Duration of the preejection phase is less preload dependent and therefore a better marker of acute response to cardiac resynchronization therapy than maximum pressure rise

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): EU’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie

Background

There is no consensus on which haemodynamic marker should be used to quantify acute response to cardiac resynchronization therapy (CRT) during implantation of the device. CRT has been shown to acutely reduce left ventricular (LV) end systolic as well as end-diastolic volume (EDV), precluding the use of preload dependent markers such as LV maximum pressure rise (dP/dtmax).

Purpose

As resynchronization will abolish the uncoordinated regional early systolic contractions of the LV, it will shorten the time to maximal pressure rise and aortic valve opening. For this reason, the purpose of this study was to investigate if duration from the time-point of ventricular pacing to dP/dtmax is less preload dependent and a better marker of acute response to CRT than dP/dtmax by comparing how the 2 markers reflected LV function during different CRT configurations.

Methods

LV pressure by micromanometer and volume by sonomicrometry were measured in 6 anaesthetized canines with left bundle branch block. Transient caval constrictions were performed to vary preload. Preload dependency of the 2 markers was compared by normalizing their values and calculating their relations to EDV. In 4 of the animals, biventricular pacing was performed at 3 different pacing sites with variations in atrioventricular delays that provided a range of response to CRT. To correct for acute

changes in preload by CRT, stroke volume (SV) at identical EDV found from transient caval constrictions, were assessed and used as reference to grade improved LV function. Linear regression analysis was used to assess the correlation of both the duration of the preejection phase and dP/dtmax with SV.

Results

The duration of the preejection phase varied less with changes in preload compared to dP/dtmax: the slopes of their relation to EDV were -0.6 ± 0.7 %/ml and 4.8 ± 2.1 %/ml (p = 0.004), respectively. Turning CRT on, acutely reduced EDV from 74 ± 16 to 69 ± 17 ml (p < 0.001) at the best pacing configuration. For the different pacing sites and settings, there was a consistent relation in all animals where the preejection phase shortened as SV increased (average r2 = 0.75) (Figure A). dP/dtmax showed no clear relation to SV (average r2 = 0.22) and included cases with both negative and positive slopes (Figure B).

Conclusions

The duration of the preejection phase correlated with changes in LV function induced by CRT while dP/dtmax performed poorly as preload was changed. Hence, the novel timing parameter was less preload dependent and may be a better marker for assessing acute response to CRT. Abstract Figure.

Mixed reality holograms for heart surgery planning: first user experience in congenital heart disease

AIMS

Proof of concept and feasibility study for preoperative diagnostic use of mixed reality (MR) holograms of individual 3D heart models from standard cardiac computed tomography angiograms (CTA) images. Optimal repair for complex congenital heart disease poses high demands on 3D anatomical imagination. Three-dimensional printed heart models are increasingly used for improved morphological understanding during surgical and interventional planning. Holograms are a dynamic and interactive alternative, probably with wider applications.

METHODS AND RESULTS

A 3D heart model was segmented from CTA images in a patient with double outlet right ventricle and transposition of the great arteries (DORV-TGA). The hologram was visualized in the wearable MR platform HoloLens® for 36 paediatric heart team members who filled out a diagnostic and quality rating questionnaire. Morphological and diagnostic output from the hologram was assessed and the 3D experience was evaluated. Locally developed app tools such as hologram rotation, scaling, and cutting were rated. Anatomy identification and diagnostic output was high as well as rating of 3D experience. Younger and female users rated the app tools higher.

CONCLUSION

This preliminary study demonstrates that MR holograms as surgical planning tool for congenital heart disease may have a high diagnostic value and contribute to understanding complex morphology. The first users experience of the hologram presentation was found to be very positive, with a preference among the female and the younger users. There is potential for improvement of the hologram manipulation tools.

Species distribution models contribute to determine the effect of climate and interspecific interactions in moving hybrid zones

Climate is a major factor delimiting species' distributions. However, biotic interactions may also be prominent in shaping geographical ranges, especially for parapatric species forming hybrid zones. Determining the relative effect of each factor and their interaction of the contact zone location has been difficult due to the lack of broad scale environmental data. Recent developments in species distribution modelling (SDM) now allow disentangling the relative contributions of climate and species' interactions in hybrid zones and their responses to future climate change. We investigated the moving hybrid zone between the breeding ranges of two parapatric passerines in Europe. We conducted SDMs representing the climatic conditions during the breeding season. Our results show a large mismatch between the realized and potential distributions of the two species, suggesting that interspecific interactions, not climate, account for the present location of the contact zone. The SDM scenarios show that the southerly distributed species, Hippolais polyglotta, might lose large parts of its southern distribution under climate change, but a similar gain of novel habitat along the hybrid zone seems unlikely, because interactions with the other species (H. icterina) constrain its range expansion. Thus, whenever biotic interactions limit range expansion, species may become 'trapped' if range loss due to climate change is faster than the movement of the contact zone. An increasing number of moving hybrid zones are being reported, but the proximate causes of movement often remain unclear. In a global context of climate change, we call for more interest in their interactions with climate change.

The Effect of Interaction Force Estimation on Performance in Bilateral Teleoperation

Measuring interaction forces in bilateral teleoperation systems may be difficult, due to size and cost restrictions on the force sensors. Obtaining the interaction forces by estimation can be a viable alternative. The primary contribution of this paper is the study of the effect of interaction force estimation on performance in bilateral teleoperation. A distinction is made between the obvious effect as a result of inaccurate estimation, and the less obvious effect as a result of the inherent theoretical properties of a system that has two points of interaction with its surroundings (a teleoperator) as opposed to one point of interaction (single robot). Specifically, the existence of a singularity property is pointed out, at which interaction force estimation is impossible, and close to which it may be infeasible. The secondary contribution of the paper is the Force Sensor Free (FSF) transformation for linear teleoperation systems, which is an automated procedure that turns a teleoperation controller with force sensing into an equivalent controller with force estimation. An experiment is reported whose objective is to validate the operation of the FSF transformation on a real teleoperator.

Detection of myocardial ischaemia by epicardial accelerometers in the pig

BACKGROUND

We describe a novel technique for continuous real-time assessment of myocardial ischaemia using a three-axis accelerometer.

METHODS

In 14 anaesthetized open-chest pigs, two accelerometers were sutured on the left ventricle (LV) surface in the perfusion areas of the left anterior descending (LAD) and circumflex (CX) arteries. Acceleration was measured in the longitudinal, circumferential, and radial directions, and the corresponding epicardial velocities were calculated. Regional LV dysfunction was induced by LAD occlusion for 60 s. Global LV function was altered by nitroprusside, epinephrine, esmolol, and fluid loading. Epicardial velocities were compared with strain by echocardiography during LAD occlusion and with aortic flow and LV dP/dt(max) during interventions on global LV function.

RESULTS

LAD occlusion induced ischaemia, shown by lengthening in systolic strain in the LV apical anterior region (P<0.01) and concurrent changes in LAD accelerometer circumferential velocities during systole (P<0.01) and during the isovolumic relaxation phase (P<0.01). The changes in accelerometer circumferential velocities during LAD occlusion were greater compared with the changes during the interventions on global function (P<0.01). For the LAD accelerometer circumferential velocities, sensitivity was 94-100% and specificity was 92-94% in detecting ischaemia.

CONCLUSIONS

Myocardial ischaemia can be detected with epicardial three-axis accelerometers. The accelerometer had the ability to distinguish ischaemia from interventions altering global myocardial function. This novel technique may be used for continuous real-time monitoring of myocardial ischaemia during and after cardiac surgery.

Measurements of heart motion using accelerometers

We have used acceleration sensors to monitor the heart motion during surgery. A three-axis accelerometer was made from two commercially available two-axis sensors, and was used to measure the heart motion in anesthetized pigs. The heart moves due to both respiration and heart beating. The heart beating was isolated from respiration by high-pass filtering at 1.0 Hz, and heart wall velocity and position were calculated by numerically integrating the filtered acceleration traces. The resulting curves reproduced the heart motion in great detail, noise was hardly visible. Events that occurred during the measurements, e.g. arrhythmias and fibrillation, were recognized in the curves, and confirmed by comparison with synchronously recorded ECG data. We conclude that acceleration sensors are able to measure heart motion with good resolution, and that such measurements can reveal patterns that may be an indication of heart circulation failure.

Virtual reality simulator training equals mechanical robotic training in improving robot-assisted basic suturing skills

BACKGROUND

This study aimed to investigate the effect of a virtual reality simulator on the learning of basic robotic suturing skills.

METHODS

Two randomized groups of students underwent a controlled training program. Both groups completed an identical test before and after training. The increase in the number of stitches placed during the pretest and posttest was used as an objective measure of the training effect. To evaluate the subjective feeling of understanding and mastering, the students indicated this on a visual analog scale.

RESULTS

Both groups showed a significant increase in the number of stitches placed during the posttest, and an increase in subjective feeling of understanding and mastering. The increase did not differ between the groups, indicating that the virtual reality simulator equaled the mechanical trainer in training of robotic suturing technique.

CONCLUSIONS

Training in basic robot-assisted suturing skills using a virtual reality simulator without additional training equaled training using a mechanical simulator.

Digital trainer developed for robotic assisted cardiac surgery

Robotic systems for cardiac surgery have been introduced in clinical trials to facilitate minimally invasive techniques. Widespread use of surgical robotics necessitates new training methods to improve skills and continue practicing as the robotic systems are frequently being upgraded. Today, robotic training is performed on expensive animal models. An integration of a digital trainer with the two present robotic systems applied in coronary artery bypass procedures on beating heart requires real time simulation of tissue mechanics, sutures, instruments and bleeding. However, it requires no extra haptic device, since the robotic master is the haptic apparatus itself. By developing new data structures and parametric geometry descriptions we have demonstrated the possibility of obtaining surgical simulation on a standard PC Linux system. This technology is beneficial when simulation is exploited over a network with limited bandwidth, especially when it comes to the handling of soft tissue dynamics.

[Image guided and robotic treatment--the advance of cybernetics in clinical medicine]

The introduction of advanced technology in hospitals has changed the treatment practice towards more image guided and minimal invasive procedures. Modern computer and communication technology opens up for robot aided and pre-programmed intervention. Several robotic systems are in clinical use today both in microsurgery and in major cardiac and orthopedic operations. As this trend develops, professions which are new in this context such as physicists, mathematicians and cybernetic engineers will be increasingly important in the treatment of patients.