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Purpose: To introduce alternating current‐controlled, conductive ink‐printed marker that could be implemented with both custom and commercial interventional devices for device tracking under MRI using gradient echo, balanced SSFP, and turbo spin‐echo sequences. Methods: Tracking markers were designed as solenoid coils and printed on heat shrink tubes using conductive ink. These markers were then placed on three MR‐compatible test samples that are typically challenging to visualize during MRI scans. MRI visibility of markers was tested by applying alternating and direct current to the markers, and the effects of applied current parameters (amplitude, frequency) on marker artifacts were tested for three sequences (gradient echo, turbo spin echo, and balanced SSFP) in a gel phantom, using 0.55T and 1.5T MRI scanners. Furthermore, an MR‐compatible current supply circuit was designed, and the performance of the current‐controlled markers was tested in one postmortem animal experiment using the current supply circuit. Results: Direction and parameters of the applied current were determined to provide the highest conspicuity for all three sequences. Marker artifact size was controlled by adjusting the current amplitude, successfully. Visibility of a custom‐designed, 20‐gauge nitinol needle was increased in both in vitro and postmortem animal experiments using the current supply circuit. Conclusion: Current‐controlled conductive ink‐printed markers can be placed on custom or commercial MR‐compatible interventional tools and can provide an easy and effective solution to device tracking under MRI for three sequences by adjusting the applied current parameters with respect to pulse sequence parameters using the current supply circuit. [ABSTRACT FROM AUTHOR]

Aims: Pressure-volume (PV) loops have utility in the evaluation of cardiac pathophysiology but require invasive measurements. Recently, a time-varying elastance model to derive PV loops non-invasively was proposed, using left ventricular (LV) volume by cardiovascular magnetic resonance (CMR) and brachial cuff pressure as inputs. Validation was performed using CMR and pressure measurements acquired on the same day, but not simultaneously, and without varying pre-loads. This study validates the non-invasive elastance model used to estimate PV loops at varying pre-loads, compared with simultaneous measurements of invasive pressure and volume from real-time CMR, acquired concurrent to an inferior vena cava (IVC) occlusion., Methods and Results: We performed dynamic PV loop experiments under CMR guidance in 15 pigs ( n = 7 naïve, n = 8 with ischaemic cardiomyopathy). Pre-load was altered by IVC occlusion, while simultaneously acquiring invasive LV pressures and volumes from real-time CMR. Pairing pressure and volume signals yielded invasive PV loops, and model-based PV loops were derived using real-time LV volumes. Haemodynamic parameters derived from invasive and model-based PV loops were compared. Across 15 pigs, 297 PV loops were recorded. Intra-class correlation coefficient (ICC) agreement was excellent between model-based and invasive parameters: stroke work (bias = 0.007 ± 0.03 J, ICC = 0.98), potential energy (bias = 0.02 ± 0.03 J, ICC = 0.99), ventricular energy efficiency (bias = -0.7 ± 2.7%, ICC = 0.98), contractility (bias = 0.04 ± 0.1 mmHg/mL, ICC = 0.97), and ventriculoarterial coupling (bias = 0.07 ± 0.15, ICC = 0.99). All haemodynamic parameters differed between naïve and cardiomyopathy animals ( P < 0.05). The invasive vs. model-based PV loop dice similarity coefficient was 0.88 ± 0.04., Conclusion: An elastance model-based estimation of PV loops and associated haemodynamic parameters provided accurate measurements at transient loading conditions compared with invasive PV loops., (Published by Oxford University Press on behalf of the European Society of Cardiology 2024.)

MIRTH (Myocardial Intramural Remodeling by Transvenous Tether) is a transcatheter ventricular remodeling procedure. A transvenous tension element is placed within the walls of the beating left ventricle and shortened to narrow chamber dimensions. MIRTH uses 2 new techniques: controlled intramyocardial guidewire navigation and EDEN (Electrocardiographic Radial Depth Navigation). MIRTH caused a sustained reduction in chamber dimensions in healthy swine. Midventricular implants approximated papillary muscles. MIRTH shortening improved myocardial contractility in cardiomyopathy in a dose-dependent manner up to a threshold beyond which additional shortening reduced performance. MIRTH may help treat dilated cardiomyopathy. Clinical investigation is warranted., Competing Interests: This work was supported by the Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health USA (grant Z01-HL006040 to Dr Lederman). Drs Bruce and Lederman are coinventors on patents, assigned to National Institutes of Health, on MIRTH-related devices. Dr Rogers is a consultant and physician proctor for Edwards Lifesciences and Medtronic; is a Medtronic advisory board member; and has an equity interest in Transmural Systems. Drs Babaliaros and Greenbaum receive institutional research support from Abbott Vascular, Ancora Heart, Edwards Lifesciences, Gore Medical, Jena Valve, Medtronic, Polares Medical, Transmural Systems, and 4C Medical; receive consulting fees from Abbott Vascular, Edwards Lifesciences, and Medtronic; and have equity interest in Transmural Systems. Drs Campbell-Washburn, Herzka, and Lederman are investigators on a U.S. Government Cooperative Research and Development Agreement with Siemens. Siemens participated in the modification of the MRI system from 1.5-T to 0.55-T and provided investigational intracardiac echocardiography devices. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.