Early discharge and home treatment of patients with acute pulmonary embolism in the tertiary care setting.

Acute pulmonary embolism (PE) is a potentially life-threatening disease. Current guidelines suggest risk-adapted management. Hospitalization is required for intermediate- and high-risk patients. Early discharge and home treatment are considered safe in the majority of low-risk patients. In this study, we describe characteristics, discharge, and outcome of outpatients diagnosed with acute PE at a tertiary care center. All outpatients undergoing computed tomography pulmonary angiography or ventilation/perfusion lung scan between 01.01.2016 and 31.12.2019 at the University Hospital Vienna, Austria, were screened for a PE diagnosis. Electronic patient charts were used to extract characteristics, clinical course, and outcomes. Within the 4-year period, 709 outpatients (median age: 62 years, 50% women) were diagnosed with PE. Thirty-three (5%) patients were classified as high-risk, 159 (22%) as intermediate-high, 332 (47%) as intermediate-low, and 185 (26%) as low-risk PE according to the European Society of Cardiology risk stratification. In total, 156 (22%) patients (47% with low-risk and 20% with intermediate-low-risk PE) were discharged as outpatients and received home treatment. Rates for home treatment increased 2.4-fold during the study period. Thirty-day mortality in the entire population was 4.9%. All low-risk patients and all but one patient with home treatment survived the first 30 days. Home treatment significantly increased over time and seems to be safe in routine clinical practice. Notably, one in five intermediate-low-risk patients was discharged immediately, suggesting that a subpopulation of intermediate-low-risk patients may also be eligible for home treatment.

Safety considerations for magnetic fields of 10 mT to 100 mT amplitude in the frequency range of 10 kHz to 100 kHz for magnetic particle imaging.

Magnetic particle imaging (MPI) is a new imaging modality using oscillating magnetic fields in the frequency range of 10 kHz to 100 kHz. The duration of data acquisition becomes smaller, and signal-to-noise ratio improves if the amplitude of these fields is increased - technically amplitudes of up to 100 mT might be feasible for human-sized systems. On the other hand, with increasing field strength, adverse health effects must be expected: oscillating magnetic fields can stimulate nerves and muscle and heat up tissue. Thresholds for stimulation with magnetic fields in this frequency range are not precisely known, neither is the local temperature rise following exposure. The ICNIRP guidelines define reference levels for magnetic field exposure for the general public that contain large safety factors - for medical diagnostics, they might be exceeded for a short time. In this article, research and guidelines in this field are briefly reviewed, and new results are presented in order to contribute to a future definition of safety limits for oscillating magnetic fields in MPI.

Experimental thresholds of magnetically induced currents via a figure-of-eight coil up to 25 kHz.

Magnetic particle imaging, uses magnetic fields of frequencies in the kilo-hertz range. Little research has been carried out upon effects on excitable tissue caused by time-varying magnetic fields in that frequency range. To learn about magnetic stimulation thresholds, a system that is capable of generating a very focused magnetic field strong enough to induce a muscular reaction was built. Stimulation thresholds at 7.38, 12.04, 16.5, and 25.27 kHz have been recorded in 31 trial participants. It has been proved that magnetic stimulation is possible up to even 25 kHz, and respective thresholds have been determined. This article presents the trial setup, procedure, and evaluation of field quantities.

Effects of time varying currents and magnetic fields in the frequency range of 1 kHz to 1 MHz to the human body - a simulation study.

Exposure to time-varying magnetic fields evokes two effects in biological tissue: Firstly, an electric field is induced that generates eddy currents in conductive tissues, and, secondly, power deposit might increase local temperatures. Field effects of frequencies up to 1 kHz and above 1 MHz are well known. The intermediate frequency range lacks intensive research. Only little attention has been paid so far. Yet due to recent innovations in medical diagnostics and therapies like Magnetic Particle Imaging or RF-Hyperthermia, the need arises to investigate the frequency range from 1kHz to 1 MHz. This work presents results of numerical field calculations of a human body model placed within simple coil configurations. Induced current densities, generated by alternating coil currents, are simulated. The effect of current densities are demonstrated and evaluated on schematic cell models of excitable tissue. In order to generate an action potential at the cell membrane, a difference in electric potential from intra- to extracellular space must be present. It can be shown that in case of sufficient field strength, stimulation of nerves and muscles is possible up to a frequency of 100 kHz. The aim of this paper is to transfer simulation results from the macroscopic model to the microscopic model in order to estimate field effects of big field generating coils.

Preventive ablation strategies in a biophysical model of atrial fibrillation based on realistic anatomical data.

Ablation strategies to prevent episodes of paroxysmal atrial fibrillation (AF) have been subject to many clinical studies. The issues mainly concern pattern and transmurality of the lesions. This paper investigates ten different ablation strategies on a multilayered 3-D anatomical model of the atria with respect to 23 different setups of AF initiation in a biophysical computer model. There were 495 simulations carried out showing that circumferential lesions around the pulmonary veins (PVs) yield the highest success rate if at least two additional linear lesions are carried out. The findings compare with clinical studies as well as with other computer simulations. The anatomy and the setup of ectopic beats play an important role in the initiation and maintenance of AF as well as the resulting therapy. The computer model presented in this paper is a suitable tool to investigate different ablation strategies. By including individual patient anatomy and electrophysiological measurement, the model could be parameterized to yield an effective tool for future investigation of tailored ablation strategies and their effects on atrial fibrillation.

Multiple wavelets, rotors, and snakes in atrial fibrillation--a computer simulation study.

BACKGROUND: Multiple wavelets and rotors are accused of maintaining atrial fibrillation (AF). However, snake-like excitation patterns have recently been observed in AF. So far, computer models have investigated AF in a simplified anatomical model. In this work, pulmonary vein firing is simulated to investigate the initiation and maintenance of AF in a realistic anatomical model. METHODS AND RESULTS: Thirty-five ectopic foci situated around all pulmonary veins were simulated by a unidirectional conduction block. The excitation propagation was simulated by an adaptive cellular automaton on a realistic 3-dimensional atrial anatomy. Atrial fibrillation was initiated in 65.7% of the simulations. Stable excitation patterns were broken up in anatomically heterogeneous regions, creating a streak-like excitation pattern similar to snakes. Multiple wavelets and rotors could be observed in anatomically smooth areas at the atria's roofs. CONCLUSIONS: The influence of macroscopic anatomical structures on the course of AF seems to play an important role in the excitation propagation in AF. The computer simulations indicate that multiple mechanisms contribute to the maintenance of AF.