QT interval variability in body surface ECG: measurement, physiological basis, and clinical value: position statement and consensus guidance endorsed by the European Heart Rhythm Association jointly with the ESCWorking Group on Cardiac Cellular Electrophysiology

This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interval variability (QTV) on surface electrocardiograms. The text covers measurement principles, physiological basis, and clinical value of QTV. Technical considerations include QT interval measurement and the relation between QTV and heart rate variability. Research frontiers of QTV include understanding of QTV physiology, systematic evaluation of the link between QTV and direct measures of neural activity, modelling of the QTV dependence on the variability of other physiological variables, distinction between QTV and general T wave shape variability, and assessing of the QTV utility for guiding therapy. Increased QTV appears to be a risk marker of arrhythmic and cardiovascular death. It remains to be established whether it can guide therapy alone or in combination with other risk factors. QT interval variability has a possible role in non-invasive assessment of tonic sympathetic activity

Video Kinematic Evaluation: new insights on the cardiac mechanical function

The cardiac mechanical function plays a critical role in governing and regulating its performance under both normal and pathological conditions. The left ventricle has historically received more attention in both congenital and acquired heart diseases and was considered as the mainstay of normal hemodynamics. However, over the past few decades, there has been increasing recognition of the pivotal role of the right ventricle in determining functional performance status and prognosis in multiple conditions. Nonetheless, the ventricles should not be considered separately as they share the septum, are encircled with common myocardial fibers and are surrounded by the pericardium. Thus, changes in the filling of one ventricle may alter the mechanical function of its counterpart. This ventricular interdependence remains even after the removal of the pericardium because of constrictive pericarditis or during open chest surgery. Interestingly, during open chest surgery, only the right ventricle mechanical activity is visually checked by the surgeon and cardiologist due to the absence of an intraoperative imaging technique able to evaluate its complex function. Noteworthy, most of the imaging techniques available to clinicians are established for the assessment of the left ventricle, with the ejection fraction being the most used parameter. However, this value is a measure of global systolic function which comes short in identifying regional myocardial impairment and the mechanical contraction. Therefore, new approaches are needed to deeply investigate the mechanics of both ventricles and correctly assess the cardiac mechanical performance. In this thesis, I studied the mechanical function of the left ventricle through different modalities of cardiac magnetic resonance and employed an innovative imaging technique for the assessment of the right ventricle mechanical function during open chest surgery

VIDEO KINEMATIC EVALUATION OF THE HEART (VI.KI.E.): AN IDEA, A PROJECT, A REALITY

Introduction: The technological development of the last 20 years pledges the intensity of efforts for implementing novel imaging contactless modalities that accelerate the translation from the research bench to the patient bedside, especially in the cardiac field. In this work, a novel intraoperative cardiac imaging approach, named Video Kinematic Evaluation (Vi.Ki.E.), is presented and explained in detail. This technology is able to monitor, contactless, the cardiac mechanics and deformation in-situ during heart surgery. Cardiac kinematics have been deeply evaluated ranging from the experimental animal approach to the human myocardial pathologies in both left and right ventricles. Methods: Vi.Ki.E. can be defined \u201cas simple as innovative\u201d. It only consists of a high-speed camera placed upon an exposed beating heart in-situ to record cardiac cycles. Afterwards a tracker software is used on the recorded video to follow the epicardial tissue movements. This tracker provides information about trajectories of the epicardium and, thanks to a custom-made algorithm, the technology supplies heart mechanical information such as: Force of contraction or cardiac fatigue, Energy expenditure, Contraction velocity, displacement of the marker and epicardial torsion. This approach has been tested on 21 rats (9 ischemia/reperfusion and/or for validation, 12 for the gender difference study) and on 37 patients who underwent different surgery between 2015 and 2019. In detail 10 patients underwent Coronary Artery Bypass Grafting, 12 underwent Valve Replacement after Tetralogy of Fallot correction surgery, 6 implanted a Left Ventricular Assist Device (1 is moved in the case study section), 6 patients with Hypoplastic Heart Syndrome underwent GLENN or FONTAN surgery, 2 patients underwent Heart Transplantation and finally 1 patient underwent double valve replacement (this patient is moved into case study section). Results: The patients\u2019 results demonstrated that the Vi.Ki.E. technology was able to discriminate, with statistic potency, the kinematic differences before and after the surgery in real-time, suggesting possible clinical implications in the treatment of the patients before the chest closure and/or in the intensive care unit. As it concerns the experimental animals, the results are the basics of the validation technology. Some of them were used as accepted model in comparison with the Vi.Ki.E. results on patients. Conclusions: In conclusion, this study has shown that Vi.Ki.E. is a safe and contactless technology with promising possible clinical application. The ease in the evaluation and the algorithm-based approach makes Video Kinematic Evaluation a widespread technique from cellular level to human cases covering the entire experimental field with in-vivo evaluation and possibly Langendorff/Working Heart approaches

VIDEO KINEMATIC EVALUATION OF THE HEART (VI.KI.E.): AN IDEA, A PROJECT, A REALITY

Introduction: The technological development of the last 20 years pledges the intensity of efforts for implementing novel imaging contactless modalities that accelerate the translation from the research bench to the patient bedside, especially in the cardiac field. In this work, a novel intraoperative cardiac imaging approach, named Video Kinematic Evaluation (Vi.Ki.E.), is presented and explained in detail. This technology is able to monitor, contactless, the cardiac mechanics and deformation in-situ during heart surgery. Cardiac kinematics have been deeply evaluated ranging from the experimental animal approach to the human myocardial pathologies in both left and right ventricles. Methods: Vi.Ki.E. can be defined \u201cas simple as innovative\u201d. It only consists of a high-speed camera placed upon an exposed beating heart in-situ to record cardiac cycles. Afterwards a tracker software is used on the recorded video to follow the epicardial tissue movements. This tracker provides information about trajectories of the epicardium and, thanks to a custom-made algorithm, the technology supplies heart mechanical information such as: Force of contraction or cardiac fatigue, Energy expenditure, Contraction velocity, displacement of the marker and epicardial torsion. This approach has been tested on 21 rats (9 ischemia/reperfusion and/or for validation, 12 for the gender difference study) and on 37 patients who underwent different surgery between 2015 and 2019. In detail 10 patients underwent Coronary Artery Bypass Grafting, 12 underwent Valve Replacement after Tetralogy of Fallot correction surgery, 6 implanted a Left Ventricular Assist Device (1 is moved in the case study section), 6 patients with Hypoplastic Heart Syndrome underwent GLENN or FONTAN surgery, 2 patients underwent Heart Transplantation and finally 1 patient underwent double valve replacement (this patient is moved into case study section). Results: The patients\u2019 results demonstrated that the Vi.Ki.E. technology was able to discriminate, with statistic potency, the kinematic differences before and after the surgery in real-time, suggesting possible clinical implications in the treatment of the patients before the chest closure and/or in the intensive care unit. As it concerns the experimental animals, the results are the basics of the validation technology. Some of them were used as accepted model in comparison with the Vi.Ki.E. results on patients. Conclusions: In conclusion, this study has shown that Vi.Ki.E. is a safe and contactless technology with promising possible clinical application. The ease in the evaluation and the algorithm-based approach makes Video Kinematic Evaluation a widespread technique from cellular level to human cases covering the entire experimental field with in-vivo evaluation and possibly Langendorff/Working Heart approaches