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the Department of Neurology (R.M., M.R., Z.G., N.A.P., E.F., J.C.G., J.Y.C.), University of Texas Health Science Center at Houston
Barrow Neurological Institute (A.V.A.), Phoenix, Ariz
Arizona State University, School of Nursing (A.W.W.-A.), Tempe, Ariz.
Abstract
Background and Purpose— Transcranial Doppler (TCD) and carotid duplex (CD) provide rapid and safe screening for stroke patients but are highly operator dependent. We explored the feasibility of telemedicine (TM)-guided TCD/CD administered by a health care provider inexperienced with ultrasound.
Methods— Dual video screens transmitted real-time TCD/CD images and sound to a neurosonographer. TM TCD/CD characteristics were compared with an in-person (IP) examination independently obtained on the same patient. We compared carotid stenosis, thrombolysis in brain ischemia (TIBI) flow grades, and the time spent on testing.
Results— We examined 8 subjects with a median age of 51 (31 to 63 range). IP and TM successfully examined 100% of internal carotid and middle cerebral arteries, 50% versus 44% of anterior cerebral artery, and 100% versus 88% of the basilar arteries, respectively. The median time in minutes IP versus TM was 15 (range 10 to 35) and 30 (15 to 50) for CD (P=0.07) and 18 (15 to 30) and 45 (30 to 55) for TCD (P=0.002), respectively. TM correctly identified all normal CD/TCD examinations in 7 subjects. In 1 patient, TM identified carotid occlusion but misread TIBI flow grades in both middle cerebral arteries.
Conclusions— Our pilot study showed the feasibility of TCD/CD by an inexperienced health professional guided by a sonographer via TM. Tests were completed within times comparable to outpatient setting in a vascular laboratory.
Key Words: Doppler, transcranial stroke telemedicine ultrasonography
Introduction
Telemedicine technology is used to provide immediate and remote expert assessment in treatment decision-making.1,2 Several studies have reported the feasibility and reliability of remote stroke consultation such as the assessment of the National Institutes of Health Stroke Scale3,4 and treatment with intravenous thrombolysis.5
Neurovascular examination with portable carotid duplex (CD) and transcranial Doppler (TCD), compared with computed tomography and magnetic resonance angiography, offer rapid, inexpensive, noninvasive bedside screening of patients and identification of vessel occlusions amenable for interventional treatment.6,7 Moreover, continuous TCD monitoring with systemic thrombolysis may improve early recanalization8 and identify candidates for bridging into intra-arterial treatment.9
Neurosonographers are not readily available around the clock in emergency rooms nationwide. Therefore, we performed a pilot study to assess the feasibility of neurovascular testing by a health care provider inexperienced with ultrasound, guided via telemedicine (TM), by an expert sonographer.
Subjects and Methods
Four experienced neurosonographers (stroke neurologists with registered vascular technologist certification or -eligible with >8 years of ultrasound practice) and 3 healthcare providers, novice to ultrasound (a stroke nurse, a neurologist, and an ophthalmologist without formal theoretical and hands-on training in ultrasound nor familiarity with operating ultrasound machines) participated in the study. All subjects gave informed written consent to participate in the study approved by the local institutional research board. Each subject was examined in random order: by a sonographer in-person (IP; gold standard) and by another sonographer, who guided a novice through a complete examination via TM. IP and TM sonographers were blinded to each other’s results.
The TM configuration is shown in the Figure. Portable ultrasound machines were used for CD examination (SonoSite180Plus; SonoSite) and TCD (power-motion Doppler TCD; 100 mol/L; Spencer Technologies). A Phonoscope Health Network high-speed fibrooptic cable connection (768 to 1920 kbp) was established between 2 Polycom Viewstation FX units in separate rooms. A peripheral hardware device, Visual Concert, allowed real-time video streaming of the ultrasound display.
Configuration of TM. The 2 images on the left show the experienced sonographer guiding novice in the images on the right.
CD and TCD were performed using standardized, previously validated scanning protocols for screening of emergency room patients.6 CD used transverse and longitudinal planes, in gray scale and power Doppler mode, to obtain images of the subject’s common carotid artery, internal carotid artery (ICA), and external carotid artery. Angle-corrected Doppler velocity measurements were obtained. The degree of carotid stenosis was determined using the Consensus criteria and was stratified into 5 categories.7 TCD examined the middle cerebral artery (MCA) and anterior cerebral artery (ACA) through transtemporal window and basilar artery (BA) through suboccipital window. The direction and depth of the Doppler signal helped identify the various arteries. Thrombolysis in brain ischemia (TIBI) flow grades were recorded according to the previously defined criteria.10
Between IP and TM, we compared insonation rates, the time length of testing, carotid stenosis, and TIBI flow grades. Analyses were performed with NCSS software. Statistical significance for intergroup differences was assessed by 2 test for categorical variables and Mann-Whitney U test for continuous variables.
Results
We examined 8 subjects: 3 were men and the median age was 51 (31 to 63; range 38 to 59; percentile 25th to 75th). Four consecutive inpatients admitted for acute ischemic stroke, 2 outpatients after ischemic stroke recruited from a tertiary stroke center, and 2 nonstroke volunteers were enrolled. Four patients experienced right hemispheric stroke 2 left hemispheric stroke. The modified Rankin score ranged from 0 to 2.
IP and TM successfully insonated ICAs and MCAs in all subjects. ACA was successfully insonated in 8 of 16 arteries (50%) by IP and 7 of 16 arteries by TM (44%; P=0.72 for difference of insonation rate). All BAs were insonated by IP and 7 of 8 by TM (88%; P=0.30). Four transtemporal windows were considered suboptimal by TM and 3 by IP.
The median times for CD examination were IP 15 minutes (10 to 35; range 15 to 20; percentile 25th to 75th), TM 30 minutes (15 to 50; range 19 to 41; percentile 25th to 75th; P=0.07), and for TCD were IP 18 minutes (15 to 30; range 15 to 28; percentile 25th to 75th), TM 45 minutes (30 to 55; range 30 to 45; percentile 25th to 75th; P=0.002).
In 7 subjects, CD/TCD exams were normal and correctly identified by TM. In 1 patient, TM correctly diagnosed proximal left ICA complete occlusion on CD. Yet TM misread TIBI flow grades in both MCAs, reading normal as blunted on the left and stenotic as normal on the right.
Discussion
Our pilot study showed that a healthcare provider inexperienced with ultrasound could perform a bedside examination guided by an experienced neurosonographer via TM. Insonation rates of TM compared very favorably to the IP examination. Relatively low ACA insonation rates and number of suboptimal insonation windows (10% to 15%) corresponded to published reports.6,9
TM took substantially longer for CD and TCD than IP. However, both neurosonological tests were completed within times comparable to outpatient testing allocated in a vascular laboratory. Moreover, we performed relatively complete studies, which is often unnecessary when the affected vascular territory is obvious from the clinical evaluation. Such a "minimalist" approach (fast-track TCD/CD protocol) has been validated in defining patients amenable for intervention.6
In our study, only 1 patient had abnormal findings. TM misread both MCA signals. This patient had occlusions of all arteries supplying brain except for 1 vertebral artery, a pattern difficult to recognize. However, our study design was not intended to validate the accuracy of TM-guided neurosonology.
A limitation of this study is that tests were performed under ideal bedside conditions. This does not reflect a busy emergency department, where space limitation, background noise, and simultaneous procedures may interfere with TM.
In conclusion, our pilot study showed the feasibility of TM-guided neurosonology for normal exams performed by an inexperienced health professional. Reliability and practical implementation remain the subject of future studies.
Acknowledgments
This project is supported by National Institutes of Health grant P50N5044227.
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