Efficacy and safety of mechanical thrombectomy in the posterior cerebral circulation– a single center study

doi:10.21203/rs.3.rs-3346178/v1

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Efficacy and safety of mechanical thrombectomy in the posterior cerebral circulation– a single center study

https://doi.org/10.21203/rs.3.rs-3346178/v1

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published 02 Apr, 2024

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Mechanical thrombectomy (MT) is the gold standard for the treatment of ischemic stroke in both the anterior (AMT) and posterior (PMT) cerebral circulation. Existing literature suggests that PMT may lead to worse patient outcomes. The aim of this study was to analyze the impact of selected clinical phenodata on favorable outcomes in patients who underwent PMT and to compare the clinical characteristics of patients who received AMT and PMT. The study group consisted of 623 patients who underwent MT. Patients with PMT had significantly lower median NIHSS scores both at admission (9 vs. 13; p < 0.001) and after MT (7 vs. 12; p = 0.006), compared with those with AMT. In multivariate analysis, the most influential parameters for favorable outcomes in the PMT group at were: National Institutes of Health Stroke Scale score 24 hours after procedure (OR: 0.865 and 0.900), time of MT (OR: 0.993), and leukocytosis (OR: 0.961 and 0.974). Patients with AMT and PMT have different clinical profiles. Most importantly, neurological status one day after MT proved to be the most important prognostic factor for a favorable outcome. In addition, several factors play an important role in predicting outcome, especially in the PMT group.

stroke

mechanical thrombectomy

outcomes

posterior circulation

anterior circulation

Mechanical thrombectomy (MT) is a well-studied method and, in combination with intravenous thrombolysis (IVT), represents the current gold standard in the treatment of ischemic stroke in the anterior cerebral vessels within a six-hour window ¹. Compared to interventions in the anterior circulation, there is a limited amount of data regarding the efficacy and safety of MT in the posterior vasculature. The incidence of acute ischemic stroke in the posterior cerebral vessels is estimated to account for 13.5–20% of all strokes ^2–4.

When comparing the efficacy, safety, and favorable outcomes of MT in the anterior (AMT) and posterior (PMT) circulation, studies often yield different results. While PMT is associated with higher mortality and a lower rate of functional independence on the 90th day ⁴, successful reperfusion and favorable outcomes may be comparable in both the AMT and PMT groups ^5–7. Jahan et al. demonstrated that PMT had similar rates of functional independence after 90 days, successful reperfusion, and mortality compared to AMT ⁸. The authors point out that by selecting patients appropriately for MT, comparable treatment results can be achieved ^8,9. Approximately 1% of ischemic strokes are associated with basilar artery occlusion, which is the most severe form of stroke and is related with a high mortality rate ¹⁰. Likewise, in this patient group, a favorable functional outcome can be achieved significantly more often with IVT and successful reperfusion treatment combined ¹¹.

The primary objective of this study was to evaluate the efficacy and safety of PMT, as well as to identify factors affecting patients' functional status at discharge and 90 days after PMT. Additionally, we aimed to analyze the factors influencing PMT outcomes in relation to those affecting MT outcomes in the entire patient group, encompassing both PMT and AMT recipients.

The retrospective research included an analysis of selected data from patients who suffered from ischemic stroke between March 1, 2019, and January 31, 2022, and were treated by MT. Participants in the study were recruited among patients treated at the Department of Neurology with Stroke Subdivision of the Upper Silesian Medical Centre, Medical University of Silesia in Katowice, Poland. Data were obtained from the hospital database.

Patient characteristics collected included: baseline demographic data (age, sex), clinical data (stroke severity as measured by the National Institutes of Health Stroke Scale (NIHSS) on admission; before MT- NIHSS1, and on the second day of stroke- NIHSS2), risk factor profile (atrial fibrillation (AF), hypertension, diabetes mellitus (DM), nicotinism, dyslipidemia, atherosclerosis), radiological data (location of artery occlusion), time from onset of symptoms to MT, duration and efficacy of MT (measured by the thrombolysis in cerebral infarction (TICI) scale, with values of 2b-3 defined as successful and 0-2a as lack of effective reperfusion), whether IVT was administrated, laboratory tests (C-reactive protein (CRP), leukocytosis) and whether a decompressive hemicraniectomy (DH) was performed. Intracranial hemorrhage (ICH) events, including hemorrhagic conversions of ischemic stroke, were classified according to the European Cooperative Acute Stroke Study scale (ECASS II). Patients' functional outcomes were measured using the modified Rankin Scale (mRS) and were obtained at the following time points: at discharge from the department and on the 90th day after the procedure. Favorable outcome was defined as a maximum of 2 points on the mRS. All factors mentioned above were compared between the AMT and PMT groups.

Continuous variables were expressed as mean ± standard deviation (SD) or median and range. Numbers and percentages were used to represent categorical variables. Normality of distribution was tested with the Shapiro-Wilk test. Appropriate parametric and nonparametric tests were used to compare the AMT and PMT groups and to determine the significance of differences. Analysis of the influence of clinical phenodata on functional status was performed with an ordinal logistic regression model. Associations are presented as odds ratio (OR) with a 95% confidence interval (CI). Statistical significance was defined as p < 0.05. Analysis was performed using the Statistica 13.3 programme.

This study was approved by the local ethics committee (“Bioethics Committee of the Medical University of Silesia in Katowice”) in accordance with local and regional laws and was therefore performed in accordance with the ethical standards of the 1964 Declaration of Helsinki and its subsequent amendments. Due to the retrospective nature of the study, informed consent of patients was waived in accordance with commission and local laws.

In the study period 2036 patients were hospitalized due to ischemic stroke at the Neurology Department in Upper-Silesian Medical Centre of the Medical University of Silesia in Katowice. The study included 623 stroke patients who underwent MT, with 57 (9.15%) in the PMT group and 566 (90.85%) in the AMT group. Among these, there were 562 (90.2%) cases of single artery occlusion (45 in PMT and 517 in AMT), 55 (8.8%) of double artery occlusion (10 in PMT and 45 in AMT), and 6 (1%) of triple artery occlusion (2 in PMT and 4 in AMT). A detailed breakdown of the occluded arteries is presented in Fig. 1.

The average age of the patients was 66.9 [20–92] years, with 44.94% of them being female. Using a comparative analysis, clinical and radiological parameters were evaluated between patients with AMT vs. PMT. The groups differed significantly in terms of age (median in AMT = 70 vs. in PMT = 63; p = 0.001), gender (46.46% women in AMT vs. 24.56% in PMT; p = 0.002), NIHSS1 (median in AMT = 13 vs. in PMT = 9 ; p < 0.001), and NIHSS2 (median in AMT = 12 vs. in PMT = 7; p = 0.007). There were no significant differences in mortality rates at any of time points. The complete group base characteristics are shown in Table 1.

Table 1

Baseline characteristics of patients with MT in AMT and PMT
	All patients	AMT	PMT	p-value
Age (mean, median, range)	66.99, 69, [20–92]	67.56, 70, [20–92]	61, 63, [23–84]	0.001¹
Women (n, %)	280 (44.94%)	263 (46.46%)	14 (24.56%)	0.002²
Hospitalization time (mean, median, range)	12.23, 9, [0–70]	12.46, 9, [1–70]	10.57, 8, [0–55]	0.32¹
NIHSS1 (mean, median, range)	12.87, 12, [0–30]	13.15, 13, [1–30]	10.54, 9, [0–43]	< 0.001¹
NIHSS2 (mean, median, range)	12.16, 12, [0–30]	12.33, 12, [0–30]	10.71, 7, [0–43]	0.007¹
mRS at discharge (0–2) (n, %)	156 (25.04%)	139 (24.56%)	17 (29.82%)	0.38²
mRS after 1 month (0–2) (n, %)	252 (40.45%)	226 (39.93%)	26 (45.61%)	0.40²
mRS after 3 months (0–2) (n, %)	322 (52.1%)	292 (51.96%)	30 (53.57%)	0.82²
AF (n, %)	237 (38.04%)	221 (39.05%)	16 (28.07%)	0.10²
Arterial hypertension (n, %)	439 (70.3%)	402 (71.02%)	37 (64.91%)	0.33²
DM (n, %)	158 (25.36%)	143 (25.27%)	16 (28.07%)	0.64²
Atherosclerosis (n, %)	234 (37.56%)	216 (38.16%)	18 (31.58%)	0.32²
Smoking (n, %)	165 (26.48%)	146 (38.5%)	19 (44.18%)	0.47²
Dyslipidemia (n, %)	233 (37.52%)	208 (36.75%)	26 (45.61%)	0.18²
Thrombolysis (n, %)	392 (62.92%)	353 (62.37%)	40 (70.18%)	0.24²
TICI 2b-3 (n, %)	449 (72.54%)	414 (73.14%)	39 (68.42%)	0.44²
Time from symptoms to MT (mean, median, range)	268.7, 270, [5- 870]	267.16, 270, [5-870]	286.1, 270, [98–780]	0.32¹
MT Time (mean, median, range)	98.22, 90, [30–270]	98.16, 90, [30–270]	102, 100, [45–190]	0.29¹
Mortality at discharge (n, %)	111 (17.82%)	98 (17.31%)	13 (22.81%)	0.30²
Mortality after 1 month (n, %)	130 (20.87%)	116 (20.49%)	14 (24.56%)	0.47²
Mortality after 3 months (n, %)	145 (23.27%)	129 (22.79%)	16 (28.07%)	0.37²
CRP concentration (mean, median, range)	20.59, 8.7, [3-254]	20.88, 8.9, [3-254]	17.71, 8, [4-127]	0.81¹
WBC count (> 10,000) (n, %)	341 (54.74%)	308 (54.42%)	33 (57.89%)	0.61²
DH (n, %)	27 (4.33%)	24 (4.24%)	3 (5.26%)	0.98³
ICH (n, %)	109 (17.5%)	101 (17.84%)	8 (14.04%)	0.47²
¹ U Mann- Whitney test, ² Pearson’s Chi² test, ³ Yates’ Chi² test
AMT- anterior mechanical thrombectomy, PMT – posterior mechanical thrombectomy, NIHSS1 - National Institutes of Health Stroke Scale at admission, NIHSS2 - National Institutes of Health Stroke Scale 24 h after intervention, mRS - modified Rankin Scale, AF - atrial fibrillation, DM - diabetes mellitus; TICI 2b-3 - Thrombolysis In Cerebral Infarction scale 2b-3, CRP - C-reactive protein; WBC- white blood cells, DH- decompressive hemicraniectomy, ICH- intracranial hemorrhage

Among all patients, favorable outcomes were achieved by 72 (11.56%) at discharge and by 335 (53.78%) on the 90th day after stroke. A detailed distribution of patients into outcome groups based on mRS scores at both time points for both PMT and AMT is provided in Fig. 2.

An ordinal univariate regression analysis was conducted to identify factors influencing the patients' functional status after MT, both at discharge and after 90 days. The following are the statistically significant factors affecting patients' conditions at discharge: age (OR: 0.957, p < 0.001), female sex (OR: 0.614, p = 0.036), NIHSS1 (OR: 0.853, p < 0.001), DM (OR: 0.505, p = 0.015), location of arterial occlusion: MCA (OR: 2.388, p = 0.040) and PCA (OR: 4.873, p = 0.011), TICI 2b-3 (OR: 1.312, p = 0.002), time from symptoms to MT (OR: 0.996, p = 0.001), MT time (OR: 0.986, p < 0.001), occurrence of ICH (OR: 0.751, p = 0.022) and performing a DH (OR: 0.217, p = 0.037). Factors influenced outcomes on the 90th day after stroke were: age (OR: 0.960, p < 0.001), NIHSS1 (OR: 0.894, p < 0.001), AF (OR: 1.553, p = 0.037), IVT (OR: 1.539, p = 0.027), TICI 2b-3 (OR: 0.792, p = 0.002), MT time (OR: 0.989, p < 0.001), performing a DH (OR: 1.214, p = 0.026), and occurrence of ICH (OR: 0.312, p = 0.039). The entire analysis is presented in Table 2.

Table 2

Ordinal regression analysis of the influence of clinical phenodata on the favorable functional status (0–2 at mRS) of all patients at discharge and on 90th day of stroke.
				At 90th day after MT
Coefficients	OR	CI 95%	P-value	OR	CI 95%	p-value
Age	0.957	(0.938–0.976)	0.000	0.960	(0.943–0.976)	0.000
Female sex	0.614	(0.388–0.967)	0.036	0.919	(0.629–1.339)	0.661
NIHSS1	0.853	(0.813–0.893)	0.000	0.894	(0.861–0.925)	0.000
AF	1.374	(0.827–2.282)	0.219	1.553	(1.029–2.359)	0.037
Arterial hypertension	1.034	(0.616–1.754)	0.900	1.379	(0.893–2.140)	0.148
DM	0.505	(0.286–0.865)	0.015	0.759	(0.500-1.149)	0.193
Atherosclerosis	1.356	(0.839–2.192)	0.213	0.981	(0.660–1.461)	0.926
Smoking	1.034	(0.801–1.334)	0.798	0.984	(0.798–1.213)	0.879
Dyslipidemy	1.177	(0.770–1.792)	0.448	1.034	(0.733–1.458)	0.850
IVT	0.854	(0.541–1.351)	0.497	1.539	(1.051–2.262)	0.027
ICA	0.996	(0.230–4.259)	0.996	0.547	(0.161–1.826)	0.327
ACA	0.814	(0.200-2.712)	0.752	0.595	(0.210–1.669)	0.321
MCA	2.388	(1.040–5.521)	0.040	1.296	(0.649–2.616)	0.465
VA	0.643	(0.155–2.404)	0.524	0.497	(0.154–1.642)	0.243
BA	1.555	(0.486–4.759)	0.444	0.897	(0.338–2.396)	0.827
PA	4.873	(1.403–16.461)	0.011	1.556	(0.511–5.055)	0.444
TICI 2b-3	1.312	(0.660–1.813)	0.002	0.792	(0.871–0.921)	0.002
Time from symptoms to MT	0.996	(0.993–0.998)	0.001	0.998	(0.996-1.000)	0.114
MT time	0.986	(0.980–0.992)	0.000	0.989	(0.984–0.994)	0.000
ICH	0.751	(0.147–1.513)	0.022	0.312	(0.311–0.864)	0.039
DH	0.217	(0.210–1.171)	0.037	1.214	(1.047–2.314)	0.026
mRS- Modified Rankin Scale, OR- odds ratio, CI-confidence interval, NIHSS1 - National Institutes of Health Stroke Scale on admission, AF- atrial fibrillation, DM - diabetes mellitus, IVT- intravenous thrombolysis, ICA - internal carotid artery; ACA - anterior cerebral artery; MCA - middle cerebral artery; VA - vertebral artery; BA- basilar artery, PA - posterior cerebral artery; TICI 2b-3 - Thrombectomy In Cerebral Infarction scale 2b-3, MT–mechanical thrombectomy, ICH- intracranial haemorrhage, DH- decompresive haemicraniectomy

The multivariate analysis for all patients without subdivision into AMT and PMT subgroups, revealed that favorable outcomes, at discharge were influenced by DM (OR: 0.496, p = 0.005), TICI 2b-3 (OR: 1.145, p < 0.001), occurrence of ICH (OR: 0.503, p = 0.021), time from symptoms to MT (OR: 0.997, p = 0.004), and MT time (OR: 0.993, p = 0.011). On the 90th day after stroke, outcomes were influenced by TICI 2b-3 (OR: 1.095, p < 0.001) and performing a DH (OR: 0.298, p = 0.009). Table 3 displays the clinical phenotypic data's influence on functional status at discharge and 90 days after discharge.

Table 3

Ordinal regression analysis of the influence of clinical phenodata on favorable functional status (0–2 at mRS) at discharge and on the 90th day after the stroke. Multivariate analysis. Only statistically significant results.
Coefficents	OR	CI 95%	P-value
at discharge
DM	0.496	(0.301–0.795)	0.005
TICI 2b-3	1.145	(1.080–1.223)	< 0.001
ICH	0.503	(0.272–0.881)	0.021
Time from symptoms to MT	0.997	(0.994–0.999)	0.004
MT time	0.993	(0.987–0.998)	0.011
at 90 day
TICI 2b-3	1.095	(1.053–1.140)	< 0.001
DH	0.298	(0.109–0.689)	0.009
mRS - Modified Rankin Scale, OR- odds ratio, CI-confidence interval, DM- diabetes mellitus, TICI 2b-3- Thrombectomy In Cerebral Infarction 2b-3, ICH- intracranial haemorrhage, MT- mechanical thrombectomy, DH- decompressive heamicraniectomy

The only statistically significant factor affecting the patients' prognosis in the AMT subgroup, both on the day of discharge (OR: 1.796, 95% CI: 1.888–3.255, p = 0.017) and on the 90th day after the procedure (OR: 1.357, 95% CI: 1.025–1.851, p = 0.040), was TICI 2b-3 score.

Statistically significant factors influencing the patients’ condition after PMT on the day of discharge were: NIHSS2 (OR: 0.865, p < 0.001), IVT (OR: 0.643, p = 0.003), TICI 2b-3 (OR: 1.058, p = 0.003), MT time (OR: 0.993, p < 0.001), and WBC count (OR: 0.961, p = 0.014). On the 90th day after stroke there were: age (OR: 0.978, p < 0.001), NIHSS2 (OR: 0.900, p < 0.001), performing a DH (OR: 0.552, p = 0.044), MT time (OR: 0.993, p < 0.001), CRP concentration (OR: 0.995, p = 0.015), and WBC count (OR: 0.974, p = 0.013). The entire analysis is presented in Table 4.

Table 4

Ordinal regression analysis of the influence of clinical phenodata on favorable functional status (0–2 at mRS) patients with MT in vertebral-basil artery supply- at discharge and on the 90th day after stroke. Multivariate analysis. Only statistically significant results.
Coefficients	OR	CI 95%	P-value
At Discharge
NIHSS2	0.865	(0.840–0.890)	0.000
IVT	0.643	(0.479–0.855)	0.003
TICI 2b-3	1.058	(1.020–1.097)	0.003
MT time	0.993	(0.989–0.996)	0.000
WBC count	0.961	(0.928–0.988)	0.014
At 90th day after stroke
Age	0.978	(0.966–0.990)	0.000
NIHSS2	0.900	(0.879–0.921)	0.000
DH	0.552	(0.315–1.008)	0.044
MT time	0.993	(0.990–0.997)	0.000
CRP concentration	0.995	(0.992–0.999)	0.015
WBC count	0.974	(0.957–0.998)	0.013
mRS - Modified Rankin Scale, OR- odds ratio, CI-confidence interval, NIHSS2 - National Institutes of Health Stroke Scale 24h after procedure, IVT- intravenous thrombolysis, TICI 2b-3 - Thrombectomy In Cerebral Infarction 2b-3, MT- mechanical thrombectomy, WBC - white blood cell, DH- decompressive haemicraniectomy

4.1 The differences between anterior and posterior groups of patients.

In our single-center study, we confronted the existence of differences between the groups of patients who underwent AMT and PMT.

Age emerged as a significant parameter exhibiting differences in both groups: the median age of AMT patients was higher than that of PMT patients (average age: 70 vs. 63 years, p < 0.001). Similar disparities have been observed in previous studies ^8,12. In addition, women constituted a smaller proportion of the study population (44.94%), with a higher percentage in the AMT group (AMT: 46.5%, PMT: 24.6%, p = 0.001). This observation also aligns with findings from other studies ^8,12. Furthermore both, the age and the gender distribution, are also relevant with a meta-analysis that analyzed data from 16 studies ⁷.

The NIHSS score both before and 24 hours after procedure were significantly higher in the AMT group, than in the PMT group (NIHSS1; mean: 13 vs. 9, p < 0.001 and NIHSS2; mean: 12 vs. 7, p = 0.006). These results imply that patients who underwent AMT initially presented with more severe neurological symptoms and were in a poorer overall condition compared to patients with PMT. Similarly, in a study by Schlemm et al. ¹², patients with PMT had lower NIHSS2, whereas other results are presented in the literature in which NIHSS scores were significantly higher in the PMT group ^5–7.

The proportion of patients with a favorable prognosis was comparable in both study groups. These results are largely consistent with other reports ^6–9,13. However, Schlemann et al. obtained different results: PMT patients exhibited significantly worse mRS scores both at discharge and on the 90th day ¹². In like manner, in the meta-analysis by Xun et al., in a subgroup analysis that included only studies with large groups, PMT was also associated with a worse mRS score on the 90th day after procedure ¹⁴.

In our study, we did not find any differences in mortality between the two groups compared, alike in the study by Jahan et. al ⁸. Nevertheless, increased mortality was observed in PMT in both: individual studies ^5,6,13 and meta-analyzes ^7,14.

We found no significant distinctions in reperfusion efficiency (TICI 2b-3), however the number of successful reperfusions was lower in the PMT group, as well as in other authors ^5,6,8,12. Additionally we did not identify significant differences in the duration of the MT; instead, the average duration of the procedure in the PMT group was slightly longer, as reported by other authors ⁶.

Strokes in the posterior vasculature are often linked to increased diagnostic challenges ¹⁵ and a higher likelihood of misdiagnosis ¹⁶. Therefore, the time from symptom onset to procedure might be longer in PMT compared with AMT. However, we did not observe such an association, in our patient cohort, which is consistent with findings from other studies ^5,8,12. A meta-analysis demonstrated a significant difference in the time interval from symptom onset to the procedure, favoring AMT ⁷.

4.2 Factors related with outcomes after MT

In our patients, younger age significantly improved further outcomes (OR: 0.957 at discharge and OR: 0.960 on the 90th day). Older age is a well-established factor associated with a poorer prognosis following MT. Numerous studies have consistently demonstrated that older patients have a reduced likelihood of achieving a good functional status and experience higher mortality rates compared to their younger counterparts ^17–22. On the other hand, influence of age on the outcomes of MT is not necessarily clear; Sweid et al. performed a study comparing outcomes in the individuals over and under 90 years of age and found no significant differences between the groups, even reporting a lower mortality rate in the elderly group (11.54% vs. 13.06%, p = 0.82) ²³.

The most important predictor of worse prognosis in our study was the NIHSS score on admission; a higher score was associated with poorer outcomes both at discharge and on the 90th day after intervention (OR: 0.853 and OR: 0.894). These results are consistent with reports from previous studies ^{8,13,18–22,24,25} and imply the conclusion, that the milder the stroke is, the better outcomes could be achieved. The occurrence of hemorrhagic transformation after MT is associated with early neurologic impairment and a lack of subsequent neurological improvement ²⁵, decreases the chances of achieving a good prognosis ^20,24,25, and is linked to higher mortality ²⁰. In our study, intracranial hemorrhage was identified as a factor associated with a poorer prognosis, with the strongest influence observed at discharge (univariate OR: 0.751, multivariate OR: 0.503), consistently with previous reports. In a study performed by Huang et al. ¹⁹ it was demonstrated that postoperative hemorrhage transformation was partly responsible for the worse mRS score on the 90th day in patients with prolonged MT time.

Successful recanalization, expressed by a TICI score ≥ 2b, was associated with a better prognosis in most studies ^{19,20,22,24,26}. Similarly, in our group, a higher TICI score was associated with better outcomes at discharge (univariate OR: 1.312 and multivariate OR: 1.145) and on the 90th day (multivariate OR: 1.095). Factors such as older age, higher baseline NIHSS score, pre-stroke mRS score, and general anesthesia are thought to be the risk factors for unsuccessful recanalization ^26–28. The duration of the procedure > 60 min is another recognized risk factor for a worse prognosis ^20,24, as is prolonged time from symptom onset to procedure ²⁵. In our study, these associations were confirmed, especially at discharge time point; a shorter time from symptoms to MT (univariate OR: 0.996, multivariate OR: 0.997) and a shorter procedure duration (univariate OR: 0.986, multivariate OR: 0.993) favored patients' outcomes.

Among the other factors, the prognosis on the 90th day was positively affected by the administration of actylise (OR: 1.539) and the presence of AF, as the comorbidity (OR: 1.533). IVT before MT can alter the thrombus structure, thus facilitating its mechanical removal. The positive effect of AF on patients’ outcomes after MT has been previously noted ^25,29, however, there are also studies indicating a negative effect of AF ^20,30, as well as the absence of an effect ^14,22,31. These discrepancies may be explained by the frequent use of anticoagulants in this disease, which may facilitate recanalization and, on the other hand, increase the likelihood of a bleeding complication. The presence of DM had a detrimental effect on discharge prognosis (univariate OR: 0.505, multivariate OR: 0.496), which is also confirmed by the literature ^14,20,24,25. Diabetic microangiopathy and the hyperglycemic environment contribute to poor development of collaterals ³². Due to insulin resistance, diabetes can also lead to endothelial damage, coagulation-fibrinolysis balance and platelet activity ³³.

4.3 Factors influencing outcomes particularly in PMT group.

At both time points, prognosis was strongly influenced by NIHSS score, as in the overall analysis mentioned above. Both the literature reports and our results concur that a higher NIHSS score is associated with a less favorable prognosis following PMT, for both short-term (OR: 0.865) and long-term (OR: 0.900) outcomes. ^34–37. Moreover, Kniep et al. ³⁵ showed that the 24-hour NIHSS score ≤ 9 best serves as a surrogate for favorable outcome (0–2 mRS) on the 90th day after PMT (AUC: 0.89, 95% Cl: 0.85, 0.92).

Similarly, prolonged procedure duration, worsens patients’ outcomes, both at discharge (OR: 0.993) and on the 90th day after the procedure (OR: 0.993). This finding aligns with general descriptions and reports from other MT studies, regardless of subgroup division into PMT and AMT ^9,20,24. Therefore, to the best of our knowledge, the influence of this factor in the PMT group has not yet been documented in the literature.

Leukocytosis and a high CRP concentration, both indirect indicators of inflammatory processes in the body, negatively impacted patients' outcomes at both discharge and on the 90th day following PMT (OR: 0.961 and OR: 0.974 for WBC, and OR: 0.995 for CRP concentration). These results suggest a robust correlation between the severity of post-MT inflammation and the likelihood of achieving a favorable prognosis, particularly in patients with PMT. This association was not observed in the overall MT patient cohort. The adverse effects of leukocytosis, elevated CRP levels, and other inflammatory markers, such as IL-6, on prognosis following stroke have been well-documented in the general stroke population ^38,39, and in patients after MT in particular ^21,40,41. A similar association was observed for leukocytosis, which also increased both mortality (multivariate OR: 1.86, CI 95%: 1.07; 2.63) and the odds of a poor outcome (mRS < 2, multivariate OR: 1.51, CI95%: 0.51; 4.60), alike without differentiation by AMT and PMT. Additionally, contemporary research has placed increasing importance on the systemic immune inflammation index, which has proven to be an effective tool for predicting poor outcomes after stroke ^42,43.

A high TICI score served as a positive predictor of a favorable prognosis at discharge following PMT (OR: 1.058), and exhibited even greater predictive power following AMT (OR: 1.769 at discharge and OR: 1.357 on the 90th day). Successful recanalization was a pivotal component of an effective therapeutic process in PMT, as corroborated by previous research ³⁷, and its absence led to increased mortality on the 90th day after the procedure ³⁴.

The IVT is the other factor affecting the post-stroke functional state. Despite the fact that studies suggest a better prognosis and lower mortality when combined with IVT compared to MT alone ^44,45, they often do not specify this effect exclusively for PMT. Additionally, the literature consistently reports a lower risk of bleeding complications in PMT compared to AMT ^46,47. However, the Capellari’s study revealed that the combination of IVT and MT was associated with a significantly higher rate of ICH (ECASS II) compared to IVT alone (3.1% vs 1.9%; OR 3.984, 95% CI 1.014–15.815), and the likelihood of a favorable outcome varied depending on the affected artery ²⁵. Another study focusing exclusively on patients with posterior artery occlusion, demonstrated an increased risk of bleeding and higher mortality after endovascular treatment, with or without IVT, compared to IVT alone ⁴⁸, but also indicated an increased chance of an excellent outcome in the MT group (OR: 1.50, 95% CI, 1.07–2.09). Moreover, Lee et al. ⁴⁶ in the meta-analysis showed worse outcomes following IVT in the PMT group compared to the AMT group.

As in the overall analysis, age was the prognostic factor in the PMT group on the 90th day after procedure; older patients were less likely to have a favorable prognosis (OR: 0.978). Similar results were obtained by other authors ^34–36.

The performance of a decompressive hemicraniectomy (DH) was a factor that significantly reduced the odds of a favorable prognosis by nearly half in the PMT group (OR: 0.552) and by approximately 70% in our overall study population (OR: 0.298). While the impact of DH on outcomes following malignant middle cerebral artery infarction (mMCAi) remains a subject of debate, there is a dearth of literature reports on its effects after posterior vascular strokes. In one study of DH after IVT, no patient over 60 years old survived to 3-month follow-up, and moderate disability at 3 months was present in 35.5% ⁴⁹. Inamasu et al. showed that despite the absence of differences in any of the demographic variables evaluated, the mortality rate was significantly higher in the group of individuals over 70 years old who underwent DH compared to those aged 61–70 ⁵⁰.

Understanding the relevance of these parameters in MT outcomes is crucial in guiding the selection of patients based on individual factors to optimize the clinical efficacy of MT, both in cases involving the anterior and posterior cerebral circulation.

Our study revealed distinct clinical profiles between patients who underwent AMT and PMT. Several sociodemographic and clinical factors were found to influence the recovery of stroke patients undergoing MT. Notably, the neurological status one day after MT emerged as the most crucial prognostic parameter for achieving a favorable functional status in both groups. Furthermore, within the PMT group, factors such as the timing of the procedure and the concentrations of inflammatory markers appeared to play pivotal roles in predicting a favorable outcome. These factors could serve as both predictive indicators and targets for modification to enhance the likelihood of a better prognosis in this specific patient cohort.

Contribution statement

MB was responsible for the research concept, data collection, the “Discussion” section, and overall manuscript preparation. MK conducted the data collection and contributed to the “Materials and Methods” and “Results” sections. AB performed the data collection and was responsible for the “Introduction” section. AŻ, ŁB and AWK conducted the data collection and organized the dataset. ALB designed the study, performed a statistical analysis, supervised the project, and provided critical revisions for the intellectual content. All authors contributed to the article and approved the submitted version.

The authors did not receive support from any organization for the submitted work.

The authors have no competing interests to declare that are relevant to the content of this article.

Data availability statement

The datasets generated and analyzed during the current study are not publicly available because they contain personal data of the patients, but they can be requested from the corresponding author upon reasoned request.

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No competing interests reported.

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Efficacy and safety of mechanical thrombectomy in the posterior cerebral circulation– a single center study

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Abstract

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1. Introduction

2. Materials and methods

3. Results

4. Discussion

4.1 The differences between anterior and posterior groups of patients.

4.2 Factors related with outcomes after MT

4.3 Factors influencing outcomes particularly in PMT group.

5. Conclusions

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References

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