Credeur DP, Holwerda SW, Restaino RM, King PM, Crutcher KL, Laughlin MH, Padilla J, Fadel PJ. Characterizing rapid-onset vasodilation to single muscle contractions in the human leg. J Appl Physiol 118: 455-464, 2015. First published December 24, 2014 doi:10.1152/japplphysiol.00785.2014 following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above-and belowheart level positions (e.g., above heart level: leg 20% MVC, ϩ138 Ϯ 28% vs. arm 20% MVC, ϩ89 Ϯ 17%; P Ͻ 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans. vascular conductance; hyperemia; exercise onset; blood flow AT THE ONSET of dynamic exercise, skeletal muscle blood flow responses are characterized by an initial rapid increase, followed by a slower rise to steady state (20,39,44). In an effort to focus on the rapidity of the blood flow responses to exercise, studies have been performed to assess the vasodilation following single 1-s isometric muscle contractions. This initial response following a single muscle contraction, termed rapidonset vasodilation (ROV), is proportional to the intensity of contraction and peaks within five cardiac cycles postcontraction (8,11,30,48,51). ROV is considered to be an important initiating event to exercise hyperemia (8, 9). Previous investigations into ROV in humans have focused on the forearm as a model of study (2,6,12,48). However, to our knowledge, no attention has been given to the lower extremities. The lower limbs exhibit large fluctuations in blood flow throughout the day due to periods of sitting, standing, and walking (32,36,47), and importantly, skeletal muscle contractions performed in this region are our primary means of locomotion. There are also known differences in resistance vessel function between the upper and lower extremities (...

The results of this study demonstrate a functional impairment of smooth muscle contractility and neurogenic relaxation in corpus cavernosum from impotent men with abnormal penile haemodynamics. Altered smooth muscle responsiveness is likely to be a factor in the aetiology of impotence in such men and may contribute to the relatively poor results of vascular surgery for impotence.

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Primary graft dysfunction (PGD) is a potentially devastating complication of heart transplantation. Understanding the risk factors for PGD in the modern era of heart transplantation is of vital importance. This study investigated the relationship between post-left ventricular assist device (LVAD) right heart failure (RHF) and transplant outcomes. Patients with durable, continuous-flow LVADs who were transplanted between 2010 and 2016 at Barnes-Jewish Hospital were included in the study. Data collection was performed through retrospective chart review. The primary outcome was the incidence of PGD stratified by pretransplant incidence of RHF while on LVAD support. Among the 141 patients included in the study, 41 developed RHF. In the RHF cohort, 18 patients developed PGD as compared to 14 patients in the group without RHF (44% vs. 14%; p < 0.001). Mortality was significantly higher in the RHF group at 30 days (20% vs. 1%; p < 0.001) and 1 year (22% vs. 6%; p = 0.013). In a multivariable logistic regression model adjusted for confounding variables, RHF was associated with a nearly fourfold increased risk of PGD (odds ratio, 3.91; p = 0.003). The results of this study show that patients supported with LVADs who develop early severe RHF or late RHF are at increased risk of PGD and death following cardiac transplantation.