Nohra Chalouhi M.D., Stavropoula Tjoumakaris M.D.,and Pascal Jabbour
M.D.
We read with great interest the article by Turk et al[1] assessing
the safety and efficacy of endovascular stroke intervention based on CT
perfusion (CTP) criteria. The authors are to be congratulated for this
excellent report and for achieving remarkably high rates of favorable
outcomes (42%) in stroke patients with poor neurological status (mean
NIHSS, 18.2). They further categorize their patient population based on
time from symptom onset and clearly show that patients treated after 8 h
had no difference in outcomes or mortality than those treated before 8 h.
The fact that time from symptom onset to intervention was as long as 16.4
h in the late group (>8h) lends further credence to their findings
because the extent of salvageable brain tissue and the prospect of
improvement significantly decrease with delayed recanalization.[2-4] This
report adds substantially to the growing body of literature supporting the
use of CTP in stroke patients and reinforces what we have always believed;
specifically, CTP can optimize and guide patient selection for
intraarterial therapy based on an individual's physiological parameters
namely the extent of salvageable ischemic penumbra.
Although we agree with the authors about the merits of CTP and stress
the importance of their results, we would like to bring to their attention
that their conclusion may not be totally supported by the presented data.
The authors have compared functional outcomes in patients treated <8 h
and >8 h after symptom onset. Although all patients were selected for
endovascular stroke intervention based on CTP criteria, they conclude that
"physiologic imaging-guided patient selection rather than time for
endovascular reperfusion in ischemic stroke may be effective and safe". We
believe the only way to reach such a conclusion is to compare two groups
of patients, one selected based on CTP criteria and the other based on
time from symptom onset. Indeed, the authors do not discuss the study by
Hassan et al[5] published in 2010 that retrospectively compared 69
patients undergoing CTP-guided and 127 patients undergoing time-guided
endovascular treatment. The authors of this study found no incremental
benefit with the use of CTP, with similar rates of recanalization,
intracranial hemorrhage, favorable outcomes, and in-hospital mortality in
both groups. It should be noted, however, that only 40% of patients in
their study underwent mechanical thrombectomy and that CTP-guided
treatment at the primary author's institution was compared to time-guided
treatment at a different institution, which could have influenced their
results. Still, this is to our knowledge the only study that has compared
time-guided to CTP-guide patient selection for acute stroke intervention.
Randomized controlled trials comparing the 2 strategies are needed
especially that many prominent centers still have not adopted CTP as a
screening tool in this setting.
We would also like to highlight some of the potential shortcomings
associated with CTP that were not discussed in this study. The inter-
observer variability remains a great concern with CTP.[6] Additionally,
the optimal post-processing algorithm for defining penumbra and core
infarct have yet to be determined, and thresholds for guiding therapy are
still under investigation.[7] The variation in reconstruction of CTP
images and qualitative interpretation of salvageable tissue may lead to
selection of a relatively heterogeneous population, leading to the
inclusion of patients with limited salvageable tissue. False negatives and
non interpretable imaging can occur with CTP due to low cardiac output,
inappropriate slow rate of bolus administration, contrast extravasation in
the subcutaneous tissue, patient movement, and operator inexperience.
Finally, despite the potential caveats of CTP imaging , Turk et al[1]
have clearly demonstrated that CTP allows effective treatment of many
patients who otherwise would be destined for supportive management or end
of life care due to presentation outside of the therapeutic window. We
commend the authors for their rigorous work and await similar
contributions that will help us determine the best approach for patient
selection for acute stroke intervention.
References
1. Turk AS, Magarick JA, Frei D, et al. CT perfusion-guided patient
selection for endovascular recanalization in acute ischemic stroke: a
multicenter study. J Neurointerv Surg 2012 doi: neurintsurg-2012-010491
[pii]
10.1136/neurintsurg-2012-010491[published Online First: Epub Date]|.
2. Wardlaw JM, Murray V, Berge E, et al. Recombinant tissue plasminogen
activator for acute ischaemic stroke: an updated systematic review and
meta-analysis. Lancet 2012;379(9834):2364-72 doi: S0140-6736(12)60738-7
[pii]
10.1016/S0140-6736(12)60738-7[published Online First: Epub Date]|.
3. Hesselmann V, Niederstadt T, Dziewas R, et al. Reperfusion by combined
thrombolysis and mechanical thrombectomy in acute stroke: effect of
collateralization, mismatch, and time to and grade of recanalization on
clinical and tissue outcome. AJNR Am J Neuroradiol 2012;33(2):336-42 doi:
ajnr.A2746 [pii]
10.3174/ajnr.A2746[published Online First: Epub Date]|.
4. Vergouwen MD, Algra A, Pfefferkorn T, et al. Time Is Brain(stem) in
Basilar Artery Occlusion. Stroke 2012 doi: STROKEAHA.112.666867 [pii]
10.1161/STROKEAHA.112.666867[published Online First: Epub Date]|.
5. Hassan AE, Zacharatos H, Rodriguez GJ, et al. A comparison of Computed
Tomography perfusion-guided and time-guided endovascular treatments for
patients with acute ischemic stroke. Stroke 2010;41(8):1673-8 doi:
STROKEAHA.110.586685 [pii]
10.1161/STROKEAHA.110.586685[published Online First: Epub Date]|.
6. Hassan AE, Zacharatos H, Chaudhry SA, et al. Agreement in endovascular
thrombolysis patient selection based on interpretation of presenting CT
and CT-P changes in ischemic stroke patients. Neurocrit Care 2012;16(1):88
-94 doi: 10.1007/s12028-011-9577-9[published Online First: Epub Date]|.
7. Amenta PS, Ali MS, Dumont AS, et al. Computed tomography perfusion-
based selection of patients for endovascular recanalization. Neurosurg
Focus 2011;30(6):E6 doi: 10.3171/2011.4.FOCUS10296[published Online First:
Epub Date]|.
Conflict of Interest:
None declared
Nohra Chalouhi M.D., Stavropoula Tjoumakaris M.D.,and Pascal Jabbour M.D.
We read with great interest the article by Turk et al[1] assessing the safety and efficacy of endovascular stroke intervention based on CT perfusion (CTP) criteria. The authors are to be congratulated for this excellent report and for achieving remarkably high rates of favorable outcomes (42%) in stroke patients with poor neurological status (mean NIHSS, 18.2). They further categorize their patient population based on time from symptom onset and clearly show that patients treated after 8 h had no difference in outcomes or mortality than those treated before 8 h. The fact that time from symptom onset to intervention was as long as 16.4 h in the late group (>8h) lends further credence to their findings because the extent of salvageable brain tissue and the prospect of improvement significantly decrease with delayed recanalization.[2-4] This report adds substantially to the growing body of literature supporting the use of CTP in stroke patients and reinforces what we have always believed; specifically, CTP can optimize and guide patient selection for intraarterial therapy based on an individual's physiological parameters namely the extent of salvageable ischemic penumbra.
Although we agree with the authors about the merits of CTP and stress the importance of their results, we would like to bring to their attention that their conclusion may not be totally supported by the presented data. The authors have compared functional outcomes in patients treated <8 h and >8 h after symptom onset. Although all patients were selected for endovascular stroke intervention based on CTP criteria, they conclude that "physiologic imaging-guided patient selection rather than time for endovascular reperfusion in ischemic stroke may be effective and safe". We believe the only way to reach such a conclusion is to compare two groups of patients, one selected based on CTP criteria and the other based on time from symptom onset. Indeed, the authors do not discuss the study by Hassan et al[5] published in 2010 that retrospectively compared 69 patients undergoing CTP-guided and 127 patients undergoing time-guided endovascular treatment. The authors of this study found no incremental benefit with the use of CTP, with similar rates of recanalization, intracranial hemorrhage, favorable outcomes, and in-hospital mortality in both groups. It should be noted, however, that only 40% of patients in their study underwent mechanical thrombectomy and that CTP-guided treatment at the primary author's institution was compared to time-guided treatment at a different institution, which could have influenced their results. Still, this is to our knowledge the only study that has compared time-guided to CTP-guide patient selection for acute stroke intervention. Randomized controlled trials comparing the 2 strategies are needed especially that many prominent centers still have not adopted CTP as a screening tool in this setting.
We would also like to highlight some of the potential shortcomings associated with CTP that were not discussed in this study. The inter- observer variability remains a great concern with CTP.[6] Additionally, the optimal post-processing algorithm for defining penumbra and core infarct have yet to be determined, and thresholds for guiding therapy are still under investigation.[7] The variation in reconstruction of CTP images and qualitative interpretation of salvageable tissue may lead to selection of a relatively heterogeneous population, leading to the inclusion of patients with limited salvageable tissue. False negatives and non interpretable imaging can occur with CTP due to low cardiac output, inappropriate slow rate of bolus administration, contrast extravasation in the subcutaneous tissue, patient movement, and operator inexperience.
Finally, despite the potential caveats of CTP imaging , Turk et al[1] have clearly demonstrated that CTP allows effective treatment of many patients who otherwise would be destined for supportive management or end of life care due to presentation outside of the therapeutic window. We commend the authors for their rigorous work and await similar contributions that will help us determine the best approach for patient selection for acute stroke intervention.
References 1. Turk AS, Magarick JA, Frei D, et al. CT perfusion-guided patient selection for endovascular recanalization in acute ischemic stroke: a multicenter study. J Neurointerv Surg 2012 doi: neurintsurg-2012-010491 [pii] 10.1136/neurintsurg-2012-010491[published Online First: Epub Date]|. 2. Wardlaw JM, Murray V, Berge E, et al. Recombinant tissue plasminogen activator for acute ischaemic stroke: an updated systematic review and meta-analysis. Lancet 2012;379(9834):2364-72 doi: S0140-6736(12)60738-7 [pii] 10.1016/S0140-6736(12)60738-7[published Online First: Epub Date]|. 3. Hesselmann V, Niederstadt T, Dziewas R, et al. Reperfusion by combined thrombolysis and mechanical thrombectomy in acute stroke: effect of collateralization, mismatch, and time to and grade of recanalization on clinical and tissue outcome. AJNR Am J Neuroradiol 2012;33(2):336-42 doi: ajnr.A2746 [pii] 10.3174/ajnr.A2746[published Online First: Epub Date]|. 4. Vergouwen MD, Algra A, Pfefferkorn T, et al. Time Is Brain(stem) in Basilar Artery Occlusion. Stroke 2012 doi: STROKEAHA.112.666867 [pii] 10.1161/STROKEAHA.112.666867[published Online First: Epub Date]|. 5. Hassan AE, Zacharatos H, Rodriguez GJ, et al. A comparison of Computed Tomography perfusion-guided and time-guided endovascular treatments for patients with acute ischemic stroke. Stroke 2010;41(8):1673-8 doi: STROKEAHA.110.586685 [pii] 10.1161/STROKEAHA.110.586685[published Online First: Epub Date]|. 6. Hassan AE, Zacharatos H, Chaudhry SA, et al. Agreement in endovascular thrombolysis patient selection based on interpretation of presenting CT and CT-P changes in ischemic stroke patients. Neurocrit Care 2012;16(1):88 -94 doi: 10.1007/s12028-011-9577-9[published Online First: Epub Date]|. 7. Amenta PS, Ali MS, Dumont AS, et al. Computed tomography perfusion- based selection of patients for endovascular recanalization. Neurosurg Focus 2011;30(6):E6 doi: 10.3171/2011.4.FOCUS10296[published Online First: Epub Date]|.
Conflict of Interest:
None declared