Intravascular pressure measurements in feeding pedicles of brain arteriovenous malformations

Hemodynamic and Anatomical Factors in Arteriovenous Malformation Clinical Presentation: 45 Case Studies

BACKGROUND

Hemodynamic factors have been implicated in hemorrhage from cerebral arteriovenous malformations (AVMs). The goal of this endovascular study is to analyze the hemodynamic variability in AVM feeders in a balanced group of ruptured and unruptured AVMs of various sizes and at both superficial and deep locations.

METHODS

We monitored feeder artery pressure (FP) using microcatheters in 45 patients with AVMs (16 with hemorrhage, 29 without) during superselective angiography and AVM embolization.

RESULTS

Mean FP was 49 mm Hg. Significant determinants of FP were the systemic pressure (p < 0.001), AVM size (p = 0.03), and the distance of the microcatheter tip from the Circle of Willis (p = 0.06), but not the presence of hemorrhage, patient age, or feeder artery diameter. The FP in ruptured AVMs was 7 mm Hg higher than in unruptured ones (53.8 mm Hg vs. 47.1 mm Hg, p = 0.032). The presence or absence of venous outflow stenosis and the position of the AVM nidus (superficial or deep to the cortical surface) were important anatomical predictors of AVM presentation.

CONCLUSION

The pressure in the feeding artery supplying an AVM is the result of factors which include the systemic arterial pressure, the size of the AVM nidus, and the distance of the AVM from the Circle of Willis. The correlation between these variables makes it difficult to study the risk of hemorrhage as a function of a single factor, which may account for the variation in the conclusions of previous studies.

Molecular feature of arterial remodeling in the brain arteriovenous malformation revealed by arteriovenous shunt rat model and RNA sequencing

PURPOSE

Morphological research suggested the feeding artery of brain arteriovenous malformation (bAVM) had vascular remodeling under the high blood flow; however, the underlying molecular mechanisms were unclear.

METHODS

We constructed 32 simplified AVM rat models in four groups: the control group (n = 6), 1-week high-blood-flow group (n = 9), 3-week high-blood-flow group (n = 7) and 6-week high-blood-flow group (n = 10). The circumference, blood velocity, blood flow, pressure, and wall shear of the feeding artery were measured or calculated. The arterial wall change was observed by Masson staining. RNA sequencing (RNA-seq) of feeding arteries was performed, followed by bioinformatics analysis to detect the potential molecular mechanism for bAVM artery remodeling under the high blood flow.

RESULTS

We observed hemodynamic injury and vascular remodeling on the feeding artery under the high blood flow. RNA-seq showed immune/inflammation infiltration and vascular smooth muscle cell (VSMC) phenotype transformation during remodeling. Weighted gene co-expression network analysis (WGCNA) and time series analysis further identified 27 key genes and pathways involved in remodeling. Upstream miRNA and molecular drugs were predicted targeting these key genes.

CONCLUSIONS

We depicted molecular change of bAVM arterial remodeling via RNA-seq in high-blood-flow rat models. Twenty-seven key genes may regulate immune/inflammation infiltration and VSMC phenotype transform in bAVM arterial remodeling.

Digital intravascular pressure wave recording during endovascular treatment reveals abnormal shunting flow in vertebral venous fistula of the vertebral artery: illustrative case

BACKGROUND

An arteriovenous fistula is an abnormal arteriovenous shunt between an artery and a vein, which often leads to venous congestion in the central nervous system. The blood flow near the fistula is different from normal artery flow. A novel method to detect the abnormal shunting flow or pressure near the fistula is needed.

OBSERVATIONS

A 76-year-old woman presented to the authors’ institute with progressive right upper limb weakness. Right vertebral angiography showed a fistula between the right extracranial vertebral artery (VA) and the right vertebral venous plexus at the C7 level. The patient underwent endovascular treatment for shunt flow reduction. Before the procedure, blood pressures were measured at the proximal VA, distal VA near the fistula, and just at the fistula and drainer using a microcatheter. The blood pressure waveforms were characteristically different in terms of resistance index, half-decay time, and appearance of dicrotic notch. The fistula was embolized with coils and N-butyl cyanoacrylate solution.

LESSONS

During endovascular treatment, the authors were able to digitally record the vascular pressure waveform from the tip of the microcatheter and succeeded in calculating several parameters that characterize the shunting flow. Furthermore, these parameters could help recognize the abnormal blood flow, allowing a safer endovascular surgery.

Recent progress understanding pathophysiology and genesis of brain AVM-a narrative review

Considerable progress has been made over the past years to better understand the genetic nature and pathophysiology of brain AVM. For the actual review, a PubMed search was carried out regarding the embryology, inflammation, advanced imaging, and fluid dynamical modeling of brain AVM. Whole-genome sequencing clarified the genetic origin of sporadic and familial AVM to a large degree, although some open questions remain. Advanced MRI and DSA techniques allow for better segmentation of feeding arteries, nidus, and draining veins, as well as the deduction of hemodynamic parameters such as flow and pressure in the individual AVM compartments. Nonetheless, complete modeling of the intranidal flow structure by computed fluid dynamics (CFD) is not possible so far. Substantial progress has been made towards understanding the embryology of brain AVM. In contrast to arterial aneurysms, complete modeling of the intranidal flow and a thorough understanding of the mechanical properties of the AVM nidus are still lacking at the present time.

Possible Association Between Rupture and Intranidal Microhemodynamics in Arteriovenous Malformations: Phase-Contrast Magnetic Resonance Angiography-Based Flow Quantification

OBJECTIVE

To examine a potential association between intranidal microhemodynamics and rupture using a phase-contrast magnetic resonance angiography (PCMRA)-based flow quantification technique in arteriovenous malformations (AVMs).

METHODS

We retrospectively collected data on 30 consecutive patients with AVMs (23 unruptured and 7 ruptured). Based on PCMRA data, maximal (V_max) and mean (V_mean) intranidal velocities were calculated. Logistic regression analysis was performed to assess factors associated with previous AVM rupture.

RESULTS

All ruptures occurred within 6 months before PCMRA. The mean nidus volume was 4.7 mL. Eleven patients (37%) had deep draining vein(s), and 6 patients (20%) had a deep-seated nidus. The mean ± standard deviation V_mean and V_max were 9.6 ± 2.8 cm/second and 66.7 ± 26.2 cm/second, respectively. The logistic regression analyses revealed that higher V_max (P = 0.075, unit odds ratio [OR] = 1.05, 95% confidence interval [95% CI] = 1.00-1.10) was significantly associated with prior hemorrhage. The receiver-operating curve analyses demonstrated that a V_mean of 10.8 cm/second (area under the curve = 0.671) and V_max of 90.2 cm/second (area under the curve = 0.764) maximized the Youden Index. A V_max > 90 cm/second was significantly associated with AVM rupture both in the univariate (P = 0.025, OR = 9.0, 95% CI = 1.3-61.1) and multivariate (P = 0.008, OR = 51.7, 95% CI = 2.8-968.3) analyses.

CONCLUSIONS

Presence of faster velocities in intranidal vessels may suggest aberrant microhemodynamics and thus be associated with AVM rupture. PCMRA-based velocimetry seems to be a promising tool to predict future AVM rupture.

Hemodynamics Associated With Intracerebral Arteriovenous Malformations: The Effects of Treatment Modalities

The understanding of the physiology of cerebral arteriovenous malformations (AVMs) continues to expand. Knowledge of the hemodynamics of blood flow associated with AVMs is also progressing as imaging and treatment modalities advance. The authors present a comprehensive literature review that reveals the physical hemodynamics of AVMs, and the effect that various treatment modalities have on AVM hemodynamics and the surrounding cortex and vasculature. The authors discuss feeding arteries, flow through the nidus, venous outflow, and the relative effects of radiosurgical monotherapy, endovascular embolization alone, and combined microsurgical treatments. The hemodynamics associated with intracranial AVMs is complex and likely changes over time with changes in the physical morphology and angioarchitecture of the lesions. Hemodynamic change may be even more of a factor as it pertains to the vast array of single and multimodal treatment options available. An understanding of AVM hemodynamics associated with differing treatment modalities can affect treatment strategies and should be considered for optimal clinical outcomes.

AVM Compartments: Do they modulate trasnidal pressures? An electrical network analysis

Background:

Arteriovenous malformation (AVM) compartments are thought as independently fed, hemodynamically independent components of the AVM nidus. Its possible role in modulating transnidal pressures have not been investigated to our knowledge.

Objective:

To investigate if AVM compartments play a role in modulating transnidal pressures by using electrical models as a method of investigation.

Materials and Methods:

Monocompartmental and multicompartmental AVM models were constructed using electrical circuits- building on Dr. Guglielmi's previous work. Each compartment was fed by two feeding arteries (resistors) and had a shared draining vein with other compartments in the AVM nidus. Each compartment is composed of a series of resistors which represents the pressure gradient along the AVM (arterial, arteriolar, venular, and venous). Pressure (voltage) readings were obtained within these nidal points.

Results:

The pressure gradient (venous-arterial) is more as there are less AVM compartments in the nidus model. The monocomparmental model had a pressure gradient of 66mmHg (V); while it was 64, 61, and 59 for the 2-, 3-, and 4-compartment models, respectively. In addition, the more the number of compartments, the greater the flow (mA) is in the whole AVM nidus, 33 ml/min for the monocompartmental AVM and 121ml/min for the 4-compartment AVM; though there was greater flow per compartment as there were less compartments, 33ml/min per compartment for the monocompartmental model versus 29ml/min for the 4-compartment model.

Conclusion:

Transnidal pressure gradients may be less the more compartments an AVM has. This electrical model represents an approach that can be used in investigating the hemodynamic contributions of AVM compartments.

Intracerebral hemorrhage following endovascular embolization of brain arteriovenous malformation with a combination of Onyx and n-butyl cyanoacrylate: a case report

We report a 29-year-old female patient who developed intracerebral hemorrhage 16 h after endovascular embolization of a brain arteriovenous malformation with a combination of liquid embolic agents of Onyx and n-butyl cyanoacrylate. After emergent craniectomy with evacuation of the hematoma, the patient recovered consciousness with mild expressive aphasia. The possible etiology of postembolization brain hemorrhage was discussed, and the literature was reviewed.

Angioarchitecture and clinical presentation of brain arteriovenous malformations

The purpose of this study was to correlate the angioarchitecture of brain arteriovenous malformations (AVM) with their clinical presentation. A total of 170 patients with AVM 78 males and 92 females, were studied. Univariate and multivariate analyses were conducted in order to test the associations between morphological features and clinical presentation. The most frequent clinical presentations at diagnosis were hemorrhage in 89 (52%) patients, headache in 79 (46%), focal neurological deficit in 54 (32%), and seizure in 52 (31%). According to the Spetzler-Martin classification, grade I was found in 15 patients, II in 49, III in 55, IV in 41, and grade V in 10 patients. AVM with small nidus size, single feeding artery and single draining vein were associated with hemorrhage. Hemorrhage was positively associated with Spetzler-Martin grade I and negatively with grade V. The association between seizure and large nidus size was positive, however negative with small nidus size.

Retrograde venonidal microsurgical obliteration of brain stem AVM: a clinical feasibility study

PURPOSE

The highly eloquent surroundings of brainstem arteriovenous malformations (AVMs) present particular surgical challenges. In the present pilot study we tried to examine whether to occlude the draining vein after control of major feeding arteries and then to coagulate the nidus retrogradely might be a viable concept for brainstem AVMs instead of the traditional perinidal dissection.

METHODS

A total of five patients harbouring pontine or mesencephalic AVMs were treated at our institution between February 2007 and August 2008. Three of them presented after haemorrhage. In two instances, partial endovascular obliteration was performed prior to surgery. Following exposure and control of major feeders, the principal draining vein was clamped to test tolerance. In none of the cases was major stasis and bleeding from the nidus seen. The draining vein was subsequently coagulated and then stepwise shrinking by retrograde coagulation of the nidus was done. The coagulated nidus was left in place.

RESULTS

The procedure was technically successful in all cases and no major postoperative complication related to the procedure was seen. Control angiography confirmed complete occlusion in all cases.

CONCLUSIONS

Due to the usually small size of brainstem AVMs, retrograde coagulation of the nidus without additional resection can be a feasible approach in order to avoid additional damage by circumferential dissection.