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Critical velocity (CV)

João Pedro Ferreira, Nicolas Girerd, Bruno Pannier, Patrick Rossignol, Gerard M London
BACKGROUND: Patients with end-stage renal disease (ESRD) are at a high risk of cardiovascular mortality (CVM). In patients with ESRD, arterial stiffness increases at an earlier age when compared to the general population and this contributes to the overall risk of cardiovascular mortality. The main objective of this study was to clarify the interplay between age and cardiovascular alterations in ESRD. METHODS: Prospective, observational cohort study initiated in April 1987 until the end of 1998 with events recorded until the end of the year 2000 at the F...
2017: American Journal of Nephrology
Anna Lisa Crowley, Eric Yow, Huiman X Barnhart, Melissa A Daubert, Robert Bigelow, Daniel C Sullivan, Michael Pencina, Pamela S Douglas
BACKGROUND: There is no broadly accepted standard method for assessing the quality of echocardiographic measurements in clinical research reports, despite the recognized importance of this information in assessing the quality of study results. METHODS: Twenty unique clinical studies were identified reporting echocardiographic data quality for determinations of left ventricular (LV) volumes (n = 13), ejection fraction (n = 12), mass (n = 9), outflow tract diameter (n = 3), and mitral Doppler peak early velocity (n = 4)...
December 2016: Journal of the American Society of Echocardiography
Gary Tse, Jie Ming Yeo, Vivian Tse, Joseph Kwan, Bing Sun
In the current study, arrhythmogenic effects of the gap junction inhibitor heptanol (0.05 mM) were examined in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricular epicardium during right ventricular pacing. Regular activity was observed both prior and subsequent to application of heptanol in all of the 12 hearts studied during 8 Hz pacing. By contrast, induced ventricular tachycardia (VT) was observed after heptanol treatment in 6/12 hearts using a S1S2 protocol (Fisher's exact test; P<0...
November 2016: Molecular Medicine Reports
Motahareh Moghtadaei, Hailey J Jansen, Martin Mackasey, Sara A Rafferty, Oleg Bogachev, John L Sapp, Susan E Howlett, Robert A Rose
KEY POINTS: Sinoatrial node (SAN) function declines with age; however, not all individuals age at the same rate and health status can vary from fit to frail. Frailty was quantified in young and aged mice using a non-invasive frailty index so that the impacts of age and frailty on heart rate and SAN function could be assessed. SAN function was impaired in aged mice due to alterations in electrical conduction, changes in SAN action potential morphology and fibrosis in the SAN. Changes in SAN function, electrical conduction, action potential morphology and fibrosis were correlated with, and graded by, frailty...
December 1, 2016: Journal of Physiology
Daniel M Lombardo, Flavio H Fenton, Sanjiv M Narayan, Wouter-Jan Rappel
Computer studies are often used to study mechanisms of cardiac arrhythmias, including atrial fibrillation (AF). A crucial component in these studies is the electrophysiological model that describes the membrane potential of myocytes. The models vary from detailed, describing numerous ion channels, to simplified, grouping ionic channels into a minimal set of variables. The parameters of these models, however, are determined across different experiments in varied species. Furthermore, a single set of parameters may not describe variations across patients, and models have rarely been shown to recapitulate critical features of AF in a given patient...
August 2016: PLoS Computational Biology
Stéphane Laurent, Louise Marais, Pierre Boutouyrie
The growing interest in the clinical measurement of arterial aging through the noninvasive assessment of arterial stiffness is associated with important developments in novel methods and apparatus. In this review, we aimed to describe the major principles of the measurement of arterial stiffness and to critically review the advantages and limitations of the different methods. The measurement of regional stiffness is recommended by international guidelines for routine clinical practice. It is most often determined through pulse wave velocity (PWV) between 2 arterial sites...
May 2016: Canadian Journal of Cardiology
Bettina Karsten, Eneko Larumbe-Zabala, Gokhan Kandemir, Tahir Hazir, Andreas Klose, Fernando Naclerio
UNLABELLED: The objectives of this study were to examine the effects of a moderate intensity strength training on changes in critical velocity (CV), anaerobic running distance (D'), sprint performance and Yo-Yo intermittent running test (Yo-Yo IR1) performances. METHODS: two recreational soccer teams were divided in a soccer training only group (SO; n = 13) and a strength and soccer training group (ST; n = 13). Both groups were tested for values of CV, D', Yo-Yo IR1 distance and 30-m sprint time on two separate occasions (pre and post intervention)...
2016: PloS One
Gary Tse, Vivian Tse, Jie Ming Yeo
Ventricular arrhythmic and electrophysiological properties were examined during normokalaemia (5.2 mM [K(+)]), hypokalaemia (3 mM [K(+)]) or hypokalaemia in the presence of 0.1 or 2 mM heptanol in Langendorff-perfused mouse hearts. Left ventricular epicardial or endocardial monophasic action potential recordings were obtained during right ventricular pacing. Hypokalaemia induced ventricular premature beats (VPBs) in 5 of 7 and ventricular tachycardia (VT) in 6 of 7 hearts (P<0.01), prolonged action potential durations (APD90) from 36...
March 2016: Biomedical Reports
Linyuan Jing, Anuj Agarwal, Abhijit Patwardhan
Spatially discordant alternans (DA) of action potential durations (APD) is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC) has been reported to suppress formation of DA. An increase in conduction velocity (CV) as activation rate increases, i.e., a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression...
2015: Frontiers in Physiology
Michelle M J Nassal, Andreas A Werdich, Xiaoping Wan, Malcolm Hoshi, Isabelle Deschênes, David S Rosenbaum, J Kevin Donahue
Connexin43 (Cx43) phosphorylation alters gap junction localization and function. In particular, phosphorylation at serine-368 (S368) has been suggested to alter gap junctional conductance, but previous reports have shown inconsistent results for both timing and functional effects of S368 phosphorylation. The objective of this study was to determine the functional effects of isolated S368 phosphorylation. We evaluated wild-type Cx43 (AdCx43) and mutations simulating permanent phosphorylation (Ad368E) or preventing phosphorylation (Ad368A) at S368...
January 2016: Journal of Cardiovascular Electrophysiology
Martina Mancini, Mahmoud El-Gohary, Sean Pearson, James McNames, Heather Schlueter, John G Nutt, Laurie A King, Fay B Horak
BACKGROUND: Difficulty turning during gait is a major contributor to mobility disability, falls and reduced quality of life in patients with Parkinson's disease (PD). Unfortunately, the assessment of mobility in the clinic may not adequately reflect typical mobility function or its variability during daily life. We hypothesized that quality of turning mobility, rather than overall quantity of activity, would be impaired in people with PD over seven days of continuous recording. METHODS: Thirteen subjects with PD and 8 healthy control subjects of similar age wore three Opal inertial sensors (on their belt and on each foot) throughout seven consecutive days during normal daily activities...
2015: NeuroRehabilitation
Mattan W Hoffman, Jeffrey R Stout, Jay R Hoffman, Geva Landua, David H Fukuda, Nurit Sharvit, Daniel S Moran, Erez Carmon, Ishay Ostfeld
The purpose of this study was to examine the relationship between critical velocity (CV) and anaerobic distance capacity (ADC) to combat-specific tasks (CST) in a special forces (SFs) unit. Eighteen male soldiers (mean ± SD; age: 19.9 ± 0.8 years; height: 177.6 ± 6.6 cm; body mass: 74.1 ± 5.8 kg; body mass index [BMI]: 23.52 ± 1.63) from an SF unit of the Israel Defense Forces volunteered to complete a 3-minute all-out run along with CST (2.5-km run, 50-m casualty carry, and 30-m repeated sprints with "rush" shooting [RPTDS])...
February 2016: Journal of Strength and Conditioning Research
Bettina Karsten, Liesbeth Stevens, Mark Colpus, Eneko Larumbe-Zabala, Fernando Naclerio
PURPOSE: To investigate the effects of a sport-specific maximal 6-wk strength and conditioning program on critical velocity (CV), anaerobic running distance (ARD), and 5-km time-trial performance (TT). METHODS: 16 moderately trained recreational endurance runners were tested for CV, ARD, and TT performances on 3 separate occasions (baseline, midstudy, and poststudy). DESIGN: Participants were randomly allocated into a strength and conditioning group (S&C; n = 8) and a comparison endurance-training-only group (EO; n = 8)...
January 2016: International Journal of Sports Physiology and Performance
Leonardo H D Messias, Homero G Ferrari, Ivan G M Reis, Pedro P M Scariot, Fúlvia B Manchado-Gobatto
The purpose of this study was to analyze if different combinations of trials as well as mathematical models can modify the aerobic and anaerobic estimates from critical velocity protocol applied in canoe slalom. Fourteen male elite slalom kayakers from Brazilian canoe slalom team (K1) were evaluated. Athletes were submitted to four predictive trials of 150, 300, 450 and 600 meters in a lake and the time to complete each trial was recorded. Critical velocity (CV-aerobic parameter) and anaerobic paddling capacity (APC-anaerobic parameter) were obtained by three mathematical models (Linear1=distance-time; Linear 2=velocity-1/time and Non-Linear = time-velocity)...
March 2015: Journal of Sports Science & Medicine
Minki Hwang, Junbeum Park, Young-Seon Lee, Jae Hyung Park, Sung Hwan Choi, Eun Bo Shim, Hui-Nam Pak
The heart characteristic length, the inverse of conduction velocity (CV), and the inverse of the refractory period are known to determine vulnerability to cardiac fibrillation (fibrillation number, FibN) in in silico or ex vivo models. The purpose of this study was to validate the accuracy of FibN through in silico atrial modeling and to evaluate its clinical application in patients with atrial fibrillation (AF) who had undergone radiofrequency catheter ablation. We compared the maintenance duration of AF at various FibNAF values using in silico bidomain atrial modeling...
February 2015: IEEE Transactions on Bio-medical Engineering
Kazushige Oshita, Misaki Ross, Kazushi Koizumi, Tenpei Tsuno, Sumio Yano
PURPOSE: Finswimming is a speed competition sport practiced on the surface or underwater, by using monofins or two fins. In surface events (SF), competitors should surface within 15 m after the start and any turns. The aim of this study was to investigate the gender differences in the aerobic contribution to SF performances in finswimming, using the critical velocity (CV) concept in the analysis. METHODS: The participants were sixteen monofin swimmers (eight males and eight females; 24±6 years)...
December 2013: Asian Journal of Sports Medicine
Pedro Guimarães Cunha, Jorge Cotter, Pedro Oliveira, Isabel Vila, Nuno Sousa
BACKGROUND: Cardiovascular disease and dementia are growing medical and social problems in aging societies. Appropriate knowledge of cardiovascular disease and cognitive decline risk factors (RFs) are critical for global CVR health preventive intervention. Many epidemiological studies use case definition based on data collected/measured in a single visit, a fact that can overestimate prevalence rates and distant from clinical practice demanding criteria. Portugal displays an elevated stroke mortality rate...
June 2014: Journal of Investigative Medicine: the Official Publication of the American Federation for Clinical Research
J Zebrowski
The variation in the stiffness of stem and leaf sheaths along the shoot axis of Triticale (Triticosecale W., cv. Jago) was examined, using an ultrasonic method, at two stages of development, (i) at the stage of high stem mechanical instability when upper internodes are forming (heading), and (ii) at milk maturity when development of strengthening tissues is completed (three weeks after anthesis). The squared velocity of low-frequency longitudinal pulse waves was used as a measure of the specific modulus of elasticity, averaged over the whole cross section of the structures and related to the unit density of the material...
June 1992: Planta
Antonio Nardone, Stefano Corna, Anna Maria Turcato, Marco Schieppati
OBJECTIVES: To compare the gait pattern in patients affected by different types of neuropathy. METHODS: We recruited healthy subjects (HS, n=38), patients with Charcot-Marie-Tooth disease type 1A (CMT1A) (n=10) and patients with diabetic neuropathy (DNP) (n=12). Neuropathy impairment score and neuropathy score were assessed. Body sway during quiet stance, and spatio-temporal gait parameters were recorded. RESULTS: Most patients had reduced or absent tendon-tap reflexes...
February 2014: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
L Huang, L A H Critchley
BACKGROUND: The ultrasound cardiac output monitor (USCOM) is a continuous wave Doppler system designed to measure cardiac output (CO) non-invasively and intermittently either from the pulmonary or from the aortic valve. USCOM scan quality is critical to obtaining reliable data and during anaesthesia it is said to deteriorate with increasing age. The aim of this study was to investigate the effect of age on supra-sternal USCOM scan repeatability during anaesthesia. METHODS: We performed a series of 6 USCOM scans in 180 patients of all ages after induction for routine surgery...
December 2013: British Journal of Anaesthesia
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