Carotid angioplasty in a pulsatile flow model: factors affecting embolic potential

Systematic review and meta-analysis of perioperative and long-term outcomes in patients receiving statin therapy before carotid endarterectomy

BACKGROUND

Carotid endarterectomy (CEA) is associated with perioperative stroke and mortality in a minority of cases. The aim of this systematic review and meta-analysis was to investigate the effect of pre-operative statins on perioperative outcomes in patients undergoing CEA for internal carotid artery (ICA) stenosis.

METHODS

A systematic review of PubMed, Medline, and the Cochrane Database of Systematic Reviews was performed. Studies were included which reported perioperative stroke and/or survival outcomes following CEA for ICA stenosis and compared patients who were and were not taking pre-operative statins. Relevant data were extracted and pooled using meta-analysis.

RESULTS

Seven studies met the inclusion criteria, comprising 21,387 patients. A total of 68.9% (14,976) were administered statins and 31.1% (6657) were statin-free. Pre-operative statin use was higher in patients with a history of cardiac disease (12.2 vs. 23.6% in the statin-free group), diabetes (31.6 vs. 25.1% in the statin-free group), and hypertension (83.5 vs. 72.2% in the statin-free group), while a greater proportion of statin-free patients had symptomatic disease (44.9 vs. 55.5% in the statin-free group). Statins were associated with reduced perioperative stroke in all patients (OR 0.57; 95% CI 0.34-0.95; p = 0.03) and in symptomatic patients (OR 0.57; 95% CI 0.35-0.93; p = 0.03). A trend towards lower perioperative mortality (OR 0.54; 95% CI 0.29, 1.03; p = 0.06) and significantly improved overall survival was observed in the statin group (HR 0.69; 95% CI 0.59-0.81; p < 0.001) at a mean follow-up of 62 months (range 27-76 months).

CONCLUSIONS

Administration of statins before CEA is associated with lower rates of perioperative stroke and improved overall survival. Compliance with optimal medical treatment associated with the use of pre-operative statins may limit the clinical significance of these findings. Future investigation to characterize the potential benefit of statin therapy in patients undergoing CEA for ICA stenosis is warranted.

Evaluation of robotic endovascular catheters for arch vessel cannulation

OBJECTIVE

Conventional catheter instability and embolization risk limits the adoption of endovascular therapy in patients with challenging arch anatomy. This study investigated whether arch vessel cannulation can be enhanced by a remotely steerable robotic catheter system.

METHODS

Seventeen clinicians with varying endovascular experience cannulated all arch vessels within two computed tomography-reconstructed pulsatile flow phantoms (bovine type I and type III aortic arches), under fluoroscopic guidance, using conventional and robotic techniques. Quantitative (catheterization times, catheter tip movements, vessel wall hits, catheter deflection) and qualitative metrics (Imperial College Complex Endovascular Cannulation Scoring Tool [IC3ST]) performance scores were compared.

RESULTS

Robotic catheterization techniques resulted in a significant reduction in median carotid artery cannulation times and the median number of catheter tip movements for all vessels. Vessel wall contact with the aortic arch wall was reduced to a median of zero with robotic catheters. During stiff guidewire exchanges, robotic catheters maintained stability with zero deflection, independent of the distance the catheter was introduced into the carotid vessels. Overall IC3ST performance scores (interquartile range) were significantly improved using the robotic system: Type I arch score was 26/35 (20-30.8) vs 33/35 (31-34; P = .001), and type III arch score was 20.5/35 (16.5-28.5) vs 26.5/35 (23.5-28.8; P = .001). Low- and medium-volume interventionalists demonstrated an improvement in performance with robotic cannulation techniques. The high-volume intervention group did not show statistically significant improvement, but cannulation times, movements, and vessel wall hits were significantly reduced.

CONCLUSION

Robotic technology has the potential to reduce the time, risk of embolization and catheter dislodgement, radiation exposure, and the manual skill required for carotid and arch vessel cannulation, while improving overall performance scores.

Distal Myocardial Protection During Percutaneous Coronary Intervention

The discrepancy between angiographic success and microvascular perfusion has been recognized for some time. In the face of an open artery, the degree of microvascular perfusion determines post-infarct prognosis. Despite successful epicardial recanalization, tissue perfusion may be absent in up to 25% patients with acute myocardial infarction. Historically associated with saphenous vein graft intervention, embolization is increasingly recognized in native coronary arteries, particularly in patients undergoing primary percutaneous coronary intervention (PCI). With more than two million PCI procedures performed worldwide each year, there is enormous interest in protecting the left ventricular myocardium from embolization during PCI. This article reviews the evidence for distal myocardial protection and discusses the relative merits of the different available techniques.

Bilateral brachial artery occlusion decreases internal carotid artery volume flow: a simple adjunct for cerebral protection?

PURPOSE

To investigate if a decrease in internal carotid artery (ICA) blood flow occurs with bilateral brachial artery occlusion (BBO), which may improve the effectiveness of cerebral protection devices during carotid interventions.

METHODS

Thirty-two asymptomatic patients (21 men; mean age 67 years) with carotid atherosclerosis between 15% and 79% were enrolled in the study. Carotid duplex ultrasound was followed by volume flow rate (VF) determination in the right ICA, external carotid (ECA), and vertebral arteries. After baseline values were obtained, BBO was induced by bilateral arm pressure cuff inflation to 30 mmHg over the systolic pressure for no more than 3 minutes. VF measurements were repeated.

RESULTS

Seventeen patients (responders) had an ICA VF decrease from 406+/-109 mL/min (+/-SD) to 303+/-90 mL/min (p=0.005), while 15 patients (nonresponders) had no significant change in their ICA VF (340+/-192 versus 447+/-267 mL/min, p=0.22). In responders, ECA VF increased (190+/-65 to 232+/-125 mL/min), as did vertebral VF (77+/-53 to 95+/-60 mL/min; p>0.05). The ratio of ICA/ECA VF dropped from 2.13 to 1.31 in responders, but did not change in nonresponders. No patient exhibited any neurological symptoms during the study. Post cuff volume flows approximated baseline values. Cerebral magnetic resonance angiograms obtained in 10 responders revealed a complete circle of Willis in 8 (80%), while only 1 (16%) of 6 nonresponders had a complete pathway.

CONCLUSIONS

A transient decrease in ICA VF, with concomitant elevations of the ECA and vertebral VFs, occurs with occlusion of the brachial arteries in the setting of a complete circle of Willis. Since no flow reversal occurs, this maneuver is insufficient to provide complete cerebral protection, but it may improve the effectiveness of cerebral protection devices and serve as an adjunctive maneuver in selected cases. Furthermore, changes in ICA VF may prove to be a noninvasive test for evaluating the integrity of the circle of Willis.

The Relationship Between Plasma MMP-1, -7, -8 and -13 Levels and Embolic Potential During Carotid Endoluminal Intervention

BACKGROUND

Patients undergoing carotid endoluminal intervention are at risk of embolic stroke even with the use of distal protection devices. Matrix metalloproteinases (MMPs) have been implicated as a causal factor in plaque instability leading to spontaneous embolisation. We investigated whether plasma MMP levels correlated with the embolisation during carotid endoluminal intervention.

METHODS

Thirty circumferentially intact carotid endarterectomy specimens were subjected to a standardised angioplasty procedure in a pulsatile ex vivo model. Emboli collected in a series of distal filters were counted and sized. Plasma samples were collected pre-operatively and analysed for MMP-7 and MMP-8 levels using Western immunoblotting. MMP-1 and MMP-13 levels were determined using ELISA. Emboli number and maximum size were correlated with plasma levels of the MMPs using Spearmans rank.

RESULTS

Total MMP-8 levels were related to maximum embolus size (r=0.442, p=0.005) but not emboli number (r=0.342, p=0.052). MMP-1, -7 and -13 were not correlated with either emboli number or with maximum embolus size.

CONCLUSION

Pre-operative plasma MMP-8 levels are related to the size of emboli from plaques during carotid endovascular intervention. Further in vivo studies need to be performed to assess the importance of this finding. There is potential for development of plasma markers to identify those patients at greater risk of embolic stroke during carotid endoluminal intervention.

Relationship of Matrix Metalloproteinases and Macrophages to Embolization During Endoluminal Carotid Interventions

PURPOSE

To investigate if relationships exist among macrophage infiltration, plasma matrix metalloproteinase (MMP) levels, and the number of emboli generated during endoluminal carotid interventions.

METHODS

Carotid endarterectomy specimens excised as intact cylinders (n=27) were subjected to a standardized angioplasty procedure under radiological guidance in an ex vivo pulsatile flow model. Emboli collected in distal filters were counted and sized using microscopy. Preoperative plasma gelatinase activity was determined by gelatin zymography and quantified using image analysis software. Levels of tissue inhibitors of metalloproteinases (TIMP) 1 and 2 were determined by ELISA. Macrophages within postangioplasty plaques were analyzed using immunohistochemical staining for CD68 antigen and graded by a blinded examiner. Statistical analysis was performed using Spearman's rank correlation.

RESULTS

The median number of emboli recorded during angioplasty was 104 (interquartile range 33.75-242.5, absolute range 13-1090). Plasma MMP-9 and MMP-2 levels correlated with emboli number (r=0.544 [p=0.003] and r=0.412, [p=0.033], respectively), while TIMP-1 and TIMP-2 levels did not. Macrophage infiltration within the plaques correlated with emboli number (r=0.722, p<0.001) and the plasma MMP-9 level (r=0.489, p=0.010).

CONCLUSIONS

These data indicate that plaque macrophage infiltration may play a role in the generation of emboli during endoluminal carotid intervention, possibly via modulation of protease activity.