Michael Vandenheuvel

A pathophysiological approach towards right ventricular function and failure.

The scope of this review is to provide a pathophysiological summary of perioperative right ventricular function and failure. In recent decades, the importance of right ventricular function in the perioperative period has been established. However, much of our current knowledge on the management of this clinical entity is based on extrapolation of results from left ventricular research, although biventricular physiology is known to be markedly different in many aspects. Here, on the basis of a thorough literature search, we review theoretical as well as practical aspects of perioperative right ventricular failure. After underlining the importance of this topic, we review basic right ventricular anatomy and physiology, with an emphasis on the role of ventricular interaction. Next, potential causes of perioperative right ventricular failure are discussed. The emphasis of this review is on the perioperative anaesthetic considerations, ranging from preoperative assessment through intraoperative monitoring to specific contemporary therapeutic options of perioperative right ventricular failure.

Three-dimensional myocardial strain estimation from volumetric ultrasound: Experimental validation in an animal model

Although real-time three-dimensional echocardiography has the potential to allow for more accurate assessment of global and regional ventricular dynamics compared to the more traditional two-dimensional ultrasound examinations, it still requires rigorous testing and validation against other accepted techniques should it breakthrough as a standard examination in routine clinical practice. Very few studies have looked at a validation of regional functional indices in an in-vivo context. The aim of the present study therefore was to validate a previously proposed 3D strain estimation-method based on elastic registration of subsequent volumes on a segmental level in an animal model. Volumetric images were acquired with a GE Vivid7 ultrasound system in five open-chest sheep instrumented with ultrasonic microcrystals. Radial (εRR), longitudinal (εLL) and circumferential strain (εCC) were estimated during four stages: at rest, during esmolol and dobutamine infusion, and during acute ischemia. Moderate correlations for εLL (r=0.63; p<;0.01) and εCC (r=0.60; p=0.01) were obtained, whereas no significant radial correlation was found. These findings are comparable to the performance of the current state-of-the-art commercial 3D speckle tracking methods.

Motion and deformation estimation of cardiac ultrasound sequences using an anatomical B-spline transformation model

We present a novel method for tracking myocardial motion in 2D ultrasound sequences based on non-rigid registration using an anatomical free-form deformation (AFFD) model where the basis functions are locally oriented along the radial and circumferential direction of the left ventricle (LV). This formulation allows us to model the LV motion more naturally compared to previously proposed FFDs defined on a regular Cartesian grid (CFFD). In this paper we compare the performance of the AFFD against the CFFD model in an in-vivo setting. Short-axis images were acquired in five open-chest sheep using sonomicrometry as ground-truth deformation estimates. We demonstrated that regional end-systolic strain values assessed with the AFFD model are comparable with CFFD, while also displaying a statistically lower drift at the end of the cardiac cycle and a better agreement with a manual end-systolic reference. Furthermore, tracking using AFFD was visually more appealing to clinical experts.

Performance of elastic image registration against speckle tracking for 2D cardiac motion and strain estimation

Despite the availability of multiple solutions for assessing myocardial strain, little is currently known about the relative performance of the different methods. In this study, we sought to contrast two popular strain estimation techniques directly (block-matching and registration) in an in-vivo setting by comparing both to a gold standard reference measurement. Mid short-axis images were acquired with a GE Vivid7 ultrasound system in five open-chest sheep instrumented with ultrasonic microcrystals. Radial (∈RR) and circumferential strain (∈CC) were estimated during four stages: at rest, during esmolol and dobutamine infusion, and during acute ischemia. While the correlations of a well-validated block matching approach and the elastic registration method were comparable for the ∈CC component (0.82 vs 0.81 respectively), imposing regularization during the motion estimation process (i.e. as embedded in the elastic registration method), showed to be advantageous to estimate ∈RR as it improved performance significantly (0.63 vs 0.83; p=0.05). Moreover, the bias and the limits of agreement were also smaller in this direction (p<;0.01).

In-vivo validation of a new clinical tool to quantify three-dimensional myocardial strain using ultrasound

Three-dimensional (3D) strain analysis based on real-time 3-D echocardiography (RT3DE) has emerged as a novel technique to quantify regional myocardial function. The goal of this study was to evaluate accuracy of a novel model-based 3D tracking tool (eSie Volume Mechanics, Siemens Ultrasound, Mountain View, CA, USA) using sonomicrometry as an independent measure of cardiac deformation. Thirteen sheep were instrumented with microcrystals sutured to the epi- and endocardium of the inferolateral left ventricular wall to trace myocardial deformation along its three directional axes of motion. Paired acquisitions of RT3DE and sonomicrometry were made at baseline, during inotropic modulation and during myocardial ischemia. Accuracy of 3D strain measurements was quantified and expressed as level of agreement with sonomicrometry using linear regression and Bland–Altman analysis. Correlations between 3D strain analysis and sonomicrometry were good for longitudinal and circumferential strain components (r = 0.78 and r = 0.71) but poor for radial strain (r = 0.30). Accordingly, agreement (bias ± 2SD) was −5 ± 6 % for longitudinal, −5 ± 7 % for circumferential, and 15 ± 19 % for radial strain. Intra-observer variability was low for all components (intra-class correlation coefficients (ICC) of respectively 0.89, 0.88 and 0.95) while inter-observer variability was higher, in particular for radial strain (ICC = 0.41). The present study shows that 3D strain analysis provided good estimates of circumferential and longitudinal strain, while estimates of radial strain were less accurate between observers.

Effects of tachycardia, increased afterload and contractility on right ventricular myocardial oxygen balance in acutely instrumented pigs: 4AP3‐7

Goal We assessed the relative role of right coronary blood flow versus oxygen extraction ratio (OER) during hemodynamic conditions associated with increased RV oxygen demand as they may occur perioperatively. Background Importance of right ventricular (RV) failure in the perioperative setting: Morbidity and mortality (chronic heart failure, ARDS, PHT) Perioperative mortality higher in RV failure Similar incidence as LV failure RV ≠ LV: Anatomic and physiologic differences