Priming cardiac function with voluntary respiratory maneuvers and effect on early exercise oxygen uptake.

Oxygen uptake (V̇o <sub>2</sub> ) at exercise onset is determined in part by acceleration of pulmonary blood flow ([Formula: see text]). Impairments in the [Formula: see text] response can decrease exercise tolerance. Prior research has shown that voluntary respiratory maneuvers can augment venous return, but the corollary impacts on cardiac function, [Formula: see text] and early-exercise V̇o <sub>2</sub> remain uncertain. We examined 1) the cardiovascular effects of three distinct respiratory maneuvers (abdominal, AB; rib cage, RC; and deep breathing, DB) under resting conditions in healthy subjects (Protocol 1, n = 13), and 2) the impact of pre-exercise DB on pulmonary O <sub>2</sub> transfer during initiation of moderate-intensity exercise (Protocol 2, n = 8). In Protocol 1, echocardiographic analysis showed increased right ventricular (RV) cardiac output and left ventricular (LV) cardiac output (RVCO and LVCO, respectively), following AB (by +23 ± 13 and +18 ± 15%, respectively, P < 0.05), RC (+23 ± 16; +14 ± 15%, P < 0.05), and DB (+27 ± 21; +23 ± 14%, P < 0.05). In Protocol 2, DB performed for 12 breaths produced a pre-exercise increase in V̇o <sub>2</sub> (+801 ± 254 mL·min <sup>-1</sup> over ∼6 s), presumably from increased [Formula: see text], followed by a reduction in pulmonary O <sub>2</sub> transfer during early phase exercise (first 20 s) compared with the control condition (149 ± 51 vs. 233 ± 65 mL, P < 0.05). We conclude that 1) respiratory maneuvers enhance RVCO and LVCO in healthy subjects under resting conditions, 2) AB, RC, and DB have similar effects on RVCO and LVCO, and 3) DB can increase [Formula: see text] before exercise onset. These findings suggest that pre-exercise respiratory maneuvers may represent a promising strategy to prime V̇o <sub>2</sub> kinetics and thereby to potentially improve exercise tolerance in patients with impaired cardiac function.NEW & NOTEWORTHY We demonstrate that different breathing maneuvers can augment both right and left-sided cardiac output in healthy subjects. These maneuvers, when performed immediately before exercise, result in a pre-exercise "cardiodynamic" increase in oxygen uptake (V̇o <sub>2</sub> ) associated with a subsequent reduction in the "cardiodynamic" V̇o <sub>2</sub> normally seen during early exercise. We conclude that pre-exercise breathing maneuvers are a plausible tool worthy of additional study to prime V̇o <sub>2</sub> kinetics and improve exercise tolerance in patients with cardiovascular disease

ACC/AHA/HRS Versus ESC Guidelines for the Diagnosis and Management of Syncope : JACC Guideline Comparison

Syncope is a commonly encountered and challenging problem in medical practice. Presentations are variable, and the causal mechanism often remains elusive even after extensive (and often expensive) evaluation. Clinical practice guidelines have been developed to help guide the multidisciplinary approach necessary to diagnose and manage the broad spectrum of patients presenting with syncope. The American College of Cardiology/American Heart Association, in collaboration with the Heart Rhythm Society, published its first syncope guidelines in 2017. The European Society of Cardiology released the fourth iteration of its syncope guidelines in 2018. This review highlights the differences and congruencies between the 2 sets of recommendations, their implications for clinical practice, the remaining gaps in understanding, and areas of future research

Consumer Wearable Health and Fitness Technology in Cardiovascular Medicine: JACC State-of-the-Art Review.

The use of consumer wearable devices (CWDs) to track health and fitness has rapidly expanded over recent years because of advances in technology. The general population now has the capability to continuously track vital signs, exercise output, and advanced health metrics. Although understanding of basic health metrics may be intuitive (eg, peak heart rate), more complex metrics are derived from proprietary algorithms, differ among device manufacturers, and may not historically be common in clinical practice (eg, peak V˙O <sub>2</sub> , exercise recovery scores). With the massive expansion of data collected at an individual patient level, careful interpretation is imperative. In this review, we critically analyze common health metrics provided by CWDs, describe common pitfalls in CWD interpretation, provide recommendations for the interpretation of abnormal results, present the utility of CWDs in exercise prescription, examine health disparities and inequities in CWD use and development, and present future directions for research and development

Electronic structure and excitations on clean and nanostructured metal surfaces

11 páginas, 11 figuras.We present a brief overview of recent studies and new theoretical results for electron-phonon interaction in the [`(Y)]Y surface states on FCC(110) noble metal surfaces as well as in surface and quantum-well states of thin films. We discuss the oscillations of electron-phonon coupling parameter λ and the respective contribution to the lifetime broadening of these states. We analyse the effect of spin-orbit splitting of surface states on an electron-electron contribution to lifetimes of excited electrons (holes). Oscillations of the electron-electron contribution and quadratic dependence of the linewidth on energy is discussed for ultrathin Pb(111) films.We gratefully acknowledge partial support by the Department of Education of the Basque Country Governement, the University of the Basque Country (project GV-UPV/EHU, grant IT-366-07), and Ministerio de Ciencia y Tecnología (grant FIS2007-66711-C02-01).Peer reviewe