This single-center, single-blind, non-placebo-controlled, two parallel-group, prospective study was conducted at the neurology and cardiology departments of Nemazee Hospital, a tertiary hospital affiliated to the Shiraz University of Medical Sciences in Shiraz, Iran, from July 2007 to June 2010.
Inclusion criteria were adult age (≥18 years), single recent (within 30 days of enrollment) transient ischemic attack or stroke which fulfilled the criteria for unknown subgroup of undetermined causes of stroke according to the Causative classification of stroke modified Trial of Org 10172 in Acute Stroke Treatment criteria (CCS-TOAST) classification,
The main criterion for exclusion was the presence of any determined cause for ischemic stroke according to the CCS-TOAST classification. These included: (1) Evident large-artery atherosclerosis defined as >50% stenosis or occlusion of a major brain artery or branch cortical artery; (2) unequivocal cardiac source of embolism defined as chronic or paroxysmal atrial fibrillation, mitral stenosis, mechanical heart valve, endocarditis, intracardiac clot or vegetation, myocardial infarction within 3 months, dilated cardiomyopathy, and ejection fraction less than 30%; (3) small-vessel disease defined as cortical, cerebellar, brainstem or subcortical infarct <1.5 cm; (4) other determined cause of stroke defined as any known vasculitis, any known thrombophilic disease, any infectious vasculopathy, arterial dissection, Moya Moya disease, radiation-induced vasculopathy, fibromuscular dysplasia, sickle cell disease, neurofibromatosis, reversible cerebral vasoconstriction syndrome, vasospasm after subarachnoid hemorrhage, and cerebral sinus venous thrombosis. Patients without a suitable temporal window for performance of c-TCD or with poor clinical condition were excluded. In addition, patients with severe aphasia (impaired comprehension), severe disabling stroke (score of 4 or 5 on the modified Rankin scale), and known dementia were excluded.
The study was approved by the Institutional Review Board of the Shiraz University of Medical Sciences (No. 88-4639) and is registered with the Iranian registry for clinical trials (www.irct.ir, registration number: IRCT138805192323N1). The study and possible outcomes were explained to all participants or their first-degree relatives and written informed consent was obtained for each participant.
Consecutive patients fulfilling all inclusion and exclusion criteria were enrolled by the principal investigators. Eligible patients who agreed to participate in the study were randomized to two treatment groups according to a computer-generated random number list and simple randomization procedure Flowchart for a single-center, single-blind, non-placebo-controlled, parallel-group randomized trial of aspirin versus warfarin in patients with cryptogenic stroke and patent foramen ovale in Iran, 2007-2010
For each participant a questionnaire was completed that included items on demographic characteristics, a checklist of inclusion and exclusion criteria, the results of basic laboratory tests and findings on neurological imaging studies. Transesophageal echocardiography and c-TCD were done for all eligible patients.
A Vivid 3 Echo machine with a 5-MHz TEE probe was used (GE Medical Systems, Oslo, Norway). Contrast (agitated saline) was injected in mid-esophageal four-chamber view during the Valsalva maneuver to detect any inter-atrial right-to-left shunt across the PFO. Agitated saline was generated by agitating a mixture of 9 mL normal saline and 1 mL air in two 10-mL syringes connected by a 3-way stopcock. Once the contrast became milky, 10 mL of the contrast was rapidly injected as a bolus into a cubital vein that had previously been cannulated with a large-gauge indwelling intravenous catheter. The diagnosis of PFO was based on the appearance of bubbles in the left atrium during five cardiac cycles after opacification of the right atrium with contrast bubbles. The maximal diameter of the PFO was measured in the same view. PFOs with a diameter < 4 mm were considered small and those ≥ 4 mm were considered large.
A Sunray version FD-T98II transcranial Doppler ultrasound device (Guangzhou Doppler Electronic Technologies, Guangzhou, China) was used for c-TCD examinations. While the patient was lying supine, both middle cerebral arteries were insonated simultaneously. Two 2-MHz transducers were fixed on the temporal windows with a helmet. The device was set to a small sample volume of 10 mm in length and minimum possible gain to provide an optimal setting for microembolic signal discrimination from the background spectrum. We defined microembolic signal as a typical visible and audible signal (click, chirp or whistle) of short duration and high intensity within the Doppler flow spectrum. The same protocol was used for contrast preparation and injection and the Valsalva maneuver as for TEE.
Patients were randomly assigned to aspirin (acetylsalicylic acid, Jalinous, Teheran, Iran), 80 mg orally 3 times daily, or warfarin (Marevan, Orion Pharma, Espoo, Finland), started at 2.5 mg orally once daily, and then adjusted to achieve an international normalized ratio target of 2 to 3. The interventions lasted for 18 months, after which the patients were free to select any therapeutic option. In the case of adverse drug reactions, the study drug was withheld temporarily and the patient was encouraged to consult a relevant specialist.
Suspected adverse drug reactions of aspirin and warfarin were followed up scrupulously by phone calls (weekly during the first month and monthly thereafter). The patients were specifically questioned regarding major hemorrhage (gastrointestinal bleeding or intracranial hemorrhage). In the warfarin-treated group, international normalized ratio was evaluated weekly during the first month, biweekly during months 2 and 3, and monthly thereafter. Patients who did not have regular blood tests for international normalized ratio for any reason during the study period were excluded from the final analysis.
The primary endpoint was recurrence of ischemic event (transient ischemic attack or stroke) or death due to any cause. The secondary endpoints were recurrence of myocardial infarction, and death due to vascular causes (stroke, myocardial infarction, and intracranial hemorrhages). Information about the occurrence of endpoints was sought monthly by phone, and the research assistant visited the patient (or next of kin) if an endpoint occurred.
All statistical analyses were done with SPSS v. 15.0 software (SPSS, Chicago, IL, USA). The population comprised all patients admitted to our hospital during one year with cryptogenic stroke. The results are expressed as absolute frequencies and percentages where appropriate. Descriptive results are presented as the mean value ± standard deviation. The Chi-square test and Mann-Whitney U test were used to compare variables between groups. Kaplan-Meier survival analysis was used to compare cumulative survival in the treatment groups. Patients were censored if they were lost to follow-up, in the case of PFO closure and at the end of follow-up. The log-rank and Cox proportional-hazards models were used to assess the predictive value of treatment with respect to primary and secondary endpoints, and the models were adjusted for age, sex, hypertension, diabetes mellitus, hyperlipidemia and smoking. A P value < 0.05 was considered as significant.