Key words ischemia/infarction - thrombolysis - angiography - brain
Purpose
Stent retriever thrombectomy represents the standard therapy of intracranial large
vessel occlusions in addition to systemic lysis in acute ischemic stroke [1 ]
[2 ]
[3 ]
[4 ]
[5 ]. Special intermediate catheters have shown promising results in ADAPT (a direct
aspiration, first-pass technique) [6 ]
[7 ]. Balloon guide catheters (BGC) combined with stent retriever seem to provide better
results than stent-retriever alone [8 ]. For large vessel occlusions different sizes of aspiration catheters are available.
The largest aspiration catheters available (6F) seem to be more effective, but only
fit in relatively rigid 9F BGCs (e. g. Merci BGC, Stryker, USA), which can result
in more difficult and prolonged navigation or in complications such as cervical artery
dissection. BGCs with higher distal flexibility (e. g. FlowGate 8F, Stryker, USA)
are only suitable for the 5F aspiration catheters. In 2017 Stampfl et al. combined
5F ADAPT and BGC in their case series with favorable results [9 ], but they did not compare their results to an ADAPT only control group.
The matter of aspiration catheter sizing and the combination with a BGC can be addressed
using different clot compositions and visualizing the interaction between the device
and the clot in a flow model under standard conditions. The purpose of this study
was to compare the efficacy of 6F ADAPT alone and 5F ADAPT combined with a reasonably
flexible BGC.
Materials and Methods
Flow model [10 ]
The experiments were performed under standardized and physiological hemodynamic conditions.
The flow model is made of transparent silicon (Elastrat, Switzerland) and is derived
from patient data. The following parts of the model have physiological curvature and
inner diameters: common carotid artery (8 mm), internal carotid artery (6 mm), proximal
external carotid artery (5 mm), M1 segment (3 mm), proximal M2 segment (2.5 mm), A1
segment (2.5 mm). To decrease friction, the inside of the phantom was coated with
a propranolol-based fluid (Elastrat Sarl, Switzerland) before each use. Glycerol solution
was used to mimic blood (60/40 by volume saline/glycerin; 37° C). A precise, programmable
piston pump (CompuFlow 1000, Shelley Medical Imaging Technologies, Canada) produced
physiological fluid dynamics, which were monitored by Doppler sonography (carotid
profile, velocity of 100 cm/s, pulse 60/min). A mean pressure of 100 mmHg was maintained.
The clots were injected into the model and flowed into the M1 segment of the MCA.
All thrombectomy procedures were video recorded (Panasonic HC-V250, Japan; Full High
Definition, 60 fps). Simultaneously, the video signal was broadcast to a monitor simulating
an angio suite-like setup ([Fig. 1 ]) [10 ].
Fig. 1 Angio suite-like experimental setup showing silicon phantom, camera, and monitor.Abb. 1 Angiografie-ähnlicher Versuchsaufbau mit Silikonmodell, Kamera und Monitor.
Clot models [10 ]
Two different clot models were used for the experimental studies [10 ]
[11 ]
[12 ]
[13 ]:
An erythrocyte-rich (red) clot: fresh human blood was put in a Chandler loop system
to create a thrombus under dynamic conditions. The clots were cut into pieces of 10 × 3.5 mm
in size.
A fibrin-rich (white) clot: citrated human blood was stored standing for 24 h. The
plasma, the buffy coat, and a few erythrocytes were aspirated. The sample was recalcified
and incubated for further 72 h. The clots were cut into pieces of 10 × 3.5 mm in size.
ADAPT Techniques
Two different recanalization techniques were used:
6F ADAPT alone: A 6F intermediate aspiration catheter (SOFIA 6F, Microvention, USA:
inner diameter 0.070 in (1.78 mm), outer diameter 0.0815–0.0825 in (2.07–2.1 mm),
length 125 cm,) was placed directly proximal to the occlusion site and continuous
machine aspiration was performed (Penumbra Aspiration Pump, USA). If the tip was blocked
by the clot, the intermediate catheter was pulled back into the long sheath (Neuron
MAX 88, Penumbra, USA: inner diameter 0.088 in (2.24 mm), outer diameter 0.100 in
(2.54 mm), length 90 cm) in the ICA. While withdrawing the distal catheter, additional
aspiration via the sheath was performed using a 20-ml Luer-Lock syringe. If necessary,
subsequent passes followed.
5F ADAPT and BGC: A 5F intermediate aspiration catheter (SOFIA 5F, Microvention, USA:
inner diameter 0.055 in (1.4 mm), outer diameter 0.067–0.068 in (1.7–1.73 mm), length
125 cm) was placed directly proximal to the occlusion site and continuous machine
aspiration was performed (Penumbra Aspiration Pump, USA). If the tip was blocked by
the clot, the intermediate catheter was pulled back into the BGC (FlowGate2 8F, Stryker,
USA: inner diameter 0.084 in (2.13 mm), outer diameter 0.106 in (2.7 mm), length 95 cm)
in the ICA. Just before the ADAPT maneuver the balloon of the BGC was inflated, creating
a complete proximal flow arrest. Simultaneously, proximal manual aspiration was performed
(20 ml Luer-Lock syringe) just before the intermediate catheter was retracted into
the BGC. After the intermediate catheter was pulled out of the BGC, the balloon was
deflated. If necessary, subsequent passes followed.
Analysis and statistics
The number of passes and the occurrence of distal emboli and emboli in new territories
were documented. Distal emboli and emboli in the anterior cerebral artery were counted
on the videos and in a filter system interposed between the phantom and the pump. The
videos of the thrombectomy procedures were analyzed after the experiments.
Chi-squared test, Kruskal-Wallis test, and Mann-Whitney U test were performed. Given
multiple comparisons, the Bonferroni correction was used. Statistical significance
was set to p < 0.05.
Results
Ten experiments were conducted per thrombus model and thrombectomy technique, resulting
in a total of n = 40 experiments. [Table 1 ] shows a summary of the results. [Fig. 2 ], [3 ], [4 ] show aspects of the clot retrieval (consecutive frames from the videos of the experiments).
Table 1
Summary of the results.Tab. 1 Zusammenfassung der Ergebnisse.
clot model
technique
median number of passes
first pass full recanalization
rate of distal emboli
total number of distal emboli
red (erythrocyte-rich)
5F ADAPT + BGC
1
90 %
10 %
1
6F ADAPT
1
80 %
10 %
2
white (fibrin-rich)
5F ADAPT + BGC
1
100 %
10 %
2
6F ADAPT
1
90 %
20 %
4
ADAPT: a direct aspiration first-pass technique; BGC: balloon guide catheter.
Fig. 2 White thrombus retrieved by 6F aspiration catheter and long sheath. The aspiration
catheter was clogged by the thrombus and had to be retracted into the long sheath.
Two distal emboli occurred (black circles in the middle picture).Abb. 2 Weißer Thrombus geborgen mittels 6F-Aspirationskatheter und langer Schleuse. Der
Aspirationskatheter wurde durch den Thrombus verstopft und musste in die lange Schleuse
zurückgezogen werden. Zwei distale Embolien traten auf (schwarze Kreise).
Fig. 3 Red thrombus retrieved by 5F aspiration catheter and balloon guide catheter. The
thrombus is aspirated directly at the occlusion site. No distal emboli occurred.Abb. 3 Roter Thrombus geborgen mittels 5F-Aspirationskatheter und Ballon-Führungskatheter.
Der Thrombus wird direkt an der Verschlussstelle aspiriert. Es sind keine distalen
Embolien aufgetreten.
Fig. 4 White thrombus retrieved by 5F aspiration catheter and balloon guide catheter (BGC).
The aspiration catheter is clogged and was pulled back into the BGC. Final retrieval
was achieved by aspiration via BGC. No distal emboli occurred.Abb. 4 Weißer Thrombus geborgen mittels 5F-Aspirationskatheter und Ballon-Führungskatheter
(BGC). Der Aspirationskatheter wurde durch den Thrombus verstopft und wurde in den
BGC zurückgezogen. Die letztliche Rekanalisation wurde durch den BGC gewährleistet.
6F ADAPT alone
Both in white and in red clots a median of one pass was needed for full recanalization
(max. 2 passes). A first-pass mTICI 3 (modified treatment in cerebral infarction score)
rate of 80 % was achieved in red clots and 90 % in white clots. The catheter was clogged
by the thrombus in 90 % of the experiments, though the thrombus had to be pulled back
into the sheath unprotected ([Fig. 2 ]). A total of six distal emboli in three experiments occurred (in one red clot and
two white clots, [Fig. 2 ]), resulting in an embolization rate of 10 % in red clots and 20 % in white clots.
The size of the emboli was < 1 mm. No emboli in new territories occurred.
5F ADAPT and BGC
As in the 6F ADAPT group, a median of one pass provided full recanalization (max.
2 passes). However, the first-pass mTICI 3 rate was higher than in the 6F ADAPT group
with 90 % in red clots and 100 % in white clots. The 5F catheter was clogged by the
thrombus in all but one case ([Fig. 3 ]), with loosening in the ICA in one case, but the flow reversal via the BGC did prevent
another pass ([Fig. 4 ]). Moreover, less distal emboli occurred: three emboli in two experiments (in one
red and one white thrombus), with a total emboli rate of 10 % per clot model. The
size of the emboli was < 1 mm. No emboli in new territories occurred.
The results showed no statistically significant differences between the thrombectomy
techniques and clot models.
Discussion
6F ADAPT alone and 5F ADAPT combined with an 8F BGC were highly effective in retrieving
both red and white clots in this experimental setting. The overall rate of distal
emboli was low in both groups. In red clots more distal emboli occurred, but the difference
was marginal. There were some slightly better first-pass recanalization rates and
lower distal emboli rates with 5F ADAPT and BGC. Due to the lack of collateral flow
in this model (missing anterior communicating artery and posterior communicating artery),
the flow reversal might be more powerful than it would be in vivo. None of the results
were statistically significant.
Stampfl et al. [9 ] showed in their case series that BGC combined with ADAPT using SOFIA 5F and Cello
8F (Medtronic, USA) is feasible and safe in a clinical setting, as well. Since 2017,
larger 6F aspiration catheters are available, those fit only into rather rigid 9F
BGCs (e. g. Mercy, Stryker; Cello, Medtronic). We did not choose the largest available
BGC because of the anatomy anticipated in an average patient with acute ischemic stroke:
A tortuous anatomy is rather common than a rarity [14 ]. A rigid system like the Mercy 9F BGC has been shown to be very challenging to place
[8 ] and could result in a relevantly longer procedure time. It might be more traumatic,
too, potentially causing dissection or severe vasospasm, and the need of further interventional
or surgical procedures [15 ]. From our point of view the FlowGate 8F BGC is a good compromise: It is more flexible
distally than any BGC available and allows placement of a 5F aspiration catheter.
Clinical trials showed superiority of stent retrievers combined with BGC compared
to thrombectomies without BGC concerning angiographical results and clinical outcome
[16 ]
[17 ]. Other clinical trials showed that ADAPT (e. g. with SOFIA or ACE) is a highly effective
thrombectomy technique, with an even faster procedure time and a non-inferior clinical
outcome compared with the outcome of the randomized stent retriever trials [18 ]
[19 ]
[20 ]. The ASTER Study [21 ] compared ADAPT with no BGC and SR combined with BGC: The results were not significantly
different. Given its superiority design to detect a 15 % difference in the primary
end point, this trial was not designed to establish non-inferiority between contact
aspiration and stent retriever as first-line endovascular strategies and was not designed
to detect a smaller yet potentially clinically important difference between groups.
In vitro studies showed similar results [10 ]. In 2019 Turk et al. showed the non-inferiority of aspiration thrombectomy as a
first-line approach compared with stent retriever in a randomized, blinded outcome,
multi-centric study (COMPASS) [22 ]. Also in 2019, the American Heart Association and American Stroke Association updated
the 2018 Guidelines for the Early Management of Acute Ischemic Stroke: Direct aspiration
is equal to stent retriever for mechanical thrombectomy – class I (strong) recommendation
[23 ]. A clinical study by Kang et al. concluded that BGC significantly increased the
final and first-pass recanalization rates of ADAPT [24 ]. However, this study has a major drawback: Very heterogeneous devices were used,
mainly distal access catheters not especially designed for ADAPT. The inner diameter
of those catheters was not mentioned. That might be the reason for the relatively
low first-pass recanalization rate of 19 % without BGC and 47 % combined with BGC.
A study from 2019 showed that larger aspiration catheters increase the first-pass
efficacy of the ADAPT technique [25 ]. No BGC was used and the first-pass recanalization rate was 53 %.
Although stent retriever thrombectomy combined with BGC is currently favored by many
groups, direct aspiration is at least a complementary alternative. Proximal thrombi
that are difficult to pass through with a microcatheter can be easily addressed with
a sufficient aspiration catheter. Long thrombotic occlusions of the distal ICA, in
which several passes are necessary, can be aspirated faster, because a pass does not
take as much time as a stent retriever pass would. Further, thrombi which “ride” on
an MCA bifurcation might be more suited for ADAPT than for a stent retriever (e. g.
kissing or dual stent retriever technique [26 ]).
Using stent retrievers it has been discussed, if clot composition has an influence
on recanalization success. For the moment the clot attenuation on non-enhanced CT
is promising in predicting clot composition: There is a link between the density of
the clot and the histological composition. Erythrocyte-rich thrombi are more hyperdense
than fibrin-rich thrombi [27 ]
[28 ]. However, to date, there are no methods available that could predict thrombus composition
reliably. In our study we used two extreme thrombi and achieved not significantly
different results.
In comparison to clinical studies, the transparent design of our silicon phantom showed
that both aspiration via the long sheath and the BGC made the procedure more safe,
because proximally fragmented parts of the clot could be aspirated. The in vitro design
of this study leads to some limitations. Many physiological aspects like the lack
of endothelium, coagulation factors, and blood cells apart from the thrombus were
not established in this experimental setting. Furthermore, the collateral flow is
missing. Overall, it is an artificial environment, which should always be considered
when interpreting the results of this study. A clinical outcome cannot be predicted,
but a low rate of distal emboli and a high first-pass recanalization rate were presumed
to be positive factors for favorable outcome.
Conclusion
6F ADAPT without BGC was as effective as 5F ADAPT combined with a flexible 8F BGC,
with both techniques showing high first-pass recanalization rates and low distal emboli
rates. 5F ADAPT with BGC showed slightly better, but statistically not significant
results. In the case of a tortuous anatomy, these setups should be considered as an
alternative to rigid 9F BGC combinations to prevent prolonged delivery and complications.
In a straight anatomy, 6F ADAPT combined with 9F BGC would probably be the better
choice. In this setting the thrombus composition had no effect on the recanalization
success, but it surely does in the clinical setting. Clinical studies are necessary
to validate these data.
6F ADAPT alone or 5F ADAPT in combination with a flexible 8F BGC should be considered
in large vessel occlusion in the case of a tortuous anatomy.
Both techniques were very effective with no statistically significant differences.
The clot composition seemed to have no effect on the recanalization results in this
setting.
Dieser Artikel wurde gemäß des Erratums vom 27.03.2025 geändert.
Erratum
Im oben genannten Artikel war ein Autorenname nicht korrekt.
Die korrekte Autorenliste lautet:
Jawid Madjidyar, Lars Nekarda, Naomi Larsen, Fritz Wodarg, Johannes Hensler, Olav
Jansen
Die Korrektur wurde in der Onlineversion des Artikels ausgeführt am: 27.03.2025.
