1. The purpose of this study was to evaluate the mechanical response to stretch in normal human ankle dorsiflexors at different levels of voluntary contraction. In an active muscle, the total mechanical response is the sum of the intrinsic response from the contractile apparatus, the response from passive tissues, and the reflex mediated response. Each of these components was investigated. 2. The total incremental stiffness was defined as the ratio between the torque increment and the amplitude of the stretch. In 14 subjects the total stiffness increased from approximately 0.6 N.m/deg to approximately 2.5 N.m/deg at 50% of MVC and remained constant (+/- 10%) from 30 to 80% of MVC. 3. The contribution to incremental stiffness from intrinsic muscle properties was measured during electrical stimulation of the deep peroneal nerve at 7-50 Hz. Intrinsic stiffness increased linearly with torque from approximately 0.5 N.m/deg to approximately 2.5 N.m/deg at 80% of MVC. 4. The reflex component (total minus intrinsic stiffness) had a maximum of 0.5-1.5 N.m/deg at 30-50% of MVC and was approximately zero at no and maximal contraction. For intermediate levels of contraction the reflex increased the stiffness with 40-100% of the intrinsic stiffness in this flexor muscle. 5. The reflex contribution to total stiffness began approximately 50 ms after onset of stretch and peaked 150-300 ms after onset of stretch. 6. Total, intrinsic, and reflex mediated stiffness were all nearly independent of the amplitude of stretch in the range from 2 to 7 degrees. The higher stiffness observed for 1 degree stretches could be due to "short range stiffness" of the cross bridges. 7. Stretching of a contracting muscle generates large force increments even for moderate amplitudes of stretch. Approximately half of this force increment is due to the stretch reflex, which makes the muscle stiffer than predicted from the intrinsic stiffness. These findings in human flexor muscles are surprisingly similar to previous findings in extensor muscles of the decerebrate cat.

Background-The present study assessed the efficacy and safety of vernakalant hydrochloride (RSD1235), a novel compound, for the conversion of atrial fibrillation (AF). Methods and Results-Patients were randomized in a 2:1 ratio to receive vernakalant or placebo and were stratified by AF duration of 3 hours to 7 days (short duration) and 8 to 45 days (long duration). A first infusion of placebo or vernakalant (3 mg/kg) was given for 10 minutes, followed by a second infusion of placebo or vernakalant (2 mg/kg) 15 minutes later if AF was not terminated. The primary end point was conversion of AF to sinus rhythm for at least 1 minute within 90 minutes of the start of drug infusion in the short-duration AF group. A total of 336 patients were randomized and received treatment (short duration, nϭ220; long duration, nϭ116

Digital stethoscopes offer new opportunities for computerized analysis of heart sounds. Segmentation of heart sound recordings into periods related to the first and second heart sound (S1 and S2) is fundamental in the analysis process. However, segmentation of heart sounds recorded with handheld stethoscopes in clinical environments is often complicated by background noise. A duration-dependent hidden Markov model (DHMM) is proposed for robust segmentation of heart sounds. The DHMM identifies the most likely sequence of physiological heart sounds, based on duration of the events, the amplitude of the signal envelope and a predefined model structure. The DHMM model was developed and tested with heart sounds recorded bedside with a commercially available handheld stethoscope from a population of patients referred for coronary arterioangiography. The DHMM identified 890 S1 and S2 sounds out of 901 which corresponds to 98.8% (CI: 97.8-99.3%) sensitivity in 73 test patients and 13 misplaced sounds out of 903 identified sounds which corresponds to 98.6% (CI: 97.6-99.1%) positive predictivity. These results indicate that the DHMM is an appropriate model of the heart cycle and suitable for segmentation of clinically recorded heart sounds.

As telehealth plays an even greater role in global health care delivery, it will be increasingly important to develop a strong evidence base of successful, innovative telehealth solutions that can lead to scalable and sustainable telehealth programs. This paper has two aims: (1) to describe the challenges of promoting telehealth implementation to advance adoption and (2) to present a global research agenda for personalized telehealth within chronic disease management. Using evidence from the United States and the European Union, this paper provides a global overview of the current state of telehealth services and benefits, presents fundamental principles that must be addressed to advance the status quo, and provides a framework for current and future research initiatives within telehealth for personalized care, treatment, and prevention. A broad, multinational research agenda can provide a uniform framework for identifying and rapidly replicating best practices, while concurrently fostering global collaboration in the development and rigorous testing of new and emerging telehealth technologies. In this paper, the members of the Transatlantic Telehealth Research Network offer a 12-point research agenda for future telehealth applications within chronic disease management.

Background-Postoperative atrial arrhythmias are common and are associated with considerable morbidity. This study was designed to evaluate the efficacy and safety of vernakalant for the conversion of atrial fibrillation (AF) or atrial flutter (AFL) after cardiac surgery. Methods and Results-This was a prospective, randomized, double-blind, placebo-controlled trial of vernakalant for the conversion of AF or AFL after coronary artery bypass graft, valvular surgery, or both. Patients were randomly assigned 2:1 to receive a 10-minute infusion of 3 mg/kg vernakalant or placebo. If AF or AFL was present after a 15-minute observation period, then a second 10-minute infusion of 2 mg/kg vernakalant or placebo was given. The primary end point was the conversion of postcardiac surgery AF or AFL to sinus rhythm within 90 minutes of dosing. In patients with AF, 47 of 100 (47%) who received vernakalant converted to SR compared with 7 of 50 (14%) patients who received placebo (PϽ0.001). The median time to conversion was 12 minutes. Vernakalant was not effective in converting postoperative AFL to sinus rhythm. Two serious adverse events occurred within 24 hours of vernakalant administration (hypotension and complete atrioventricular block). There were no cases of torsades de pointes, sustained ventricular tachycardia, or ventricular fibrillation. There were no deaths. Conclusions-Vernakalant was safe and effective in the rapid conversion of AF to sinus rhythm in patients who had AF after cardiac surgery. Clinical Trial Registration-clinicaltrials.gov. Identifier: NCT00125320.(Circ Arrhythm Electrophysiol. 2009;2:652-659.)