Bruhn, Eric J.

Heart failure with preserved ejection fraction (HFpEF) is associated with exercise intolerance, with respiratory muscle dysfunction as a contributing factor. Patients with HFpEF have exaggerated cardiovascular responses to respiratory muscle metaboreflex activation. In this study, we determined the impact of inspiratory muscle training (IMT) on the respiratory muscle metaboreflex in HFpEF. We found that 8 wk of IMT improved inspiratory muscle strength and attenuated the respiratory muscle metaboreflex-mediated cardiovascular responses in patients with HFpEF.

Introduction: An elevated blood pressure (mean arterial pressure, MAP) response to exercise is an independent predictor of hypertension (HTN) development. HTN is highly prevalent in postmenopausal females. Postmenopausal, compared to premenopausal, females have a higher MAP at rest and during exercise primarily due to higher systemic vascular resistance (SVR). Studies using small muscle mass exercise have suggested that postmenopausal females have augmented increases in MAP from rest to exercise. However, it is unclear if postmenopausal females have augmented MAP responses from rest to exercise during whole-body exercise. Hypothesis: We hypothesized that postmenopausal females would have greater increases in MAP and smaller decreases in SVR from rest to peak exercise than premenopausal females. Methods: Normotensive premenopausal (n=16; age: 30±7 yrs; BMI: 23±4 kg/m 2 ) and postmenopausal (n=14; age: 57±7 yrs; BMI: 27±4 kg/m 2 ) female participants performed an incremental cycling test until task failure. Blood pressure was measured by manual sphygmomanometry, cardiac output (Q) via open-circuit acetylene wash-in technique, and SVR was calculated. Data are reported at rest and peak oxygen uptake (VO 2 ). Data are also reported as % change from rest to VO 2 peak. Results: Postmenopausal females had higher MAP and SVR at rest and at VO 2 peak than premenopausal females (all, p<0.05). Postmenopausal, compared to premenopausal, females had lower Q at VO 2 peak commensurate with the lower achieved VO 2 peak (p<0.01). Resting MAP was positively related to MAP at VO 2 peak in postmenopausal females (r=0.85, p<0.01), but not premenopausal females (p=0.22). % change in MAP from rest to VO 2 peak was not different between groups (Post: 18±8 vs. Pre: 18±9%) (p=0.94). However, postmenopausal females had smaller % decreases in SVR from rest to VO 2 peak (Post: -44±7 vs. Pre: -54±8%) and smaller % increases in Q compared to premenopausal females (Post: 113±31 vs. Pre: 162±50%) (both, p<0.01). Conclusion: Our findings indicate that postmenopausal and premenopausal females have similar increases in MAP from rest to VO 2 peak; however, the mechanisms contributing to the MAP response differed by menopausal status. Postmenopausal females relied on smaller decreases in SVR, whereas premenopausal females had greater increases in Q. These findings provide important insight into the mechanisms contributing to the clinically relevant higher MAP response during exercise in postmenopausal females.

Introduction: Obesity and hypertension (HTN) are highly prevalent comorbid risk factors for heart failure with preserved ejection fraction (HFpEF). Obesity and HTN independently increase sympathetic nervous activity and impair muscle blood flow during exercise. Previous work has reported attenuated limb blood flow in patients with HFpEF; however, these findings were compared to controls with dissimilar comorbidities and during small muscle mass exercise. It is unclear if HFpEF alters muscle blood flow responses independent of the obesity- and HTN-mediated alterations. Hypothesis: We hypothesized the muscle blood flow response during cycling would be lower in HFpEF patients than age, sex, BMI, and HTN matched controls (CTL). Methods: HFpEF patients (n=14, 9M/5W, 71±7yrs, 32±4 kg/m 2 ) and CTL (n=12, 8M/4W, 69±7yrs, 31±4 kg/m 2 ) performed an incremental cycling test. Blood pressure was measured by manual sphygmomanometry, cardiac output (Q) by open-circuit acetylene wash-in technique, and systemic vascular resistance (SVR) was calculated. Vastus lateralis blood flow index (BFI) was measured by near-infrared spectroscopy and indocyanine green dye injections and venous norepinephrine concentration was measured. Changes from rest to 40 W of the incremental test are reported. Results: Resting Q, mean arterial pressure, SVR, and venous norepinephrine concentration were not statistically different between groups (p>0.18). From rest to 40 W, the increases in Q (CTL: 3.9±0.8 vs. HFpEF: 3.6±0.7 L/min), mean arterial pressure (CTL: 5.7±2.7 vs. HFpEF: 6.6±6.1 mmHg), and SVR (CTL: -7.3±2.1 vs. HFpEF: -6.0±2.0 mmHg/L/min) were not statistically different between groups (all, p>0.13). The HFpEF group had smaller increases in vastus lateralis BFI at 40 W compared to CTL (CTL: 7.2±3.6 vs. HFpEF: 4.2±2.6 fold-increase from rest) (p=0.02). The HFpEF group had greater increases in venous norepinephrine concentration from rest to 40 W than CTL (CTL: 164±216 vs. HFpEF: 377±247 pg/mL) (p=0.05). Conclusions: Our findings suggest that, compared to age, sex, BMI, and HTN matched controls, patients with HFpEF have an impaired locomotor muscle blood flow response during submaximal cycling exercise likely due to higher locomotor muscle vascular resistance.

Respiratory muscle dysfunction is thought to contribute to exercise intolerance in heart failure with preserved ejection fraction (HFpEF); however, the underlying mechanisms are unknown. In the present study, patients with HFpEF had greater increases in leg muscle vascular resistance index and greater decreases in leg muscle blood flow index compared with controls during inspiratory resistive breathing (to activate the metaboreflex). Furthermore, respiratory muscle blood flow index responses normalized to pressure generation during inspiratory resistive breathing were exaggerated in HFpEF compared with controls.

Introduction: Obesity is common in heart failure with preserved ejection fraction (HFpEF) and is directly linked with lower levels of physical activity (PA). Visceral adiposity (VAT) is more common in HFpEF than controls and may play a role in its pathogenesis, characterized by impaired exercise capacity (peak VO 2 ). The direct relationship between VAT and PA in HFpEF is unknown. Hypothesis: Compared to controls, HFpEF patients will have excess regional adiposity (VAT, subcutaneous (SAT), and intramuscular (IMAT)), and these fat depots will be associated with lower levels of chronic physical activity. Methods: HFpEF patients (n=51; age 70±9) and non-HFpEF controls (n=49; age 65±5) prospectively underwent body composition measurement by dual-energy x-ray absorptiometry and magnetic resonance imaging. Peak VO 2 was measured by standard cardiopulmonary exercise testing. PA was monitored continuously via accelerometry over two weeks. Data were binned in arbitrary accelerometry units, averaged and stored in 30-second epochs (counts per epoch, CPE). Models were adjusted for age, sex, and ideal body weight. Results: HFpEF were less active overall (3.15±0.80 vs 3.59±0.73 CPE), had less moderate intensity PA (10.13±0.04 vs 10.15±0.03 CPE), and less morning (3.83±1.15 vs 4.24±1.09 CPE) and afternoon (3.84± 1.20 vs 4.53± 0.97 CPE) (p<0.05 for all) PA. Patients with HFpEF spent a greater proportion of time sedentary (0.71±0.08 vs 0.67±0.08 CPE) and less time in moderate (0.04±0.03 vs 0.06±0.03 CPE) and vigorous (0.02±0.01 vs 0.03±0.03 CPE) PA (p<0.01 for all). Chronic PA was significantly associated with regional fat depots (VAT β= -0.003, 95% CI: -0.004-0.001; SAT β= -0.003, 95%CI: -0.004-0.001; IMAT β=-0.02, 95% CI: -0.04—0.01) as a combined cohort (p<0.01 for all). Muscle quality (β=0.28, 95%CI: 0.15-0.40), peak VO 2 (β=0.08, 95% CI: 0.03-0.13), and peak watts (β=0.01, 95% CI: -0.004-0.02) were associated with PA in HFpEF only (p≤0.01 for all). Conclusions: The amount and pattern of PA differs between HFpEF and controls, as do relationships between regional fat depots and PA, and the relationship of PA and peak VO 2 . Further investigation is needed to better understand the temporality and mechanisms related to the pathophysiology and severity of HFpEF.

Introduction: Obesity is prevalent in HFpEF, a syndrome that disproportionality affects women, and is associated with poor exercise tolerance (VO 2 ), reduced quality of life, and greater symptoms. Visceral adipose tissue (VAT), more than general obesity, is related to metabolic and cardiovascular dysfunction common to HFpEF. While fat deposition varies between sexes, these differences and the relation to exercise tolerance remain unclear in HFpEF. Hypothesis: Compared to sex-matched controls, HFpEF patients will demonstrate reduced lean mass, excess VAT, subcutaneous, visceral, and intramuscular fat, and will be associated with reduced VO 2 . Methods: HFpEF females (F) and males (M) (n=78; 37 F/41 M; age 70±9) and non-HFpEF controls (n=50; 30 F/20 M; age 65±5) prospectively underwent body composition measurement via dual-energy x-ray absorptiometry and magnetic resonance imaging (MRI) and cardiopulmonary exercise testing for measurement of peak oxygen consumption (peak VO 2 ). Muscle quality calculated as peak Watts (W) achieved divided by MRI thigh lean mass. Results: HFpEF had greater VAT, subcutaneous (SAT) and intramuscular (IMAT), and poorer muscle quality than controls (all p<0.01). Exercise performance was lower in HFpEF (peak VO 2 : 14±4 vs. 22±6; peak W: 69±29 vs. 116±34; both p<0.01). HFpEF demonstrated increased odds for VAT (OR: 2.02, 95% CI: 1.22-3.37), SAT (OR: 2.05, 95% CI: 1.20-3.49), and IMAT (OR: 2.04, 95% CI: 1.35-3.39) (all p<0.01). Sex-stratification revealed increased odds of excess VAT in HFpEF females (OR: 2.76, 95% CI: 1.16-7.72, p=0.03), SAT in HFpEF males (OR: 3.64, 95% CI: 1.10-12.07, p=0.03), and IMAT in HFpEF females (OR: 2.38, 95%CI: 1.10-5.29, p=0.03) with a trend in males (OR: 1.67, 95%CI: 0.97-2.86, p=0.06). Impaired VO 2 was associated with all AT depots as a combined cohort and among controls (all p<0.01) and linked to poor muscle quality individually for men and women in HFpEF and controls (all p<0.01). Conclusion: HFpEF patients have significantly altered body composition profiles and reduced exercise tolerance compared to controls. Sex differences in regional fat deposition impact peak VO 2 and may serve a distinct role in the pathophysiology of HFpEF.

Introduction: Peripheral factors contribute to exercise limitations in heart failure (HF) with preserved ejection fraction (HFpEF) and may be related to excess regional adiposity. Slowed oxygen uptake (VO 2 ) kinetics are common in HF with reduced ejection fraction (HFrEF) and reflect peripheral O 2 transport impairments and abnormal muscle metabolic control. Differences in VO 2 kinetics between HFpEF and HFrEF may reveal phenotype-specific impairments in peripheral O 2 transport but remain unknown. Hypothesis: We hypothesized that VO 2 kinetics are slower in HFpEF (compared to HFrEF) and associated with greater leg adiposity. Methods: Patients with HFpEF (n=12; 3 women; 66±6 yrs; 29±3 kg/m 2 ; ejection fraction: 59±5%), HFrEF (n=12; 3 women; 62±9 yrs; 28±4 kg/m 2 ; ejection fraction: 37±8%), and controls (n=12; 3 women; 65±5 yrs; 28±3 kg/m 2 ) cycled at 20 W for 5 minutes prior to a maximal exercise test to determine VO 2peak . Age, sex, and BMI were matched by design and were not different among groups (p>0.05). A monoexponential function with a time delay was used to describe the VO 2 transition from rest to 20 W and calculate the O 2 deficit. Leg fat mass was measured via dual energy X-ray absorptiometry. Results: VO 2peak was lower in HFpEF (18.6±6.2 mL/kg/min) and HFrEF (19.0±3.7 mL/kg/min) compared to controls (26.0±3.1; both p<0.05). Amplitude (HFpEF: 507±97 mL/min; HFrEF: 443±91 mL/min; controls: 477±117 mL/min) and time delay (HFpEF: 16±9 s; HFrEF: 11±7 s; controls: 11±6 s) were not different among groups (p>0.05). The time constant was slower in HFrEF compared to controls (45±9 s vs. 32±6 s; p=0.03) and further slowed in HFpEF (66±18 s; p<0.001). The O 2 deficit was significantly greater in HFpEF (895±201 mL) and HFrEF (649±131 mL) compared to controls (590±125 mL; both p<0.05). There were no differences in percent leg fat mass among groups (HFpEF: 33±8%; HFrEF: 31±6%; controls: 34±9%) and no associations were detected between percent leg fat mass and any VO 2 parameters (all p>0.05). Conclusions: Patients with HFpEF exhibited slower VO 2 kinetics compared to HFrEF with no association to leg adiposity. These data suggest differences in peripheral O 2 transport and intramuscular metabolic control abnormalities between HF phenotypes.