Annually, about 4000 Swedes suffer a recurrent stroke, and for many, their lives change dramatically. To prevent recurring strokes, knowledge about the individual's risk of recurrence is needed to tailor an effective preventive medical treatment.

The purpose of the SALSA study is to investigate whether an expanded risk assessment and subsequent treatment can reduce the recurrence of stroke in study patients. Stroke, i.e., infarction/bleeding in the brain, has several different causes that individually or together constitute the risk of recurrence. Furthermore, stroke patients often have concomitant vascular diseases in other vascular beds, which further increases the risk.

Every fourth patient with acute stroke or transient ischemic attack (TIA) admitted to any of the stroke wards at Danderyd Hospital, Stockholm, Sweden, is consecutively invited to participate in the SALSA study. Those who accept the study invitation, receive an expanded investigation of the most common causes of cerebral infarction (atherosclerosis, atrial fibrillation, narrowing of the brain's small vessels) or brain haemorrhage (presence of the protein amyloid in the vessels, high blood pressure). Due to the high risk of stroke patients having a vascular disease, such as atherosclerosis, the presence of arterial stiffness in the aorta, 24-hour blood pressure, and blood circulation in the legs are examined at the follow-up visit. If vascular disease is detected, expanded preventive treatment is provided. Neither a general investigation of the most common stroke aetiologies in addition to the one assessed to have caused the current stroke nor examinations of other vascular beds are recommended in national stroke guidelines. In addition to the extended risk assessment, the patient will get a written treatment program tailored after the individual patient's risk profile. The compliance to this treatment program will be assessed during a return visit one year after the hospital stay. After this visit, the active participation in the study is completed for the study participant. During the remainder of the follow-up, the study participant will be followed in national medical registers.

The remaining 3/4 of patients at Danderyd Hospital constitute the comparison group, who are investigated and treated according to routine and hence do not undergo the additional vascular examinations. Stroke recurrence and other cardiovascular events occurring within the next 5-10 years will be compared between study patients and the comparison group via the national stroke registry containing all stroke and TIA patients at Danderyd Hospital.

Background

Stroke and TIA are caused by circulatory disorders in the cerebral vasculature, but the etiological mechanisms vary greatly. In clinical practice in Sweden today, stroke and TIA patients are investigated with the aim of finding the primary cause of the acute ischemic event, after which preventive treatment is initiated. Beyond identifying the proposed causative aetiology, concomitant subclinical stroke aetiologies and risk factors are not routinely examined, despite the fact that presence of multiple cerebrovascular aetiologies are likely to pose an increased risk of stroke recurrence. Moreover, national guidelines do not recommend a complete etiological assessment or screening for other vascular diseases in acute stroke and TIA patients, even though general vascular disease poses an increased risk for recurrent vascular events. This complicates the shift towards individualized preventive treatment based on a risk stratification strategy.

Aims/Hypotheses

The aim of the SALSA study is to investigate in a consecutive, representative hospital population with stroke and TIA patients (study cohort):

1. The prevalence of one/multiple cerebrovascular disease aetiologies classified according to known classification systems such as TOAST and ASCOD.

   Hypothesis: A significant proportion of stroke/TIA patients have two or more potential subclinical/clinical stroke aetiologies.

2. The presence of concomitant arterial stiffness, hypertension, and/or peripheral arterial disease, mirroring macrovascular vascular disease in multiple vascular territories, and its association with stroke aetiology, clinical severity, and radiological extent of infarction/intracerebral haemorrhage.

   Hypothesis: The presence of other macrovascular diseases in stroke/TIA patients is higher than previously reported and differs between different subgroups within this patient population.

3. The prevalence and levels of inflammatory, neuronal, and metabolic biomarkers in blood and urine after a stroke/TIA and their association to stroke subtype and risk of recurrence.

   Hypothesis: Biomarkers indicating an increased risk of new vascular events can be used to predict the risk of future vascular events in stroke/TIA patients.

4. The prevalence of left atrial cardiomyopathy with echocardiography and defined according to the EHRA/HRS/APHRS/SOLAECE consensus document in groups with or without concomitant atrial fibrillation (AF) and in relation to inflammatory biomarkers and future diagnosis of atrial fibrillation and/or ischemic stroke.

   Hypothesis: Left atrial cardiomyopathy is a condition associated with both AF and the risk of cardiac embolism and ischemic stroke/TIA, and underlying inflammation may provide a breeding ground for atrial remodelling.

5. The difference in risk of future cardiovascular events (CVE) between different groups of stroke/TIA patients based on underlying etiological conditions and macrovascular vascular disease to identify risk groups within the stroke population.

   Hypothesis: Different individual and combinations of etiological conditions and vascular diseases imply different risks for future CVE.

6. The difference in risk of future CVE between the more extensively investigated group with individually tailored extended pharmacological treatment (study cohort) and the patients investigated and treated according to current guidelines (comparison cohort).

   Hypothesis: Lower risk of recurrence or other future CVE is the benefit of extended investigation and treatment.

7. The difference in adherence to prescribed medications in the more extensively investigated and treated group compared to previous studies on adherence to pharmacological treatment in patient groups with cardio-/cerebrovascular disease.

   Hypothesis: Greater adherence exists in a group that has undergone a more extensive investigation, greater understanding of the cumulative vascular risk, and, if necessary, expanded prophylactic treatment.

8. Presence of post-stroke/TIA depression and association with 1) stroke aetiology and 2) inflammatory biomarkers.

Hypothesis: There is an association between depression after stroke/TIA and stroke aetiology and inflammatory biomarkers, respectively.

Method

The source population consists of patients >18 years old with ischemic stroke/TIA admitted to the Danderyd Hospital Stroke Unit during the inclusion period. The pilot study (n=50) was included in the spring of 2023, and inclusion in the main study (n=550) started in the fall of 2023. With a total of 550 study participants, we have 80% power to detect a difference of 5 percentage points in the recurrence rate of cardiovascular and cerebrovascular outcomes after 5 years with a 5% significance level and accounting for 20% loss to follow-up.

Screening, consent, and cohort allocation: All patients admitted to the Danderyd Hospital Stroke Unit, are screened for the study, and every fourth patient admitted to the Stroke Unit is consecutively asked. The reason we do not plan to ask all patients is that the study is pragmatic, and capacity constraints regarding investigation resources, especially radiology and physiology labs, need to be considered.

The remaining three out of four patients admitted to the Danderyd Hospital Stroke Unit, during the inclusion period are allocated to the comparison cohort. This cohort also includes patients who could not make an informed decision about consent or who did not wish to participate in the study. However, these patients are categorized as screening patients and will therefore be distinguished from the rest of the comparison cohort in analyses of Riksstroke data.

Etiological mapping Study cohort: Study participants undergo a complete stroke etiological investigation according to the protocol, regardless of whether the triggering cause of the cerebrovascular event has been identified or not.

• Computed tomography (CT) of the brain. Grading of a potential infarction is done according to radiological scoring scales for infarct extension: Alberta Stroke Program Early CT Score (ASPECTS) and Posterior Circulation ASPECTS (PC-ASPECTS).
• CT angiography for the visualization of potential pathology in the pre- and intracerebral vessels such as occlusions, non-significant and significant stenoses, and description and localization of atherosclerotic lesions in general.
• Carotid duplex (ultrasound) with expanded macroscopical analysis of atherosclerotic plaques in the internal carotid artery, estimation of intima media thickness and carotid distensibility i.e. arterial stiffness in the common carotid artery.
• Inpatient ECG telemetry for all patients with ischemic stroke/TIA without a diagnosis of paroxysmal/chronic atrial fibrillation (AF).
• Outpatient long-term ECG recording with either 1) Thumb-ECG, i.e. AF screening for 3 weeks with the patient placing his/her thumbs on the electrodes of the device for 30 seconds in the morning and evening, and when symptomatic, or 2) Holter ECG, i.e. ambulatory continuous ECG monitoring, for 24-72 hours for patients with ischemic stroke/TIA without known AF.
• Magnetic resonance imaging (MRI) of the brain in all stroke patients (not TIA) regardless of ischemic or haemorrhagic cerebrovascular event. Signs of microvascular disease e.g. white matter changes are graded according to the Fazekas scale. In addition, the modified Boston criteria are used to assess the presence of cerebral amyloid angiopathy (CAA) as a risk factor for future intracerebral haemorrhage. In addition, grading of infarction is done according to radiological scoring scales for infarct extension: ASPECTS and PC-ASPECTS.
• Routine blood tests: repeated glucose measurements over the first 24 hours, HbA1c, fasting lipid panel, liver, electrolyte, and blood panels, APTT (activated partial thromboplastin time) and PK-INR.
• In study participants <60 years, a coagulation assessment (Antithrombin, Factor II DNA, Factor V DNA, Cardiolipin IgM, Cardiolipin IgG, Protein C) is performed to identify patients with increased thrombogenicity.
• Echocardiography is performed on all study participants to investigate the presence of cardiac embolic sources such as atrial appendage thrombus, increased spontaneous contrast, patent foramen ovale, atrial septal aneurysm, and morphology with signs of atrial pathology such as enlarged atria and pathological flow and/or motion patterns indicating the presence of AF/risk of thrombosis. Transoesophageal echocardiography (TEE) is performed in patients ≤60 years for optimal diagnosis of patent foramen ovale and atrial septal aneurysm and for a thorough examination of deviations in the left atrial appendage. Transthoracic ECG (TTE) is performed on patients >60 years of age.

Comparison cohort: Patients admitted to the Stroke Unit during the inclusion period undergo routine etiological investigation according to national and local guidelines at the Danderyd Hospital Neurology Clinic.

Macrovascular disease mapping (study cohort only) Study participants are investigated at the follow-up visit after 3 months for the presence of extra cerebral macrovascular disease. The assessment consists of indirect measurement of arterial stiffness, 24-hour blood pressure monitoring, and automatic ankle-brachial index (ABI) measurement.

Indirect measurement of arterial stiffness: Arterial stiffness will be quantified through indirect estimation of arterial stiffness using two different measurement instruments: Arteriograph (TensioMed) and Microlife WatchBP Office Vascular (Microlife).

Arteriograph, which is easy to use and has been validated in various populations, measures blood pressure by means of oscillometry in the brachial artery. The arterial stiffness parameters pulse wave velocity, measure of arterial stiffness, and the augmentation index, measure of endothelial function and resistance in peripheral arteries are provided.

With Microlife WatchBP Office Vascular, ankle-brachial pulse wave velocity is estimated non-invasively using oscillometry via a cuff on the upper arm and one on the same side's ankle.

With two different measures of arterial stiffness, we will obtain more information about the condition of the vessels but also have the opportunity to validate Microlife against Arteriograph in a stroke cohort.

24-hour blood pressure monitoring: 24-hour blood pressure monitoring, especially nocturnal values, is superior in predicting fatal and non-fatal cardiovascular events and all-cause mortality compared to blood pressure values measured in clinic context. The GE Healthcare Tonoport VI blood pressure cuff with an attached measuring device is attached by a nurse on the Stroke Unit, after which the patient receives a diary to report their activities and any symptoms. The device is disconnected after one day, and the results are interpreted by a stroke physician affiliated with the unit trained in interpreting 24-hour blood pressure monitoring. Parameters evaluated include mean blood pressures daytime and night-time, blood pressure variability, and the presence/absence of nocturnal blood pressure dipping.

ABI measurement: Peripheral arterial disease is diagnosed and graded using ABI, an index between the blood pressure in one ankle and the arm on the same side. Ankle blood pressure has traditionally been measured with a handheld pen Doppler, but the technique is cumbersome and difficult to handle for inexperienced users. We will use Microlife WatchBP Office Vascular (Microlife), a non-invasive automated ABI meter with four connected blood pressure cuffs to each extremity. In addition to ABI, volume plethysmographic data provides information about the pulse wave's shape. The method is less sensitive to variations in vessel compressibility than traditional Doppler, which cannot reliably measure ABI in patients with diabetes and arterial medial sclerosis, for example, and can therefore be used as a complement to ABI in these patients.

Follow-up

Study cohort: Follow-up visit at the Stroke Unit after 3 months +/- 2 weeks and after 12 months +/- 1 month. Examinations and findings in the study are reviewed together with the study participant and recommended actions (lifestyle changes, medications, follow-up, need for referrals, etc.) are discussed.

Comparison cohort: Follow-up at the Stroke Unit is done according to local routines after about 3 months.

Blood and urine sampling (study cohort only) At the follow-up visit or in connection with the outpatient vascular investigations, study participants will submit fasting routine blood tests for follow-up of lipids and liver status, as well as urine samples for albumin/creatinine ratio analysis and frozen urine for later analysis. In addition, plasma and whole blood samples are frozen and stored in a Biobank at -80°C for subsequent analysis of inflammatory and metabolic markers using traditional ELISA techniques as well as Olink and DNA analyses on whole blood. Metabolomics analyses will be performed in both plasma and urine.

Assessment of functional impairment and cognition (study cohort only) At the follow-up visit, study participants undergo an assessment of residual disability and dependency on others' assistance using the modified Rankin Scale (mRS) and assessment of cognitive status using the Montreal Cognitive Assessment (MoCA), both performed by a physician certified in the use of these rating scales.

To assess the presence of post-stroke depression, participants are given the PHQ-9 depression scale before the follow-up visits. Results on PHQ-9 will later be analysed in relation to inflammatory biomarkers.

Follow-up via registers Study cohort: After inclusion and follow-up at the Stroke Unit, study participants will be prospectively followed in national Swedish registers such as the national stroke register, Riksstroke, the National Patient Register containing all in-patient care in Sweden, the Cause of Death Register registering all deceased in Sweden, and the Prescription Register with data on all retrieved prescribed medications to relate findings from examinations and laboratory analyses in the study to future cardiovascular events, atrial fibrillation in relation to atrial pathology on echocardiography, and other morbidities and all-cause mortality. To assess compliance with medication prescriptions, extracts from the Prescription Register will be made regarding dispensing of medications prescribed during the acute stroke onset.

Comparison cohort: Since all stroke and TIA patients admitted to the Danderyd Hospital Stroke Unit are registered in the national stroke register Riksstroke, the comparison cohort can be followed via Riksstroke allowing comparison of recurrence and mRS after 3 and 12 months as well as all-cause mortality between groups.

Inclusion Criteria:

• Admitted to the Danderyd Hospital Stroke Unit for acute stroke or TIA

Exclusion Criteria:

• The medical condition is assessed not to be a stroke or TIA
• The patient is not able to make an informed decision to enter the study