Bissen, Thomas G.

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.

Introduction: The COVID-19 pandemic imposed significant constraints to delivery of cardiac rehabilitation (CR) with many programs relying on delivery of home-based cardiac rehabilitation (HBCR). We sought to compare the effects of HBCR vs conventional center-based CR (CBCR) on clinical metrics, health-related quality of life, and modifiable risk factors in CR patients. Methods: Retrospective cohort study comparing 511 HBCR patients (March 2020-April 2021; COVID-19 pandemic) and 765 age and sex matched CBCR patients (Jan 2018-Jan2020; immediately pre-pandemic) from the Mayo Clinic Health System. We assessed changes in clinical outcomes before and after CR. HBCR included 12 sessions (one in-person assessment + weekly education and exercise monitoring phone/video calls). Conventional CBCR included 36 sessions (3 sessions per week for 12 weeks). Continuous data were described as mean±SD, and comparisons of change between groups were assessed with linear regression adjusting for baseline value, in complete cases. Results: HBCR and CBCR patients were 65±14 yrs old (68% male) and 65±14 yrs old (67% male) respectively. HBCR patients demonstrated greater improvement in exercise days/week whereas CBCR patients had greater improvement in exercise min/day. HBCR patients had greater improvement in blood glucose with a trend towards greater improvement in non-HDL cholesterol. Both groups demonstrated similar improvement on nutrition, depression, health-related quality of life surveys and total, LDL and HDL cholesterol, as well as HbA1c between the groups. Conclusions: Collecting clinical metrics during the COVID-19 pandemic proved challenging due to the initial closure of out-patient services. For patients in whom data was captured, HBCR appears to be similarly effective at improving several intermediate outcomes compared to CBCR. HBCR may be an effective alternative for improving clinical outcomes in patients who are unable to participate in CBCR.

Introduction: Many center-based cardiac rehabilitation programs were forced to close during the pandemic resulting in a programmatic shift to delivering cardiac rehabilitation remotely in the home-based setting. This study examined sex differences in the change of exercise frequency and exercise capacity in patients participating in home-based cardiac rehabilitation (HBCR) during the COVID-19 pandemic. Methods: Retrospective cohort study of 567 HBCR patients between March 2020 and May 2021. Patients who completed the Duke Activity Status Index questionnaire before and after HBCR were included. We calculated the number of reported exercise days/ week, exercise min/day, and VO 2 peak estimated. Patients were divided into two groups according to sex (Male/Female). Continuous data are described as mean±SD and baseline data compared with a two-sample t-test. The delta change from pre-post between groups also are compared with a two-sample t-test. Results: Of 567 HBCR patients, 118 patients completed both pre and post HBCR questionnaires (Male, n=82, 66±12 yo vs Female, n=36, 65±12 yo, p=0.80). There were no differences between groups for baseline exercise days/week or exercise min/day pre HBCR (4.0±2.8 vs 4.1±3.0 days, p=0.87; 22±20 vs 18±20 min, p=0.33); however, VO 2 peak at baseline HBCR was higher in males than females (22.3±8.1 vs 18.9±5.9 ml/kg/min, p<0.05). Both groups improved exercise days/week (4.0±2.8 to 5.7±1.5 vs 4.1±3.0 to 5.7±1.4 days, p<0.05 for both), exercise min/day (22±20 to 40±15 vs 18±20 to 37±21 min, p<0.05 for both), and VO 2 peak (22.3±8.1 to 27.8±8.0 vs 18.9±5.9 to 22.7±6.5, ml/kg/min, p<0.05 for both). In addition, there was no significant difference for the delta change of the three outcomes between groups (1.7±2.7 vs 1.6±2.5 days; 18±19 vs 19±18 min; 5.5±6.5 vs 3.8±4.5 ml/min/kg, p>0.05 for all). Conclusions: Female patients entering HBCR during the COVID-19 pandemic demonstrated lower exercise capacity compared to males; however, both female and male patients increased exercise frequency (days/week and min/day) and exercise capacity (estimated VO 2 peak) similarly after attending HBCR during the COVID-19 pandemic.

Introduction: The COVID-19 pandemic resulted in the closure of many center-based cardiac rehabilitation programs leading many institutions to rely on home-based cardiac rehabilitation (HBCR) to provide critical secondary cardiovascular disease prevention and rehabilitation. The impact of age on the change of exercise frequency and exercise capacity as a result of HBCR during the COVID-19 pandemic remains unknown. Methods: Retrospective cohort study of 567 HBCR patients between March 2020 and May 2021. Patients who completed the Duke Activity Status Index questionnaire at enrollment and completion of HBCR were included. We calculated the number of reported exercise days/week , exercise min/day, and VO 2 peak estimated. Patients were divided into two groups according to age (Younger<65 y.o; Older≥65 y.o). Continuous data are described as mean ±SD and baseline data compared with a two-sample t-test. The delta change from pre-post between groups also are compared with a two-sample t-test. Results: Of 567 HBCR patients, 118 patients completed both pre and post HBCR questionnaires (Younger, n=54, 56±8 years old vs Older, n=64, 74±7 y.o, p<0.05). Both groups improved exercise days/week (4.4±2.8 to 5.8±1.3 vs 3.8±2.9 to 5.6±1.6 days, p<0.05 for both), exercise min/day (21±20 to 41±17 vs 20±20 to 37±17 min, p<0.05 for both), and VO 2 peak (20.5±7.1 to 27.6±8.0 vs 21.9±8.1 to 25.1±7.7 ml/min/kg, p<0.05 for both). The delta change for exercise days/week and exercise min/day were not significantly different between groups (1.4±2.7 vs 1.9±2.7 days and 19±19 vs 17±18 min, p>0.05); however, the Younger patients significantly increased their VO 2 peak more than the older patients (7.1±6.1 vs 3.2±5.3 ml/min/kg, p<0.05). Conclusions: During the COVID-19 pandemic, exercise frequency (days/week and min/day) and exercise capacity (estimated VO2peak) increased in all patients participating in HBCR. With this, the increase in estimated exercise capacity was greater in younger patients compared with older patients. These findings suggest that additional work is needed to explore factors potentially limiting improvement and strategies to maximize improvement in exercise capacity in older patients participating in HBCR.

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.