High baseline nih stroke scale is the best predictor of resistance to intravenous thrombolysis

Abstract

Objectives: The effectiveness of intravenous thrombolysis is limited in stroke patients with proximal cerebral artery oclusion. Intra-arterial rescue therapies can be used to treat these patients with persistent occlusion (PO), but they require the rapid mobilization of complex multidisciplinary teams. We compared the value of several baseline clinical, biochemical and radiological variables in order to predict candidates for intra-arterial therapies due to PO of large vessels despite intravenous thrombolysis. Methods: Seventy consecutive patients with acute stroke in the carotid territory treated with tPA in a Comprehensive Stroke Center with a program of iv thrombolysis and rescue therapy. We measured age, time from onset, clinical severity (NIHSS), baseline glucose levels, hyperdense middle cerebral artery (MCA) sign and ASPECTS score in CT. PO was evaluated in an angio-CT obtained after 40 minutes of iv tPA perfusion and was defined as a TIMI score of 0-1 in the intracranial carotid, M1/M2 segments of the MCA and A1/A2 segments of the anterior cerebral artery. We compared the capacity (area under the ROC curve) of different logistic regression models to predict PO. We also compared the diagnostic value of different cut-off points in the NIHSS: Sensibility (Se), Specificity (Sp), Positive predictive value (PPV), Negative predictive value (NPV). Results: 30 patients (42.9%) had PO after 40 minutes of tPA treatment. NIHSS was by far the best predictor of PO (overall predictive capacity=84.1%), followed by ASPECTS score, hyperdense MCA sign, glucose levels, time from onset and age. Adding other variables to the NIHSS only marginally increased the predictive value of the models. The analysis of the ROC curve showed that a cut-off point of NIHSS of (greater-than or equal to)12 was the most accurate (Se=80%; Sp=82.5%; PPV=77.4%; NPV=84.6%). Compared to this, the often used cut-off point of NIHSS (greater-than or equal to)10was more sensitive but had lower specificity and lower PPV (Se=83.3%; Sp=75%; PPV=71.4%; NPV=85.7%). Conclusions: Baseline NIHSS is simple tool that allows the early identification of candidates for intra-arterial rescue therapies due to persistent occlusion after intravenous thrombolysis. Whereas the criterion of NIHSS (greater-than or equal to)10 is sensitive and may be suitable for centers where rescue therapies are available, a cut-off point of 12 is more specific and may be preferred in centers where emergency transfer to other hospitals is required.