Abstract: Risk factors that can determine knee and ankle injuries have been investigated and causes are probably multifactorial. A possible explanation could be related by the temporary inhibition of muscular control following an alteration of proprioceptive regulation due to the ankle imbalance pathology. The purpose of our study was to validate a new experimental set up to quantify two kinesiologic procedures (Shock Absorber Test (SAT) and Kendall and Kendall's Procedure (KKP)) to verify if a subtalus stimulus in an ankle with imbalance can induce a non-appropriate response of controlateral tensor fascia lata muscle (TFL). Fifteen male soccer players with ankle imbalance (AIG) and 14 healthy (CG) were tested after (TEST) before (NO-TEST) a manual percussion in subtalus joint (SAT). A new tailor-made device equipped with a load cell was used to quantify TFL's strength activation in standardized positions. Two trials for each subject were performed, separated by at least one 4-min resting interval. In NO-TEST conditions both AIG and CG showed a progressive adaptation of the subject to the force imposed by operator. No reduction in mean force, mean peak force, and muscle force duration (p>0.5). AIG presented significant differences (mean difference 0.92+/-0.46s; p=0.000) in muscle force duration in TEST conditions. Our results indicated that "wrong" proprioceptive stimuli coming from the subtalus joint in AIG might induce inhibition in terms of duration of TFL muscle altering the knee stability. This kinesiological evaluation might be useful to prevent ankle and knee injuries.
Abstract: To devise and to build a mechanical simulator of the cardiovascular system of increasing complexity is a fascinating experience for a medical Physicist. We did it, and the effort to match the solutions with the objectives forced us to deepen the knowledge of the physiological aspects, to devise different solutions and to compare their results. This paper describes the final solution and shows the results, discussing the theoretical and practical aspects of the different choices. The ventricle is simulated by a pumping syringe with an external pulsing chamber to accomplish the Frank-Starling mechanism; the coronary circulation by a nonlinear hydraulic resistance device; the aorta by different wall thickness rubber tubes; the arterial vascular resistance by a thin, variable length tube; the venous reservoir by a variable volume chamber connected to a reservoir simulating the atrium. The simulator was mainly devoted to teaching purposes, but the possibility to modify the mechanical characteristics of the single components moved it to be used also for research, with an unexpected satisfaction.
Abstract: OBJECTIVE: The study focused on the safety of electrosurgical devices in endoscopic fetal surgery. The thermic effects of monopolar electric waves were studied in vitro in order to obtain safety indications in terms of mode of intramniotic application of electrical devices (time and number of shots; volts; and distance from tissues to be preserved). STUDY DESIGN: A glass model filled with saline solution, and an electrical device with resistor and voltage supply, were constructed to reproduce the physical effects of thermic conductivity in vitro; a Swan-Ganz thermic sensor was used to measure the temperature inside the beuta. Different series of tests were carried out. RESULTS: The maximal increase (8.60 +/- 0.04 degrees C) takes place at the external surface of the resistor (distance: 0 cm), while at 2 cm, the temperature of the saline solution does not change. CONCLUSIONS: Our tests demonstrate that in order to avoid any kind of risk during electrosurgical procedures on fetuses, the electrode must be placed at least 0.5 cm from delicate tissues.
Abstract: In clinical practice, oxygen uptake is an indicator of cardiopulmonary performance. Most commercial systems measure oxygen uptake by collecting expired air through masks or mouthpieces which are often poorly tolerated by the patient. We have developed and validated a novel mask-free system to improve patient comfort and performance. The prototype is composed of a soft walled funnel that collects and conveys the expired air, together with some external air, in a mixing chamber by means of an aspiration system. Oxygen concentration and airflow are measured and then oxygen uptake is calculated. Direct comparison between calculated and preset oxygen uptake values obtained by a mechanical simulator was performed. Errors ranged between 1% and 3.3%, depending on the absolute value of oxygen consumption. Then the prototype was connected "in-series" with a breath-by-breath commercial system, and ten subjects were submitted to a standard stress test. The results showed good agreement (R=0.94) and a mean difference of 5% between the peak values. The longer response time of the prototype caused a delay between the two .V(O2)(t) curves, leading to an underestimation in the exercise phase and an overestimation in the recovery phase, suggesting more technical improvements. Nevertheless in its present form the new system can be used in the whole exercise phase and, with caution, also in the recovery phase.
Abstract: Stanford type A aortic dissection often rapidly leads to death from aortic rupture. We considered the possibility of introducing a passive counterpulsating damper into the dissected aorta in order to limit the physical stress associated with ventricular ejection and increase the diastolic aorto-ventricular pressure gradient. We conceived a damping device comprising an intravascular balloon connected to an adjustable external reservoir to regulate the air pressure inside the balloon, and performed a simulation study using a mechanical model of the cardiovascular system, mimicking aortic dissection. When the balloon was completely deflated, the behavior of the aortic pressure signal was typical of low-compliance aortic dissection, as characterized by an augmented maximum systolic value, accentuated diastolic decay, and a very low end-diastolic value. Balloon inflation (at incremental steps to 90 mmHg) progressively restored the aorto-ventricular pressure gradient and reduced peak systolic pressure values, leading to progressive improvements in the characteristics of the aortic pressure curve in terms of reduction in the maximum systolic value and slower diastolic decay. The proposed mechanism might exert beneficial effects at two levels: (1) directly, by reducing mechanical stress on the arterial wall; (2) indirectly, by allowing safer use of pharmaceutical agents (beta-blockers etc.). In vivo animal simulation studies are warranted to verify the effects of the device and optimize balloon shape and volume in a realistic pathophysiological setting.
Abstract: BACKGROUND: P wave dispersion has been previously suggested as a potential tool for predicting the risk of recurrence of atrial fibrillation after electrical cardioversion. We investigated whether different P wave dispersion values are associated with recurrence of atrial fibrillation in the short (< or =1 month after cardioversion) and longer term. METHODS: In 37 patients with long-lasting persistent atrial fibrillation (mean duration 21 +/- 36 months) with (n = 19) or without (n = 18) amiodarone pretreatment as antiarrhythmic prophylaxis, maximum and minimum P wave duration and P wave dispersion were measured 1 min after internal cardioversion. RESULTS: P wave dispersion was lower in patients with amiodarone pretreatment (28.3 +/- 9.5 vs. 21.9 +/- 7.3 ms, P = 0.029). The subgroups of patients with recurrence of atrial fibrillation at 1 month or in the long-term did not differ from the rest of the study sample regarding age, sex, atrial fibrillation duration, left atrial dimensions or ejection fraction. P wave dispersion was significantly higher in patients with short-term atrial fibrillation recurrence (< or = 1 month) than in the rest of the population. Furthermore, P wave dispersion values >25 ms were associated with a higher short-term relapse rate. No significant relation was present in the long-term. CONCLUSIONS: Our results suggest that P wave dispersion analysis immediately after internal cardioversion may help predict short-term recurrences of atrial fibrillation. These findings may be related to different mechanisms and predisposing factors for short-term and late recurrences. The long-term predictive value of serial evaluations of P wave dispersion during follow-up deserves investigation.
Abstract: BACKGROUND: The effects of atrial internal cardioversion on QT interval and QT dispersion (parameters associated with increased risk of ventricular tachyarrhythmias) are unknown. We investigated changes in QT interval, QTc and QT dispersion immediately after shock delivery for internal cardioversion in patients with chronic persistent atrial fibrillation. METHOD: Twenty-two patients with chronic persistent atrial fibrillation (mean duration, 17+/-23 months) underwent transvenous low-energy internal atrial cardioversion with a step-up protocol of shocks delivered between catheters in the right atrium and coronary sinus. (successful shock, 7.2+/-4.2 J). RR interval, QT interval, QTc interval, QT dispersion, and QTc dispersion were all measured on three consecutive beats (at 75 mm/s on at least 9 of 12 leads) and then averaged both before and after (1) the last unsuccessful shock, and (2) sinus rhythm restoration. RESULTS: All parameters remained similar in the minute before and after the last unsuccessful shock. At 1 min after the successful shock, abrupt increases in QT dispersion (+43.8% vs. pre-shock; P<0.001 at least significant difference analysis) and QTc dispersion (+30.0%; P<0.05) were observed, followed by a gradual return to pre-shock values at 15 min. CONCLUSIONS: These findings strongly suggest the likely existence of a brief period of increased electrical vulnerability immediately after restoration of sinus rhythm by internal cardioversion. Particular caution should therefore be applied whenever class III antiarrhythmic drugs are administered immediately after successful internal atrial cardioversion.
Abstract: Various modalities of cardiac pacing have been proposed in the past to improve hemodynamics, either directly or indirectly. Some of these are conventional ways of cardiac stimulation, others such as biventricular or left ventricular pacing, represent dedicated pacing techniques. Left ventricular and biventricular pacing are successfully applied in those patients with congestive heart failure who have conduction disturbances (i.e. left bundle branch block) as they correct the ensuing intra- and interventricular dyssynchrony. This is the reason why these pacing modalities are described as cardiac resynchronization therapy. According to the results of a series of studies, the cardiac resynchronization therapy seems to have a favourable clinical impact in terms of quality of life, morbidity and hospitalization rate. On-going and future studies should assess the impact of resynchronization therapy on overall mortality and its cost-effectiveness profile in specific subgroups of patients. Other open issues regard (i) the convenience of using biventricular pacing as a pacing-alone therapy or in combination with ventricular defibrillation capability, especially for potential candidates to heart transplantation, and (ii) the ways to identify properly the responders to resynchronization therapy.
Abstract: Internal cardioversion can restore sinus rhythm with energies below 6-10 J, often without anaesthesia/sedation. We investigated its safety and short-/medium-term efficacy in patients with persistent atrial fibrillation (AF) with left ventricular dysfunction (defined as ejection fraction < or = 40%). Among 34 patients with persistent AF who agreed to receive internal cardioversion, 16 had left ventricular dysfunction and 18 did not (the groups were similar as regards age, duration of AF and pretreatment with amiodarone). Internal CV was performed delivering 3.0/3.0-ms biphasic shocks between coil catheters using a step-up protocol. Sinus rhythm was always restored. General anaesthesia (administered only when discomfort was not tolerated) was required only in 2 of the 16 (12.5%) patients with left ventricular dysfunction. The defibrillation threshold was similar in patients with and without left ventricular dysfunction (10.2+/-6.9 vs. 8.4+/-4.9 J; p=0.37). Short-term (within 72 h) AF recurrence rates in the presence and absence of left ventricular dysfunction were 19% (3/16) and 6% (1/18), respectively (p=0.51). After cardioversion, all patients received antiarrhythmic drugs (mostly amiodarone in patients with left ventricular dysfunction and class IC agents in the remainder). With mean follow-up periods of about 220 days, AF recurrence rates among patients with and without left ventricular dysfunction were 50% (8/16) and 28% (5/18), respectively (p=0.328). We conclude that even in patients with left ventricular dysfunction, internal CV is safe and effective, minimizing risks from anaesthesia. Although these patients may have a higher risk of short- or medium-term AF recurrence, 6-month maintenance of sinus rhythm is possible in about 50% of cases.
Abstract: INTRODUCTION: Induced versus spontaneous atrial fibrillation (AF) is of interest for assessing atrial defibrillation threshold reproducibility. METHODS AND RESULTS: Twenty-one patients with chronic AF underwent internal cardioversion with assessment of atrial defibrillation threshold at baseline and at reinduced AF. High right atrial (HRA) and coronary sinus (CS) bipolar recordings were analyzed to measure the mean local atrial period, its coefficient of variation, the 5th (P5) and 95th (P95) percentiles of atrial intervals, and the percentage of points lying at the baseline (number of occurrences), and to quantify AF organization. Atrial defibrillation threshold was comparable in baseline and reinduced AF in terms of leading-edge voltage and delivered energy. Baseline and reinduced AF were comparable with regard to overall signal parameters (both in HRA and CS) and the presence of an organized arrhythmia pattern. As for individual variables, P5 increased while P95 and coefficient of variation decreased in reinduced AF compared with spontaneous AF (statistical significance was achieved for all these parameters in HRA, but only for coefficient of variation and P95 in CS). CONCLUSION: Sustained AF reinduced after cardioversion of chronic AF is comparable with baseline AF in terms of atrial defibrillation threshold, atrial cycle length, and pattern of organization. Therefore, a clinical model based on reinduction of sustained AF after cardioversion is suitable for studying the effects of a series of interventions on atrial defibrillation threshold. However, because this model does not yield a form of AF with comparable indices of local refractoriness (e.g., P5), it is not recommended when analyzing local electrophysiologic properties.
Abstract: At present the approach to atrial fibrillation treatment is based on the electrophysiological patterns of atrial fibrillation (on the basis of multiple intra-atrial recordings or sophisticated new mapping techniques) only in a restricted minority of patients, those who are candidate to ablation of the substrate and/or of the triggers. Atrial fibrillation has a broad spectrum of clinical presentations and a heterogeneous electrophysiological pattern. The treatment of this arrhythmia, both with drugs and non pharmacological treatments, has been based, classically, on empirical basis and on a clinically-guided staged-approach. The limitations of pharmacological treatment led in recent years to the development of a wide spectrum of non pharmacological treatments. This implies a change in the approach to atrial fibrillation and the need to identify potentially ideal candidates to complex and expensive treatments. In this view it is currently under investigation the possibility to identify potential responders to a definitive treatment or a combination of treatments (both pharmacological and non-pharmacological) on the basis of the electrophysiological pattern.
