCLUSIONS: Second generation endovascular stent-graft designs such as the Zenith are associated with low rates of intra-operative technical complications. Few secondary interventions have been necessary during follow-up; however, surveillance is essential to ensure they continue to perform.

Endovascular repair of a ruptured chronic type B aortic dissection.

Aneurysm formation is a common sequel of chronic type B aortic dissection. Ruptured false lumen aneurysms have traditionally been treated with open repair. These procedures are associated with high morbidity and mortality rates. We report the first successful endovascular repair of a ruptured chronic type B aortic dissection in a patient who had been turned down for elective surgery. The endovascular management of chronic dissection with rupture is difficult and may necessitate stenting of both entry and reentry points to induce false channel thrombosis. The long-term efficacy of this technique is unknown.