The rise of telestroke networks

Telestroke has quickly spread throughout the USA, with at least 56 networks in 27 states linking a stroke center with local hospitals that lack around the clock stroke expertise.41 The particulars of each arrangement have led to network based experimentation as individual programs have explored a range of services and delivery models.

A remote neurologist can offer a range of services through a telemedicine platform, through either video or telephone contact. A variety of different models exist, but evidence suggests telestroke (or more broadly telemedicine), with audio and video, is superior to telephone consultation alone.43 Practice models include the following:

1. Teleconsultation: a remote neurologist offers only advisory services,44 and the referring hospital maintains responsibility and liability for the patient.

2. Telethrombolysis: a remote neurologist decides on thrombolysis and is responsible to varying degrees for the patient's course, typically in the context of a pre-existing agreement between hospitals.

3. Integrated telehealth system: exchange of patients, information, and therapeutic suggestions between centers involved in acute stroke care, often with disseminated responsibilities and no clearly dominant hub.

These services are offered through a variety of stroke networks, ranging from individual arrangements between hospitals to multilayered referral networks. The earliest American model was a one to one partnership, where a remote island hospital contracted with a tertiary referral center for around the clock stroke coverage.45 Building on this, the early German pilot studies pioneered the classic spoke and hub model,39 ,40 where a central referral center partners with multiple local facilities to provide around the clock stroke coverage. This is now the dominant network model. The spoke and hub model has since become more nuanced, as rural hospitals partner with local primary stroke centers (sub-hubs) who are themselves partnered with a comprehensive stroke center (hub). The sub-hub provides routine stroke care services, but patients requiring subspecialty care or intervention are transferred to the hub, which is usually a comprehensive stroke center. More recently, an English telestroke network pioneered a horizontal telestroke model in rural hospitals that have local neurologists but lack both around the clock coverage and access to a tertiary referral center.46 Through a reciprocal agreement, hospitals take turns providing after hours stroke coverage, and patients continue stroke therapy the following day at the local hospital.46 By leveraging the speed and reach of telecommunication, all delivery networks are able to extend specialty and subspecialty care to broad geographic regions using preexisting resources.

Once a telestroke service identifies an AIS case, patients can either be transported to a referral hospital or kept at the local hospital. In the ‘drip and ship’ model, a remote neurologist decides to initiate thrombolysis and transfer the patient for admission to their service. The patient immediately receives tPA and is then transferred to the hub or sub-hub facility. This most frequently occurs with small local hospitals without the staff or capacity to provide stroke care. Alternatively, many remote hospitals have stroke care capacity, but lack around the clock stroke coverage. In these circumstances, teleconsultations for mild to moderate strokes may result in ‘drip and keep,’ where tPA is administered and patients remain at the local hospital with local neurology coverage the following morning. A remote specialist can also continue to advise regarding a patient's care through a telemedicine enabled local hospital unit. Patients with severe strokes, requiring endovascular intervention, surgical intervention (e.g., hemicraniectomy), and critical care should be transferred to the tertiary center in the absence of local expertise or facilities. In all models, network hospitals have specific agreements and protocols to transfer patients with stroke or thrombolysis complications.

Telestroke technology

Telemedicine is dependent on the technology that makes it possible. Initial experiences with video teleconferencing were limited by the transmission rates of integrated services digital network (ISDN) or dedicated local area network (LAN) connections.38 ,40 Rare but notable interruptions complicated initial pilot studies.37 The proliferation of broadband and cellular access, combined with high resolution video capability, has since facilitated high resolution, low latency audiovisual connections.47 Initial videoconferencing technology required the remote neurologist to be present at a fixed workstation,38 ,40 but technical advances have since led to laptop47 ,48 and even smartphone based videoconferencing.49–51 Now that telemedicine capability is routine with a low barrier to entry, the principle concern has shifted away from technical to practical limitations over the implementation and utility of remote assessment.

Telestroke and diagnostic accuracy

Initial experimentation with telestroke has consistently demonstrated that video teleconference facilitates rapid and accurate remote diagnosis. In an initial pilot study done in the non-acute setting, remote application of the National Institutes of Health Stroke Scale (NIHSS) was assessed in tPA ineligible AIS patients.38 Nurse assisted remote evaluation by a neurologist was comparable with that of a bedside neurologist, with a discordance rate similar to that observed between two bedside examiners.52 ,53 Nonetheless, while remote diagnostic assessment is rapid, it is slower than a bedside assessment (9.7 vs 6.5 min, respectively).38 The reliability of remote NIHSS assessment has since been replicated in the acute setting,54 ,55 demonstrating the fidelity of telestroke assessment in AIS. In an attempt to further optimize remote diagnosis, video teleconference and telephone consultation were directly compared in the prospective Stroke Team Remote Evaluation Using a Digital Observation Camera (STRokE DOC) trial.43 Using a mobile, laptop based system, video teleconference led to a correct diagnosis and thrombolysis in over 97% of cases, with an OR for a correct diagnosis of 10.9 compared with telephone consultations. Based on initial experiences with telestroke, the AHA now endorses remote clinical and radiographic assessments of patients in underserved medical settings as safe and reliable (class IA).42

Safety of remote thrombolysis

The emphasis on accuracy of remote diagnosis is essential because of the safety concerns of remote thrombolysis. Given the potential for tPA induced ICH, the risk is that inappropriate thrombolysis could precipitate an iatrogenic ICH. The most likely reasons for inappropriate thrombolysis are protocol violations and misdiagnosis of a stroke mimic. Stroke mimics are equally common among local and referral hospitals,56 ,57 and telestroke is effective in identifying cases of stroke mimics.56 Even when stroke mimics are inappropriately thrombolysed, ICH is extremely rare and less likely to occur than in thrombolysed AIS patients.58 Alternatively, protocol violations could result in either inappropriate thrombolysis or inadequate perithrombolysis management, increasing the risk of ICH.29–31 While protocol violations are not uncommon in community practice,29 violations are rare at local hospitals in a telestroke network36 ,40 ,43 and are comparable with rates observed in the network hub.40 ,43 This is likely due to the fact the same pool of hub based neurologists are deciding on thrombolysis for the entire telestroke network. Ultimately, the safety of telestroke is measured by rates of ICH, irrespective of the appropriate diagnosis or management. Multiple telestroke networks have now demonstrated that remote thrombolysis does not increase the risk of ICH compared with either in-person thrombolysis at a referral center or published trial data.43 ,59–62 Remote thrombolysis is therefore both accurate and safe.

Telestroke and thrombolysis rates

The increasing use of telestroke has created a body of data to test the assumption that telestroke would increase thrombolysis rates (and by extension improve clinical outcomes).63 Universally, implementation of a telestroke network is associated with a significant increase in thrombolysis in remote or underserved hospitals.40 ,43 ,59 ,61 ,62 ,64–67 Consider rural Georgia, where as recently as 2002, tPA was simply not administered to patients with AIS due to the lack of available neurologists. After a telestroke network was implemented the following year, tPA utilization rates immediately increased to 16% in networked hospitals.54 ,68 Similarly, in rural Bavaria, Germany, tPA utilization increased nearly 10-fold after the implementation of a telestroke network while out of network tPA utilization lagged behind.67 ,69 Critically, remote hospitals in a telestroke network use tPA at equivalent rates to referral centers, demonstrating a tractable response to the rural penalty in AIS.54 ,66 ,69

Telestroke and stroke outcomes

Telestroke improves stroke outcomes. This is the most important component of this therapeutic modality. The increased use of tPA with telestroke has led to direct comparisons of clinical outcomes in networked and out of network hospitals. In a prospective study comparing 3 month outcomes after an AIS in 3122 cases, the composite outcome of death, institutionalization, or disability was significantly less likely in telestroke hospitals than comparable out of network hospitals (44% and 54%, respectively).60 In a multivariate regression analysis, presentation to a telestroke hospital was independently associated with a reduced risk of a poor outcome.60 The benefit of telestroke also extends beyond thrombolysis, as demonstrated in a separate German telestroke network.39 Remote consultation led to higher rates of diagnostic and therapeutic interventions in cases of AIS, with at least 75% of consultations resulting in a meaningful change in management. This is consistent with a previous observation from the Veterans Administration Acute Stroke study where neurologist management of AIS was associated with both increased testing and improved clinical outcomes, including reduction in death and disability.70

Consequently, the availability of telestroke not only improved clinical outcomes relative to other remote hospitals, but it has also closed the rural gap in outcomes compared with large referral centers. Multiple telestroke networks throughout Europe and the USA have reported comparable rates of disability and mortality between stroke centers and telestroke hospitals.59–61 ,64 ,69 ,71 ,72 In a retrospective review of 296 cases of thrombolysis in a Boston based telestroke network, there was no difference in symptomatic ICH, mortality, discharge disposition, and long term functional outcomes between patients thrombolysed remotely in small community hospitals or at a regional stroke center.59 Notably, all thrombolysed patients were transferred in this network, but improved clinical outcomes do not require patient transfer. This was demonstrated in a Finnish telestroke network that was based on a drip and keep delivery model.61 Even when patients were kept at small remote hospitals, there was no difference in mortality or functional outcome. Telestroke therefore improves clinical outcomes across multiple delivery models, providing subspecialty care to underserved communities. Effectively, the functional characteristics of the specialist center are brought to the local hospital emergency room.

Telestroke and endovascular therapy

It is now clear from recent data that in selected patients with emergent large vessel occlusions, endovascular management improves functional outcomes and mortality.10–12 ,73 Similar to IV thrombolysis, remote and underserved communities have limited access to endovascular therapy,74 but limited access is also a concern in urban regions with eccentric service provision. Telestroke provides an opportunity to extend the reach of endovascular therapy evaluation to patients who would otherwise do poorly.

Accurate identification of potential embolectomy candidates is the primary focus, most readily through accurate video assessment of NIHSS. Any patient with an NIHSS score greater than 6 is a potential endovascular candidate,75 but higher NIHSS thresholds more accurately predict proximal vessel occlusions.76 Additionally, if vascular imaging is obtained at the referral source, central review of images can be performed remotely to determine anatomic candidacy for therapy (level of occlusion, tortuosity, collateral vasculature, etc). Telestroke in this fashion provides effective triage of patients likely to benefit from more invasive treatment options.

Beyond appropriate identification and triage of endovascular candidates, telestroke availability may potentially facilitate prompt transfer, potentially overcoming time delays that represent a major barrier to endovascular therapy77 ,78 by allowing preparation for the endovascular case to occur while the patient is in transit. In addition, telestroke based consent from family members for mechanical thrombectomy can be accomplished through a video interface, allowing a detailed discussion of the planned intervention. This has been demonstrated in a Spanish telestroke network where remote assessment facilitated prompt thrombolysis and transfer for endovascular management of AIS.79 In this ‘drip, ship, and retrieve’ model, informed consent was obtained remotely and the angiography suite was prepared while the patient was en route, facilitating faster groin puncture times in telestroke versus out of network transfers. Three months post-infarct, functional outcomes were comparable between patients initially treated at the referral center or via telestroke, but significantly worse in patients in out of network facilities.

Telestroke is therefore a strategy with the potential to bridge the geographic gap in access to both pharmacologic and mechanical recanalization (box 1).

Impact of telestroke beyond acute stroke treatment

Beyond the acute phase, telestroke has led to improvements in a range of overall AIS management at network hospitals. Critically, these interventions benefit both thrombolysed and untreated patients. For instance, a German telestroke network implemented local stroke units in all networked hospitals, providing standardized treatment protocols and medical education to the local staff on optimal stroke management and secondary prevention.80 Compared with out of network hospitals, telestroke hospitals had a decreased composite risk of death, disability, or institutionalization.80 Similarly, evidence based guideline implementation interventions in the USA, such as the Get With the Guidelines-Stroke program, are likely more accessible in telestroke hospitals than non-telestroke centers. In the subacute setting, telestroke has also been used to remotely provide transient ischemic attack management and secondary prevention.81 ,82 By harnessing the reach of telecommunication, telestroke has the potential to provide both preventative and acute management to underserved communities.

Summary

Despite the advent of effective pharmacologic and mechanical treatments, healthcare delivery for AIS is limited by the current allocation of resources. Telestroke was developed as a response to geographic disparities, leveraging modern telecommunication technology to extend existing resources into underserved communities. Now, with more than a decade of experience, the safety, efficacy, and improved long term outcomes demonstrated by telestroke have firmly established it as a durable healthcare delivery model. With the advent of data strongly supporting the use of endovascular therapy in stroke, the relevance of telestroke has never been greater. In the second part of this two part review, we will discuss the challenges telestroke faces for wider adoption.