Influence of the Metaboreflex on Pulmonary Vascular Capacitance in Heart Failure

Effects of exertional dyspnea on early mobilization of patients with acute decompensated heart failure

[Purpose] In this study, we investigated the association between exertional dyspnea and length of the mobilization program in patients with acute decompensated heart failure. [Participants and Methods] We recruited all consecutive patients with heart failure who were hemodynamically stabilized after administration of intravenous medication and were able to walk >10 m before admission. Exertional dyspnea was evaluated using the visual analog scale in all patients after the 10-m walk during each session of the mobilization program. Multiple regression analysis was used to determine the factors associated with length of the mobilization program. [Results] Our study included 52 patients. Multiple regression analysis showed that the length of the mobilization program was significantly associated with the visual analog scale on day 3 and the length before the start of the mobilization program; however, the length of the mobilization program showed no significant association with age and blood urea nitrogen levels. The standardized coefficients for the visual analog scale scores on day 3 and the length before the start of the mobilization program were 0.49 and 0.33, respectively. [Conclusion] Exertional dyspnea is a good predictor of the length of the mobilization program. Our findings highlight the importance of evaluation of exertional dyspnea.

Contemporary Strategies to Manage High Blood Pressure in Patients with Coexistent Resistant Hypertension and Heart Failure With Reduced Ejection Fraction

Resistant hypertension (RH) represents an advanced subtype of hypertension that is complex to diagnose and treat. Compared with general hypertension, RH increases the risk patients will develop more advanced cardiovascular complications, including heart failure with reduced ejection fraction (HFrEF). As expected, the prevalence of RH has increased since the introduction of lower blood pressure targets included in the recent 2017 American blood pressure guidelines. The array of pharmacotherapies available to treat both hypertension and HFrEF has also expanded within the past decade. However, the efficacy of these cutting-edge pharmacotherapies has not come without a more advanced understanding of the important adjunct role non-pharmacological therapies play in helping with the management of both hypertension and HFrEF. In this review, we provide a summary of the latest pharmacological and non-pharmacological strategies that can be used to initiate treatment and optimize long-term blood pressure control in patients with coexistent RH and HFrEF.

Clinical safety of blood flow-restricted training? A comprehensive review of altered muscle metaboreflex in cardiovascular disease during ischemic exercise

Blood flow restriction training (BFRT) is an increasingly widespread method of exercise that involves imposed restriction of blood flow to the exercising muscle. Blood flow restriction is achieved by inflating a pneumatic pressure cuff (or a tourniquet) positioned proximal to the exercising muscle before, and during, the bout of exercise (i.e., ischemic exercise). Low-intensity BFRT with resistance training promotes comparable increases in muscle mass and strength observed during high-intensity exercise without blood flow restriction. BFRT has expanded into the clinical research setting as a potential therapeutic approach to treat functionally impaired individuals, such as the elderly, and patients with orthopedic and cardiovascular disease/conditions. However, questions regarding the safety of BFRT must be fully examined and addressed before the implementation of this exercise methodology in the clinical setting. In this respect, there is a general concern that BFRT may generate abnormal reflex-mediated cardiovascular responses. Indeed, the muscle metaboreflex is an ischemia-induced, sympathoexcitatory pressor reflex originating in skeletal muscle, and the present review synthesizes evidence that BFRT may elicit abnormal cardiovascular responses resulting from increased metaboreflex activation. Importantly, abnormal cardiovascular responses are more clearly evidenced in populations with increased cardiovascular risk (e.g., elderly and individuals with cardiovascular disease). The evidence provided in the present review draws into question the cardiovascular safety of BFRT, which clearly needs to be further investigated in future studies. This information will be paramount for the consideration of BFRT exercise implementation in clinical populations.

V̇o2 kinetics associated with moderate-intensity exercise in heart failure: impact of intrathecal fentanyl inhibition of group III/IV locomotor muscle afferents

Heart failure (HF) patients demonstrate impaired pulmonary, circulatory, and nervous system responses to exercise. While HF demonstrates prolonged [time constant (τ)] pulmonary O₂ uptake (V̇o₂) on-kinetics, contributing to exercise intolerance, it is unknown whether abnormal V̇o₂ kinetics couple with ventilatory and circulatory dysfunction secondary to impaired group III/IV afferents in HF. Because lower lumbar intrathecal fentanyl inhibits locomotor muscle afferents, resulting in improved exercise ventilation and hemodynamics, we tested these hypotheses: HF will demonstrate 1) rapid V̇o₂ on-kinetics and 2) attenuated steady-state V̇o₂ amplitude and O₂ deficit (O₂def) during exercise with fentanyl versus placebo. On separate visits (randomized), breath-by-breath V̇o₂ was measured in HF (ejection fraction: 27 ± 6%, New York Heart Association class I-III) and age- and sex-matched controls (both n = 9, ages: 60 ± 6 vs. 63 ± 8 yr, P = 0.37) during cycling transitions at 65% peak workload (78 ± 24 vs. 115 ± 39 W, P < 0.01) with intrathecal fentanyl or placebo. Regardless of group or condition, optimal phase II (primary component) curve fits reflected a phase I period equal to 35 s (limb-to-lung timing) via single-exponential functions. Condition did not affect steady-state V̇o₂, the phase II τ of V̇o₂, or O₂def within controls (P > 0.05). Without differences in steady-state V̇o₂, reduced O₂def in fentanyl versus placebo within HF (13 ± 4 vs. 22 ± 15 ml/W, P = 0.04) was accounted for by a rapid phase II τ of V̇o₂ in fentanyl versus placebo within HF (45 ± 11 vs. 57 ± 14 s, P = 0.04), respectively. In an integrative manner, these data demonstrate important effects of abnormal locomotor muscle afferents coupled to pulmonary and circulatory dysfunction in determining impaired exercise V̇o₂ in HF. Effects of abnormal muscle afferents on impaired exercise V̇o₂ and hence exercise intolerance may not be discernable by independently assessing steady-state V̇o₂ in HF.NEW & NOTEWORTHY Inhibition of locomotor muscle afferents results in rapid primary-component O₂ uptake (V̇o₂) on-kinetics accounting for the decreased O₂ deficit in heart failure (HF). This study revealed that abnormal musculoskeletal-neural afferents couple with pulmonary and circulatory dysfunction to provoke impaired exercise V̇o₂ in HF. Steady-state V̇o₂ cannot properly phenotype abnormal muscle afferent contributions to impaired exercise V̇o₂ in HF.