The application of augmented reality-based navigation for accurate target acquisition of deep brain sites: advances in neurosurgical guidance.

OBJECTIVE: The objective of this study is to quantify the navigational accuracy of an advanced augmented reality (AR)-based guidance system for neurological surgery, biopsy, and/or other minimally invasive neurological surgical procedures. METHODS: Five burr holes were drilled through a plastic cranium, and 5 optical fiducials (AprilTags) printed with CT-visible ink were placed on the frontal, temporal, and parietal bones of a human skull model. Three 0.5-mm-diameter targets were mounted in the interior of the skull on nylon posts near the level of the tentorium cerebelli and the pituitary fossa. The skull was filled with ballistic gelatin to simulate brain tissue. A CT scan was taken and virtual needle tracts were annotated on the preoperative 3D workstation for the combination of 3 targets and 5 access holes (15 target tracts). The resulting annotated study was uploaded to and launched by VisAR software operating on the HoloLens 2 holographic visor by viewing an encrypted, printed QR code assigned to the study by the preoperative workstation. The DICOM images were converted to 3D holograms and registered to the skull by alignment of the holographic fiducials with the AprilTags attached to the skull. Five volunteers, familiar with the VisAR, used the software/visor combination to navigate an 18-gauge needle/trocar through the series of burr holes to the target, resulting in 70 data points (15 for 4 users and 10 for 1 user). After each attempt the needle was left in the skull, supported by the ballistic gelatin, and a high-resolution CT was taken. Radial error and angle of error were determined using vector coordinates. Summary statistics were calculated individually and collectively. RESULTS: The combined angle of error of was 2.30° ± 1.28°. The mean radial error for users was 3.62 ± 1.71 mm. The mean target depth was 85.41 mm. CONCLUSIONS: The mean radial error and angle of error with the associated variance measures demonstrates that VisAR navigation may have utility for guiding a small needle to neural lesions, or targets within an accuracy of 3.62 mm. These values are sufficiently accurate for the navigation of many neurological procedures such as ventriculostomy.

Sleep disordered breathing as a risk of cardiac events in subjects with diabetes mellitus and normal exercise echocardiographic findings.

Sleep disordered breathing (SDB) is associated with type 2 diabetes mellitus (T2DM) and cardiovascular disease; however, the contribution of SDB to incident heart failure (HF), coronary artery disease (CAD), and atrial fibrillation (AF) in patients with T2DM is unknown. We followed up 834 consecutive asymptomatic patients with T2DM (age 56 ± 11 years, 369 women) with normal exercise echocardiographic findings for ≤8 years using electronic health records. The demographics, cardiac risk factors, symptoms, diagnoses, and medications were collected at the echocardiography and validated from the electronic health records. SDB was confirmed by a comprehensive sleep evaluation and/or polysomnography before echocardiography. SDB was diagnosed in 188 patients (21%) at baseline; 116 were untreated. During a median follow-up of 4.9 years (interquartile range 3.9 to 6.1), 22 congestive HF, 72 CAD, and 40 AF incident events were observed. In the Cox proportional hazards models, SDB was associated with incident CAD (hazard ratio 1.8, 95% confidence interval 1.1 to 3.0, p = 0.01; adjusted hazard ratio 1.9, 95% confidence interval 1.2 to 3.2, p <0.01) and AF (hazard ratio 2.6, 95% confidence interval 1.4 to 4.7, p = 0.01; adjusted hazard ratio 2.9, 95% confidence interval 1.5 to 5.9, p <0.01). Limiting SDB to only those patients diagnosed using polysomnography (n = 132), SDB was associated with incident CAD (hazard ratio 1.9, 95% confidence interval 1.1 to 3.3, p = 0.03; adjusted hazard ratio 2.2, 95% confidence interval 1.2 to 3.9, p = 0.01) and HF (hazard ratio 2.7, 95% confidence interval 1.1 to 7.0, p = 0.03; adjusted hazard ratio 3.5, 95% confidence interval 1.4 to 9.0, p <0.01). Female gender, age, elevated blood pressure, and left ventricular mass were additional correlates of CAD in those with asymptomatic T2DM. In conclusion, the association of SDB with incident CAD, AF, and HF in patients with T2DM justifies more liberal screening for SDB in patients with T2DM, realizing that SDB is a potentially modifiable risk factor.

Quantitation of the diastolic stress test: filling pressure vs. diastolic reserve.

AIMS: The diastolic stress test (DST) may facilitate the attribution of exertional dyspnoea to cardiac and non-cardiac diseases. However, there is currently no consensus as to the optimal marker of exertional diastolic dysfunction (DD)-the main alternatives being estimated left ventricular (LV) filling pressure (exercise E/e') and diastolic functional reserve (DFRI). We sought to compare the correlates of these parameters. METHODS AND RESULTS: DST was performed by adding the measurement of the transmitral (E) and annular (e') velocities to standard exercise echo in 559 consecutive patients without significant rest or exercise mitral regurgitation. Exertional DD was separately defined by post-stress E/e' >13 or DFRI <13.5. Logistic regression was used to identify the correlates of abnormal responses and linear regression was used to identify the contribution of both to exercise capacity. Abnormal exercise E/e' (n = 112, 20%) and DFRI (n = 317, 57%) were modestly associated (κ 0.35, P < 0.0001). In a linear regression, abnormal exercise E/e' (ß = -0.19, P < 0.001) and DFRI (ß = -0.15, P = 0.001) were associated with exercise capacity, independent of age, body mass index, wall thickness, haemodynamics or abnormal stress results. Logistic regression revealed abnormal exercise E/e' (R(2)= 0.34) to be independently associated with female gender (ß = 0.26, 95% CI: 0.11-0.60, P = 0.002), age (ß = 1.04, 95% CI: 1.01-1.07, P = 0.01), hypertension (ß = 0.35, 95% CI: 0.15-0.80, P = 0.01) and wall thickness (ß = 4.3, 95% CI: 1.3-14.1, P = 0.02). The closest association of abnormal DFRI was exercise capacity (ß = 0.89, 95% CI: 0.79-1.02, P = 0.09); no other clinical or stress variable was independently associated. CONCLUSION: Exercise E/e' and DFRI are both associated with exercise capacity, but E/e' is more closely associated with the expected parameters of DD.

Association of myocardial deformation with outcome in asymptomatic aortic stenosis with normal ejection fraction.

BACKGROUND: Current guidelines recommend intervention for symptomatic aortic stenosis, but the management of asymptomatic aortic stenosis remains controversial. As left ventricular global longitudinal strain (GLS) has been shown to predict cardiovascular outcome, we sought to find whether its use could guide the assessment of risk in these patients. METHODS AND RESULTS: We prospectively followed 79 patients with severe asymptomatic aortic stenosis (39 men; mean age, 77 ± 12 years; aortic valve [AV] area index, 0.36 cm(2)/m(2)). In addition to standard echocardiography, speckle strain was measured to assess GLS. Patients were followed for cardiac death and AV replacement driven by symptom development. A multivariable Cox regression was performed to identify associations with events. During 23 ± 20 months, 3 patients had cardiac death and 49 underwent AV replacement. Event-free survival was 72 ± 5% at 1 year, 50 ± 5% at 2 years, and 24 ± 5% at 4 years. Death and AV replacement were predicted by GLS (hazard ratio [HR], 1.14 [95% CI, 1.01-1.28]; P=0.037), as well as extent of AV calcification (HR, 2.44 [95% CI, 1.17-5.12]; P=0.018), peak transaortic pressure gradient (HR, 1.03 [95% CI, 1.01-1.04]; P<0.001), valvulo-arterial impedance (HR, 1.32 [95% CI, 1.04-1.67]; P=0.045), and Society of Thoracic Surgeons Predicted Risk of Morbidity and Mortality (HR, 0.95 [95% CI, 0.90-1.00]; P=0.052). A mean absolute GLS <15% was associated with a significant excess mortality, and this measurement added incremental prognostic value to the Society of Thoracic Surgeons Predicted Risk of Morbidity and Mortality, transaortic peak pressure gradient, AV calcification, and valvulo-arterial impedance. CONCLUSIONS: GLS is associated with outcomes in patients with severe asymptomatic aortic stenosis, incremental to other clinical and echocardiographic variables.