First-ever ischemic stroke in elderly patients: predictors of functional outcome following carotid artery stenting

Abstract

Age is an important risk factor for stroke, and carotid artery stenosis is the primary cause of first-ever ischemic stroke. Timely intervention with stenting procedures can effectively prevent secondary stroke; however, the impact of stenting on various periprocedural physical functionalities has never been thoroughly investigated. The primary aim of this study was to investigate whether prestenting characteristics were associated with long-term functional outcomes in patients presenting with first-ever ischemic stroke. The secondary aim was to investigate whether patient age was an important factor in outcomes following stenting, measured by the modified Rankin scale (mRS). In total, 144 consecutive patients with first-ever ischemic stroke who underwent carotid artery stenting from January 2010 to November 2014 were included. Clinical data were obtained by review of medical records. The Barthel index (BI) and mRS were used to assess disability before stenting and at 12-month follow-up. In total, 72/144 patients showed improvement (mRS[+]), 71 showed stationary and one showed deterioration in condition (mRS[−]). The prestenting parameters, ratio of cerebral blood volume (1.41 vs 1.2 for mRS[−] vs mRS[+]), BI (75 vs 85), and high-sensitivity C-reactive protein (hsCRP 5.0 vs 3.99), differed significantly between the two outcome groups (P<0.05). The internal carotid artery/common carotid artery ratio (P=0.011), BI (P=0.019), ipsilateral internal carotid artery resistance index (P=0.003), and HbA1c (P=0.039) were all factors significantly associated with patient age group. There was no significant association between age and poststenting outcome measured by mRS with 57% of patients in the ≥75 years age group showing mRS(−) and 43% showing mRS(+) (P=0.371). Our findings indicate that in our elderly patient series, carotid artery stenting may benefit a significant proportion of carotid stenotic patients regardless of age. Ratio of cerebral blood volume, BI, and admission hsCRP could serve as important predictors of mRS improvement and may facilitate differentiation of patients at baseline.

Keywords:

• modified Rankin scale
• resistance index
• Barthel index
• common carotid artery
• cerebral blood volume ratio

Supplementary material

Protocols of neuroradiological examinations

Magnetic resonance imaging and angiography

Structural and functional magnetic resonance imaging and angiographic (MRI/A) examinations were performed using a 3-T (Magnetom Verio, Siemens Healthcare, Malvern, PA, USA) or a 1.5-T imager (Magnetom Aera; Siemens Healthcare) with a cervical coil. Standard protocol to evaluate a stroke including axial diffusion weighted imaging, apparent diffusion coefficient, and fluid-attenuated inversion-recovery sequences was followed. Three-dimensional time-of-flight MR angiography without contrast enhancement was performed in the transverse plane using a sliding interleaved kY acquisition sequence comprising six overlapping slabs of eleven sections and the following parameters: section thickness, 1.2 mm; repetition time (milliseconds)/echo time (milliseconds), 242/7; flip angle, 20°; field of view, 200×200 mm; matrix, 205×320 mm². The final pixel size was 0.975×0.625 mm. The entire imaging time was ~7 minutes. Contrast-enhanced MR angiography was not routinely performed.

The following three parameters were derived from the MRI/A studies: 1) Ipsilateral middle cerebral artery stenosis or occlusion was diagnosed in patients with concomitant middle cerebral artery focal stenosis or occlusion on MRA and was confirmed by digital subtraction angiography (DSA) (1: disease, 0: no disease). 2) Intracranial posterior circulation stenosis or occlusion was diagnosed in patients with incidental (either intracranial vertebral or basilar artery) focal stenosis or occlusion on MRA and was confirmed by DSA (1: disease, 0: no disease). 3) Stroke location was categorized as cortical, subcortical, or cortical and subcortical regions. We examined whether the locations revealed on MRI were associated with mRS scores (1: cortical, 2: subcortical, and 3: cortical and subcortical regions).

Computed tomography angiography/perfusion imaging

Computed tomography (CT) angiography examinations were performed using a second-generation dual-source CT scanner (SOMATOM Definition Flash; Siemens Healthcare). After an 18-gauge intravenous catheter was placed in the antecubital vein, 100 mL of contrast material (Iodixanol, Visipaque 320; GE Healthcare, Carrigtwohill, Ireland; or Iohexol, Omnipaque 350; GE Healthcare) was infused at a rate of 5 mL/s. An initial injection delay was estimated using the bolus-tracking technique, in which the threshold was 100 Hounsfield units. Scanning was performed using a dual-energy mode with a pitch of 0.9, a rotation time of 0.28 seconds, and collimation of 2×32×0.6 mm at 100 kV/150 ref mAs (Tube A) and Sn140 kV/178 ref mAs (Tube B). The scanned area extended from the aortic arch to the top of the neurocranium. CT images were reconstructed using a slice thickness of 0.6 mm, increment of 0.3 mm, and medium–smooth kernel. CT perfusion scans were subsequently performed with a contrast bolus of 50 mL of Omnipaque 350 (GE Healthcare). Perfusion data sets were postprocessed on a Siemens Multimodality Workplace Workstation (Siemens Healthcare), yielding mean transit time (MTT), cerebral blood volume (CBV), cerebral blood flow (CBF), time to peak (TTP), and time to drain (TTD) maps. The arterial input and venous outflow curves were analyzed to ensure complete data sets. The other CT perfusion parameters included difference in MTT (dMTT: ipsilateral MTT − contralateral MTT), MTT ratio (rMTT: ipsilateral MTT/contralateral MTT), CBV ratio (rCBV: ipsilateral CBV/contralateral CBV), CBV index (ipsilateral CBV − contralateral CBV/contralateral CBV), CBF ratio (rCBF: ipsilateral CBF/contralateral CBF), CBF index (ipsilateral CBF − contralateral CBF)/contralateral CBF), TTP index: (ipsilateral TTP − contralateral TTP)/contralateral TTP), and TTD ratio (rTTD: ipsilateral TTD/contralateral TTD).

DSA and stenting procedure

Biplanar intra-arterial DSA was performed using a biplanar flap panel rotational angiography unit (Axiom Artis Zee; Siemens Healthcare). An image intensifier matrix of 1,024×1,024 pixels and a final pixel size of 0.37 mm was used. Using the right femoral artery approach, a 7-F catheter (Mach 1, Boston Scientific, Marlborough, MA, USA) was inserted into the right or left common carotid arteries near the bifurcation. Posteroanterior and lateral projection views were acquired at the level of the carotid bifurcation. A third projection with an oblique angle was acquired if overlapping vessels were noted on the original two projections. For each projection, 11 mL of nonionic iodinated contrast material (Omnipaque 350; GE Healthcare) was intra-arterially injected at a flow rate of 7 mL/s by an automatic injector (Mark V ProVis, Medrad, Whippany, NJ, USA). Subsequently, the stenting procedure was performed. A guidewire was inserted into the carotid artery on either side of the stenotic region and an E-Z filter wire was used to prevent major complications, such as recurrent stroke, caused by distal embolic migration. Overall, 5,000 units of prophylactic heparin were administered. A self-expandable Carotid Wallstent was used (7×30 mm). The stent was delivered coaxially through the guiding catheter into the stenotic area (Figure 1).

Acknowledgments

We specially thank Ping-Yi Lin, PhD, of Changhua Christian Hospital for her constructive comments. This project is partially supported by Ministry of Science and Technology and Big Data Research Center of National Chiao Tung University, Taiwan.

Author contributions

Chih Ming Lin, MD, MPH: collecting data and study design. Yu-Jun Chang, PhD: biostatistical analysis. Chi-Kuang Liu, MD: data collection. Cheng-Sheng Yu, MS: data analysis. Henry Horng-Shing Lu, PhD: study design and data analysis. All authors contributed toward data analysis, drafting and critically revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.