Joris van Houte

This original work challenges the traditional view of the aorta as a passive conduit by investigating its vasoactive response to phenylephrine during cardiac surgery. Luminal area was measured by transesophageal echocardiography while simultaneously recording blood pressure. A mean pressure-independent increase in luminal area and stiffness was observed, suggesting a paradoxical vasodilative response. However, strong patient-to-patient variability in the response to phenylephrine highlights the need to measure effects patient specifically.

Local carotid pulse wave velocity (cPWV), a hemodynamic variable related to arterial stiffness, is a recognized risk indicator for cardiovascular disease. Yet, current methods for its estimation pose challenges, requiring multiple simultaneous local measurements, as is the case for the established Bramwell-Hill (BH) method, or relying on assumptions that may not universally apply, as for single-measurement loop-based methods. This study introduces a novel, non-invasive, single-measurement method for estimating local cPWV. The proposed method relies solely on morphological indices derived from the carotid velocity waveform, measured via pulsed wave Doppler (pw-D) ultrasound. A multivariate regression (MVR) model relating eight such indices to cPWV was trained on a large available virtual cohort (N=5,160), previously generated via one-dimensional hemodynamic modeling. The MVR model was then tested on a clinical dataset of 27 cardiac surgery patients, showing moderate but significant correlation with the reference Bramwell-Hill method (r=0.54, p<0.01), and Bland-Altman values falling within clinically acceptable thresholds (mean difference 0.16 m/s, limits of agreement ±1.98 m/s). The proposed method outperformed the alternative pressure-less flow-area loop (QA-loop) method, which compared poorly to reference BH values (r=0.47, p<0.05, mean difference 0.72 m/s, and limits of agreement ±5.41 m/s). Furthermore, the proposed method showed the lowest intra-subject coefficient of variation (median 2.4%, interquartile range (IQR) 0-4.2%), and measurement-related uncertainty (median 0.11 m/s, IQR 0.07-0.23 m/s) among the three compared methods.

The induction of anesthesia is often followed by hypotension and the depth and duration of the hypotensive period influence the occurrence and severity of post-operative end-organ damage. The depth and duration of the hypotensive period might be reduced by predicting postinduction hypotension and administering fluids or medication at an earlier stage. While many methods to predict postinduction hypotension have been proposed, they require invasive measurements, lack explainability, or are not freely available. The recent emergence of carotid ultrasound patches makes carotid ultrasound a suitable alternative for patient monitoring, as it allows continuous non-invasive measurement of a central vessel. The present study aimed to build and validate a logistic regression model combining features from carotid ultrasound and clinical variables to predict postinduction hypotension. The model was trained and tested on a clinical dataset from adult patients scheduled for elective surgery under spinal anesthesia. At the preoperative holding area, carotid ultrasound imaging was performed and baseline vital signs were measured. Postinduction hypotension was defined as either 1) systolic blood pressure (SBP) reduction of >30% or mean arterial pressure (MAP) reduction of >20% from baseline, 2) an absolute SBP <90 mmHg or an absolute MAP <65 mmHg, or 3) the onset of hypotension-related symptoms. In total, 42 patients were included, of whom 19 (45%) became hypotensive after the induction of spinal anesthesia. The dataset was split in a ratio of 80:20% for training and testing. A total of 19 ultrasound and clinical features were studied and, after feature selection, five features were used to build the model. On the test dataset, the model had an AUROC of 0.88 and, using a threshold of 0.5, a sensitivity and a specificity of 75%. These preliminary results show that our logistic regression model might be able to predict postinduction hypotension. The next step is to test the proposed model on a large dataset and improve it if necessary. Moreover, other model types and features will be explored to evaluate if this improves the performance.

Background: Systemic hypothermia with bilateral antegrade selective cerebral perfusion (ASCP) is the preferred cerebral protective strategy for type A aortic dissection surgery. The optimal ASCP flow rate remains uncertain and the target flow cannot always be reached due to pressure limitations. The aim of this study was to assess the correlation between ASCP flow and regional cerebral oxygen saturation (rSO2). Methods: A retrospective analysis was performed on 140 patients with acute type A aortic dissection who underwent surgery with moderate hypothermic circulatory arrest and bilateral ASCP between 2015 and 2021. Pearson correlation analysis was performed between ASCP flow and rSO2. Results: The median circulatory arrest duration was 46.5 (IQR:37.0-61.0) minutes. There was no significant correlation between ASCP flow and rSO2 for both the right (r = -.02, p = .851), and the left hemisphere (r = - .04, p = .618). The rSO2 values for ten patients who received > 10 mL/kg/min flow did not differ significantly from 130 patients who received 10 mL/kg/min or less for both the left hemisphere ( p = .135), and the right hemisphere ( p = .318). The ASCP flow was 5.1 (IQR:5.0- 6.5) mL/kg/min in five patients with, and 7.2 (IQR:5.8-8.3) mL/kg/min in 135 patients without a watershed infarction ( p = .098). Conclusions: There was no correlation between ASCP flow rate and rSO2 in patients with acute type A aortic dissection. Furthermore, ASCP flow below 10 mL/kg/min was not associated with a reduction in rSO2. Definitive associations between ASCP flow and neurological outcome after type A aortic dissection surgery need further investigation.

Bedside quantification of stroke volume (SV) and left ventricular ejection fraction (LVEF) is valuable in hemodynamically compromised patients. Miniaturized handheld ultrasound (HAND) devices are now available for clinical use. However, the performance level of HAND devices for quantified cardiac assessment is yet unknown. The aim of this study was to compare the validity of HAND measurements with standard echocardiography (SE) and three-dimensional echocardiography (3DE). Thirty-six patients were scanned with HAND, SE and 3DE. LVEF and SV quantification was done with automated software for the HAND, SE and 3DE dataset. The image quality of HAND and SE was evaluated by scoring segmental endocardial border delineation (2 = good, 1 = poor, 0 = invisible). LVEF and SV of HAND was evaluated against SE and 3DE using correlation and Bland–Altman analysis. The correlation, bias, and limits of agreement (LOA) between HAND and SE were 0.68 [0.46:0.83], 1.60% [− 2.18:5.38], and 8.84% [− 9.79:12.99] for LVEF, and 0.91 [0.84:0.96], 1.32 ml [− 0.36:4.01], 15.54 ml [− 18.70:21.35] for SV, respectively. Correlation, bias, and LOA between HAND and 3DE were 0.55 [0.6:0.74], − 0.56% [− 2.27:1.1], and 9.88% [− 13.29:12.17] for LVEF, and 0.79 [0.62:0.89], 6.78 ml [2.34:11.21], 12.14 ml [− 26.32:39.87] for SV, respectively. The image quality scores were 9.42 ± 2.0 for the apical four chamber views of the HAND dataset and 10.49 ± 1.7 for the SE dataset and (P < 0.001). Clinically acceptable accuracy, precision, and image quality was demonstrated for HAND measurements compared to SE. In comparison to 3DE, HAND showed a clinically acceptable accuracy and precision for LVEF quantification.