CineECG for visualization of changes in ventricular electrical activity during ischemia

BACKGROUND

CineECG offers a visual representation of the location and direction of the average ventricular electrical activity throughout a single cardiac cycle, based on the 12‑lead ECG. Currently, CineECG has not been used to visualize ventricular activation patterns during ischemia.

PURPOSE

To determine the changes in ventricular activity during acute ischemia with the use of CineECG, and relating this to changes in the ECG.

METHODS

Continuous ECG's during percutaneous coronary intervention with prolonged balloon inflation from the STAFF III database were analyzed with CineECG at baseline and every 10 s throughout the first 150 s of balloon inflation. The CineECG direction was determined for the initial QRS-complex, terminal QRS-complex, ST-segment and T-wave. Changes in the CineECG were quantified by calculating the Δangle between the direction at baseline and the direction at every 10 s of inflation. Additionally, the root mean square amplitude (rmsA) of the ST-segment was computed.

RESULTS

94 patients were included. At start inflation, the median Δangle was 14.7° [7.5-33.4], 21.8° [11.4-34.2], 20.6° [8.0-43.9], and 23.5° [11.8-48.0] for the initial QRS-complex, terminal QRS-complex, ST-segment and T-wave, respectively. Meanwhile, the median rmsA increased from 0.039 mV [0.027-0.058] at baseline to 0.045 mV [0.033-0.075] at start of inflation.

CONCLUSIONS

CineECG was able to detect immediate changes in ventricular electrical activity during induced ischemia, while changes in the ST-segment of the ECG were still subtle. Therefore, CineECG might support the early detection of acute ischemia, even before distinct ECG changes become visible.

Modeling ventricular repolarization gradients in normal cases using the equivalent dipole layer

Background Electrical activity underlying the T-wave is less well understood than the QRS-complex. This study investigated the relationship between normal T-wave morphology and the underlying ventricular repolarization gradients using the equivalent dipole layer (EDL). Methods Body-surface-potential-maps (BSPM, 67‑leads) were obtained in nine normal cases. Subject specific MRI-based anatomical heart/torso-models with electrode positions were created. The boundary element method was used to account for the volume conductor effects. To simulate the measured T-waves, the EDL was used to apply different ventricular repolarization gradients: a) transmural, b) interventricular c) apico-basal and d) all three gradients (a-c) combined. The combined gradient (d) was optimized using an inverse procedure (Levenberg-Marquardt). Correspondence between simulated and measured T-waves was assessed using correlation coefficient (CC) and relative difference (RD). Results Realistic T-waves were simulated if repolarization times of: (a) the epicardium were smaller than the endocardium; (b) the left ventricle were smaller than the right ventricle and (c) the apex increased towards the base. The apico-basal gradient resulted in the highest correspondence between measured and simulated T-waves (CC = 0.84(0.81-0.91);RD = 0.68(0.60-0.71)) compared to a transmural gradient (CC = 0.77(0.71-0.80);RD = 1.46(0.82-1.75)) and an interventricular gradient (CC = 0.71(0.67-0.80);RD = 0.85(0.75-0.87)). All three gradients combined further improved the correspondence between measured and simulated T-waves (CC = 0.83(0.82-0.89);RD = 0.60(0.51-0.63)), especially after optimization (CC = 0.96(0.94-0.98);RD = 0.27(0.22-0.34)). Conclusion The application of all repolarization gradients combined resulted in the largest agreement between simulated and measured T-waves, followed by the apico-basal repolarization gradient. With these findings, we will optimize our EDL-based inverse procedure to assess repolarization abnormalities.

Lumbar puncture for treating acute hydrocephalus after aneurysmal subarachnoid haemorrhage

BACKGROUND

External ventricular drainage (EVD) for acute hydrocephalus after aneurysmal subarachnoid haemorrhage (aSAH) carries a risk of complications. We studied the proportion of patients in whom EVD can be avoided by treating acute hydrocephalus with ≥1 lumbar punctures (LP).

METHODS

From a prospectively collected database, we retrieved data on all aSAH patients admitted between 2007 and 2017 who developed acute hydrocephalus (i.e. neurological deterioration and ventricular enlargement <72 h after aSAH). Our regime is to consider LP as initial treatment. We calculated the proportions of patients (with corresponding 95% confidence interval (CI)) who improved after the initial LP and the extent of clinical improvement, the proportions of patients who were treated with only ≥1 LP(s), and those of patients needing continuous external ventricular or external lumbar drainage, or permanent ventriculoperitoneal or lumboperitoneal drainage.

RESULTS

Of 1391 consecutive aSAH patients, 473 (34%) had acute hydrocephalus, of whom 388 (82%) were treated. Of the 86 patients with LP as initial treatment, 70 (81% [95% CI 72-88]) showed initial improvement (with increase in median Glasgow Coma Score from 10 (IQR 7-12) to 12 (IQR 9-14) after initial LP), 39 (45% [95% CI 35-56]) improved with LP only, 41 (48% [95% CI 37-58]) needed continuous drainage and six (7% [95% CI 3-14]) needed permanent drainage.

CONCLUSION

Around half the patients treated with LP for deterioration from acute hydrocephalus after aSAH does not require continuous extraventicular or extralumbar drainage.

Data-efficient deep learning of radiological image data for outcome prediction after endovascular treatment of patients with acute ischemic stroke

Treatment selection is becoming increasingly more important in acute ischemic stroke patient care. Clinical variables and radiological image biomarkers (old age, pre-stroke mRS, NIHSS, occlusion location, ASPECTS, among others) have an important role in treatment selection and prognosis. Radiological biomarkers require expert annotation and are subject to inter-observer variability. Recently, Deep Learning has been introduced to reproduce these radiological image biomarkers. Instead of reproducing these biomarkers, in this work, we investigated Deep Learning techniques for building models to directly predict good reperfusion after endovascular treatment (EVT) and good functional outcome using CT angiography images. These models do not require image annotation and are fast to compute. We compare the Deep Learning models to Machine Learning models using traditional radiological image biomarkers. We explored Residual Neural Network (ResNet) architectures, adapted them with Structured Receptive Fields (RFNN) and auto-encoders (AE) for network weight initialization. We further included model visualization techniques to provide insight into the network's decision-making process. We applied the methods on the MR CLEAN Registry dataset with 1301 patients. The Deep Learning models outperformed the models using traditional radiological image biomarkers in three out of four cross-validation folds for functional outcome (average AUC of 0.71) and for all folds for reperfusion (average AUC of 0.65). Model visualization showed that the arteries were relevant features for functional outcome prediction. The best results were obtained for the ResNet models with RFNN. Auto-encoder initialization often improved the results. We concluded that, in our dataset, automated image analysis with Deep Learning methods outperforms radiological image biomarkers for stroke outcome prediction and has the potential to improve treatment selection.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study

BACKGROUND AND PURPOSE

Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted.

MATERIALS AND METHODS

Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics.

RESULTS

We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76).

CONCLUSIONS

Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

Percutaneous vertebroplasty as treatment for Kummell's disease

We report a case with classic clinical findings and imaging features of Kummell's disease. Kummell's disease is a post-traumatic vertebral body collapse. Initially after the trauma patients are usually asymptomatic but after months they develop a symptomatic and progressive kyphosis of the lower thoracic or lumbar spine. On a conventional radiograph a collapsed vertebral body with a fracture cleft is typical and on MRIT2 weighted images the double line sign is characteristic for Kummell's disease; an increased linear area of hyper-intensity surrounded by an area of low signal. Percutaneous vertebroplasty is an adequate treatment for stabilization of the fracture and pain reduction in patients with Kummell's disease.

Age- and anatomy-related values of blood-brain barrier permeability measured by perfusion-CT in non-stroke patients

BACKGROUND AND PURPOSE

The goal of this study was to determine blood-brain barrier permeability (BBBP) values extracted from perfusion-CT (PCT) using the Patlak model and possible variations related to age, gender, race, vascular risk factors and their treatment and anatomy in non-stroke patients.

MATERIALS AND METHODS

We retrospectively identified 96 non-stroke patients who underwent a PCT study using a prolonged acquisition time up to 3 minutes. Patients' charts were reviewed for demographic data, vascular risk factors and their treatment. The Patlak model was applied to calculate BBBP values in regions of interest drawn within the basal ganglia and the gray and white matter of the different cerebral lobes. Differences in BBBP values were analyzed using a multivariate analysis considering clinical variables and anatomy.

RESULTS

Mean absolute BBBP values were 1.2 ml 100 g(-1) min(-1) and relative BBBP/CBF values were 3.5%. Statistical differences between gray and white matter were not clinically relevant. BBBP values were influenced by age, history of diabetes and/or hypertension and aspirin intake.

CONCLUSION

This study reports ranges of BBBP values in non-stroke patients calculated from delayed phase PCT data using the Patlak model. These ranges will be useful to detect abnormal BBBP values when assessing patients with cerebral infarction for the risk of hemorrhagic transformation.

Endovascular treatment of vein of Galen aneurysmal malformation

A vein of Galen aneurysmal malformation represents an arteriovenous fistula draining in a dilated precursor of the vein of Galen. We report a case of an incidentally detected large aneurysmal malformation of the vein of Galen in a 25-year-old man.The malformation was visualized with CT, MRI and digital subtraction angiography.This uncommon vascular malformation is rarely detected in adults as symptoms usually arise during childhood. This patient had no neurological complaints but the angiography showed, however, a steal phenomenon from the anterior circulation. The lesion was treated with good results by means of endovascular embolization with coils.

Dynamic perfusion CT assessment of the blood-brain barrier permeability: first pass versus delayed acquisition

BACKGROUND AND PURPOSE

The Patlak model has been applied to first-pass perfusion CT (PCT) data to extract information on blood-brain barrier permeability (BBBP) to predict hemorrhagic transformation in patients with acute stroke. However, the Patlak model was originally described for the delayed steady-state phase of contrast circulation. The goal of this study was to assess whether the first pass or the delayed phase of a contrast bolus injection better respects the assumptions of the Patlak model for the assessment of BBBP in patients with acute stroke by using PCT.

MATERIALS AND METHODS

We retrospectively identified 125 consecutive patients (29 with acute hemispheric stroke and 96 without) who underwent a PCT study by using a prolonged acquisition time up to 3 minutes. The Patlak model was applied to calculate BBBP in ischemic and nonischemic brain tissue. Linear regression of the Patlak plot was performed separately for the first pass and for the delayed phase of the contrast bolus injection. Patlak linear regression models for the first pass and the delayed phase were compared in terms of their respective square root mean squared errors (square root MSE) and correlation coefficients (R) by using generalized estimating equations with robust variance estimation.

RESULTS

BBBP values calculated from the first pass were significantly higher than those from the delayed phase, both in nonischemic brain tissue (2.81 mL x 100 g(-1) x min(-1) for the first pass versus 1.05 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001) and in ischemic tissue (7.63 mL x 100 g(-1) x min(-1) for the first pass versus 1.31 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001). Compared with regression models from the first pass, Patlak regression models obtained from the delayed data were of better quality, showing significantly lower square root MSE and higher R.

CONCLUSION

Only the delayed phase of PCT acquisition respects the assumptions of linearity of the Patlak model in patients with and without stroke.

CT after subarachnoid hemorrhage: Relation of cerebral perfusion to delayed cerebral ischemia

BACKGROUND

Delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) is difficult to predict. The authors studied the relation between several parameters of brain perfusion at admission and development of DCI.

METHODS

The authors analyzed the admission CT perfusion (CTP) scans of 46 patients scanned within 72 hours after SAH. They assessed cerebral blood volume (CBV) and flow (CBF), mean transit time (MTT), and time to peak (TTP) for eight predefined regions of interest. For patients with and without DCI, the authors compared perfusion quantitatively and semiquantitatively. With receiver-operator characteristic (ROC) curves, the authors assessed the relationship between DCI and perfusion parameters. To assess the potential prognostic value, they calculated sensitivity and specificity of optimal threshold values for the semiquantitative data.

RESULTS

DCI was not significantly related with quantitative perfusion values. For the semiquantitative data, patients with DCI had significantly more asymmetry in perfusion, and ROC curves indicated a good relation (0.75 to 0.81). Optimal threshold values distinguishing between patients with and without DCI were 0.77 for CBV and 0.72 for CBF ratios, and 0.87 seconds for MTT and 1.0 second for TTP differences. The corresponding sensitivity was 0.75 for all parameters; the specificity was 0.70 for CBV, 0.93 for CBF, 0.70 for MTT, and 0.90 for TTP.

CONCLUSIONS

Delayed cerebral ischemia (DCI) is related to perfusion asymmetry on admission CT perfusion (CTP). The cerebral blood flow ratio (comparing contralateral regions of interest) seems the best prognosticator for development of DCI. Further studies are needed to investigate the additional value of CTP to other prognosticators for DCI and to validate the chosen threshold values.

Minimizing clip artifacts in multi CT angiography of clipped patients

PURPOSE

To optimize the multi CTA (MSCTA) protocol, the influence of pitch, kilovoltage peak (kVp), reconstruction algorithm, type, and orientation of the clip on clip-induced artifacts was investigated in a phantom study. Also, the influence of kVp, concentration of contrast material, and clip orientation in clipped patients was studied.

METHODS

A phantom containing a clip was scanned with varying parameters. Artifact was quantified with 3D volumetry. Artifact volumes were compared for the different parameters. In addition, the number of artifact streaks was presented as a function of the pitch. Five clipped patients were scanned with 90 kVp and 120 kVp and 5 with 120 kVp and 140 kVp. The artifact area was compared. The visualization at the clip site was evaluated for different clip orientations in 50 patients, and for 140 kVp with 370 mg iodine/mL contrast (I/mL) compared with 120 kVp/300 mg I/mL in 7 patients.

RESULTS

Up to a pitch of 0.6, there was hardly an increase in artifact. Higher kVp and linear interpolation resulted in fewer artifacts. Alloy clips containing cobalt produced more artifact than did titanium clips. Clips positioned perpendicular to the scan plane led to significantly less artifact. In patients with clips, scanning with 140 kVp/370 mgI/mL led to a decrease of artifact area and a better visualization of the clip site. The visualization at the clip site was also better for clips perpendicular to the scan plane.

CONCLUSIONS

If clip artifacts are to be minimized, we suggest scanning with a pitch of 0.6, by using 140 kVp and 370 mgI/mL contrast.

Influence of partial volume on venous output and arterial input function

BACKGROUND

CT perfusion (CTP) is an important diagnostic tool for the imaging of cerebral hemodynamics. To obtain quantitative values of cerebral blood volume (CBV), blood flow (CBF), and mean transit time (MTT), measurement of the arterial input function (AIF) is required. To correct for partial volume effects (PVEs), it is common to normalize the AIF with respect to the venous output function (VOF). This correction assumes that measurement of the VOF is unhampered by PVEs. The purpose of this study was to evaluate the effect of PVE on the measurement of the AIF and VOF and, consequently, on the absolute perfusion parameters.

METHODS

In 10 patients the mean area under the curve (AUC) of the AIF and VOF were quantified for 3-, 6-, and 12-mm-thick sections. Differences in the mean (1) AUC of the VOF, (2) AUC of the AIF, and (3) width of the AIF were compared for the 3 section thicknesses, and the influence on the absolute values of CBV, CBF, and MTT were studied.

RESULTS

With thinner sections, the AUC of the VOF and the AIF increased significantly and the width of the AIF decreased slightly. Differences in AUC between the 3 section thicknesses were larger for the AIF than for the VOF.

CONCLUSION

PVEs affect not only the AIF, but also the VOF. This results in an overestimation of CBV and CBF when a thicker section is used. To avoid PVE, VOF measurements should be performed at lower section thicknesses.

Endovascular coiling versus neurosurgical clipping for patients with aneurysmal subarachnoid haemorrhage

BACKGROUND

Patients who have had an aneurysmal subarachnoid haemorrhage (SAH) are at very high risk of rebleeding if the aneurysm is not treated. The standard treatment for several decades has been surgical clipping of the neck of the aneurysm. In recent years, an alternative, the introduction of detachable coils to occlude the aneurysm, has become more common.

OBJECTIVES

To compare the effects of endovascular coiling versus neurosurgical clipping in patients with aneurysmal subarachnoid haemorrhage.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched in February 2005). In addition we searched MEDLINE (1966 to January 2004) and EMBASE (1980 to January 2004), and contacted trialists.

SELECTION CRITERIA

We included randomised trials in which endovascular coiling of aneurysms was compared with neurosurgical clipping in patients with SAH who have proven aneurysm.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data and assessed trial quality. Trialists were contacted to obtain missing information.

MAIN RESULTS

We identified three randomised trials: two published and one unpublished. The trials included a total of 2272 patients (range per trial: 20 to 2143 patients). Most of the patients were in good clinical condition and had an aneurysm on the anterior circulation. After one year of follow up, the relative risk (RR) of poor outcome for coiling versus clipping was 0.76 (95% confidence interval (CI) 0.67 to 0.88). The absolute risk reduction was 7% (95% CI 4% to 11%). In the worst-case scenario analysis for poor outcome overall, the relative risk for coiling versus clipping was 0.81 (95% CI 0.70 to 0.92) and the absolute risk reduction was 6% (95% CI 2% to 10%). For patients with anterior circulation aneurysm the relative risk of poor outcome was 0.78 (95% CI 0.68 to 0.90) and the absolute risk decrease was 7% (95% CI 3% to 10%). For those with a posterior circulation aneurysm the relative risk was 0.41 (95% CI 0.19 to 0.92) and the absolute decrease in risk 27% (95% CI 6% to 48%).

AUTHORS' CONCLUSIONS

The evidence comes mainly from one large trial. For patients in good clinical condition with ruptured aneurysms of either the anterior or posterior circulation we have firm evidence that, if the aneurysm is considered suitable for both surgical clipping and endovascular treatment, coiling is associated with a better outcome.