Outcome Analysis of Intravenous Thrombolytic Therapy in Patients with Acute Ischaemic Stroke and its Association with Critical Time Intervals: An Ambispective Study

Abstract

Introduction: Intravenous thrombolytic therapy has become the standard of care in patients with acute ischaemic stroke. The success of this therapy depends on achieving the shortest time between the onset of stroke and reperfusion. Many clinical tasks like neurological assessment, imaging and its interpretation, exclusion of contraindications and informed consent must be taken care of, prior to administration of thrombolytic therapy. As this is a time sensitive intervention, it may have variable outcomes in different settings. Aim: To evaluate the immediate and 90-day neurological outcome of the patients who had received intravenous thrombolytic therapy in acute ischaemic stroke and to evaluate its association with stipulated critical time intervals. Materials and Methods: This was an ambispective observational study conducted for a period of 18 months (April 2018-October 2019) in the Emergency Department of Pushpagiri Institute of Medical Sciences, Thiruvalla, a tertiary care hospital in central Kerala, India. For the prospective arm of the study, data were collected from the patients who came to the Emergency Department with acute ischaemic stroke in the window period (three hours) or in the extended window period (3 to 4.5 hours). Onset to door time, door to imaging time, door to needle time and onset to needle time were assessed and recorded. National Institute of Health Stroke Scale (NIHSS) score at presentation and at 24 hours post-thrombolysis was noted. Magnetic Resonance Imaging (MRI)/ Computed Tomography (CT) brain report 24 hours post-thrombolysis was followed-up. The functional outcome at 90 days was assessed using Modified Rankin Scale (MRS) score. For the retrospective arm of the study, the relevant data were collected from the hospital records and the patients were followed-up. The association between the stipulated critical time intervals and 24 hours post-thrombolysis NIHSS score, as well as MRS score at 90 days were calculated using the statistical analysis tool STATA v.14. Statistical comparisons were performed between subgroups using the Chi-square test, Fisher’s exact test, Wilcoxon signedrank test, and Mann-Whitney U-test as indicated for dichotomous or continuous variables. For all statistical analyses, a p-value of <0.05 was taken as statistically significant. Results: Of the total 110 patients, 105 patients (95.5%) reached the hospital within three hours (window period), and five patients (5%) reached within 4.5 hours (extended window period). A total of 58 patients (52.7%) received thrombolytic treatment within three hours and 52 patients (47.3%) within 4.5 hours. After 24 hours of thrombolysis, improvement in neurological function, as defined by an improvement in NIHSS score by 4 or more was found in 73 patients (66.4%). At 90 days follow-up, 76 patients (69.1%) became functionally independent with an MRS score of 0-2. There was a significant association between NIHSS score 24- hours post-thrombolysis and the functional outcome at 90 days. Of the various stipulated critical time intervals, a significant association was seen only with onset-to-door time and NIHSS score 24 hours post-thrombolysis. Conclusion: 69.1% of the patients who have received intravenous thrombolytic therapy for acute ischaemic stroke in this study have shown favourable functional outcome at 90 days. The NIHSS score 24 hours post-thrombolysis compared to baseline is a good predictor of the neurological outcome at 90 days.