E. Marcelli

Validation of a peak endocardial acceleration-based algorithm to optimize cardiac resynchronization: early clinical results

Aims Cardiac resynchronization therapy (CRT) involves time-consuming procedures to achieve an optimal programming of the system, at implant as well as during follow-up, when remodelling occurs. A device equipped with an implantable sensor able to measure peak endocardial acceleration (PEA) has been recently developed to monitor cardiac function and to guide CRT programming. During scanning of the atrioventricular delay (AVD), PEA reflects both left ventricle (LV) contractility (LV dP/dtmax) and transmitral flow. A new CRT optimization algorithm, based on recording of PEA (PEAarea method) was developed, and compared with measurements of LV dP/dtmax, to identify an optimal CRT configuration. Methods and results We studied 15 patients in New York Heart Association classes II–IV and with a QRS duration >130 ms, who had undergone implantation of a biventricular (BiV) pulse generator connected to a right ventricular (RV) PEA sensor. At a mean of 39 ± 15 days after implantation of the CRT system, the patients underwent cardiac catheterization. During single-chamber LV or during BiV stimulation, with initial RV or LV stimulation, and at settings of interventricular intervals between 0 and 40 ms, the AVD was scanned between 60 and 220 ms, while LV dP/dtmax and PEA were measured. The area of PEA curve (PEAarea method) was estimated as the average of PEA values measured during AVD scanning. A ≥10% increase in LV dP/dtmax was observed in 12 of 15 patients (80%), who were classified as responders to CRT. In nine of 12 responders (75%), the optimal pacing configuration identified by the PEAarea method was associated with the greatest LV dP/dtmax. Conclusion The concordance of the PEAarea method with measurements of LV dP/dtmax suggests that this new, operator-independent algorithm is a reliable means of CRT optimization.

A novel telerobotic system to remotely navigate standard electrophysiology catheters

Remote manipulation of electrophysiology (EP) catheters by means of magnetically-guided or robotically controlled navigation systems has been recently proposed; however, these systems usually require dedicated catheters and devices. This study aims at evaluating the feasibility of using a novel Telerobotic System (TS) to remotely manipulate standard steerable EP catheters. In order to prevent cardiac tissue damage the TS was equipped with a force sensor to measure the resistance encountered by the catheter while advancing. The use of this novel TS was evaluated in three sheep, by performing remote navigation of a standard EP catheter to selected catheter-endocardium contact targeted sites in the right atrium. Remote catheter navigation by means of the TS was achieved for all targets and the force sensor showed to provide reliable information about catheter advancing and indication about catheter-endocardium contact.

Initial experience with a telerobotic system to remotely navigate and automatically reposition standard steerable EP catheters.

The use of robotic systems in cardiac interventional procedures is growing. The insertion and maneuvering in the human body of electrophysiology (EP) catheters is currently carried out manually under fluoroscopic guidance, resulting in operator fatigue and prolonged x-ray exposure. We report our initial animal experience with a novel telerobotic system (TS) to remotely navigate and automatically reposition standard steerable EP catheters within the heart. We developed a TS able to guide, as a “robotic hand,” EP catheters without the need of dedicated catheters and cumbersome devices. During tests on three sheep, catheter navigation and repositioning to 12 predefined endocardial targets were previously performed by conventional manual procedure and then using the TS implemented with an automatic catheter repositioning function. All the predefined targets were reached under fluoroscopy visualization, and procedural times were measured during catheter navigation and repositioning. The use of the TS slightly reduced the time necessary for catheter navigation compared with the conventional manual procedure (13.0 ± 5.6 vs 16.1 ± 6.4 seconds, p < 0.001) and significantly decreased the time for a precise catheter repositioning (9.2 ± 2.5 vs 17.8 ± 7.1 sec, p < 0.001). The TS proved to be a promising tool for remote navigation of standard EP catheters reducing the time necessary for catheter repositioning.

Assessment of cardiac rotation by means of gyroscopic sensors

During the cardiac cycle, contraction of the helically oriented myocardial fibers results in torsion, a wringing motion as the cardiac apex rotates with respect to the base about the left ventricle (LV) long axis. We evaluated in animals the use of gyroscopic sensors to quantify cardiac rotation, which was demonstrated to be a sensitive index of cardiac function. Three gyroscopes were epicardially glued at different levels along the LV long axis (apex, middle, base) to assess LV twist dynamics: angular velocity (Ang V) and angle of cardiac rotation (angle) were measured and evaluated against hemodynamic measurements of LV pressure (LVP, LVdP/dt), at baseline and after acute ischemia induced by coronary ligation. Results demonstrated the feasibility of assessing cardiac rotation and LV twist alterations by means of gyroscopic sensors, especially at apical level: compared with baseline, acute ischemia caused a significant decrease of both Angle and the maximum value of Ang V (mean variation of -37plusmn6% and -21plusmn4%, respectively); a concomitant reduction of LVdP/dtMAX (-43plusmn4%) was observed.

AN ENDOCARDIAL ACCELERATION SENSOR FOR MONITORING CARDIAC FUNCTION OF ISCHEMIC HEARTS

Previous experimental studies demonstrated that in normal hearts, Peak Endocardial Acceleration (PEA), during isovolumic contraction phase, measured with an endocardial sensor (Best, Sorin) in the right ventricle (RV), tracks changes of left ventricular (LV) contractility. Aim of the study: To assess if PEA also tracks LV contractility changes in ischemic hearts resulting from coronary microembolizations (ME). Methods: Under general anaesthesia, six adult beagle dogs (12 ± 2 kg) were instrumented for chronic monitoring of LV pressure, ECG and PEA. Latex beads mixed with fluoroscopy dye were injected into the circumflex coronary artery to cause LV ischemia. Before and after ME, incremental dobutamine infusions were performed to evaluate the contractile response to adrenergic stimulation. Results: A significant correlation between PEA and LVdP/dtmax was observed before and after ME. Such a strong correlation was maintained even during adrenergic stimulation (r = 0.83 to 0.99, p < 0.001). The sensor PEA appears to be an effective means for the chronic monitoring of the mechanical function of ischemic hearts.

IMPLANTABLE SENSORS TO ASSESS CARDIAC FUNCTION

The quest to discover effective methodologies to monitor the course of disease and response to therapeutic agents in patients with chronic heart failure continues. Clinical trials of specific therapeutic agents have shown efficacy in large groups of patients, but the outcome even with the most effective agents is recognized to be heterogeneous for largely unexplained reasons. The idea that the treatment of individual patients with heart failure could be guided by serial measurements of surrogate end points for mortality and morbidity remains attractive to clinicians. A new approach for clinicians is the guiding of heart failure care by hemodynamic implantable sensors, and in this paper, a brief review of the implantable technologies available to assess cardiac function for monitoring the course of chronic heart failure (CHF) is presented. Early results suggest that measurements arising from these implantable devices should help in guiding the long-term management of CHF patients. Careful consideration of measurements to make, end points to assess, and therapy in control patients will be essential in validating new approaches.

Is “silent ischemia” detectable by endocardial pacemaker leads?

The purpose of the following pilot study is to evaluate the possibility to detect the asymptomatic ischemic episodes which often precede dangerous events by means of endocardial signals. Intracardiac electrograms (IEGMs) have been detected in patients undergoing percutaneous transluminal coronary angioplasty (PTCA), a procedure during which ischemic episodes are induced. For 10 patients IECGs have been examined and compared with the surface 12-lead ECGs, used in current clinical practice to make a diagnosis of ischemia. This work takes part in a project (Body Worn) aimed at planning a prompt aid system for patients at high cardiovascular risk implanted with a pacemaker. In case of abnormalities in the endocardial signals detected by pacemaker leads, the intervention procedure is thought to be activated. However, results from primary data show that a diagnosis of silent ischemia cannot be made on the basis of the only IEGMs.

Assessment of cardiac apex kinematics using a real-time 3D magnetic tracking system

The assessment of left ventricular apex (LVA) kinematics throughout the cardiac cycle could be useful for evaluating cardiac performance and efficiency. We proposed and evaluated in a sheep the use of a real-time 3D magnetic tracking system for the analysis of LVA kinematics. LVA kinematics was assessed using a real-time 3D magnetic tracking system, whose sensor was epicardially glued on the exposed LVA. Two indexes were calculated from the 3-Dimensional apex path traced by the magnetic sensor: the 3D Apex Path Length (3DAPL, length of 3D apex path) and the 3D Apex Path Volume (3DAPV, volume containing 3D apex path). Hemodynamic index of cardiac contractility (LVdP/dtMAX) was derived from Left Ventricular Pressure (LVP) measurement and evaluated against LVA kinematics parameters, at baseline and after acute ischemia, experimentally induced by coronary ligation. Results showed an opposite trend between LV hemodynamics and LVA kinematics: in the ischemic heart an increase of both 3DAPL (+24.5%) and 3DAPV (+151.7%) occurred compared with baseline, while LVdP/dtMAX decreased (-36.9%).