Olson, Thomas P.

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.

Introduction: Physical activity is protective against cardiovascular (CV) disease and mortality, yet more than 25% of adults do not perform any regular exercise. Whole body electronic muscle stimulation (WB-EMS) is a novel FDA-approved device used for physical training that simultaneously stimulates all major muscle groups using percutaneous electrical impulse transmission during exercise. Preliminary studies demonstrated increased muscle mass, reduced fat mass, and improved functional capacity in elderly individuals who trained with WB-EMS. We evaluated the effects of training with WB-EMS on measures of CV health. Methods: Healthy adults were randomized to physical training with versus without WB-EMS for one 20-minute session each week for 16 weeks. Participants wore a specifically designed vest and arm and leg straps connected to the WB-EMS device (Miha Bodytec, Germany). Biphasic electrical stimulation was delivered through the vest and straps (4 sec on, 4 sec off) at a frequency that elicited a score of 5-6 on the Borg perceived exertion scale when each major muscle group was stimulated. Individuals randomized to no WB-EMS wore the same equipment but received no stimulation. Sessions were provided by trainers certified in WB-EMS training and consisted of a fixed protocol of simple exercises such as squats and lunges. Temporal changes in measures of CV health were compared between groups. Results: Forty-one individuals were recruited between 02/2021 and 02/2022 (n=24 WB-EMS, n=17 no WB-EMS; mean age 35.9±11.2 yrs; 61.3% females; median BMI 24.3 (21.8, 28.1) kg/m 2 . After 16 weeks there were significant and favorable differences in the intervention group compared to controls in waist: hip ratio (-1.2 cm vs. 0.9, p=0.05); total cholesterol (-1.1 mg/kg vs. 14.2 mg/kg, p=0.02); anaerobic threshold (68.2% vs. 30.8%, p=0.03); breathing efficiency (VE/VCO2: -10.36 vs -7.38, p=0.01); and peripheral endothelial function, measured with reactive hyperemia peripheral arterial tonometry (-0.009 vs. -0.29, p=0.06). Conclusions: Once weekly training with WB-EMS yielded more favorable changes in CV biomarkers compared to conventional training alone in healthy adults, and thus may offer an effective and time-efficient method of physical training.

Background: The role of minute ventilation/carbon dioxide production ( / CO2) slope, a ventilation efficiency marker, in predicting short-term and long-term health outcomes for patients with nonsmall-cell lung cancer (NSCLC) undergoing lung resection has not been well investigated. Material and Methods: This prospective cohort study consecutively enrolled NSCLC patients who underwent a presurgical cardiopulmonary exercise test from November 2014 to December 2019. The association of / CO2 slope with relapse-free survival (RFS), overall survival (OS), and perioperative mortality was evaluated using the Cox proportional hazards and logistic models. Covariates were adjusted using propensity score overlap weighting. The optimal cut-off point of the E/ CO2 slope was estimated using the receiver operating characteristics curve. Internal validation was completed through bootstrap resampling. Results: A cohort of 895 patients [median age (interquartile range), 59 (13) years; 62.5% male] was followed for a median of 40 (range, 1–85) months. Throughout the study, there were 247 relapses or deaths and 156 perioperative complications. The incidence rates per 1000 person-years for relapses or deaths were 108.8 and 79.6 among patients with high and low E/ CO2 slopes, respectively [weighted incidence rate difference per 1000 person-years, 29.21 (95% CI, 7.30–51.12)]. A E/ CO2 slope of greater than or equal to 31 was associated with shorter RFS [hazard ratio for relapse or death, 1.38 (95% CI, 1.02–1.88), P=0.04] and poorer OS [hazard ratio for death, 1.69 (1.15–2.48), P=0.02] compared to a lower / CO2 slope. A high E/ CO2 slope increased the risk of perioperative morbidity compared with a low E/ CO2 slope [odds ratio, 2.32 (1.54–3.49), P<0.001]. Conclusions: In patients with operable NSCLC, a high E/ CO2 slope was significantly associated with elevated risks of poorer RFS, OS, and perioperative morbidity.

Importance Reduced heart rate during exercise is common and associated with impaired aerobic capacity in heart failure with preserved ejection fraction (HFpEF), but it remains unknown if restoring exertional heart rate through atrial pacing would be beneficial. Objective To determine if implanting and programming a pacemaker for rate-adaptive atrial pacing would improve exercise performance in patients with HFpEF and chronotropic incompetence. Design, Setting, and Participants Single-center, double-blind, randomized, crossover trial testing the effects of rate-adaptive atrial pacing in patients with symptomatic HFpEF and chronotropic incompetence at a tertiary referral center (Mayo Clinic) in Rochester, Minnesota. Patients were recruited between 2014 and 2022 with 16-week follow-up (last date of follow-up, May 9, 2022). Cardiac output during exercise was measured by the acetylene rebreathe technique. Interventions A total of 32 patients were recruited; of these, 29 underwent pacemaker implantation and were randomized to atrial rate responsive pacing or no pacing first for 4 weeks, followed by a 4-week washout period and then crossover for an additional 4 weeks. Main Outcomes and Measures The primary end point was oxygen consumption (V̇ o 2 ) at anaerobic threshold (V̇ o 2,AT ); secondary end points were peak V̇ o 2 , ventilatory efficiency (V̇ e /V̇ co 2 slope), patient-reported health status by the Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels. Results Of the 29 patients randomized, the mean age was 66 years (SD, 9.7) and 13 (45%) were women. In the absence of pacing, peak V̇ o 2 and V̇ o 2 at anaerobic threshold (V̇ o 2,AT ) were both correlated with peak exercise heart rate ( r = 0.46-0.51, P &amp;lt; .02 for both). Pacing increased heart rate during low-level and peak exercise (16/min [95% CI, 10 to 23], P &amp;lt; .001; 14/min [95% CI, 7 to 21], P &amp;lt; .001), but there was no significant change in V̇ o 2,AT (pacing off, 10.4 [SD, 2.9] mL/kg/min; pacing on, 10.7 [SD, 2.6] mL/kg/min; absolute difference, 0.3 [95% CI, −0.5 to 1.0] mL/kg/min; P = .46), peak V̇ o 2 , minute ventilation (V̇ e) /carbon dioxide production (V̇ co 2 ) slope, KCCQ-OSS, or NT-proBNP level. Despite the increase in heart rate, atrial pacing had no significant effect on cardiac output with exercise, owing to a decrease in stroke volume (−24 mL [95% CI, −43 to −5 mL]; P = .02). Adverse events judged to be related to the pacemaker device were observed in 6 of 29 participants (21%). Conclusions and Relevance In patients with HFpEF and chronotropic incompetence, implantation of a pacemaker to enhance exercise heart rate did not result in an improvement in exercise capacity and was associated with increased adverse events. Trial Registration ClinicalTrials.gov Identifier: NCT02145351

Cardiac rehabilitation (CR) is a guideline-recommended, multidisciplinary program of exercise training, risk factor management, and psychosocial counseling for people with cardiovascular disease (CVD) that is beneficial but underused and with substantial disparities in referral, access, and participation. The emergence of new virtual and remote delivery models has the potential to improve access to and participation in CR and ultimately improve outcomes for people with CVD. Although data suggest that new delivery models for CR have safety and efficacy similar to traditional in-person CR, questions remain regarding which participants are most likely to benefit from these models, how and where such programs should be delivered, and their effect on outcomes in diverse populations. In this review, we describe important gaps in evidence, identify relevant research questions, and propose strategies for addressing them. We highlight 4 research priorities: (1) including diverse populations in all CR research; (2) leveraging implementation methodologies to enhance equitable delivery of CR; (3) clarifying which populations are most likely to benefit from virtual and remote CR; and (4) comparing traditional in-person CR with virtual and remote CR in diverse populations using multicenter studies of important clinical, psychosocial, and cost-effectiveness outcomes that are relevant to patients, caregivers, providers, health systems, and payors. By framing these important questions, we hope to advance toward a goal of delivering high-quality CR to as many people as possible to improve outcomes in those with CVD.

Abstract Over 50 years ago, John Wahren and Lennart Jorfeldt published a manuscript in Clinical Science where they detailed a series of studies of leg blood flow during exercise. They used a novel approach to indicator dye dilution: continuous arterial infusions of dye using venous samples. This technique allowed them to describe for the first time the fundamental relationships between large muscle group exercise, muscle blood flow, and pulmonary and muscle oxygen uptake. They also defined mechanical efficiency, a key measurement of muscle function. This paper formed the basis for research into muscle blood flow and exercise in health and disease and continued to be cited by modern research. In this commentary, we describe the innovations they made, the key observations that came out of their results, and the importance of this manuscript to current research.

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.