Clinical relevance of intracranial hemorrhage after thrombectomy versus medical management for large core infarct: a secondary analysis of the SELECT2 randomized trial

BACKGROUND

The incidence of intracerebral hemorrhage (ICH) and its effect on the outcomes after endovascular thrombectomy (EVT) for patients with large core infarcts have not been well-characterized.

METHODS

SELECT2 trial follow-up imaging was evaluated using the Heidelberg Bleeding Classification (HBC) to define hemorrhage grade. The association of ICH with clinical outcomes and treatment effect was examined.

RESULTS

Of 351 included patients, 194 (55%) and 189 (54%) demonstrated intracranial and intracerebral hemorrhage, respectively, with a higher incidence in EVT (134 (75%) and 130 (73%)) versus medical management (MM) (60 (35%) and 59 (34%), both P<0.001). Hemorrhagic infarction type 1 (HBC=1a) and type 2 (HBC=1b) accounted for 93% of all hemorrhages. Parenchymal hematoma (PH) type 1 (HBC=1c) and type 2 (HBC=2) were observed in 1 (0.6%) EVT-treated and 4 (2.2%) MM patients. Symptomatic ICH (sICH) (SITS-MOST definition) was seen in 0.6% EVT patients and 1.2% MM patients. No trend for ICH with core volumes (P=0.10) or Alberta Stroke Program Early CT Score (ASPECTS) (P=0.74) was observed. Among EVT patients, the presence of any ICH did not worsen clinical outcome (modified Rankin Scale (mRS) at 90 days: 4 (3-6) vs 4 (3-6); adjusted generalized OR 1.00, 95% CI 0.68 to 1.47, P>0.99) or modify EVT treatment effect (Pinteraction=0.77).

CONCLUSIONS

ICH was present in 75% of the EVT population, but PH or sICH were infrequent. The presence of any ICH did not worsen functional outcomes or modify EVT treatment effect at 90-day follow-up. The high rate of hemorrhages overall still represents an opportunity for adjunctive therapies in EVT patients with a large ischemic core.

Endovascular Thrombectomy for Large Ischemic Stroke Across Ischemic Injury and Penumbra Profiles

Importance

Whether endovascular thrombectomy (EVT) efficacy for patients with acute ischemic stroke and large cores varies depending on the extent of ischemic injury is uncertain.

Objective

To describe the relationship between imaging estimates of irreversibly injured brain (core) and at-risk regions (mismatch) and clinical outcomes and EVT treatment effect.

Design, Setting, and Participants

An exploratory analysis of the SELECT2 trial, which randomized 352 adults (18-85 years) with acute ischemic stroke due to occlusion of the internal carotid or middle cerebral artery (M1 segment) and large ischemic core to EVT vs medical management (MM), across 31 global centers between October 2019 and September 2022.

Intervention

EVT vs MM.

Main Outcomes and Measures

Primary outcome was functional outcome-90-day mRS score (0, no symptoms, to 6, death) assessed by adjusted generalized OR (aGenOR; values >1 represent more favorable outcomes). Benefit of EVT vs MM was assessed across levels of ischemic injury defined by noncontrast CT using ASPECTS score and by the volume of brain with severely reduced blood flow on CT perfusion or restricted diffusion on MRI.

Results

Among 352 patients randomized, 336 were analyzed (median age, 67 years; 139 [41.4%] female); of these, 168 (50%) were randomized to EVT, and 2 additional crossover MM patients received EVT. In an ordinal analysis of mRS at 90 days, EVT improved functional outcomes compared with MM within ASPECTS categories of 3 (aGenOR, 1.71 [95% CI, 1.04-2.81]), 4 (aGenOR, 2.01 [95% CI, 1.19-3.40]), and 5 (aGenOR, 1.85 [95% CI, 1.22-2.79]). Across strata for CT perfusion/MRI ischemic core volumes, aGenOR for EVT vs MM was 1.63 (95% CI, 1.23-2.16) for volumes ≥70 mL, 1.41 (95% CI, 0.99-2.02) for ≥100 mL, and 1.47 (95% CI, 0.84-2.56) for ≥150 mL. In the EVT group, outcomes worsened as ASPECTS decreased (aGenOR, 0.91 [95% CI, 0.82-1.00] per 1-point decrease) and as CT perfusion/MRI ischemic core volume increased (aGenOR, 0.92 [95% CI, 0.89-0.95] per 10-mL increase). No heterogeneity of EVT treatment effect was observed with or without mismatch, although few patients without mismatch were enrolled.

Conclusion and Relevance

In this exploratory analysis of a randomized clinical trial of patients with extensive ischemic stroke, EVT improved clinical outcomes across a wide spectrum of infarct volumes, although enrollment of patients with minimal penumbra volume was low. In EVT-treated patients, clinical outcomes worsened as presenting ischemic injury estimates increased.

Trial Registration

ClinicalTrials.gov Identifier: NCT03876457.

Abstract WMP91: The Penumbra Salvage Index (PSI) As A Novel Measure Of Successful Reperfusion

Objective: We propose a novel measure, the PSI, to evaluate procedural success and prognostication after EVT and compare its prognostic ability with successful reperfusion (mTICI ≥2b).

Methods: SELECT EVT patients with adequate follow-up MR DWI imaging were stratified based on PSI [ratio of salvaged tissue volume (Tmax >6s volume at baseline – f/up DWI infarct volume) to the Tmax >6s volume at baseline] into good (PSI≥50%) and poor penumbral salvage (PSI<50%). Multivariable regression models examined the association of PSI with functional outcomes as well as predictors of PSI. ROC curve analysis evaluated the predictive ability of PSI and compared it with mTICI≥2b.

Results: 142/206(69%) had good penumbral salvage, with better CT ASPECTS (Good PSI: 9(7-10) vs Poor PSI: 7(6-9),p<0.001), baseline core infarct (Good PSI: 5.9(0.0-20.0)ml vs Poor PSI: 19.4(3.4-46.3)ml, p<0.001) and mTICI≥2b (Good PSI:91% vs Poor PSI: 64%, p<0.001). Good PSI was independently associated with higher odds of mRS 0-2 (Good PSI: 69% vs Poor PSI: 26%, aOR:5.89, 95%CI:2.25-15.45, p<0.001) and mRS 0-1 (Good PSI: 56% vs Poor PSI: 16%, aOR: 4.98, 95%CI:1.86-13.31, p=0.001). Predictors of a good PSI included a lower presenting NIHSS (aOR: 0.93, 95%CI: 0.87-0.99, p=0.026), smaller ischemic core (aOR: 0.96, 95%CI: 0.95-0.98, p<0.001) larger Tmax>6s volume (aOR: 1.01, 95%CI: 1.00-1.02, p=0.003) and mTICI≥2b (aOR: 8.84, 95%CI: 3.16-24.71, p<0.001). PSI demonstrated better AUC values (0.811) as compared to mTICI≥2b (0.786) in the ROC analysis.

Conclusion: Good penumbral salvage is associated with higher odds of functional independence, and has a better predictive value than successful reperfusion on cerebral angiogram after EVT. Prospective studies are needed to confirm the predictive utility of the PSI.

Abstract WP56: Improvement In Motor And Language Domains Mediates Most Of The Effect Of 24h NIHSS Improvement On Functional Independence

Introduction: Improvement in NIH stroke scale scores on 24h follow-up is considered a key prognostic element after endovascular thrombectomy (EVT). We aimed to evaluate the proportion of effect of 24h NIHSS improvement on mRS 0-2 at 90d mediated through improvement in motor and language domains.

Methods: From SELECT study, EVT patients with detailed NIHSS components on presentation and 24h follow-up as well as complete mRS on discharge and 90d were selected. Motor improvement was defined as ≥2 point in cumulative arms and legs score or 0 score at 24h and language improvement was defined as ≥1 point in cumulative aphasia and dysarthria scores at 24h. Mediation analysis framework using 4-step method (Figure 1a) was used to evaluate the effect of 24h NIHSS improvement mediated through improvement in motor and language scores.

Results: Of 192 eligible EVT patients, 176 demonstrated motor deficits and 187 demonstrated language deficits. 24h NIHSS improvement was significantly associated with mRS 0-2 (aOR:1.15[1.07-1.23], p<0.001) - step 1. 24h NIHSS improvement was also significantly associated with motor (aOR:1.77[1.48-2.12],p<0.001) and speech improvement (aOR:1.25[1.16-1.36],p<0.001) - step 2. In the full model, motor (aOR:3.00[1.07-8.46],p=0.037) and speech improvement (aOR:3.15[1.37-7.27],p=0.007) were significantly associated with mRS 0-2, whereas 24h NIHSS improvement was no longer a significant predictor (aOR:1.05[0.96-1.15],p=0.33) - step 3 of figure 1a. Motor improvement mediated 68% and speech improvement mediated 27% of the association of 24h NIHSS improvement with mRS 0-2 (Figure 1b) - step 4.

Conclusions: Almost all (~95%) of the effect of 24h NIHSS improvement on functional independence (mRS 0-2) was mediated through specific improvement in motor and language domains, suggesting a large role of improvement in motor and language domains in achieving better functional independence. Further studies are needed to confirm the findings.

Association of Endovascular Thrombectomy vs Medical Management With Functional and Safety Outcomes in Patients Treated Beyond 24 Hours of Last Known Well: The SELECT Late Study

Importance

The role of endovascular thrombectomy is uncertain for patients presenting beyond 24 hours of the time they were last known well.

Objective

To evaluate functional and safety outcomes for endovascular thrombectomy (EVT) vs medical management in patients with large-vessel occlusion beyond 24 hours of last known well.

Design, Setting, and Participants

This retrospective observational cohort study enrolled patients between July 2012 and December 2021 at 17 centers across the United States, Spain, Australia, and New Zealand. Eligible patients had occlusions in the internal carotid artery or middle cerebral artery (M1 or M2 segment) and were treated with EVT or medical management beyond 24 hours of last known well.

Interventions

Endovascular thrombectomy or medical management (control).

Main Outcomes and Measures

Primary outcome was functional independence (modified Rankin Scale score 0-2). Mortality and symptomatic intracranial hemorrhage (sICH) were safety outcomes. Propensity score (PS)-weighted multivariable logistic regression analyses were adjusted for prespecified clinical characteristics, perfusion parameters, and/or Alberta Stroke Program Early CT Score (ASPECTS) and were repeated in subsequent 1:1 PS-matched cohorts.

Results

Of 301 patients (median [IQR] age, 69 years [59-81]; 149 female), 185 patients (61%) received EVT and 116 (39%) received medical management. In adjusted analyses, EVT was associated with better functional independence (38% vs control, 10%; inverse probability treatment weighting adjusted odds ratio [IPTW aOR], 4.56; 95% CI, 2.28-9.09; P < .001) despite increased odds of sICH (10.1% for EVT vs 1.7% for control; IPTW aOR, 10.65; 95% CI, 2.19-51.69; P = .003). This association persisted after PS-based matching on (1) clinical characteristics and ASPECTS (EVT, 35%, vs control, 19%; aOR, 3.14; 95% CI, 1.02-9.72; P = .047); (2) clinical characteristics and perfusion parameters (EVT, 35%, vs control, 17%; aOR, 4.17; 95% CI, 1.15-15.17; P = .03); and (3) clinical characteristics, ASPECTS, and perfusion parameters (EVT, 45%, vs control, 21%; aOR, 4.39; 95% CI, 1.04-18.53; P = .04). Patients receiving EVT had lower odds of mortality (26%) compared with those in the control group (41%; IPTW aOR, 0.49; 95% CI, 0.27-0.89; P = .02).

Conclusions and Relevance

In this study of treatment beyond 24 hours of last known well, EVT was associated with higher odds of functional independence compared with medical management, with consistent results obtained in PS-matched subpopulations and patients with presence of mismatch, despite increased odds of sICH. Our findings support EVT feasibility in selected patients beyond 24 hours. Prospective studies are warranted for confirmation.

Abstract TP45: Promoting High Value Care For Stroke Patients Within A Stroke System Of Care: Reducing Unnecessary Hospital Transfers For Patients Not Taken For Thrombectomy

Introduction: High value care aims to provide the best patient outcomes while avoiding defects and waste. Our previous work determined that 39% of patients transferred for possible thrombectomy based on clinical criteria and CT only did not have a large vessel occlusion (LVO) which led to a health system-wide guideline to improve transfer selection by adding criteria for emergent CT angiography. This study aims to describe the impact of that guideline and reanalyze the reasons why patients transferred for consideration of thrombectomy do not receive the procedure.

Methods: All patients transferred from within and outside of the health system as a potential thrombectomy candidate between 1/1/19- 6/30/21 were reviewed for reasons why thrombectomy was not pursued.

Results: Over 30 months, 316 patients transferred for possible thrombectomy were not taken to the angio suite primarily due to absence of LVO on vessel imaging (26.3%), lack of suspicion of LVO on assessment (18%) and significant improvement in clinical symptoms (12%). Other reasons included too large of core infarct (13.3%), CT head ASPECT score (8.2%), lack of perfusion imaging mismatch (6.3%), poor baseline functional status (4.7%), lesion too distal (3.8%), ICH (3.2%), time since last known well (1.9%), chronic ICA occlusion preventing access to acute lesion (1.9%), and medically unstable (0.3%).

Conclusions: Despite the institution of a system-wide protocol for acute CTA imaging to guide patient selection, the major reason for not proceeding to thrombectomy was still absence of LVO, some of which was related to out-of-system hospital transfers. Drawbacks of unnecessary patient transfer include increased cost of care, moving patients farther away from their home and family, and non-essential use of tertiary hospital bed space, particularly in the setting of a pandemic. Given the prevalence of potentially preventable unnecessary transfers, protocols that support in-the-field triage and transport based on clinical criteria alone, without CT or CTA, are destined to worsen health system efficiency and decrease the value of care for patients with major acuteischemic stroke.

Abstract 36: Endovascular Thrombectomy Beyond 24 Hours From Last Known Well: A Pooled Multicenter International Cohort

Background: Limited data are available on endovascular thrombectomy (EVT) efficacy and safety in large vessel occlusion (LVO) patients presenting >24hr from last known well (LKW). We compared outcomes between patients receiving EVT and best medical management (MM) in a multicenter international cohort.

Methods: Consecutive patients with anterior circulation LVO presenting >24h after LKW from 13 centers from 7/2012-4/2021 were analyzed. Multivariable models for 90d mRS distribution and symptomatic ICH were adjusted for age, NIHSS, glucose, IV tPA, transfer status, clot location, time from LKW, CT ASPECTS and ischemic core (rCBF<30%) and Tmax >6s volumes.

Results: Of 240 patients with a median (IQR) LKW to presentation 28.3h (24.9-38.2), 153 (64%) received EVT. Baseline characteristics were similar except for NIHSS (EVT: 13 (8-20) vs MM: 17 (10-22), p=0.005), CT ASPECTS (EVT: 8(6-9) vs MM: 4(3-6), p<0.001) and ischemic core 2.5(0-13) vs 15(0-71) mL, p<0.001. EVT was associated with a better shift in 90d mRS (acOR: 2.45, 95% CI=1.42-4.22, p=0.001), higher functional independence (42% vs 10%, aOR: 4.84, 95% CI=2.02-11.64, p<0.001) and numerically lower mortality (22% vs 42%, aOR: 0.50, 95% CI=0.23-1.06, p=0.071), Fig 1A. However, EVT was associated with numerically higher sICH (5.5% vs 0%, p=0.10). Following EVT, 82% achieved successful reperfusion (mTICI 2b-3), which was associated with better shift in 90d mRS (acOR: 5.82, 95% CI: 1.77-19.10, p=0.004), higher functional independence (44% vs 22%, aOR: 5.03, 95% CI: 0.87-29.12, p=0.07) and lower mortality (20% vs 52%, aOR: 0.08, 95% CI: 0.01-0.57, p=0.01), Fig 1B.

Conclusions: EVT may be associated with better functional outcomes, despite numerically increased risk of sICH in patients presenting with anterior circulation LVO beyond 24 hours. Further prospective studies are warranted.

Abstract P364: Use of the Electronic Alberta Stroke Program Early CT Score Software to Guide Treatment of Patients With Acute Ischemic Stroke

Introduction: Rapid recognition of large-vessel middle cerebral artery (lvMCA) stroke in patients with acute stroke symptoms is critical to guide thrombectomy and hemicraniectomy decisions. The Electronic Alberta Stroke Program Early CT Score (e-ASPECTS; Brainomix, LLC) is an automated, artificial intelligence software which quantifies acute ischemic volume (AIV) on CT head scans in the MCA territory. In this study, we investigate if e-ASPECTS-derived AIV could help guide treatment and predict outcomes for patients transferred from community hospitals.

Hypothesis: E-ASPECTS can help identify patients that may benefit from thrombectomy or hemicraniectomy.

Methods: We performed a retrospective chart review on patients age 18-90 transferred to our comprehensive stroke center (CSC) between 2013-2017. Non-contrast CT head scans performed at community hospitals prior to transfer were processed by e-ASPECTS to calculate AIV. Logistic regressions were used to test the relationship between AIV and eventual treatment (thrombectomy, hemicraniectomy).

Results: 228 patient CT scans were analyzed by e-ASPECTS. In all transferred patients, higher AIV predicted patients with later confirmed lvMCA strokes (defined as an ICA or M1 occlusion; OR 1.03, CI 1.02-1.05, P<0.001). Higher AIV also trended toward thrombectomy but was not statistically significant (P=0.15). In the subgroup analysis of patients later confirmed to have lvMCA strokes, lower AIV was predictive for thrombectomy (OR 0.95, CI 0.92-0.97, P<0.001). Additionally, higher AIV predicted outcomes of malignant cerebral edema (MCE; OR 1.03, CI 1.02-1.05, P<0.001) and hemicraniectomy (OR 1.04, CI 1.00-1.07, P=0.03).

Conclusions: Our study suggests that e-ASPECTS may be useful in identifying patients who would, or would not, benefit from transfer to a CSC from hospitals without thrombectomy or hemicraniectomy resources. Patients with stroke mimics or lvMCA strokes with large penumbras have lower AIVs, while patients with higher AIVs are at risk for MCE and may benefit from hemicraniectomy.

Glioma incidence and survival variations by county-level socioeconomic measures

BACKGROUND

Multiple studies have reported higher rates of glioma in areas with higher socioeconomic status (SES) but to the authors' knowledge have not stratified by other factors, including race/ethnicity or urban versus rural location.

METHODS

The authors identified the average annual age-adjusted incidence rates and calculated hazard ratios for death for gliomas of various subtypes, stratified by a county-level index for SES, race/ethnicity, US region, and rural versus urban status.

RESULTS

Rates of glioma were highest in counties with higher SES (rate ratio, 1.18; 95% CI, 1.15-1.22 comparing the highest with the lowest quintiles [P < .001]). Stratified by race/ethnicity, higher rates in high SES counties persisted for white non-Hispanic individuals. Stratified by rural versus urban status, differences in incidence by SES were more pronounced among urban counties. Survival was higher for residents of high SES counties after adjustment for age and extent of surgical resection (hazard ratio, 0.82; 95% CI, 0.76-0.87 comparing the highest with the lowest quintile of SES [P < .001]). Survival was higher among white Hispanic, black, and Asian/Pacific Islander individuals compared with white non-Hispanic individuals, after adjustment for age, SES, and extent of surgical resection, and when restricted to those individuals with glioblastoma who received radiation and chemotherapy.

CONCLUSIONS

The incidence of glioma was higher in US counties of high compared with low SES. These differences were most pronounced among white non-Hispanic individuals and white Hispanic individuals residing in urban areas. Better survival was observed in high SES counties, even when adjusting for extent of surgical resection, and when restricted to those who received radiation and chemotherapy for glioblastoma. Differences in incidence and survival were associated with SES and race, rather than rural versus urban status.

Exploring the diversity and metabolic potential of actinomycetes from temperate marine sediments from Newfoundland, Canada

Marine sediments from Newfoundland, Canada were explored for biotechnologically promising Actinobacteria using culture-independent and culture-dependent approaches. Culture-independent pyrosequencing analyses uncovered significant actinobacterial diversity (H'-2.45 to 3.76), although the taxonomic diversity of biotechnologically important actinomycetes could not be fully elucidated due to limited sampling depth. Assessment of culturable actinomycete diversity resulted in the isolation of 360 actinomycetes representing 59 operational taxonomic units, the majority of which (94 %) were Streptomyces. The biotechnological potential of actinomycetes from NL sediments was assessed by bioactivity and metabolomics-based screening of 32 representative isolates. Bioactivity was exhibited by 41 % of isolates, while 11 % exhibited unique chemical signatures in metabolomics screening. Chemical analysis of two isolates resulted in the isolation of the cytotoxic metabolite 1-isopentadecanoyl-3β-D-glucopyranosyl-X-glycerol from Actinoalloteichus sp. 2L868 and sungsanpin from Streptomyces sp. 8LB7. These results demonstrate the potential for the discovery of novel bioactive metabolites from actinomycetes isolated from Atlantic Canadian marine sediments.

Multilevel modeling of fetal and placental growth using echo-planar magnetic resonance imaging

OBJECTIVE

To quantify longitudinal increases in fetal, fetal liver, and fetal brain volume using echo-planar magnetic resonance imaging and to quantify the results using appropriate statistical modeling.

METHODS

Fifty-six singleton fetuses were studied using echo-planar (snap-shot) magnetic resonance imaging, between 19 weeks and term. They were assessed at a variety of different gestations and on a different number of occasions, thereby requiring multilevel statistical modeling to analyze the pattern of fetal growth.

RESULTS

Fetal volume varied according to the following equation: square root (radical) [fetal volume]=-37.71+2.17 x gestational age (GA)-0.004 x GA(2). The equation for fetal liver volume was radical[fetal liver volume]=9.47+0.56 x GA-0.02 x GA(2), for fetal brain volume was radical[fetal brain volume]=15.50+0.69 x GA-0.014 x GA(2), and for placental volume radical[placental volume]=28.54+0.95 x GA-0.039 x GA(2), where GA is the gestational age in weeks -30.

CONCLUSION

The assessment of fetal, fetal organ, and placental volume was feasible using echo-planar magnetic resonance imaging from 20 weeks to term. Multilevel statistical modeling can be applied to analyze sets of data with different measurements on different occasions. This information is useful clinically to assess abnormal fetal growth.

Fetal and placental volumetric and functional analysis using echo-planar imaging

Recent and past work using echo-planar imaging (EPI) in pregnancy has allowed important anatomic and physiological information to be obtained, giving advantages over conventional radiological methods such as ultrasound. EPI is a quick, convenient method of measuring organ volumes. The volumetric estimates throughout gestation correlate well with known fetal weight at these gestations. Relaxation time measurements also can be made in the placenta and lungs. By combining the changes in relaxation and volume with gestation in the future, it may be possible to develop an "index of maturity." This could be used to accurately reflect lung maturation. T1 and T2 parameters in the placenta decreased with gestational age and with abnormal placentation. EPI can be used to assess perfusion in the placenta and flow in the uterine arteries because of its rapid acquisition times. These techniques have been applied to assess perfusion within the fetal brain.

Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome

OBJECTIVE

We sought to identify clinical factors at diagnosis that predict outcome in twin-twin transfusion syndrome.

STUDY DESIGN

In this retrospective series 23 patients with twin-twin transfusion syndrome were seen in a tertiary referral fetal medicine center over a 3-year period. Ten antenatal factors were assessed to determine their ability to predict outcome by use of ordered logistic regression. These factors were the following: (1) absent or reversed end-diastolic flow in the umbilical artery, nonvisible bladder, anhydramnios, and estimated fetal weight of <3rd percentile in the donor; (2) pulsatile umbilical vein, either absent or reversed end-diastolic flow in the ductus venosus, or both, and tricuspid-mitral valve regurgitation in the recipient; and (3) gestational age at presentation, estimated fetal weight discordancy, absent arterioarterial anastomosis, and spontaneous rupture of the membranes or cervical change as pregnancy factors. Management comprised serial amnioreduction (n = 10), selective feticide (n = 5; 4 also had amnioreduction), septostomy (n = 4; 1 also had amnioreduction), and delivery (n = 2). Two patients miscarried before treatment.

RESULTS

The chance of survival of both twins fell and double deaths increased linearly with increasing number of adverse factors (P =.026). A low chance of survival was independently associated with absent or reversed end-diastolic flow in the donor umbilical artery (P =.02) and with a pulsatile umbilical vein or absent or reversed end-diastolic flow in the ductus venosus (P =.03) of the recipient. The probability of at least one twin surviving was only 33% if there was absent or reversed end-diastolic flow in the donor umbilical artery or 37% when abnormal venous recordings were seen in the recipient. An arterioarterial anastomosis detected at diagnosis also influenced prognosis, with all twins surviving when an arterioarterial anastomosis was identified (P =.04).

CONCLUSIONS

Three factors identified at diagnosis independently predict poor survival in twin-twin transfusion syndrome-absent or reversed end-diastolic flow in the donor umbilical artery, abnormal pulsatility of the venous system in the recipient, and absence of an arterioarterial anastomosis. These may have a role in the counseling of parents and in selecting the appropriate treatment strategy.

In utero perfusing fraction maps in normal and growth restricted pregnancy measured using IVIM echo-planar MRI

The aim of this study was to measure and portray blood movement in the placenta in vivo in normal and growth restricted pregnancies, using Intra Voxel Incoherent Motion (IVIM) magnetic resonance imaging. Thirteen patients with apparently normal healthy pregnancies were scanned at 31+/-7 (mean+/-s.d.) weeks gestation and seven patients with intrauterine growth restriction (IUGR) were scanned at 31+/-4 weeks. A region of interest (ROI) was defined encompassing the placenta between the decidual and chorionic plates. The volume of moving blood within each imaging voxel of the ROI was then calculated as a percentage of the total voxel volume (f per cent). This information was colour coded to produce maps of moving blood volume. The placenta was segmented length ways into two zones of approximately equal area, termed inner and outer, the latter being adjacent to the uterine wall. f was fitted for the average in the outer zone (f(out)) and inner zone (f(in)). The parameter (f(out)-f(in)) was then calculated for each subject. This was positive in 12/13 of the normal cases and zero for one case (+10 per cent+10, mean+/-s.d.). For pregnancy affected by IUGR this value was negative in all cases (-4 per cent+/-3). Perfusion fraction mapping identified differences in function within the normal placenta in vivo, and between the placentae of normal and IUGR pregnancies. The technique has potential applications in managing, and investigating the aetiology of, pregnancy compromise.

In vivo intravoxel incoherent motion measurements in the human placenta using echo-planar imaging at 0.5 T

This paper presents the first in vivo measurements of intravoxel incoherent motion in the human placenta, obtained using the pulsed gradient spin echo (PGSE) sequence. The aims of this study were two-fold. The first was to provide an initial estimate of the values of the IVIM parameters in this organ, which are currently unknown. The second aim was then to use these results to optimize the sequence timings for future studies. The moving blood fraction (f), diffusion coefficient (D), and pseudo-diffusion coefficient (D*) were measured. The average value of f was 26 +/- 6 % (mean +/- SD), D was 1.7 +/- 0.5 x 10(-3) mm2/sec, and D* was 57 +/- 41 x 10(-3) mm2/sec. For the optimized values of b, the expected percentage uncertainty in the fitted values of f, D, and D* for the placenta were sigmaf/f = 14.9%, sigmaD/D = 14.3%, sigmaD*/D* = 44.9%, for an image signal-to-noise of 20:1, and a total imaging time of 800 sec.

Infants exposed to MRI in utero have a normal paediatric assessment at 9 months of age

Any differences in detailed paediatric assessment at 9 months of age in infants exposed to echo planar MRI in utero from 20 weeks gestation to term were investigated by performing a case controlled prospective observational study of 20 infants. They had all had serial echo planar MRI in the antenatal period and were compared with a control group born at the same time who had not. Statistical analysis employed likelihood ratios, odds ratios and 95% confidence intervals. The mothers of the control infants had a significantly higher standard of educational attainment (p = 0.005). A small but significant decrease in length (p = 0.047), and an increase in gross motor function (p = 0.023) of the fetuses exposed to echo planar imaging were demonstrated. No other significant developmental or social differences were seen between the two groups. Infants at 9 months of age did not demonstrate any gross abnormality likely to be related to exposure to echo planar MRI in utero.

High failure rate of umbilical vessel occlusion by ultrasound-guided injection of absolute alcohol or enbucrilate gel

The success rate for injected umbilical vascular occlusion in the published literature exceeds 85 per cent. In this study we assessed the efficacy of two forms of injected sclerosants in achieving umbilical vessel occlusion. 12 cases of attempted ultrasound-guided occlusion over a 2 1/2 year period were reviewed. These were monochorionic (MC) twins (n=6), dichorionic twins (n=3) and singletons (n=3) undergoing fetocide for severe anomalies, or impending fetal demise. Absolute alcohol (n=6), enbucrilate gel (n=5) or both (n=1) were used in an attempt to achieve vascular occlusion. Complete vessel occlusion was achieved in only a third of cases (4/12), three with absolute alcohol and one with enbucrilate gel. In MC twins occlusion was successful in two of six cases. In contrast to previously published data, this large series, containing more cases than the total previously reported, shows considerably poorer success rates for injected umbilical vascular occlusion. Injection of currently available sclerosants can no longer be recommended for umbilical vascular occlusion in human fetuses.

First-trimester cord entanglement in monoamniotic twins

OBJECTIVE

Monoamniotic twinning occurs in only 1% of twin pregnancies, but carries a high perinatal mortality rate. Early and reliable diagnosis is essential if attempts are to be made to reduce the complication rate. We report color Doppler demonstration of cord entanglement in the first trimester, which is diagnostic of monoamnionicity.

METHODS

Two patients with twin pregnancies were examined in the first trimester with pulsed and color Doppler insonation of their umbilical arteries.

RESULTS

Cord entanglement was suspected and proved by demonstrating differing fetal heart rate patterns in the same direction on umbilical artery Doppler analysis of a common mass of cord vessels. Following appropriate counselling, medical amnioreduction was induced at 20 weeks of gestation to reduce fetal movements and worsening cord entanglement. Delivery was by elective Cesarean section at 32 weeks' gestation and monoamnionicity was confirmed.

CONCLUSION

We report a new sign for the demonstration of monoamnionicity in twin pregnancies in the first trimester. This should improve the reliability of early diagnosis, but further studies are required to confirm that, if cord entanglement occurs, it is usually present by the end of the first trimester.

The changes in magnetic resonance properties of the fetal lungs: a first result and a potential tool for the non-invasive in utero demonstration of fetal lung maturation

OBJECTIVE

To measure magnetic resonance parameters T1 and T2 of the fetal lungs and investigate the relationship of these parameters to changes in volume and gestation.

DESIGN

Prospective cross-sectional study.

SETTING

Large teaching hospital in Nottingham and the Magnetic Resonance Centre at the University of Nottingham.

POPULATION

Normal pregnancies from 20 weeks to term.

METHODS

T1, T2, and lung volume were measured in the fetus using echo-planar magnetic resonance imaging.

MAIN OUTCOME MEASURES

The relationship of T1 and T2 to gestational age and lung volume.

RESULTS

Linear regression demonstrated a significant relationship (P < 0.001) between gestational age and lung volume, T1 and T2. There was also a significant relationship between lung volume and T1 and T2 (P < 0-001).

CONCLUSIONS

Relaxation time measurements give additional information to lung volume estimation in the assessment of lung physiology in utero. We have demonstrated the progressive changes which take place in the fetal lungs between 20 weeks and term. The physiological changes which can be demonstrated with this non-invasive technique may have an important application in the demonstration of fetal lung maturity in a prospective non-invasive manner.

Assessment of fetal lung growth in utero with echo-planar MR imaging

PURPOSE

To measure changes in normal fetal lung volume with increasing gestation by using echo-planar magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Fifty-six singleton fetuses were examined longitudinally with respect to lung volume by using echo-planar MR imaging between 19 weeks gestation and term.

RESULTS

Lung volume increased exponentially with gestation from 8 to 125 mL. Volume was related to gestation by using the equation, volume = 0.8375e0.1249g (R2 = 0.77), where g = gestation. Lung volume had a direct relationship to fetal volume with increasing gestation (R2 = 0.75). There was no significant relationship between amniotic fluid volume and lung volume (R2 = 0.11).

CONCLUSION

Variation in lung volumes can be assessed by using echo-planar MR imaging, regardless of variations in amniotic fluid volume. These measurements are less than those obtained from postmortem and neonatal studies but are similar to those obtained by using three-dimensional ultrasonography. Lung volume estimations obtained by using echo-planar imaging may have important clinical and research applications when noninvassive assessment of lung volume is required.

The investigation of placental relaxation and estimation of placental perfusion using echo-planar magnetic resonance imaging

Echo-planar imaging (EPI) is a form of magnetic resonance imaging (MRI) which acquires images in milliseconds rather than minutes as with conventional MRI. The images produced using EPI are affected by the physiological environment in which the hydrogen atoms producing the signals are found, a process referred to as relaxation. Also by producing images a matter of milliseconds apart, quantification of perfusion within the tissue being imaged is feasible. The objective of this study was to investigate T1 and T2 relaxation times along with perfusion in placentae from normal pregnancies at different gestations and also to compare these to pregnancies complicated by abnormal placental function. A cross-sectional study of normal and compromised pregnancies from 20 weeks to term and a longitudinal study of normal pregnancy were performed. Placental T1, T2 relaxation times, and perfusion were measured using echo-planar magnetic resonance imaging. Placental T1 and T2 relaxation times decreased in normal pregnancy (P<0.001). Relaxation times in pregnancies associated with placental pathology appeared to be reduced for that gestation although the numbers were too small to allow any statistical validation. No differences in placental perfusion with gestation or between normal and compromised pregnancy were demonstrated using this technique. This is the first demonstration of placental magnetic resonance relaxation and perfusion measurements in normal pregnancy using echo-planar magnetic resonance imaging. In the future it may be possible to identify compromised pregnancies by differences in placental T1 and T2 relaxation times, using this novel non-invasive technique.

In vivo perfusion measurements in the human placenta using echo planar imaging at 0.5 T

This paper presents the first in vivo measurements of perfusion in the human placenta from 20 weeks gestational age until term, using the non-selective/selective inversion recovery echo-planar imaging sequence, in which data is alternately acquired following a selective and non-selective inversion pulse. Twenty pairs of images were collected, two each at the following inversion times: 20, 310, 610, 910, 1110, 1410, 1910, 2810, 3310, and 4510 ms with the sequence being repeated with a repetition time (TR) of 10 s. The results of these measurements were used to suggest the optimum sequence for future work in terms of the signal to noise ratio in the measured perfusion rate in a given measurement time. The sequence was also analyzed to determine the expected variability in the measurements. In normal pregnancies the average value of perfusion rate was found to be 176 (standard error = +/-24) ml/100 mg/min. (n = 16, standard deviation = 96 ml/100 mg/min). The expected variability in the measured parameters due to signal to noise ratio considerations alone was calculated to be 71%. For a maximum scanning time of 400 s, the optimum sequence for measuring placental perfusion was found to require 8 repetitions at each of 10 inversion times which were geometrically spaced (given by a(o), a(o)r, a(o)r2, a(o)r3, . . .), with a(o) = 850 ms, r = 1.073 and TR = 5 s, giving a pixel variability of 38%. Other timing schemes are recommended for measuring perfusion in other anatomical regions with different values of perfusion rate and longitudinal relaxation time.

Non-invasive mapping of placental perfusion

BACKGROUND

We aim to develop a clinical technique for the non-invasive measurement of placental perfusion, to enable early detection of intrauterine growth restriction (IUGR). Pregnancies with this complication are characterised by low placental perfusion.

METHODS

We measured placental perfusion by means of perfusion-sensitive echoplanar imaging (EPI); a rapid method of making magnetic resonance images. Perfusion measurements were done on six healthy volunteers with normal pregnancies and nine with pregnancies complicated by IUGR. Perfusion maps were created to assess the relation between placental perfusion and fetal size at birth.

FINDINGS

Pregnancies complicated by IUGR differed significantly from normal pregnancies in patterns of perfusion within the placenta (p<0.0001, ANOVA). Subsequent analysis showed that the proportion of placentas with low perfusion rates was higher in the IUGR group than in the normal group. A significant correlation between areas of reduced placental perfusion and fetal size was demonstrated (p=0.041, Spearman's rank correlation).

INTERPRETATION

Non-invasive imaging of placental perfusion by means of EPI has potential as a clinical tool in assessing the dynamics of placental perfusion.

Failure to detect intrauterine growth restriction following in utero exposure to MRI

Echo planar imaging is a form of MRI with short image acquisition times, which permits in utero fetal imaging without motion artefacts. Echo planar imaging has been used to measure accurately fetal organ volume and to assess placental function. Two small animal studies have suggested the possibility of intrauterine growth restriction consequent upon MRI. We thus performed a prospective study of pregnancies in which fetuses were exposed to echo planar imaging, compared with a control group in which there was no in utero echo planar imaging exposure. There were no significant differences between the groups when maternal age, parity, proportion of smokers and proportion of Caucasian women were compared. Although the gestational age of delivery was lower in the echo planar imaging group, the proportion of women delivering prematurely was not significantly different. Although infant birthweights were significantly lower in the MRI group, the corrected birthweight for gestational age centiles (individualized birthweight ratio) was not significantly different between the two groups. In utero exposure to echo planar imaging thus did not have a marked effect on intrauterine fetal growth. A 10 year follow-up study of all infants imaged in utero is being performed.

In vivo relaxation time measurements in the human placenta using echo planar imaging at 0.5 T

This paper presents the first in vivo measurements of the nuclear magnetic resonance relaxation times T1 and T2 at 0.5 T in the human placenta from 20 weeks gestational age until term, in both normal and compromised pregnancies. T1 measurements were performed by using both an inversion recovery sequence and the Look-Locher echo planar imaging (EPI) sequence on a total of 41 women with normal pregnancies and 11 women with compromised pregnancies. T2 measurements were performed by using a spin-echo EPI sequence on 36 women with normal pregnancies and 14 women with compromised pregnancies. In normal pregnancies, both the T1 values measured with the inversion recovery sequence and the T2 values were found to decrease with gestational age, the linear regression results gave T1 = -9.1t + 1538 r2 = 0.23 p = 0.03. T2 = -4.0t + 338 r2=0.47 p =410(-6) where t is the gestational age in weeks, and T1 and T2 are the relaxation times in milliseconds. T1 values measured very rapidly with the Look-Locher EPI sequence, but, therefore, with a much lower signal-to-noise ratio, showed no significant trends. The T1 values measured in the abnormal group were significantly lower than those measured in the normal group. Four out of eight patients with compromised pregnancies had placental T1 values lying outside the 90% confidence limits for the normal population based about the regression line, significantly more than expected by chance (p = 0.005). Ten out of fourteen of the T2 measurements in the abnormal group were below the regression line established for the normal group, with 4 lying below the 90% confidence interval, although these trends were only just significant (p = 0.06 and p = 0.03).

The aetiology and management of twin-twin transfusion syndrome

Twin-to-twin transfusion syndrome presents in the mid-trimester with gross discordance in amniotic fluid volume, and complicates 10-15 per cent of monochorionic twins. Recent studies suggest a primary vascular basis in which a paucity of the bidirectional superficial anastomoses normally found in monochorionic twins is unable to compensate for haemodynamic imbalance resulting from unidirectional transfusion along deeper arterio-venous anastomoses. It is associated with high rates of perinatal mortality from ruptured membranes, hydrops and growth restriction, and a significant morbidity from cardiac and neurological sequelae in particular. Serial aggressive amnioreduction is the current treatment of choice, with survival in around two thirds of cases. In the remaining third, with features suggesting a poor outcome, selective fetocide may have a role. Current attempts at vascular ablative therapies have been associated with inferior survival rates, but the long term therapeutic goal remains the identification and ablation of the shared chorionic vasculature.

Demonstration of changes in fetal liver erythropoiesis using echo-planar magnetic resonance imaging

This study investigated the variation in magnetic resonance characteristics of the fetal liver during a time of changing erythropoietic function. Echo-planar imaging was carried out in 25 normal pregnant women at 20 and 26 wk gestation. The signal intensity from regions of the fetal liver, background image, and maternal back muscle and the highest signal intensity from the maternal spinal cord were measured and compared with the signal intensity of amniotic fluid. Data are expressed as ratios, in arbitrary units (median pixel values; interquartile range shown in parentheses), and analyzed with the use of Wilcoxon's signed-rank test. At 20 wk, the signal intensity ratio of liver to amniotic fluid was 0.309 (0.231-0.365). At 26 wk, the ratio was 0.544 (0.429-0.616). The change was highly significant (P < 0.0001). No change in the signal intensity ratios of amniotic fluid compared with other measured parameters was noted. These data are consistent with known changes in fetal liver erythropoiesis occurring between 20 and 26 wk gestation and have potential use in early noninvasive physiological assessment of the fetus.

The development of magnetic resonance imaging in obstetrics

Following recent developments in imaging techniques which overcome the problem of fetal motion, magnetic resonance imaging (MRI) has the potential to improve non-invasive fetomaternal assessment. This article catalogues the development of MRI and the potential that exists for its use in obstetrics in the future.