Perfusion computed tomography in patients with stroke thrombolysis

Abstract

See Saver (doi:10.1093/awx020) for a scientific commentary on this article.Stroke shortens an individual's disability-free life. We aimed to assess the relative prognostic influence of pre- and post-treatment perfusion computed tomography imaging variables (e.g. ischaemic core and penumbral volumes) compared to standard clinical predictors (such as onset-to-treatment time) on long-term stroke disability in patients undergoing thrombolysis. We used data from a prospectively collected international, multicentre, observational registry of acute ischaemic stroke patients who had perfusion computed tomography and computed tomography angiography before treatment with intravenous alteplase. Baseline perfusion computed tomography and follow-up magnetic resonance imaging were analysed to derive the baseline penumbra volume, baseline ischaemic core volume, and penumbra salvaged from infarction. The primary outcome measure was the effect of imaging and clinical variables on Disability-Adjusted Life Year. Clinical variables were age, sex, National Institutes of Health Stroke Scale score, and onset-to-treatment time. Age, sex, country, and 3-month modified Rankin Scale were extracted from the registry to calculate disability-adjusted life-year due to stroke, such that 1 year of disability-adjusted life-year equates to 1 year of healthy life lost due to stroke. There were 772 patients receiving alteplase therapy. The number of disability-adjusted life-year days lost per 1 ml of baseline ischaemic core volume was 17.5 (95% confidence interval, 13.2-21.9 days, P < 0.001). For every millilitre of penumbra salvaged, 7.2 days of disability-adjusted life-year days were saved (β = -7.2, 95% confidence interval, -10.4 to -4.1 days, P < 0.001). Each minute of earlier onset-to-treatment time resulted in a saving of 4.4 disability-free days after stroke (1.3-7.5 days, P = 0.006). However, after adjustment for imaging variables, onset-to-treatment time was not significantly associated with savings in disability-adjusted life-year days. Pretreatment perfusion computed tomography can (independently of clinical variables) predict significant gains, or loss, of disability-free life in patients undergoing reperfusion therapy for stroke. The effect of earlier treatment on disability-free life appears explained by salvage of penumbra, particularly when the ischaemic core is not too large.

Keywords: acute stroke; disability; perfusion CT; thrombolysis.

Figure 1

Relationship between disability adjusted life-days, baseline penumbra volume (A), salvaged penumbra volume (B), onset-to-treatment time (C) and baseline NIHSS score (D) in all patients, patients with recanalization, and patients with poor recanalization. (A) Patients lost 4.1 DALY-days per 1 ml baseline penumbra (β = 4.1, 95% CI, 0.8–7.5 days, P = 0.015). In patients with recanalization, baseline penumbra volume did not affect the DALY-days lost due to stroke (β = 0.7, 95% CI, −4.8–13.5 days, P = 0.808). However, patients without recanalization lost 7.5 DALY-days per 1 ml of baseline penumbra (β = 7.5, 95% CI, 2.8–12.3, P = 0.002). (B) Each 1 ml of salvaged penumbra resulted in a saving of 7.2 DALY-days (β = −7.2, 95% CI, −10.4 to −4.1, P < 0.001). In patients with recanalization, each 1 ml of salvaged penumbra resulted in a saving of 11.8 DALY-days (β = −11.8, 95% CI, −16.6 to −7.1, P < 0.001). In patients without recanalization, the small volumes of salvaged penumbra volume did not save DALY-days (β = −4.1, 95% CI, −9.4−1.2, P = 0.128). (C) Each minute reduction in onset-to-treatment time resulted in a saving of 4.4 DALY-days after stroke (β = 4.4, 95% CI, 1.3–7.5, P = 0.006). In patients with recanalization, each 1 min decrease in onset-to-treatment time saved 10.9 DALY-days (β = 10.9, 95% CI, 5.1–16.7 days, P < 0.001). In those without recanalization, reduction in onset-to-treatment time did not save DALY-days (β = 1.2, 95% CI, −3.1– 5.4, P = 0.589). (D) Each point increase of baseline NIHSS score resulted in an increase of 98.9 days of DALY lost (β = 98.9, 95% CI, 67.2–130.7 days, P < 0.001). In patients with recanalization, each point increase of baseline NIHSS score resulted in an increase of 77.7 DALY-days (β = 77.7, 95% CI, 11.4–144.0, P = 0.022). The effect was even stronger in patients without recanalization, with 128.2 days of DALY lost (β = 128.2, 95% CI, 85.4–171.0 days, P < 0.001).