CTP-Based Tissue Outcome: Promising Tool to Prove the Beneficial Effect of Mechanical Recanalization in Acute Ischemic Stroke

Abstract

Purpose: To prove the tissue-protecting effect of mechanical recanalization, we assessed the CT perfusion-based tissue outcome (“TO”) and correlated this imaging parameter with the 3-month clinical outcome (“CO”).

Materials and Methods: 159 patients with large intracranial artery occlusions revealing mechanical recanalization were investigated by CCT, CT angiography (CTA) and CT perfusion (CTP) upon admission. For the final infarct volume, native CCT was repeated after 24 h. The “TO” (“percentage mismatch loss” = %ML) was defined as the difference between initial penumbral tissue on CTP and final infarct volume on follow-up CCT. We monitored the three-month modified Rankin Scale (mRS), age, bleeding occurrence, time to recanalization, TICI score and collateralization grade, infarct growth and final infarct volume. Spearman’s correlation and nominal regression analysis were used to evaluate the impact of these parameters on mRS. 

Results: Significant correlations were found for %ML and mRS (c = 0.48, p < 0.001), for final infarct volume and mRS (c = 0.52, p < 0.001), for TICI score and mRS (c = – 0.35, p < 0.001), for initial infarct core and mRS (c = 0.14, p = 0.039) as well as for age and mRS (c = 0.37, p < 0.001). According to the regression analysis, %ML predicted the classification of mRS correctly in 38.5 % of cases. The subclasses mRS 1 and 6 could be predicted by %ML with 86.4 % and 60.9 % reliability, respectively. No correlations were found for time to recanalization and mRS, for collateralization grade and mRS, and for post-interventional bleeding and mRS. 

Conclusion: Better than the TICI score, CT-based TO predicts the clinical success of mechanical recanalization, showing that not recanalization, but reperfusion should be regarded as a surrogate parameter for stroke therapy.

Key Points:

• %ML as well as the final infarct volume can make a direct point about the immediate effect of successful mechanical recanalization.

• The clinical outcomes after mechanical recanalization are reliably predicted by %ML, reflecting the benefit of escalation therapy including interventional reopening of parent vessel occlusions.

• Not recanalization but rather reperfusion should be regarded as a surrogate parameter for successful stroke therapy.

Citation Format:

• Drewer-Gutland F, Kemmling A, Ligges S et al. CTP-Based Tissue Outcome: Promising Tool to Prove the Beneficial Effect of Mechanical Recanalization in Acute Ischemic Stroke. Fortschr Röntgenstr 2015; 187: 459 – 466

Zusammenfassung

Hintergrund: Zur Überprüfung des gewebsprotektiven Effekts der mechanischen Rekanalisation, untersuchten wir das CTP-basierende Gewebe Outcome („GO“) und korrelierten diesen Parameter mit dem 3-Monats klinischen Outcome („KO“).

Material und Methoden: 159 Patienten mit zerebralen Gefäßverschlüssen wurden mittels CCT, CT-Angiografie (CTA) und CT-Perfusion (CTP) untersucht und anschließend mechanisch rekanalisiert. Für das finale Infarktvolumen wurde ein natives CCT nach 24 Std. angefertigt. Das „GO“ („Prozentualer Mismatch Loss“ = %ML) wurde als Differenz zwischen initialer Penumbra des CTP und finalem Infarktvolumen im Kontroll-CCT definiert. Das 3-Monats „modified-Rankin-Scale“ (mRS), Alter, Auftreten von Blutungen, Rekanalisationszeit, TICI-Score, Kollateralstatus, Infarktzunahme und finales Infarktvolumen wurden bestimmt. Mithilfe des Spearman’s Korrelationskoeffizienten und der nominalen Regressionsanalyse überprüften wir den Einfluss dieser Parameter auf das mRS.

Ergebnisse: Signifikante Korrelationen mit dem mRS bestehen für die Parameter %ML (c = 0,48, p < 0,001), finales Infarktvolumen (c = 0,52, p < 0,001), TICI score (c = –0,35, p < 0,001), initialer Infarktkern (c = 0,14, p = 0,039) und Alter (c = 0,37, p < 0,001). In der Regressionsanalyse konnte %ML die mRS-Klassifikation zu 38,5 % korrekt vorhersagen; die Subklassen mRS 1 oder 6 konnten zu 86,4 % bzw. 60,9 % vorhergesagt werden. Es konnten keine Korrelationen mit mRS für die Parameter Rekanalisationszeit, Kollateralstatus und Auftreten von Blutungen festgestellt werden.

Schlussfolgerung: Das CT-basierte GO beschreibt besser als der TICI-Score den klinischen Erfolg der mechanischen Rekanalisation, so dass nicht die Rekanalisation selbst, sondern die Reperfusion den geeigneten Kontrollparameter darstellt.

Kernaussagen:

• %ML und finales Infarktvolumen sind direkte Kontrollparameter für eine erfolgreiche mechanische Rekanalisation.

• Das klinische Outcome nach mechanischer Rekanalisation wird durch %ML zuverlässig vorhergesagt, welches den Nutzen der interventionellen Therapie zerebraler Gefäßverschlüsse widerspiegelt.

• Anstelle der Rekanalisation sollte die Gewebsreperfusion den geeigneten Kontrollparameter einer erfolgreichen interventionellen Schlaganfallstherapie darstellen.

Key words

ischemia/infarction - acute - interventional procedures - brain - arteries - obstruction/occlusion

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