Study design and setting
This retrospective study was approved by our hospital’s institutional review board with a waiver of informed consent (Committee reference number 2016-16/11) and was conducted in compliance with Health Insurance Portability and Accountability Act guidelines.
This study was conducted in a university hospital with 150,000 adult patient emergency visits annually. Our institution’s picture archiving and communication system (Centricity; GE Healthcare, Little Chalfont, UK) was used to conduct a search for patients having a cranial CT or MRI between 1 January 2011 and 1 December 2016. The database was investigated for all patients who visited the ED with a symptom containing any of the following terms: syncope, fainting, passing out, and loss of consciousness. The patient history and clinical information were gathered from electronic medical record system. The risk factors were evaluated by the in-depth evaluation of the initial electronic patient notes recorded by the ED physician or physician assistant including vital signs and laboratory findings.
Clinical variables that were missing from or not referred in the electronic patient note were considered as not present. Patients with multiple head CT and MRI during the study period were included only once.
Patients were excluded from the study if primary symptoms did not consist of any of the designated search terms, were under 18 years of age, were not from the ED, presented due to a history of trauma, had existing intracranial pathology, and had a known primary or metastatic brain tumor. Persistent altered mental status, alcohol, or illicit drug-related loss of consciousness, seizure, and coma were also excluded. Patients with a history of malignancy without metastatic tumor in the brain were still included into the study. Visits to other hospitals during time period were also not included to the study. Electrocardiogram (ECG) findings were gathered from patient reports retrospectively. Electrocardiography findings were available in only 168 out of 1230 (13%) syncope patients; a concerning finding including ST-segment changes, atrial fibrillation/flutter, or second- or third-degree heart block, was reported in 13 (8%) patients. The ECG data were not sufficient to be used as a factor in statistical analyses.
In our department, cranial MRI is utilized following head CT imaging if considered necessary in patients admitted to the ED with syncope. Patients with an initially negative CT and subsequent positive MRI are included as a positive MRI finding. Whereas, if pathology is identified on head CT scan initially, consequent cranial MRI is excluded from the study to obviate sample bias.
Outcome measures
Cranial CT and MRI studies were interpreted by board-certified neuro-radiologists with 15 and 25 years’ experience, consecutively. The referring emergency physician did not play a role in image interpretation. The primary outcomes were abnormal cranial CT or MRI findings characterized by an acute intracranial hemorrhage, acute or subacute infarct, a newly diagnosed brain mass or other clinically important abnormality that required intervention. According to the results gathered from previous studies [10, 12], the following risk factors were identified: sex, age, focal neurologic deficit, history of malignancy, history of drug abuse including alcohol, fever or leukocytosis, hypertension, diabetes mellitus, disturbances in coagulation profile, nausea or vomiting, and laboratory findings of metabolic derangement such as hypoglycemia. Cranial CT and MRI examinations were considered abnormal only if patient’s condition was related to the imaging finding.
Coagulopathy included abnormal international normalized ratio (INR), abnormal partial thromboplastin time (PTT), abnormal prothrombin time (PT), thrombocytopenia, active anticoagulant therapy, and history of the coagulopathic disorder (e.g., hemophilia, Factor V Leiden).
Vital signs were considered to be normal if the patient’s temperature was between 35 °C (95 °F) and 38 °C (100.4 °F), pulse 60–100 beats/min, respiration 14 to 20 breaths/min, blood pressure ranging from systolic blood pressure 90 to 140 mmHg, oxygen saturation over 90% room air.
Syncope was defined as a transient loss of consciousness with a brief period of unresponsiveness and a loss of postural tone, resulting in spontaneous recovery without any resuscitation.
Statistical analysis
All statistical comparisons were performed by using the software of Statistical Package for the Social Sciences (SPSS, version 23.0; SPSS, Chicago, IL). We examined separately the distribution of associated symptoms (predictive variables) in the different categories. The discrepancy in their distribution was analyzed with the x2 test and, when expected frequencies were < 5 for any categories, the Fisher’s exact test was used. Univariate logistic regression analysis was utilized to identify the predictor variables of abnormal cranial CT and MRI findings. Those that were significantly associated with the primary outcome in univariate analysis were also processed with multivariate regression analysis. The strength of association of each predictor variable with the primary outcome was expressed as an odds ratio and 95% confidence interval. A p value of less than 0.05 was considered as the statistically significant difference.
