Off-patient assessment of pre-cordial impact mechanics among medical professionals in North-East Italy involved in emergency cardiac resuscitation.

Pre-cordial thump (PT) relies on cardiac mechano-electric transduction to transform mechanically-delivered energy into an electrophysiologically relevant stimulus. Its use for emergency resuscitation has declined recent years, amidst concerns about effectiveness and side-effects. In addition, there is insufficient knowledge about bio-mechanical properties and mechanisms of PT. Using a PT-mechanics recorder, we measured PT off-patient among healthcare professionals (n = 58) in North-East Italy, and related this to retrospective information on self-reported PT outcomes. Impact-speed and peak-force were 4.7 ± 1.3 m s⁻¹ (2.2-7.8 m s⁻¹) and 394 ± 110 N (202-648 N), respectively. Average self-reported cardioversion rate by PT was 35%. No adverse events were stated. All but 3 of PT providers with self-reported cardioversion rates ≥50% had pre-impact fist-speeds of ≥3.7 m s⁻¹. In comparison with previously-reported data from UK and US (n = 22 each), self-reported success-rates and pre-impact fist-speeds were more similar to US (PT-induced cardioversion rate 27.7%; fist-speed 4.17 ± 1.68 m s⁻¹) than to UK participants (PT-induced cardioversion rate 13.3%; fist-speed 1.55 ± 0.68 m s⁻¹). Small cohort-size, retrospective nature of data-gathering, and 'self-selection bias' (participants who have used PT on patients) limits the extent to which firm conclusions can be drawn. Observations are compatible, though, with the possibility that pre-impact fist-speed may affect success-rate of PT. Thus, where PT is used for acute resuscitation, it is delivered because it is immediately 'at hand'. Negative side effects are rare or absent in witnessed cardiac arrest cases. Pre-impact fist-speed may be a determinant of outcome, and this could be trained using devices suitable for self-assessment.

In migrating cells, the Golgi complex and the position of the centrosome depend on geometrical constraints of the substratum.

Although cells migrate in a constrained 3D environment in vivo, in-vitro studies have mainly focused on the analysis of cells moving on 2D substrates. Under such conditions, the Golgi complex is always located towards the leading edge of the cell, suggesting that it is involved in the directional movement. However, several lines of evidence indicate that this location can vary depending on the cell type, the environment or the developmental processes. We have used micro contact printing (microCP) to study the migration of cells that have a geometrically constrained shape within a polarized phenotype. Cells migrating on micropatterned lines of fibronectin are polarized and migrate in the same direction. Under such conditions, the Golgi complex and the centrosome are located behind the nucleus. In addition, the Golgi complex is often displaced several micrometres away from the nucleus. Finally, we used the zebrafish lateral line primordium as an in-vivo model of cells migrating in a constrained environment and observe a similar localization of both the Golgi and the centrosome in the leading cells. We propose that the positioning of the Golgi complex and the centrosome depends on the geometrical constraints applied to the cell rather than on a precise migratory function in the leading region.

Soft tissue impact characterisation kit (STICK) for ex situ investigation of heart rhythm responses to acute mechanical stimulation.

Both mechanical induction and mechanical termination of arrhythmias have been reported in man. Examples include pre-cordial impacts by sports implements (baseballs, pucks) that can trigger arrhythmias, including ventricular fibrillation, or via the so-called pre-cordial thump, used as an emergency resuscitation measure to convert arrhythmias to normal sinus node rhythm. These interventions have been partially reproduced in experimental studies on whole animals. Relating observations at the system's level to underlying mechanisms has been difficult, however, largely because of: (i) a deficit in efficient and affordable pharmacological agents to selectively target (sub-)cellular responses in whole animal studies, and (ii) the lack of suitable experimental models to study the above responses at intermediate levels of functional and structural integration, such as the isolated heart or cardiac tissue. This paper presents a soft tissue impact characterisation kit (STICK), suitable for quantitative investigations into the effects of acute mechanical stimulation on cardiac electro-mechanical function in rodent isolated heart or tissue preparations. The STICK offers independent control over a range of relevant biophysical parameters, such as impact location and energy, pre-impact projectile speed and contact area, as well as over the timing of a mechanical stimulus relative to the cardiac cycle (monitored via electrocardiogram, ECG, here recorded directly from the cardiac surface). Projectile deceleration upon interaction with the tissue is monitored, contact-free, with a resolution of 175 microm, providing information on tissue deformation dynamics, force, pressure and work of the mechanical intervention. In order to study functional effects of cardiac mechanical stimulation in the absence of tissue damage, impacts must be limited (for juvenile Guinea pig heart) to 2-2.5 mJ in the slack left ventricle (diastolic impact) and 5-10 mJ in contracture (systolic impact), as confirmed by enzyme assay and histological investigation. Impacts, timed to coincide with the early T-wave of the ECG, are capable of triggering short runs of ventricular fibrillation. Thus, the STICK is a suitable tool for the study of acute cardiac mechano-electric feedback effects, caused by short impulse-like mechanical stimulation, at the level of the isolated organ or tissue.