Locomotor muscle group III/IV afferents constrain stroke volume and contribute to exercise intolerance in human heart failure.

KEY POINTS: Heart failure patients with reduced ejection fraction (HFrEF) exhibit severe limitations in exercise capacity ( V̇O2 peak). One of the primary peripheral mechanisms suggested to underlie exercise intolerance in HFrEF is excessive locomotor muscle group III/IV afferent feedback; however, this has never been investigated in human heart failure. HFrEF patients and controls performed an incremental exercise test to volitional exhaustion to determine V̇O2 peak with lumbar intrathecal fentanyl or placebo. During exercise, cardiac output, leg blood flow and radial artery and femoral venous blood gases were measured. With fentanyl, compared with placebo, patients with HFrEF achieved a higher peak workload, V̇O2 peak, cardiac output, stroke volume and leg blood flow. These findings suggest that locomotor muscle group III/IV afferent feedback in HFrEF leads to increased systemic vascular resistance, which constrains stroke volume, cardiac output and O2 delivery thereby impairing V̇O2 peak and thus exercise capacity. ABSTRACT: To better understand the underlying mechanisms contributing to exercise limitation in heart failure with reduced ejection fraction (HFrEF), we investigated the influence of locomotor muscle group III/IV afferent inhibition via lumbar intrathecal fentanyl on peak exercise capacity ( V̇O2 peak) and the contributory mechanisms. Eleven HFrEF patients and eight healthy matched controls were recruited. The participants performed an incremental exercise test to volitional exhaustion to determine V̇O2 peak with lumbar intrathecal fentanyl or placebo. During exercise, cardiac output and leg blood flow ( Q̇L ) were measured via open-circuit acetylene wash-in technique and constant infusion thermodilution, respectively. Radial artery and femoral venous blood gases were measured. V̇O2 peak was 15% greater with fentanyl compared with placebo for HFrEF (P < 0.01), while no different in the controls. During peak exercise with fentanyl, cardiac output was 12% greater in HFrEF secondary to significant decreases in systemic vascular resistance and increases in stroke volume compared with placebo (all, P < 0.01). From placebo to fentanyl, leg V̇O2 , Q̇L and O2 delivery were greater for HFrEF during peak exercise (all, P < 0.01), but not control. These findings indicate that locomotor muscle group III/IV afferent feedback in patients with HFrEF leads to increased systemic vascular resistance, which constrains stroke volume, cardiac output and O2 delivery, thereby impairing V̇O2 peak and thus exercise capacity. These findings have important clinical implications as V̇O2 peak is highly predictive of morbidity and mortality in HF.

Correction to: ST­segment changes during tilt table testing for postural tachycardia syndrome: correlation with exercise stress test results.

Unfortunately, the 3rd author name was incorrectly published in the original publication. The complete correct name is given below.

ST-segment changes during tilt table testing for postural tachycardia syndrome: correlation with exercise stress test results.

BACKGROUND: Prior studies have reported ECG (Electrocardiogram) changes during tilt table testing (TTT), specifically during repolarization with ST-segment and T-wave changes. The correlation with ischemic evaluation remains unclear. The purpose of this study was to analyze the prevalence of ST-segment changes during TTT in a young, otherwise healthy population of patients with postural tachycardia syndrome (POTS), and correlate them with exercise stress test results. METHODS: Two hundred and fifty-five patients with POTS who underwent TTT and an exercise treadmill test (ETT) were analyzed. RESULTS: Forty-five had ST-segment changes/depressions during TTT (91% female, average age 36 years). Of the 45, three had ST-segment depression during ETT; all three had negative exercise stress echocardiograms (ESEs). Two others had ST-segment depressions on ETT (but not TTT), with negative ESEs. CONCLUSION: In a cohort of young, female, otherwise healthy patients with POTS, ST-segment changes occurred in a significant portion (18%) of patients during TTT. When evaluated with exercise stress testing, these patients had no evidence of underlying ischemia on ETT or ESE.

Alveolar Air and O2 Uptake During Exercise in Patients With Heart Failure.

BACKGROUND: Peak exercise pulmonary oxygen uptake (V̇O2) is a primary marker of prognosis in heart failure (HF). The pathophysiology of impaired peak V̇O2 is unclear in patients. To what extent alveolar airway function affects V̇O2 during cardiopulmonary exercise testing (CPET) has not been fully elucidated. This study aimed to describe how changes in alveolar ventilation (V̇A), volume (VA), and related parameters couple with exercise V̇O2 in HF. METHODS AND RESULTS: A total of 35 patients with HF (left ventricular ejection fraction 20 ± 6%, age 53 ± 7 y) participated in CPET with breath-to-breath measurements of ventilation and gas exchange. At rest, 20 W, and peak exercise, arterial CO2 tension was measured via radial arterial catheterization and used in alveolar equations to derive V̇A and VA. Resting lung diffusion capacity for carbon monoxide (DLCO) was assessed and indexed to VA for each time point. Resting R2 between V̇O2 and V̇A, VA, DLCO, and DLCO/VA was 0.68, 0.18, 0.20, and 0.07, respectively (all P < .05 except DLCO/VA). 20 W R2 between V̇O2 and V̇A, VA, DLCO, and DLCO/VA was 0.64, 0.32, 0.07, and 0.18 (all P < .05 except DLCO). Peak exercise R2 between V̇O2 and V̇A, VA, DLCO, and DLCO/VA was 0.55, 0.31, 0.34, and 0.06 (all P < .05 except DLCO/VA). CONCLUSIONS: These data suggest that alveolar airway function that is not exclusively related to effects caused by localized lung diffusivity affects exercise V̇O2 in moderate-to-severe HF.

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.

Reliability of Triaxial Accelerometry for Measuring Load in Men's Collegiate Ice Hockey.

Van Iterson, EH, Fitzgerald, JS, Dietz, CC, Snyder, EM, and Peterson, BJ. Reliability of triaxial accelerometry for measuring load in men's collegiate ice hockey. J Strength Cond Res 31(5): 1305-1312, 2017-Wearable microsensor technology incorporating triaxial accelerometry is used to quantify an index of mechanical stress associated with sport-specific movements termed PlayerLoad. The test-retest reliability of PlayerLoad in the environmental setting of ice hockey is unknown. The primary aim of this study was to quantify the test-retest reliability of PlayerLoad in ice hockey players during performance of tasks simulating game conditions. Division I collegiate male ice hockey players (N = 8) wore Catapult Optimeye S5 monitors during repeat performance of 9 ice hockey tasks simulating game conditions. Ordered ice hockey tasks during repeated bouts included acceleration (forward or backward), 60% top-speed, top-speed (forward or backward), repeated shift circuit, ice coasting, slap shot, and bench sitting. Coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimum difference (MD) were used to assess PlayerLoad reliability. Test-retest CVs and ICCs of PlayerLoad were as follows: 8.6% and 0.54 for forward acceleration, 13.8% and 0.78 for backward acceleration, 2.2% and 0.96 for 60% top-speed, 7.5% and 0.79 for forward top-speed, 2.8% and 0.96 for backward top-speed, 26.6% and 0.95 for repeated shift test, 3.9% and 0.68 for slap shot, 3.7% and 0.98 for coasting, and 4.1% and 0.98 for bench sitting, respectively. Raw differences between bouts were not significant for ice hockey tasks (p > 0.05). For each task, between-bout raw differences were lower vs. MD: 0.06 vs. 0.35 (forward acceleration), 0.07 vs. 0.36 (backward acceleration), 0.00 vs. 0.06 (60% top-speed), 0.03 vs. 0.20 (forward top-speed), 0.02 vs. 0.09 (backward top-speed), 0.18 vs. 0.64 (repeated shift test), 0.02 vs. 0.10 (slap shot), 0.00 vs. 0.10 (coasting), and 0.01 vs. 0.11 (bench sitting), respectively. These data suggest that PlayerLoad demonstrates moderate-to-large test-retest reliability in the environmental setting of male Division I collegiate ice hockey. Without previously testing reliability, these data are important as PlayerLoad is routinely quantified in male collegiate ice hockey to assess on ice physical activity.

Influence of menopause status and age on integrated central and peripheral hemodynamic responses to subsystolic cuffing during submaximal exercise.

Although pathophysiological links between postmenopause and healthy aging remain unclear, both factors are associated with increased blood pressure and sympathetic nerve activity (SNA) in women. Activation of polymodal musculoskeletal neural afferents originating within adventia of venules modulates SNA and blood pressure control during exercise in healthy adults. We hypothesized transient subsystolic regional circulatory occlusion (RCO) during exercise sensitizes these afferents leading to augmented systemic vascular resistance (SVR)-mediated increased mean arterial pressure (MAP) in postmenopause vs. premenopause. Normotensive women in premenopause or postmenopause (n = 14 and 14; ages: 30 ± 9 and 55 ± 7 yr, respectively; P < 0.01) performed: 1) peak exercise testing and 2) fixed-load cycling at 30% peak workload (48 ± 11 and 38 ± 6 W, respectively; P < 0.01), whereby the initial 3 min were control exercise without RCO (CTL), thereafter including 2 min of bilateral-thigh RCO to 20, 40, 60, 80, or 100 mmHg (randomized), with 2 min deflation between RCO. Both MAP (17 ± 4 vs. 4 ± 4%, P = 0.02) and SVR (16 ± 8 vs. -3 ± 8%, P = 0.04) increased at 80 mmHg from CTL in postmenopause vs. premenopause, respectively. However, cardiac index was similar in postmenopause vs. premenopause at 80 mmHg from CTL (1 ± 6 vs. 7 ± 6%, respectively; P = 0.15). There was no continuous effect of aging in MAP (P = 0.12), SVR (P = 0.07), or cardiac index (P = 0.18) models. These data suggest transient locomotor subsystolic RCO sensitizes musculoskeletal afferents, which provoke increased SVR to generate augmented MAP during exercise in postmenopause. These observations provide a novel approach for understanding the age-independent variability in exercise blood pressure control across the normotensive adult pre- to postmenopause spectrum.

Impaired cardiac and peripheral hemodynamic responses to inhaled ß2-agonist in cystic fibrosis.

BACKGROUND: Pulmonary system dysfunction is a hallmark of cystic fibrosis (CF) disease. In addition to impaired cystic fibrosis transmembrane conductance regulator protein, dysfunctional ß2-adrenergic receptors (ß2AR) contribute to low airway function in CF. Recent observations suggest CF may also be associated with impaired cardiac function that is demonstrated by attenuated cardiac output (Q), stroke volume (SV), and cardiac power (CP) at both rest and during exercise. However, ß2AR regulation of cardiac and peripheral vascular tissue, in-vivo, is unknown in CF. We have previously demonstrated that the administration of an inhaled ß-agonist increases SV and Q while also decreasing SVR in healthy individuals. Therefore, we aimed to assess cardiac and peripheral hemodynamic responses to the selective ß2AR agonist albuterol in individuals with CF. METHODS: 18 CF and 30 control (CTL) subjects participated (ages 22 ± 2 versus 27 ± 2 and BSA = 1.7 ± 0.1 versus 1.8 ± 0.0 m(2), both p < 0.05). We assessed the following at baseline and at 30- and 60-minutes following nebulized albuterol (2.5mg diluted in 3.0mL of normal saline) inhalation: 12-lead ECG for HR, manual sphygmomanometry for systolic and diastolic blood pressure (SBP and DBP, respectively), acetylene rebreathe for Q and SV. We calculated MAP = DBP + 1/3(SBP-DBP); systemic vascular resistance (SVR) = (MAP/Q)•80; CP = Q•MAP; stroke work (SW) = SV•MAP; reserve (%change baseline to 30- or 60-minutes). Hemodynamics were indexed to BSA (QI, SVI, SWI, CPI, SVRI). RESULTS: At baseline, CF demonstrated lower SV, SVI, SW, and SWI but higher HR than CTL (p < 0.05); other measures did not differ. At 30-minutes, CF demonstrated higher HR and SVRI, but lower Q, SV, SVI, CP, CPI, SW, and SWI versus CTL (p < 0.05). At 60-minutes, CF demonstrated higher HR, SVR, and SVRI, whereas all cardiac hemodynamics were lower than CTL (p < 0.05). Reserves of CP, SW, and SVR were lower in CF versus CTL at both 30 and 60-minutes (p < 0.05). CONCLUSIONS: Cardiac and peripheral hemodynamic responsiveness to acute ß2AR stimulation via albuterol is attenuated in individuals with CF, suggesting ß2AR located in cardiac and peripheral vascular tissue may be dysfunctional in this population.

Clinical Classification of Heart Failure Patients Using Cardiac Function during Exercise.

An effective approach for determining the clinical classification of heart failure (HF) patients is to estimate cardiac hemodynamics during exercise. This approach is strengthened further when measurements including cardiac power are used to describe cardiac hemodynamics. We hypothesize that cardiac power quantifies the hemodynamic and pressure-generating capability of the heart, relating with exercise tolerance better than traditional measurements in HF.

Association of pulse pressure with death, myocardial infarction, and stroke among cardiovascular outcome trial participants.

Background: Prior evidence demonstrates that pulse pressure (PP), a surrogate marker of arterial stiffness, is an independent risk factor for mortality and major adverse cardiovascular (CV) events. Objectives: The study aimed to identify the association of PP with death, myocardial infarction, and stroke among participants enrolled in large CV outcome clinical trials and determine if this association was impacted by pre-existing CV disease, or specific CV risk factors. Methods: A total of 65,382 individuals, ages 19 to 98 years, that were enrolled in one of five CV outcome trials were analyzed. Baseline demographics, history, blood pressures, and medications were collected. Univariate and multivariable analyses were conducted to explore temporal patterns, risks, and adjusted survival rates. Results: Mean baseline PP was 52 ± 12 mmHg. For every 10 mmHg increase in PP, there was an increased risk of death, stroke, or myocardial infarction (hazard ratio (HR) 1.11, 95 % CI 1.08 to 1.14, p < 0.001). Similarly, a PP ≥ 60 mmHg demonstrated an HR of 1.27 (95 % CI 1.19 to 1.36, p < 0.001) compared with PP < 60 mmHg. A similar association existed for all subgroups analyzed except for participants with a history of stroke where increasing PP did not increase risk (HR 1.02, 95 % CI 0.95 to 1.10, p = 0.53). PP was a better predictor of adverse outcomes when compared to both systolic and diastolic blood pressures using the AIC and C-index. Conclusions: Among participants enrolled in CV outcome trials, baseline PP is associated with increased risk of death, myocardial infarction, and stroke for those with pre-existing CV disease and risk factors with the exception of a prior history of stroke.

Comparable Ventilatory Inefficiency at Maximal and Submaximal Performance in COPD vs. CHF subjects: An Innovative Approach. / Ineficiência Ventilatória Comparável no Desempenho Máximo e Submáximo em Indivíduos com DPOC e ICC: Uma Abordagem Inovadora.

BACKGROUND: Currently, excess ventilation has been grounded under the relationship between minute-ventilation/carbon dioxide output ( V ˙ E - V ˙ CO 2 ). Alternatively, a new approach for ventilatory efficiency ( η E V ˙ ) has been published. OBJECTIVE: Our main hypothesis is that comparatively low levels of η E V ˙ between chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) are attainable for a similar level of maximum and submaximal aerobic performance, conversely to long-established methods ( V ˙ E - V ˙ CO 2 slope and intercept). METHODS: Both groups performed lung function tests, echocardiography, and cardiopulmonary exercise testing. The significance level adopted in the statistical analysis was 5%. Thus, nineteen COPD and nineteen CHF-eligible subjects completed the study. With the aim of contrasting full values of V ˙ E - V ˙ CO 2 and η V ˙ E for the exercise period (100%), correlations were made with smaller fractions, such as 90% and 75% of the maximum values. RESULTS: The two groups attained matched characteristics for age (62±6 vs. 59±9 yrs, p>.05), sex (10/9 vs. 14/5, p>0.05), BMI (26±4 vs. 27±3 Kg m2, p>0.05), and peak V ˙ O 2 (72±19 vs. 74±20 %pred, p>0.05), respectively. The V ˙ E - V ˙ CO 2 slope and intercept were significantly different for COPD and CHF (27.2±1.4 vs. 33.1±5.7 and 5.3±1.9 vs. 1.7±3.6, p<0.05 for both), but η V ˙ E average values were similar between-groups (10.2±3.4 vs. 10.9±2.3%, p=0.462). The correlations between 100% of the exercise period with 90% and 75% of it were stronger for η V ˙ E (r>0.850 for both). CONCLUSION: The η V ˙ E is a valuable method for comparison between cardiopulmonary diseases, with so far distinct physiopathological mechanisms, including ventilatory constraints in COPD.

FUNDAMENTO: Atualmente, o excesso de ventilação tem sido fundamentado na relação entre ventilação-minuto/produção de dióxido de carbono ( V ˙ E − V ˙ CO 2 ). Alternativamente, uma nova abordagem para eficiência ventilatória ( η E V ˙ ) tem sido publicada. OBJETIVO: Nossa hipótese principal é que níveis comparativamente baixos de η E V ˙ entre insuficiência cardíaca crônica (ICC) e doença pulmonar obstrutiva crônica (DPOC) são atingíveis para um nível semelhante de desempenho aeróbico máximo e submáximo, inversamente aos métodos estabelecidos há muito tempo (inclinação V ˙ E − V ˙ CO 2 e intercepto). MÉTODOS: Ambos os grupos realizaram testes de função pulmonar, ecocardiografia e teste de exercício cardiopulmonar. O nível de significância adotada na análise estatística foi 5%. Assim, dezenove indivíduos elegíveis para DPOC e dezenove indivíduos elegíveis para ICC completaram o estudo. Com o objetivo de contrastar valores completos de V ˙ E − V ˙ CO 2 e η E V ˙ para o período de exercício (100%), correlações foram feitas com frações menores, como 90% e 75% dos valores máximos. RESULTADOS: Os dois grupos tiveram características correspondentes para a idade (62±6 vs 59±9 anos, p>.05), sexo (10/9 vs 14/5, p>0,05), IMC (26±4 vs 27±3 Kg m2, p>0,05), e pico V ˙ O 2 (72±19 vs 74±20 % pred, p>0,05), respectivamente. A inclinação V ˙ E − V ˙ CO 2 e intercepto foram significativamente diferentes para DPOC e ICC (207,2±1,4 vs 33,1±5,7 e 5,3±1,9 vs 1,7±3,6, p<0,05 para ambas), mas os valores médios da η E V ˙ foram semelhantes entre os grupos (10,2±3,4 vs 10,9±2,3%, p=0,462). As correlações entre 100% do período do exercício com 90% e 75% dele foram mais fortes para η E V ˙ (r>0,850 para ambos). CONCLUSÃO: A η E V ˙ é um método valioso para comparação entre doenças cardiopulmonares, com mecanismos fisiopatológicos até agora distintos, incluindo restrições ventilatórias na DPOC.

National, regional, and urban-rural patterns in fixed-terrestrial broadband internet access and cardiac rehabilitation utilization in the United States.

Objective: Sparse patterns in fixed-terrestrial broadband internet access are predominantly observed among older adults and low income areas, which are interrelated factors also associated with low center-based cardiac rehabilitation (CR) utilization in the United States (US). Telehealth CR is proposed to increase CR utilization under an assumption that fixed-terrestrial broadband internet access is readily available nationwide and parallels CR utilization demand. We aimed to characterize national, geographical, and urban-rural patterns in fixed-terrestrial broadband internet access, CR eligibility rates, and center-based utilization throughout the US. Methods: Centers for Disease Control data were used to estimate CR eligibility rates and center-based utilization for 2017-2018 among Medicare fee-for-service beneficiaries aged ≥65 years. Census Bureau data for 2018 were used to estimate fixed-terrestrial broadband internet access among households of adults aged ≥65 years. Results: Southern states exhibited the highest percentage of households without broadband internet [median (IQR): 32% (24-39)] coupled with the highest CR eligibility rates [per 1,000 beneficiaries, median (IQR): 18 (15-21)] and lowest participation rates [percentage completing ≥1 session, median (IQR): 25% (17-33)]. Compared with urban areas, rural areas demonstrated significantly higher eligibility rates [15.5 (13.2-18.4) vs. 17.4 (14.5-21.0)], participation rates [30.6% (22.0-39.4) vs. 34.6% (22.6-48.3)], and percentage of households without broadband internet [23.8% (18.1-29.2) vs. 31.6% (26.5-37.6)], respectively. Conclusion: Overlapping patterns in fixed-terrestrial broadband internet access and CR eligibility rates and center-based utilization suggest telehealth CR policies need to account for the possibility that lack of broadband-quality internet access could be a barrier to accessing telehealth CR delivery models.

Prognostic Role of Metabolic Exercise Testing in Heart Failure.

Heart failure is a clinical syndrome with significant heterogeneity in presentation and severity. Serial risk-stratification and prognostication can guide management decisions, particularly in advanced heart failure, when progression toward advanced therapies or end-of-life care is warranted. Each currently utilized prognostic marker carries its own set of challenges in acquisition, reproducibility, accuracy, and significance. Left ventricular ejection fraction is foundational for heart failure syndrome classification after clinical diagnosis and remains the primary parameter for inclusion in most clinical trials; however, it does not consistently correlate with symptoms and functional capacity, which are also independently prognostic in this patient population. Utilizing the left ventricular ejection fraction as the sole basis of prognostication provides an incomplete characterization of this condition and is prone to misguide medical decision-making when used in isolation. In this review article, we survey and exposit the important role of metabolic exercise testing across the heart failure spectrum, as a complementary diagnostic and prognostic modality. Metabolic exercise testing, also known as cardiopulmonary exercise testing, provides a comprehensive evaluation of the multisystem (i.e., neurological, respiratory, circulatory, and musculoskeletal) response to exercise performance. These differential responses can help identify the predominant contributors to exercise intolerance and exercise symptoms. Additionally, the aerobic exercise capacity (i.e., oxygen consumption during exercise) is directly correlated with overall life expectancy and prognosis in many disease states. Specifically in heart failure patients, metabolic exercise testing provides an accurate, objective, and reproducible assessment of the overall circulatory sufficiency and circulatory reserve during physical stress, being able to isolate the concurrent chronotropic and stroke volume responses for a reliable depiction of the circulatory flow rate in real time.

Individualized exercise prescription and cardiac rehabilitation following a spontaneous coronary artery dissection or aortic dissection.

Aims: Prescribed aerobic-based exercise training is a low-risk fundamental component of cardiac rehabilitation (CR). Secondary prevention therapeutic strategies following a spontaneous coronary artery dissection (SCAD) or aortic dissection (AD) should include CR. Current exercise guidance for post-dissection patients recommends fundamental training components including target heart rate zones are not warranted. Omitting fundamental elements from exercise prescriptions risks safety and makes it challenging for both clinicians and patients to understand and implement recommendations in real-world practice. We review the principles of exercise prescription for CR, focusing on translating guidelines and evidence from well-studied high-risk CR populations to support the recommendation that exercise testing and individualized exercise prescription are important for patients following a dissection. Methods and results: When patients self-perceive exercise intensity there is a tendency to underestimate intensities within metabolic domains that should be strictly avoided during routine exercise training following a dissection. However, exercise testing associated with CR enrolment has gained support and has not been linked to adverse events in optimally medicated post-dissection patients. Graded heart rate and blood pressure responses recorded throughout exercise testing provide key information for developing an exercise prescription. An exercise prescription that is reflective of medical history, medications, and cardiorespiratory fitness optimizes patient safety and yields improvements in blood pressure control and cardiorespiratory fitness, among other benefits. Conclusion: This clinical practice and education article demonstrates how to develop and manage a CR exercise prescription for post-acute dissection patients that can be safe and effective for maintaining blood pressure control and improving cardiorespiratory fitness pre-post CR.

Influence of locomotor muscle group III/IV afferents on cardiovascular and ventilatory responses in human heart failure during submaximal exercise.

The purpose of this study is to determine the influence of locomotor muscle group III/IV afferent inhibition on central and peripheral hemodynamics at multiple levels of submaximal cycling exercise in patients with heart failure with reduced ejection fraction (HFrEF). Eleven patients with HFrEF and nine healthy matched controls were recruited. The participants performed a multiple stage [i.e., 30 W, 50%peak workload (WL), and a workload eliciting a respiratory exchange ratio (RER) of ∼1.0] exercise test with lumbar intrathecal fentanyl (FENT) or placebo (PLA). Cardiac output ([Formula: see text]tot) was measured via open-circuit acetylene wash-in technique and stroke volume was calculated. Leg blood flow ([Formula: see text]l) was measured via constant infusion thermodilution and leg vascular conductance (LVC) was calculated. Radial artery and femoral venous blood gases were measured. For HFrEF, stroke volume was higher at the 30 W (FENT: 110 ± 21 vs. PLA: 100 ± 18 mL), 50%peak WL (FENT: 113 ± 22 vs. PLA: 103 ± 23 mL), and RER = 1.0 (FENT: 119 ± 28 vs. PLA: 110 ± 26 mL) stages, whereas heart rate and systemic vascular resistance were lower with fentanyl than with placebo (all, P < 0.05). [Formula: see text]tot in HFrEF and [Formula: see text]tot, stroke volume, and heart rate in controls were not different between fentanyl and placebo (all, P > 0.19). During submaximal exercise, controls and patients with HFrEF exhibited increased leg vascular conductance (LVC) with fentanyl compared with placebo (all, P < 0.04), whereas no differences were present in [Formula: see text]l or O2 delivery with fentanyl (all, P > 0.20). Taken together, these findings provide support for locomotor muscle group III/IV afferents playing a role in integrative control mechanisms during submaximal cycling exercise in patients with HFrEF and older controls.NEW & NOTEWORTHY Patients with HFrEF exhibit severe exercise intolerance. One of the primary peripheral mechanisms contributing to exercise intolerance in patients with HFrEF is locomotor muscle group III/IV afferent feedback. However, it is unknown whether these afferents impact the central and peripheral responses during submaximal cycling exercise. Herein, we demonstrate that inhibition of locomotor muscle group III/IV afferent feedback elicited increases in stroke volume during submaximal exercise in HFrEF, but not in healthy controls.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review.

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Invasive Hemodynamic and Metabolic Evaluation of HFpEF.

PURPOSE OF REVIEW: Heart failure with preserved ejection fraction (HFpEF) is a complex and heterogeneous condition of multiple causes, characterized by a clinical syndrome resulting from elevated left ventricular filling pressures, with an apparently unimpaired left ventricular systolic function. Although HFpEF has been long recognized as a distinct entity with significant morbidity for patients, its diagnosis remains challenging to this day. In recent years, few diagnostic algorithms have been postulated to aid in the identification of this condition. Invasive hemodynamic and metabolic evaluation is often warranted for the conclusive diagnosis and risk stratification of HFpEF, in patients presenting with undifferentiated DOE. RECENT FINDINGS: Rest and provoked hemodynamics remain the golden-standard diagnostic tool to unequivocally confirm the diagnosis of both established and incipient HFpEF, respectively. Cycle exercise hemodynamics is the paramount provocative maneuver to unveil this condition. Rapid saline loading does not offer a significant benefit over that of cycle exercise. Vasoactive agents can also uncover and confirm incipient HFpEF disease. The role of metabolic evaluation in patients presenting with idiopathic dyspnea on exertion (DOE) is of unparalleled value for those who have expertise in cardiopulmonary exercise test (CPET) interpretation; however, the average clinician who focuses solely on oxygen consumption will find it underwhelming. Invasive CPET stands alone as the ultimate diagnostic tool to discriminate between pulmonary, cardiovascular, and skeletal muscle disorders, and their respective contribution to DOE and exercise intolerance. SUMMARY: Several hemodynamic and metabolic parameters have demonstrated not only strong diagnostic value, but also predictive power in HFpEF. Additionally, these diagnostic methods have given rise to several therapeutic interventions that are now part of our clinical armamentarium. Regrettably, due to the heterogeneity and multicausality of HFpEF, none of the targeted interventions have been so far successful in decreasing the mortality burden of this prevalent condition.

The obesity paradox in heart failure: What is the role of cardiorespiratory fitness?

The obesity paradox describes a survival benefit for higher body mass index in patients with heart failure. But other factors like cardiorespiratory fitness may play a role in heart failure development, severity, and survival. Although more research is needed to better understand the relationships between body mass index and fitness in patients with heart failure, evidence indicates that recommending weight loss and an exercise program is appropriate for most patients.

Spontaneous coronary artery dissection: Principles of management.

Spontaneous coronary artery dissection (SCAD) is an acute noniatrogenic tear in the coronary arterial wall, leading to disruption of coronary blood flow and myocardial infarction. Previously considered rare, it is now recognized as a common cause of acute coronary syndrome, particularly in young women. Despite growing awareness of this disease, there is a paucity of data on acute and long-term therapy. This review summarizes the existing literature on treatment of SCAD and describes a comprehensive management strategy.