Heart Rate Responses Research Articles

Abstract Mo056: Cholinergic Activation Suppresses Optogenetic Stimulation of Intrinsic Cardiac Catecholaminergic Neurons in Perfused Mouse Hearts

Balance of cholinergic and catecholaminergic activation is necessary to maintain heart health. Interrogating the acute interaction of these autonomic pathways can be done using optogenetics via selective expression of channelrhodopsin (ChR2) within intrinsic cardiac neurons. We tested the hypothesis that cholinergic activation via exogenous acetylcholine (ACh) would suppress the beta-adrenergic heart rate (HR) acceleration induced by tyrosine hydroxylase (TH) neuron stimulation, with the prominence of AV block increasing with increased ACh concentration. ECGs were recorded during perfused heart studies using wild-type (WT) mice and transgenic mice that selectively expressed ChR2 in TH neurons that secrete norepinephrine (NE). HR responses were measured for WT while increasing [NE] and for TH by illuminating the right atrium (465nm, microLED) at a range duty cycles and frequencies. Duty cycles (at 5Hz) increasing from 5-50% caused proportional increases in HR however HR was unstable at duty cycles >30%. At 20% duty cycle, HR increased by 39.43±6.79% (n=6). HR increased sigmoidally at frequencies from 2.5-15Hz (with 30ms pulse width) but HR was unstable at 15Hz. At 10Hz, heart rate increased by 64.24±13.47% (n=4). When comparing HR increases for TH (n=5) and WT+NE (n=4), optogenetic activation resulted in similar maximum HRs but drastically different rise times (7.6±1.25 vs 46.43±5.01 beats/sec, respectively). HR suppression at increasing doses of ACh was measured while perfusing WT hearts with NE and photostimulating TH hearts. The addition of ACh caused beta-adrenergic HR increases to diminish, eventually reaching below baseline HR. In WT+NE animals this occurred at 400nM ACh and in TH animals this did not occur until 1800nM ACh. As ACh increased in TH animals, onset of AV block occurred sooner and more prominently. In conclusion, optogenetic activation of TH neurons caused rapid HR acceleration that was suppressed by ACh at concentrations much higher than that required to suppress acceleration during NE perfusion. AV block also occurred more rapidly during TH neuron activation as [ACh] increased, demonstrating a time-dependent effect in the interaction of cholinergic and catecholaminergic activation.

Thermal and Cardiovascular Responses during Exertional Heat Stress after Diphenhydramine Use: A Randomized Crossover Trial.

Despite sparse systematic evidence, current exercise heat safety recommendations suggest that antihistamines blunt sweating and increase the risk for heat-related injury during exertional heat stress. The primary purpose of the present study was to examine whether diphenhydramine hydrochloride (DPH), a first-generation antihistamine, effects the sweating, core temperature, and heart rate response during exertional heat stress using a double-blind randomized crossover design. On two occasions separated by >48 h, 20 healthy adults (10 females, 23 ± 3 y, BSA: 1.9 ± 0.2 m2, BMI: 23.7 ± 2.2 kg·m-2) orally consumed either 50 mg of DPH or placebo (PLA), and then rested for 2 h in a climate-controlled room maintained at 30 °C and 35%RH (Heat Index of ~29 °C), followed by a 60-minute fixed-heat production treadmill walk (6.3 ± 1.0 W·kg-1). Whole-body sweat loss (WBSL), local sweat rate (LSR), rectal temperature (Trec), and heart rate (HR) were measured. WBSL was not different between conditions (PLA: 406 ± 78 g; DPH: 396 ± 75 g, P = 0.26, treatment effect: -10 g 95%CI [-28, 8]). No differences were observed for the onset for sweating (PLA: 13.5 ± 2.4 min; DPH: 13.3 ± 2.7 mins, P = 0.79), and steady-state LSR (PLA: 0.83 ± 0.26 mg·cm-2·min-1; DPH: 0.82 ± 0.27 mg·cm-2·min-1, P = 0.99). No difference in baseline Trec was observed (PLA: 37.09 ± 0.35 °C, DPH: 37.13 ± 0.33 °C, P = 0.68), and the 60-min ΔTrec was not different (P = 0.99) between PLA (0.83 ± 0.29 °C) and DPH (0.81 ± 0.30 °C). HR was similar at baseline (PLA: 86 ± 13 BPM, DPH: 84 ± 11 BPM, P = 0.30) and end-exercise (PLA: 134 ± 28 BPM, DPH: 132 ± 26BPM, P = 0.90). 50 mg of DPH does not modify the sweating, core temperature, and heart rate response during exertional heat stress in young healthy adults.

Lung Volume Changes in Stable Preterm Infants Weaned From Nasal CPAP to High Flow: A Prospective Cohort Study

BackgroundWeaning preterm infants off nasal continuous positive airway pressure (nCPAP) using nasal high-flow therapy has gained popularity. The effects of such a weaning strategy on lung volumes are unclear. Research QuestionHow does the transition from nCPAP to high-flow as well as varying flow levels affect lung volumes in stable preterm infants? Study Design and MethodsThis was a prospective cohort study in infants 30-35 weeks postmenstrual age. After a baseline period on nCPAP 5 cm H2O, infants were switched to high-flow 8 L/min for 30 minutes. The flow level was reduced by 2 L/min every 30 minutes to a minimum of 2 L/min and subsequently increased to the initial level of 8 L/min, followed by another nCPAP period. Using electrical impedance tomography (EIT), end-expiratory lung impedance (EELZ) as a proxy for end-expiratory lung volume (EELV) and cardiorespiratory parameters were recorded at each flow level and compared to baseline. ResultsOverall, 8438 breaths from 19 infants were analyzed. EELV changed significantly during the study (P = 0.002), which was mainly attributable to a loss of EELV when high-flow was reduced to 6 and 4 L/min and re-escalated to 4, 6, and 8 L/min. Apart from a reduction in minute ventilation (P = 0.004), no other significant changes were found in EIT ventilation parameters. Alterations in lung volume were accompanied by an increase in heart rate (P = 0.02) and a decrease in SpO2/FiO2 ratio (P < 0.001). InterpretationThe transition from nCPAP to high-flow is likely to result in a reduced EELV, accompanied by physiological responses in heart rate and oxygenation. Despite a stepwise escalation to pre-weaning flow levels, only partial recovery of lung volume losses is achievable with high-flow. Clinical Trial RegistrationClinicalTrials.gov (NCT05237622)

Which Components of the Haemodynamic Response to Active Stand Predict Cardiovascular Disease and Mortality? Data From The Irish Longitudinal Study on Ageing.

An integrated haemodynamic response during standing may serve as an integrative marker of neuro-cardiovascular function. Individual components of both heart rate (HR) and blood pressure (BP) responses to active stand (AS) have been linked with cardiovascular disease (CVD) and mortality. We assessed longitudinal associations between entire HR/BP response curves during AS, incident CVD and mortality over 12 years. Beat-to-beat measurements of dynamic HR/BP responses to AS were conducted in 4,336 individuals (61.5±8.2 years; 53.7% female). Functional Principal Components Analysis was applied to HR/BP response curves and their association with CVD and mortality assessed. We hypothesised that integrating BP/HR information from the entire haemodynamic response curve may uncover novel associations with both CVD and mortality. Higher systolic BP (SBP) before AS and blunted recovery of SBP during AS was associated with all-cause mortality over 12-years (Hazard Ratio [HR]: 1.14; 1.04, 1.26; p=0.007). Higher baseline/peak HR and lower HR from 30 seconds post stand onwards were associated with lower mortality due to circulatory causes (HR: 0.78; 0.64, 0.95; p = 0.013). Higher HR throughout AS was associated with mortality from other causes (HR: 1.48; 1.22, 1.80; p<0.001). Findings persisted on robust covariate adjustment. We observed distinct relationships between HR/BP responses to AS and 12-year incident CVD and mortality. Integrating the entire haemodynamic response may reveal more nuanced relationships between HR/BP responses to AS, CVD and mortality - serving as an integrative marker of neuro-cardiovascular health in midlife and beyond.

Self-blame, posttraumatic stress, and cardiovascular reactivity among sexual trauma survivors.

Although trauma is closely linked with hyperarousal and cardiovascular health, little research has examined the effects of posttraumatic stress symptoms (PTSS) on cardiovascular reactivity to trauma reminders among sexual trauma survivors. One type of negative appraisal after trauma, self-blame, is common after sexual trauma, but its relation to cardiovascular reactivity is unknown. The present study aimed to examine the influence of both PTSS and self-blame on blood pressure and heart rate (HR) reactivity to a trauma reminder. Cardiovascular reactivity was measured before, during, and after a laboratory-based sexual trauma reminder among 72 young adult women who have experienced sexual trauma. Higher PTSS predicted lower diastolic blood pressure (DBP) reactivity during the trauma reminder. Higher levels of self-blame predicted higher HR and systolic blood pressure (SBP) reactivity during and after the trauma reminder. Overall, these findings suggest that survivors of sexual trauma with higher levels of PTSS experience a blunting reaction of DBP when exposed to trauma reminders, as opposed to a more typical cardiovascular stress reaction that may elevate and then extinguish to baseline levels. Meanwhile, individuals with higher levels of self-blame have heightened cardiovascular SBP and HR responses during trauma reminders that do not return to baseline levels, perhaps due to self-blame leading individuals to be more 'on guard' to prevent future threats. Longitudinal studies are needed to explore the potential long-term cardiovascular impacts of heightened self-blame and PTSS and their associated cardiovascular reactivity patterns.

A quasi-experimental study on the energy expenditure, exercise intensity, and rating of perceived exertion of a male bodybuilding posing training.

This study is novel in classifying bodybuilding posing training as vigorous intensity exercise using metabolic equivalents (METs) and heart rate (HR) responses. It provides empirical evidence showing that posing training meets the vigorous intensity benchmarks, with METs and %HRmax values comparable to established vigorous exercise standards. The research highlights the novel finding that stimulant usage and the peak week phase of preparation significantly influence physiological responses and perceived exertion in bodybuilders. Specifically, athletes using stimulants and those in peak week displayed higher ratings of perceived exertion (RPE) and maximum heart rates, indicating that these factors notably affect the intensity and perceived difficulty of posing training.

CITED4 gene therapy protects against maladaptive cardiac remodeling after ischemia/reperfusion injury in mice

Cardiac signaling pathways functionally important in the heart's response to exercise often protect the heart against pathological stress, potentially providing novel therapeutic targets. However, it is important to determine which of these pathways can be feasibly targeted invivo. Transgenic overexpression of exercise-induced CITED4 has been shown to protect against adverse remodeling after ischemia/reperfusion injury (IRI). Here we investigated whether somatic gene transfer of CITED4 in a clinically relevant time frame could promote recovery after IRI. Cardiac CITED4 gene delivery via intravenous AAV9 injections in wild type mice led to an approximately 3-fold increase in cardiac CITED4 expression. After 4weeks, CITED4-treated animals developed physiological cardiac hypertrophy without adverse remodeling. In IRI, delivery of AAV9-CITED4 after reperfusion resulted in a 6-fold increase in CITED4 expression 1week after surgery, as well as decreased apoptosis, fibrosis, and inflammatory markers, culminating in a smaller scar and improved cardiac function 8weeks after IRI, compared with control mice receiving AAV9-GFP. Somatic gene transfer of CITED4 induced a phenotype suggestive of physiological cardiac growth and mitigated adverse remodeling after ischemic injury. These studies support the feasibility of CITED4 gene therapy delivered in a clinically relevant time frame to mitigate adverse ventricular remodeling after ischemic injury.

A Descriptive Exploration of Heart Rate Response to Live Professional Irish Dance Performance.

Introduction: Research investigating the physiological demands of dance performance has documented exercise intensity and time spent in work and rest; however, available data are across limited dance genres and often use rehearsal or simulated conditions. Real-time data recorded during live performance with an audience are limited. The aim of the study is to provide a detailed description of the physiological demands of live professional Irish dance performance. Method: The entire Irish dance cast of Riverdance participated in the study (n = 24). Approval was granted by the Institutional Research Ethics Committee. Matinee and evening performances on the first day of a tour were examined in a descriptive, cross-sectional design. Heart rate (HR) monitors worn discretely under costumes recorded data every 5-seconds. Video analysis allowed calculation of time spent in work and rest. All descriptive analyses were split by role (troupe/lead) and sex (male/female). Results: Dancers worked at hard/very hard intensities (mean > 72%, peak > 91% HRmax) for ~3 minutes at a time for 3-9 individual dance numbers. There was a high variation in overall demand experienced by individual dancers due to variation in both duration and intensity of on-stage time, dependent upon their role. Mean total on-stage time was 18.18 ± 5.82 minutes, 19.43 ± 5.80 minutes, 29.71 ± 0.62 minutes, 20.00 ± 0.00 minutes for male troupe, female troupe, male lead, and female lead dancers, respectively. Recovery periods were varied in terms of duration, activity undertaken, and HR response. Conclusion: Individual dance numbers within a professional Irish dance show were high intensity for a short duration when considered in isolation, but overall physiological demand experienced by any one dancer across the entire show varied dependent upon their role and off-stage/recovery practices. Future research investigating the physiological demands of dance performance should ensure analysis accounts for the individual dancer's role and should capture the entire show duration in repeated exposures.

Influence of endogenous and exogenous hormones on the cardiovascular response to lower extremity exercise and group III/IV activation in young females.

Oral contraceptive (OC) use can increase resting blood pressure (BP) in females as well as contribute to greater activation of group III/IV afferents during upper body exercise. It is unknown, however, whether an exaggerated BP response occurs during lower limb exercise in OC users. We sought to elucidate the group III/IV afferent activity-mediated BP and heart rate responses while performing lower extremity tasks during early and late follicular phases in young, healthy females. Females not taking OCs (NOC: n = 8; age: 25 ± 4 yr) and those taking OCs (OC: n = 10; age: 23 ± 2 yr) completed a continuous knee extension/flexion passive stretch (mechanoreflex) and cycling exercise with subsystolic cuff occlusion (exercise pressor reflex), which was followed by a 2-min postexercise circulatory occlusion (PECO) (metaboreflex). Data collection occurred on two occasions: once during the early follicular phase (days 1-4) and once during the late follicular phase (days 10-14) of their menstrual cycle (NOC) or during the placebo and active pill phases (OC). Resting mean arterial BP and heart rate were not different between phases in NOC and OC participants (P > 0.05). Hemodynamic responses to metaboreflex, mechanoreflex, and collective exercise pressor reflex activation were not different between phases in both groups (P > 0.05). In conclusion, although OCs are known to increase BP at rest, our findings indicate that neither endogenous nor exogenous (OC) sex hormones modulate BP during large, lower limb muscle exercise with or without group III/IV afferent activation in young, healthy females.NEW & NOTEWORTHY Sex differences in the cardiovascular response to exercise have been demonstrated and may be dependent on sex hormone levels. Furthermore, oral contraceptives (OCs) have been shown to exaggerate the blood pressure response to upper extremity exercise. The results of this study indicate that neither endogenous nor exogenous (OC) sex hormones modulate BP during lower extremity dynamic exercise or with group III/IV afferent activation in young, healthy females.

Cardiovascular autonomic and peripheral sensory neuropathy in women with obesity.

A higher incidence of neural dysfunction in people with obesity has been described. We determined the prevalence of neuropathic lesions in obese women and evaluated their potential association with anthropometric and laboratory parameters. In our cross-sectional study, we enrolled female patients with obesity and without diabetes before obesity treatment. Voluntary female subjects were controls with a normal body mass index (BMI). Autonomic function was assessed by Ewing's cardiovascular reflex tests, while comprehensive peripheral neuropathic assessments were conducted utilizing the Neurometer®, Tiptherm®, Monofilament®, and Rydel-Seiffer tuning fork tests. Sudomotor function was assessed by the Neuropad®-test. Body composition was examined using the InBody 770. 71 patients (mean ± SD; age: 36.1 ± 8.3 years; BMI: 40.2 ± 8.5 kg/m2) and 36 controls (age: 36.4 ± 13.3 years; BMI: 21.6 ± 2.1 kg/m2) were enrolled. Patients had significantly higher systolic (patients vs. controls; 137.5 ± 16.9 vs. 114.6 ± 14.8 mmHg, p<0.001) and diastolic (83.0 ± 11.7 vs.69.8 ± 11.2 mmHg, p<0.001) blood pressure compared to controls. Among autonomic tests, only the heart rate response to Valsalva maneuver (Valsalva-ratio) revealed significant impairment in patients (1.4 ± 0.2 vs. 1.7 ± 0.4, p<0.001). Neurometer® at the median nerve revealed increased current perception threshold (CPT) values at all stimulating frequencies in patients (CPT at 2000Hz: 204.6 ± 70.9 vs. 168.1 ± 66.9, p=0.013; 250Hz: 84.4 ± 38.9 vs. 56.5 ± 34.8, p<0.001; CPT at 5Hz: 58.5 ± 31.2 vs 36.9 ± 29.1, p<0.001). The Rydel-Seiffer tuning fork test has revealed a significant impairment of vibrational sensing on the lower limb in patients (right hallux: 6.8 ± 0.9 vs. 7.4 ± 0.8, p=0.030; left hallux: 6.9 ± 0.8 vs. 7.3 ± 0.9, p=0.029). The Neuropad® testing showed a significant impairment of sudomotor function in women with obesity. A negative correlation was found in patients between BMI and the 25-hydroxy-D3/D2-vitamin levels (r=-0.41, p=0.00126) and a positive correlation between the BMI and resting systolic blood pressure (r=0.26, p=0.0325). Peripheral sensory neuronal and sudomotor function impairments were detected in female patients with obesity compared to the controls with normal BMI. Cardiovascular autonomic dysfunction was also revealed by the Valsalva-ratio in these patients, suggesting the presence of parasympathetic dysfunction. The negative correlation between BMI and the 25-hydroxy-D3/D2-vitamin highlights the potential deficiency of vitamin D in the population affected by obesity.

Cardiac autonomic response to acute painful stimulus in individuals with chronic neck pain: A case-control study

PurposeCharacterize heart rate and cardiac autonomic response to painful stimulus on neck pain. MethodsTwenty-five individuals with neck pain and 25 healthy subjects were included. Heart rate variability and heart rate were assessed in the conditioned pain modulation test at pretest rest, during testing and in recovery. Heart rate variability indices were obtained using linear and nonlinear methods. ResultsNo significant differences were observed between groups regarding heart rate and the linear methods (p > 0.05). However, significant difference was observed between groups regarding nonlinear methods (standard deviation of the instantaneous variability of beat-to-beat interval variability, p = 0.005) ConclusionsIndividuals with chronic neck pain showed autonomic responses similar to those of their healthy counterparts during the conditioning stimulus.

Effect of zamicastat on blood pressure and heart rate response to cold pressor test: A double-blind, randomized, placebo-controlled study in healthy subjects.

Dopamine beta-hydroxylase (DβH) inhibitors, like zamicastat, hold promise for treating pulmonary arterial hypertension. This study aimed to validate the mechanism of action of zamicastat by studying its effect on the overdrive of the sympathetic nervous system (SNS). A single-centre, prospective, double-blind, randomized, placebo-controlled, crossover study evaluated the effect of 400 mg zamicastat in 22 healthy male subjects. Cold pressor test (CPT) was performed at screening and each treatment period on Days -1 and 10. Plasma and 24 h-urine levels of dopamine (DA), epinephrine (EPI) and norepinephrine (NE), and plasma DβH activity, were measured. Compared to placebo, zamicastat showed a - 4.62 mmHg decrease in systolic blood pressure during the cold stimulus vs. rest phases on Day 10 of CPT (P = .020). Zamicastat decreased mean arterial pressure response to cold stimulus during CPT (-2.62 mmHg; P = .025). At Day 10, zamicastat significantly increased plasma DA, before CPT (12.63 ng/L; P = .040) and after CPT (19.22 ng/L; P = .001) as well as the estimated plasma EPI change from baseline after CPT (P = .040). Inhibition of plasma DβH activity ranged from 19.8% to 25.0%. At Day 10, significant reductions in 24-h urinary excretion of EPI (P = .002) and NE (P = .001) were observed. Zamicastat Cτ geometric mean ± GSD ranged from 45.86 ± 1.46 ng/mL on Day 3 to 58.64 ± 1.52 ng/mL on Day 10, with moderate inter-individual variability (CV: 32.6%-36.6%). Steady state was already achieved on Day 6. Our results demonstrated the effect of zamicastat on the overdrive sympathetic response to cold stimulus, confirming its potential as SNS modulator.

Assessment of cardiorespiratory fitness in Chinese patients with early to mid-stage Parkinson’s disease

Purpose To evaluate cardiorespiratory fitness in patients with early to mid-stage Parkinson’s disease by cardiopulmonary exercise test (CPET) on a stationary cycle ergometer. Methods To compare the differences in each index of the cardiopulmonary exercise test between the two groups of subjects; general data such as disease duration, medication use and exercise habits were also collected. Results (1) Finally, 36 Parkinson’s disease patients and 12 healthy controls successfully completed the cardiopulmonary exercise test without any adverse events. (2) The V’O2peak, Metspeak, RERpeak, MVVpeak, Wpeak, HRpeak, HRpeak/pre, percentage of HRR-1 min decay > 12 bpm, SBPpeak in the Parkinson’s disease group were lower than those in the control group (p < .05, each). Detailed data: V’O2peak (15.7 ± 4.5vs21.5 ± 3.6 ml/kg/min, p < .01), Metspeak (4.5 ± 1.3 vs 6.1 ± 1.0, p < .01), RERpeak (1.04 ± 0.10 vs 1.15 ± 0.10, p = .001), MVVpeak (37.22 ± 11.58 vs 53.00 ± 16.85L/min, p = .009), Wpeak (49.17 ± 29.72 vs 49.17 ± 29.72W, p < .01), HRpeak (111.08 ± 16.67 vs 111.08 ± 16.67bpm, p < .01), HRpeak/pre (71.19 ± 10.06 vs 96.00 ± 21.13, p = .002), percentage of HRR-1min decay > 12bpm (33.3% vs 100%, p < .01), systolic blood pressure (155.81 ± 31.83 vs 175.83 ± 17.84 mmHg, p = .01). (3) Divided Parkinson’s disease patients into high V’O2peak group (V’O2peak ≥ 15 mL/kg/min) and low V’O2peak group (V’O2peak < 15 mL/kg/min). The age of patients, Hoehn–Yahr grade and incidence of symptom fluctuation in high V’O2peak group were lower (p < .05, respectively), percentage of males and percentage of HRR-1 min decay > 12 bpm were higher (p < .05, respectively); p < .05 is considered a statistically significant difference. Detailed data: age of patients(61.05 ± 6.93 vs 68.57 ± 7.99 years, p = .005), Hoehn–Yahr grade(1.75 ± 0.48 vs 2.18 ± 0.64, p = .028), incidence of symptom fluctuation (59.1 vs 92.9%, p = .03), percentage of males (77.7 vs 42.9%, p = .041), percentage of HRR-1 min decay > 12 bpm (50 vs 7.1%, p = .008). Conclusions Cardiopulmonary exercise test was safe to perform and the cardiorespiratory fitness is significantly reduced in patients with early and middle stage Parkinson’s disease. Patients with Parkinson’s disease presented blunted heart rate and systolic blood pressure responses to exercise test. Females, older age, fluctuating symptoms, high H-Y staging and higher activities of daily living may be associated with lower oxygen uptake.

The heart rate response to the 6-min walk test in atrial fibrillation patients with or without beta-blockers: Referring to patients with sinus rhythm.

The aim was to evaluate the effect of beta-blockers (BB) on the response of heart rate (HR) to 6-min walk test (6MWT) in atrial fibrillation (AF) and whether the AF patients treated with BB have a similar HR response to 6MWT as the AF and sinus rhythm (SR) patients without BB treatment at the same resting HR level. The before-after study involving 74 AF patients was to evaluate the effect of BB treatment (pre-BB and with BB). The comparison study included 74 BB-treated AF patients (with BB), 74 matched AF patients without BB (no BB), and 74 SR patients. The percentage increase amplitude of HR (HR-PIA) in 6MWT was calculated: [(the exercise HR - the resting HR)/(the resting HR)] × 100%. The before-after study showed that BB treatment decreased the resting and mean exercise HR (98.6 ± 15.2 vs. 85.5 ± 11.2 bpm and 121.3 ± 17.3 vs. 109.0 ± 16.7 bpm) during 6MWT. The comparison study demonstrated that against the SR, the AF with BB and no BB groups have higher mean exercise HR-PIA (28.2 ± 17.1% and 22.0 ± 9.6%, vs. 6.9 ± 3.7%) when their resting HR is similar. Moreover, the mean exercise HR-PIA was also significantly higher in the with BB group than in the no BB group. In AF patients with relatively higher resting HR, BB treatment could decrease the resting and exercise HR during 6MWT. However, BB treatment could not effectively attenuate the exercise HR rise as compared with AF without BB treatment, even with similar resting HR levels.

Clinical Pharmacogenetics Implementation Consortium Guideline (CPIC)for CYP2D6, ADRB1, ADRB2, ADRA2C, GRK4, and GRK5 Genotypes and Beta-Blocker Therapy.

Beta-blockers are widely used medications for a variety of indications, including heart failure, myocardial infarction, cardiac arrhythmias, and hypertension. Genetic variability in pharmacokinetic (e.g., CYP2D6) and pharmacodynamic (e.g., ADRB1, ADRB2, ADRA2C, GRK4, GRK5) genes have been studied in relation to beta-blocker exposure and response. We searched and summarized the strength of the evidence linking beta-blocker exposure and response with the six genes listed above. The level of evidence was high for associations between CYP2D6 genetic variation and both metoprolol exposure and heart rate response. Evidence indicates that CYP2D6 poor metabolizers experience clinically significant greater exposure and lower heart rate in response to metoprolol compared with those who are not poor metabolizers. Therefore, we provide therapeutic recommendations regarding genetically predicted CYP2D6 metabolizer status and metoprolol therapy. However, there was insufficient evidence to make therapeutic recommendations for CYP2D6 and other beta-blockers or for any beta-blocker and the other five genes evaluated (updates at www.cpicpgx.org).

Apnea or normal breathing during repeated high-intensity swimming enhance sprint efficiency and which metabolic disorder?

The aim of this study was to investigate the effect of normal breath and apnea swimming on acid-base balance, physiological responses and performance during high-intensity interval training in swimming. Sixteen swimmers completed 6×50 m intervals of freestyle swimming with normal breath and apnea at maximum intensity, with 1 minute rest. Capillary blood gases (pH, PCO<inf>2</inf>, PO<inf>2</inf>, HCO<inf>3</inf>, Hct, Hb) were collected at four (4) measurement time points: 1) at rest once; 2) at rest just after the 3rd repetition; 3) at finish; and 4) at 10 min of recovery. Heart rate (HR) during swimming, lactate acid (La) concentration and swimming time (t<inf>50</inf>) were measured. Our study showed uncompensated metabolic acidosis due to increased lactic acidosis in both breathing conditions, more pronounced in apnea, and faster swimming times in apnea without different heart rate responses. Apnea during repetitive high intensity long distance interval 50 m freestyle swimming causes uncompensated metabolic acidosis but improves sprint performance.

Blunted brachial blood flow velocity response to acute mental stress in PTSD females.

Post-traumatic stress disorder (PTSD) is associated with increased cardiovascular disease (CVD) risk. Compared with males, females are twice as likely to develop PTSD after trauma exposure, and cardiovascular reactivity to stress is a known risk factor for CVD. We aimed to examine hemodynamic responses to acute mental stress in trauma-exposed females with and without a clinical diagnosis of PTSD. We hypothesized that females with PTSD would have higher heart rate (HR), blood pressure (BP), and lower blood flow velocity (BFV) responsiveness compared with controls. We enrolled 21 females with PTSD and 21 trauma-exposed controls. We continuously measured HR using a three-lead electrocardiogram, BP using finger plethysmography, and brachial BFV using Doppler ultrasound. All variables were recorded during 10 min of supine rest, 5 min of mental arithmetic, and 5 min of recovery. Females with PTSD were older, and had higher BMI and higher resting diastolic BP. Accordingly, age, BMI, and diastolic BP were covariates for all repeated measures analyses. Females with PTSD had a blunted brachial BFV response to mental stress (time × group, p = 0.005) compared with controls, suggesting greater vasoconstriction. HR and BP responses were comparable. In conclusion, our results suggest early impairment of vascular function in premenopausal females with PTSD.

Effects of Resistance Exercise with and without Blood Flow Restriction on Acute Hemodynamic Responses: A Systematic Review and Meta-Analysis.

Low-load intensity resistance exercise with blood flow restriction (BFR) is an alternative method for enhancing strength and muscle mass. However, acute cardiovascular responses to a complete training session remain uncertain compared to high-load intensity resistance exercise (HI). Therefore, the objective of this study to examine acute and post-exercise hemodynamic responses to low-load BFR and HI protocols. This systematic review and meta-analysis (RD42022308697) followed PRISMA guidelines to investigate whether the responses of heart rate (HR), blood systolic (SBP), blood diastolic pressure (DBP), and rate pressure product (RPP) immediately after and up to 60 min post-exercise from BFR were consistent with those reported after resistance exercises performed at HI in healthy individuals. Searches using PICO descriptors were conducted in databases from January 2011 to December 2023, and effect sizes were determined by Hedge's g. The selected studies involved 160 participants in nine articles, for which the responses immediately after BFR and HI exercises showed no differences in HR (p = 0.23) or SBP (p = 0.57), but significantly higher DBP (p < 0.01) and lower RPP (p < 0.01) responses were found when comparing BFR to HI. Furthermore, the BFR and HI protocols showed no differences regarding SBP (p = 0.21) or DBP (p = 0.68) responses during a 15 to 60 min post-exercise period. Thus, these results indicated that hemodynamic responses are similar between BFR and HI, with a similar hypotensive effect up to 60 min following exercise.

Cognitive interference of respiratory versus limb muscle dual tasking in healthy adults.

Inspiratory threshold loading (ITL) and associated dyspnoea have been shown to interfere with cognition during cognitive-motor dual tasking. However, ITL has not been compared with another rhythmic muscle activity, such as lower limb pedalling. While ITL has been shown to interfere with cognition, the mechanism of the prefrontal cortex (PFC) during ITL or other rhythmical muscle dual tasking, has not been elucidated. Given the cognitive interference that arises during ITL, we hypothesise that ITL cognitive-motor dual tasking will result in greater cognitive decrements and increased PFC activity compared with the pedalling cognitive-motor dual task. 30 healthy participants (16 females; median age 23 (interquartile range 23-24) years) were recruited. They performed five 3-min tasks in a single visit in a random order: single tasks were ITL, pedalling and Stroop task and dual tasks were ITL-Stroop and pedalling-Stroop. Participant's PFC activity was assessed bilaterally using functional near-infrared spectroscopy throughout each task. Single- and dual-task cognitive performance was evaluated by measuring Stroop task reaction time and accuracy. Dyspnoea and rating of perceived exertion were evaluated at the end of each task. ITL-Stroop resulted in greater impairments in reaction time (p<0.001), accuracy (p<0.01) and increased medial/dorsolateral PFC activity (p≤0.006) than pedalling-Stroop. ITL-Stroop elicited greater Borg dyspnoea and rating of perceived exertion than pedalling-Stroop (p<0.001), despite pedalling-Stroop having a greater heart rate response (p<0.001). The heightened cognitive decrements, perceptual response and PFC activity suggest that inspiratory muscle loading and its accompanied dyspnoea results in greater cognitive interference than rhythmic pedalling.

Cerebrovascular Autoregulation in Preterm Infants Using Heart Rate or Blood Pressure: A Pilot Study.

Cerebrovascular autoregulation (CAR) is often impaired in preterm infants but requires invasive mean arterial blood pressure (MABP) measurements for continuous assessment. We aimed to assess whether using heart rate (HR) results in different CAR assessment compared with using MABP. We compared CAR (moving window correlation-coefficient with cerebral oxygenation saturation (rcSO2)), and percentage of time with impaired CAR (%timeCARi) calculated by either HR (TOHRx, tissue oxygenation heart rate reactivity index) or MABP (COx, cerebral oximetry index) during the first 72 h after birth, and its association with short-term cerebral injury. We included 32 infants, median gestational age of 25 + 5/7 weeks (interquartile range 24 + 6/7-27 + 5/7). COx and TOHRx correlation coefficients (cc) were significantly different in the first two days after birth (individual means ranging from 0.02 to 0.07 and -0.05 to 0.01). %TimeCARi using MABP (cc cut-off 0.3), was higher on day 1 (26.1% vs. 17.7%) and day 3 (23.4% vs. 16.9%) compared with HR (cc cutoff -0.3). During 65.7-69.6% of the time, both methods indicated impaired CAR simultaneously. The aforementioned calculations were not associated with early cerebral injury. In conclusion, HR and MABP do not seem interchangeable when assessing CAR in preterm infants.