The primary aim of this prospective observational study is to investigate whether an enhanced diagnostic MRI work-up (including cardiac MRI, angiography of the aortic arch and the brain-supplying arteries) combined with an in-hospital Holter-ECG of up to 5 days duration leads to a significant increase in relevant pathologic findings with respect to stroke aetiology as compared to the findings obtained by a routine diagnostic work-up (including stroke unit monitoring, 24h-Holter-ECG, echocardiography, Doppler-ultrasound of the brain-supplying arteries) in patients with acute ischemic stroke and no atrial fibrillation according to past medical history or baseline ECG. A better understanding of the stroke aetiology may improve secondary stroke prevention and long term outcome.

Variations and delays in the diagnostic procedures during hospitalization after acute ischemic stroke are still common, and at the same time, stroke aetiology remains cryptogenic in about 20-25% of stroke unit patients. Recent studies have shown that (a) cardiac MRI is now able to detect cardiac sources of embolism (thrombi and aortic plaques) with equal sensitivity as compared to echocardiography, and (b) prolonged ECG monitoring up to several days/weeks/years can significantly increase the detection rate of atrial fibrillation. These developments might allow a faster and more effective diagnostic work-up in patients with acute ischemic stroke compared to standard diagnostic procedures including doppler-ultrasound of the extracranial brain-supplying arteries, echocardiography, 24-h-Holter ECG and stroke unit monitoring. This prospective observational trial therefore aims to assess the detection rate of pathologic findings relevant to stroke aetiology as obtained by an enhanced MRI set-up (including cardiac MRI, MR-angiography of the brain-supplying arteries) and a prolonged Holter-ECG (of up to 5 days after the stroke) in comparison to findings obtained by routine diagnostic procedures after acute stroke.

Moreover, cumulating evidence implies that acute ischemic stroke can lead to cardiac damage. Since the underlying pathophysiological mechanisms are still poorly understood, the HEBRAS study attempts to tackle the relationship between stroke localization (e.g. insular involvement), observed cardiac damage (as indicated by troponin elevation) and activation of autonomic nervous system (as indicated by impairment of heart rate variability and elevated urinary norepinephrine levels), respectively.

Finally, to clarify the prognostic impact of stroke-induced autonomic dysfunction, heart rate variability will be analysed with respect to functional outcome, mortality, recurrent stroke and myocardial injury.

Inclusion Criteria:

• Age ≥18 years
• Written informed consent by the patient
• Acute ischemic stroke, as confirmed by cerebral MRI or CT
• Admission to the stroke unit of the Department of Neurology, Charité, Campus Benjamin Franklin

Exclusion Criteria:

• Atrial fibrillation known by past medical history or documented by routine electrocardiogram (ECG) on hospital admission
• Participation in an interventional clinical trial
• Pre-stroke life expectancy <1 year
• Mechanic heart valve, cardiac pacemaker or other contraindications to undergo MRI
• History of adverse response to MRI contrast agents
• Known Liver disease prior to stroke
• Mild to severe renal dysfunction (creatinine > 1.3 mg/dl (females); creatinine > 1,7 mg/dl (males))
• Severe congestive heart failure (NYHA III or IV).

Patients admitted to the specialized stroke unit at the Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin (CBF), due to an acute ischemic stroke.