[Patient experience, epistemic authority and health challenges: the example of long COVID].

Since February 2020, hundreds of thousands of patients have been left with persistant symptoms after their infection. Along with their clinicians, these patients are exposed to a high degree of uncertainty and the urgent need to produce conceptual frameworks aimed at recognising, treating and validating their experience as patients suffering from new and protracted symptoms and witnessing debates as to how these symptoms should be qualified. In this respect, long covid illustrates the need to combine the collective experiential knowledge of patients and scientific knowledge for the benefit of the patients, clinicians and research.

Spatiotemporal dynamics of reentrant ventricular tachycardias in canine myocardial infarction: pharmacological modulation.

During the transition from a slow to rapid depolarization rhythm, rate-dependent sodium channel blockade develops progressively and increases from beat to beat under procainamide but more abruptly under lidocaine. We investigated the consequences of such differences on the dynamic course and stability of reentrant tachycardias at their onset. Procainamide and lidocaine were infused to equipotent plasma concentrations in canines with three-day-old myocardial infarction.

Spontaneous changes in ventricular tachycardia cycle length and their relation to earliest sites of epicardial activation in a canine model.

Background: The purpose of this study was to examine the spontaneous changes in cycle length during episodes of sustained monomorphic (MVT) and polymorphic (PVT) ventricular tachycardias and to relate these changes with the earliest epicardial activation site of the beat.

Methods: Isochronal activation maps were obtained from 127 unipolar electrograms recorded from the surface of both ventricles with a sock electrode array in 24 open chest anesthetized dogs. After atrioventricular block, the left anterior descending coronary artery was occluded for 60 min under ventricular pacing (140/min), followed by reperfusion.

Cycle length dynamics at the onset of postinfarction ventricular tachycardias induced in canines: dependence on interval-dependent excitation properties of the reentrant substrate.

Introduction: Postinfarction monomorphic ventricular tachycardias induced by programmed stimulation may display initial cycle length (CL) variations before stabilizing.

Methods And Results: To show that tachycardia onset dynamics depend on rate-dependent electrical properties of the reentrant substrate, we extracted activation times and maximum negative slopes of local activation complexes (-dV/dt(max)) from 191 unipolar electrograms recorded in the anterior left ventricular wall of anesthetized, 3-day-old infarct canine preparations. Measurements were made of the responses to programmed stimulation, as well as in early and later beats of tachycardias, which displayed either a constant trend in CL (group A, n = 5 preparations) or one in which CL prolongation occurred according to an exponential course before stabilizing (group B, n = 9).

Cycle length dynamics and spatial stability at the onset of postinfarction monomorphic ventricular tachycardias induced in patients and canine preparations.

Background: The aim of this study was to determine whether cycle length (CL) variations at the onset of monomorphic ventricular tachycardias follow distinctive patterns.

Methods And Results: We retrospectively analyzed 59 monomorphic ventricular tachycardias induced in 40 patients in whom intraoperative mapping was performed with 63 epicardial and 64 endocardial electrograms recorded simultaneously. Activation times and CL were determined at each electrode site over several beats (36+/-10 beats, mean+/-SD) starting with the first after programmed stimulation.

Electrode polarity does not alter the initial ventricular activation sequence during pacing with extracardiac electrodes.

Ventricular epicardial mapping was performed in six closed-chest anesthetized dogs to investigate the cardiac electrical response to external pacing. A right thoracotomy was performed, complete AV block was produced by formaldehyde injected into the AV node and a sock electrode array, comprised of 127 unipolar electrodes, was placed over the ventricles. Isopotential and isochronal epicardial maps were generated by computer from the unipolar electrograms.

Body surface potential distributions during idiopathic ventricular tachycardia.

Background: The purpose of this report is to describe the body surface potential maps (BSPMs) during idiopathic ventricular tachycardia (VT) and to determine what differences exist between different idiopathic VT morphologies.

Methods And Results: We performed BSPMs during VT on 12 consecutive patients (3 women and 9 men; mean age, 42 +/- 13 years) presenting symptomatic idiopathic VT referred to our institution for electrophysiological study. Basal ECG, chest radiograph, and echocardiogram were normal in all patients.

Differential effects of lignocaine and hypercalcaemia on anisotropic conduction and reentry in the ischaemically damaged canine ventricle.

Objective: Anisotropic conduction characteristics, which may be expressed as the ratio of conduction velocities in the longitudinal (Vlong) and transverse (Vtrans) fibre directions, have been shown to stabilise reentry and favour the induction of sustained, uniform ventricular tachycardia. The aim of this study was to investigate whether interventions affecting either excitability (lignocaine) or both excitability and cell coupling (hypercalcaemia) might produce differential effects on the Vlong/Vtrans ratio, and whether an intervention reducing this ratio might prevent the induction of sustained reentrant ventricular tachycardia.

Methods: The effects of hypercalcaemia [8.

Anisotropic conduction and functional dissociation of ischemic tissue during reentrant ventricular tachycardia in canine myocardial infarction.

We measured the conduction characteristics at the epicardial surface of the left anterior ventricular wall in the in situ canine heart before and 3 to 5 days (n = 9 dogs) after permanent occlusion of the left anterior descending coronary artery (LAD). During ventricular stimulation generating wavefronts conducted along the longitudinal or the transverse fiber direction, 61 unipolar electrograms were recorded with a fine-meshed plaque electrode. Before occlusion, the fastest conduction velocity was consistently found in a direction perpendicular to the nearby LAD segment (longitudinal direction), and the slowest velocity in a direction parallel to the LAD segment (transverse fiber direction).