Emanuela Marcelli

First experimental evaluation of cardiac apex rotation with an epicardial coriolis force sensor.

Cardiac apex rotation, quantified by sophisticated techniques (radiopaque markers and tagged magnetic resonance), has been shown to provide a sensitive index of left ventricle (LV) dynamics. The authors describe the first experimental assessment of cardiac apex rotation using a gyroscopic sensor based on Coriolis force, epicardially glued on the apex. Dynamics of apex rotation were evaluated in a sheep at baseline, after a positive inotropic drug infusion, and after impairment of cardiac function induced by coronary ligation. To evaluate the efficacy of the sensor to monitor cardiac function, results were compared to contractility variations expressed by the maximum value of the first derivative of LV pressure (LVdP/dtMAX). After inotropic drug infusion, a parallel increasing trend resulted for LVdP/dtMAX, for the maximum value of angular velocity measured by the sensor, and for apex rotation angle derived from velocity signal (+146%, +155%, and +11% from baseline, respectively), whereas a decreasing trend of all three parameters resulted after coronary ligation (–35%, –31%, and –65%). The twist pattern also was altered from baseline. These initial results suggest that the use of an implantable rotation sensor based on Coriolis force can be an efficient and effective tool to assess LV torsional deformation both in normal and failing hearts.

Peak Endocardial Acceleration Reflects Heart Contractility Also in Atrial Fibrillation

Previous studies demonstrated that peak endocardial acceleration (PEA) in sinus rhythm is related to LV dP/dtmax. Until now, PEA was never evaluated during R‐R interval variations in AF. The aim of this study was to establish the behavior of PEA in AF and the relationship of PEA versus LV dP/dtmax. Six sheep (65 ± 6 kg) were instrumented with a LV Millar catheter and with an accelerometer lead. AF was induced and PEA, LV dP/dtmax, and ECG were monitored. AF persisted for 5 ± 1.3 minutes. From sinus rhythm to AF, the heart rate went from 92 ± 3 to 130 ± 35 beats/mm (P < 0.05), LV dP/dtmax from 684 ± 18 to 956 ± 344 mmHg/s (P = NS) and PEA from 0.82 ± 0.06 to 0.94 ± 0.33 g (P = NS). The correlation between PEA and LV dP/dtmax was significative in sinus rhythm (r = 0.7, P < 0.05) and in AF (r = 0.8, P < 0.05). A positive relationship was found between the preceding interval and PEA (r = 0.4 ± 0,07, P < 0.05) and LV dP/dtmax (r = 0.61 ± 0.08, P < 0.05), while a negative one was found between the prepreceding interval and both PEA (r =− 0.39 ± O.11.P < 0.05) and LV dP/dtmax (r =− 0.64 ± 0.05, P < 0.05). At the onset of AF, LV dP/dtmax and PEA showed similar changes: beat‐to‐beat correlation between PEA and LV dP/dtmax was high. As for LV dP/dtmax, PEA is positively related to the preceding interval and negatively related to the prepreceding interval. These data confirm that PEA reflects heart contractility also during AF and hold promise for the use of this sensor in therapeutic implantable devices.

Effect of Right Ventricular Pacing on Cardiac Apex Rotation Assessed by a Gyroscopic Sensor

To quantify cardiac apex rotation (CAR), the authors recently proposed the use of a Coriolis force sensor (gyroscope) as an alternative to other complex techniques. The aim of this study was to evaluate the effects of right ventricular (RV) pacing on CAR. A sheep heart was initially paced from the right atrium to induce a normal activation sequence at a fixed heart rate (AAI mode) and then an atrioventricular pacing was performed (DOO mode, AV delay = 60 ms). A small gyroscope was epicardially glued on the cardiac apex to measure the angular velocity (Ang V). From AAI to DOO pacing mode, an increase (+9.2%, p < 0.05) of the maximum systolic twisting velocity (Ang VMAX) and a marked decrease (–19.9%, p < 0.05) of the maximum diastolic untwisting velocity (Ang VMIN) resulted. RV pacing had negligible effects (–3.1%, p = 0.09) on the maximum angle of CAR, obtained by integrating Ang V. The hemodynamic parameters of systolic (LVdP/dtMAX) and diastolic (LVdP/dtMIN) cardiac function showed slight variations (–3.8%, p < 0.05 and +3.9%, p < 0.05, respectively). Results suggest that cardiac dyssynchrony induced by RV pacing can alter the normal physiological ventricular twist patterns, particularly affecting diastolic untwisting velocity.

Multi-Sense CardioPatch: A Wearable Patch for Remote Monitoring of Electro-Mechanical Cardiac Activity.

This study describes the conceptual design and the first prototype implementation of the Multi-Sense CardioPatch, a wearable multi-sensor patch for remote heart monitoring aimed at providing a more detailed and comprehensive heart status diagnostics. The system integrates multiple sensors in a single patch for detection of both electrical (electrocardiogram, ECG) and mechanical (heart sounds, HS) cardiac activity, in addition to physical activity (PA). The prototypal system also comprises a microcontroller board with a radio communication unit and it is powered by a Li-Ion rechargeable battery. Results from preliminary evaluations on healthy subjects have shown that the prototype can successfully measure electro-mechanical cardiac activity, providing useful cardiac indexes. The system has potential to improve remote monitoring of cardiac function in chronically diseased patients undergoing home-based cardiac rehabilitation programs.

A mechanical simulator of cardiac wall kinematics.

Aim of this study is to develop a mechanical simulator (MS) reproducing cardiac wall kinematics [i.e., radial (R), longitudinal (L) and rotational (RT) motions] to test piezoelectric gyroscopic sensors (GS) that are able to measure cardiac torsion that has proved to be a sensitive index of cardiac performance. The MS consists of three brushless motors controlled by a dedicated software either separately or simultaneously reproducing the three main cardiac wall movements (R, L, RT) obtained by implementing different physiologic or pathologic velocity profiles derived from in vivo data. GS accuracy (max % error) was experimentally tested by connecting it to the MS driven in velocity in different working conditions [i.e., cardiac period (515–1030 ms), RT angle (4–16 degrees), GS axis inclination (0–90 degrees) with respect to the cardiac rotation axis]. The MS reproduced the tested velocity profiles well. The GS showed high accuracy in measuring both physiologic and pathologic RT velocity profiles, whereas they proved insensitive to R and L motions. GS axis inclination influenced measurements; however, it was possible to correct this taking the inclination angle cosine into account. The MS proved to be a useful tool to study cardiac wall kinematics and test GS reliability with a view to in vivo application.

SacLab: A toolbox for saccade analysis to increase usability of eye tracking systems in clinical ophthalmology practice

PURPOSE Many open source software packages have been recently developed to expand the usability of eye tracking systems to study oculomotor behavior, but none of these is specifically designed to encompass all the main functions required for creating eye tracking tests and for providing the automatic analysis of saccadic eye movements. The aim of this study is to introduce SacLab, an intuitive, freely-available MATLAB toolbox based on Graphical User Interfaces (GUIs) that we have developed to increase the usability of the ViewPoint EyeTracker (Arrington Research, Scottsdale, AZ, USA) in clinical ophthalmology practice. METHODS SacLab consists of four processing modules that enable the user to easily create visual stimuli tests (Test Designer), record saccadic eye movements (Data Recorder), analyze the recorded data to automatically extract saccadic parameters of clinical interest (Data Analyzer) and provide an aggregate analysis from multiple eye movements recordings (Saccade Analyzer), without requiring any programming effort by the user. RESULTS A demo application of SacLab to carry out eye tracking tests for the analysis of horizontal saccades was reported. We tested the usability of SacLab toolbox with three ophthalmologists who had no programming experience; the ophthalmologists were briefly trained in the use of SacLab GUIs and were asked to perform the demo application. The toolbox gained an enthusiastic feedback from all the clinicians in terms of intuitiveness, ease of use and flexibility. Test creation and data processing were accomplished in 52±21s and 46±19s, respectively, using the SacLab GUIs. CONCLUSIONS SacLab may represent a useful tool to ease the application of the ViewPoint EyeTracker system in clinical routine in ophthalmology.

CathROB: A Highly Compact and Versatile Remote Catheter Navigation System

Several remote catheter navigation systems have been developed and are now commercially available. However, these systems typically require specialized catheters or equipment, as well as time-consuming operations for the system set-up. In this paper, we present CathROB, a highly compact and versatile robotic system for remote navigation of standard tip-steerable electrophysiology (EP) catheters. Key features of CathROB include an extremely compact design that minimizes encumbrance and time for system set-up in a standard cath lab, a force-sensing mechanism, an intuitive command interface, and functions for automatic catheter navigation and repositioning. We report in vitro and in vivo animal evaluation of CathROB. In vitro results showed good accuracy in remote catheter navigation and automatic repositioning (1.5 ± 0.6 mm for the left-side targets, 1.7 ± 0.4 mm for the right-side targets). Adequate tissue contact was achieved with remote navigation in vivo. There were no adverse events, including absence of cardiac perforation or cardiac damage, indicative of the safety profile of CathROB. Although further preclinical and clinical studies are required, the presented CathROB system seems to be a promising solution for an affordable and easy-to-use remote catheter navigation.

How to transform a fixed stroke alternating syringe ventricle into an adjustable elastance ventricle

Most devices used for bench simulation of the cardiovascular system are based either on a syringe-like alternating pump or an elastic chamber inside a fluid-filled rigid box. In these devices, it is very difficult to control the ventricular elastance and simulate pathologies related to the mechanical mismatch between the ventricle and arterial load (i.e., heart failure). This work presents a possible solution to transforming a syringe-like pump with a fixed ventricle into a ventricle with variable elastance. Our proposal was tested in two steps: (1) fixing the ventricle and the aorta and changing the peripheral resistance (PHR); (2) fixing the aorta and changing the ventricular elastance and the PHR. The signals of interest were acquired to build the ventricular pressure-volume (P-V) loops describing the different physiological conditions, and the end-systolic pressure-volume relationships (ESPVRs) were calculated with linear interpolation. The results obtained show a good physiological behavior of our mock for both steps. (1) Since the ventricle is the same, the systolic pressures increase and the stroke volumes decrease with the PHR: the ESPVR, obtained by interpolating the pressure and volume values at end-systolic phases, is linear. (2) Each ventricle presents ESPVR with different slopes depending on the ventricle elastance with a very good linear behavior. In conclusion, this paper demonstrates that a fixed stroke alternating syringe ventricle can be transformed into an adjustable elastance ventricle.

Quantitative Approach for the Analysis of Fusional Convergence Using Eye-Tracking and SacLab Toolbox

Fusional vergence is a disjunctive movement of the eyes that is made in order to obtain single vision. The aim of the study was to provide a quantitative and objective approach for analyzing the fusional convergence response using eye tracking (ET) technology and automatic data analysis provided by the intuitive SacLab toolbox previously developed by our group. We evaluated the proposed approach in a population of 26 subjects with normal binocular vision, who were tested with base-out prisms (magnitudes 4Δ, 6Δ, and 10Δ) in order to elicit fusional convergence response. Eye movements were recorded using the Viewpoint ET and analyzed using SacLab. Parameters describing both the vergence and the version components of the fusional response (convergence duration, CD; peak convergence velocity, PCV; number of intrusive saccades, NS; and mean saccadic amplitude, MSA) were automatically calculated and provided to clinicians for an objective evaluation. Results showed that the number of subjects achieving fusional convergence decreased with prism magnitude. For subjects achieving fusion CD and PCV increased significantly (p < 0.05) when increasing the prism magnitude. For NS and MSA, there were no significant changes when passing to 6Δ, but a significant increase resulted when passing to 10Δ (p < 0.05). Noninvasive ET associated with the intuitive SacLab toolbox may represent a valid option to objectively characterize the fusional vergence response in clinical setting. The analysis may be extended to patients with vergence disorders.

Navigation-guided resection of maxillary tumors: Can a new volumetric virtual planning method improve outcomes in terms of control of resection margins?

INTRODUCTION In the present study, our aim was to confirm the role of navigation-guided surgery in reducing the percentage of positive margins in advanced malignant pathologies of the mid-face, by introducing a new volumetric virtual planning method for resection. MATERIALS AND METHODS Twenty-eight patients were included in this study. Eighteen patients requiring surgery to treat malignant midface tumors were prospectively selected and stratified into two different study groups. Patients enrolled in the Reference Points Resection group (RPR - 10 patients) underwent resection planning using the anatomical landmarks on CT scan; patients enrolled in the Volume Resection group (VR - 8 patients) underwent resection using the new volumetric virtual planning method. The remaining 10 patients (Control group) were treated without the use of a navigation system. RESULTS In total, 127 margins were pathologically assessed in the RPR group, 75 in the VR group, and 85 in the control group. In the control group, 16% of the margins were positive, while in the RPR group the value was 9%, and in the VR group 1%. CONCLUSIONS The volumetric tumor resection planning associated to the navigation-guide resection appeared to be an improvement in terms of control of surgical margins in advanced tumors involving the mid-face.