Taylor, Bryan J.

During severe exercise, expiratory and inspiratory muscle fatigue develops by ∼50% of the tolerable exercise duration. The magnitude of expiratory and inspiratory muscle fatigue increases progressively toward exercise intolerance but is not different between muscle groups; this is despite the expiratory muscles being less fatigue-resistant. Inspecting esophageal and gastric twitches via cervical stimulation, we speculate that the progressive magnitude of exercise-induced inspiratory muscle fatigue is a function of recruitment and fatigue of the accessory inspiratory muscles.

Purpose: Despite the 2022 American Heart Association/American College of Cardiology guidelines recommending cardiac rehabilitation (CR) after aortic dissection repair, both patient participation in CR and the associated clinical outcomes remain poorly understood. Methods: Adults (≥18 years of age) discharged alive following thoracic aortic dissection surgery across the Mayo Clinic Enterprise (January 2012 to November 2022), with follow-up until May 2024, were included (IRB #24-001141). Data were presented using summary statistics and logistic regression modeling. Results: A total of 186 patients were referred; 37% were female, and the median age was 64 (51, 73) years. Dissections were classified as type A (43%), type B (18%), or a combination, and 55% had residual dissection. Over half (53%) did not start CR, with older age (aOR = 0.97: 95% CI, 0.94 - 0.99; P = .003), family history of aortic dissections and/or aneurysms (aOR = 0.17: 95% CI, 0.04 - 0.54; P = .005), and tobacco use (aOR = 0.35: 95% CI, 0.13 - 0.91; P = .037) being associated with lower odds of enrollment. Of the 87 who enrolled, 34 did so at a Mayo Clinic facility. There were no complications, with no difference in adverse outcomes. Among those with evaluations at graduation from CR (n = 21), quality of life (Dartmouth index 16 [14, 19] vs 25 [22, 30]; P = .002) and 6-minute walk distance (488 [375, 531] vs 302 [235, 398] m; P = .001) improved. Conclusions: Following thoracic aortic dissection repair, CR significantly improved quality of life and functional capacity without adverse events. Further work is needed to improve enrollment and establish data-driven safety margins for exercise.

Introduction: Cardiovascular risks following SARS-CoV-2 infection are incompletely defined. We evaluated evolving cardiovascular outcomes across COVID-19 variant eras using a large community-based cohort to inform risk stratification and clinical care. Methods: We conducted a retrospective cohort study of 162,471 adults with COVID-19 between March 2020 and December 2023 using the Rochester Epidemiology Project. Patients were stratified by variant era (Pre-Delta, Delta, and Omicron). Cardiovascular outcomes included major adverse cardiovascular events (MACE: myocardial infarction, stroke, death), ischemic and inflammatory heart disease, thrombotic events, and dysrhythmias. Diagnoses were identified using ICD-10 codes and validated in a subset. Cumulative incidence was estimated using Kaplan-Meier and competing risk models. Cox proportional hazards regression was used to assess differences by era and age. Results: MACE occurred in 4,922 patients, primarily in those ≥80 (2-year incidence: 17%). Event rates peaked within 30 days post-infection, with marked variation by variant. In patients ≥80, 30-day MACE risk was highest in the Pre-Delta (HR 3.85; 95% CI, 3.14–4.71) and Delta (HR 2.72; 95% CI, 2.13–3.47) eras versus Omicron. After 30 days, event rates fell and era differences narrowed. Thrombotic events (n=2,090; 1.4%) decreased across eras. Ischemic and inflammatory heart disease rates were stable. Myocarditis/pericarditis were rare (0.1%) without age trends. Dysrhythmias affected 6,765 patients (2-year incidence: 4.9%) and rose with age (2.0% in <40 vs. 19.9% in ≥80). Within 30 days, risk was higher in the Pre-Delta and Delta eras for age ≥40, especially ≥80 (Delta HR 3.08; 95% CI, 2.08–4.56) and 60–79 (HR 2.23; 95% CI, 1.75–2.85). Among those 40–59, Delta posed the highest risk (HR 2.74; 95% CI, 1.94–3.86 vs. Pre-Delta HR 1.77; 95% CI, 1.26–2.49). No differences were observed in <40. Beyond 30 days, risk converged across variants. Conclusion: Cardiovascular risk after SARS-CoV-2 infection was concentrated in the first 30 days, with attenuation thereafter. While MACE and thrombotic event rates declined over time, early dysrhythmia risk varied by variant and age, especially in older adults. These findings define a time-sensitive, variant-specific risk window and support short-term, risk-stratified post-COVID monitoring. This work informs targeted follow-up protocols by infection era and age, with implications for quality improvement, resource use, and equitable care.

Respiratory muscle fatigue could occur following involuntary breathing movements during maximal breath-holds. We measured respiratory muscle strength pre and post three preparatory and maximal breath-holds. We found significant reductions in diaphragm strength and total inspiratory and expiratory strength in some, but not all, divers. Divers that had respiratory muscle fatigue had a lower pseudo O 2 delivery (HR × [Formula: see text]) during the struggle phase. This suggests that reduced oxygen delivery may contribute to respiratory muscle fatigue during a breath-hold.

Background: Cardiac rehabilitation (CR) is essential to secondary cardiovascular disease prevention and management of cardiac patients. Despite its proven benefits, CR remains underutilized with enrollment and completion rates ranging from 10-30% in the US. Yet, there is a scarcity of nationally representative data among diverse populations on socioeconomic differences in barriers and beliefs of CR participation and delivery mode preferences. Hypothesis: The perceptions (barriers, beliefs), CR delivery mode preferences, and CR utilization (prior enrollment) varies by socioeconomic status (SES) among CR-eligible individuals. Methods: We conducted an anonymous national electronic survey from March 2023 to January 2024 of individuals self-reporting a prior CR-eligible diagnosis. The 22-item CR Barriers Scale assessed perceived barriers to CR enrollment and participation using a 5-point Likert scale (strongly disagree to strongly agree). A 13-item, validated questionnaire assessed 4 subscales pertaining to patients’ beliefs about CR, each rated on a 5-point Likert scale (strongly disagree to strongly agree): perceived necessity, concerns about exercise, practical barriers and perceived suitability. CR delivery mode preferences were ascertained (eg, virtual, at-home, etc.). Mean barriers and belief scores as well as delivery mode preferences were stratified by SES. Low SES was defined as ≤ high school education, Medicaid insurance, or uninsured. High SES was defined as > high school education and non-Medicaid health insurance. Responses were analyzed using descriptive statistics with R software. Results: A total of 466 participants completed the survey (38.1% women, 30.6% minoritized racial/ethnic group, 29.6% low SES, 95% response rate) ( Table 1 ). The majority indicated prior enrollment in CR (81.5%) with no difference by SES. CR barrier scores did not differ significantly by SES (p=0.331) ( Table 2 ). Beliefs about CR perceived necessity and perceived suitability differed by SES (p<0.001 and p=0.025), but beliefs regarding concerns about exercise and practical barriers did not. The low SES group reported a higher preference for completely at-home CR compared to the high SES group (33.6% vs 7.4%, p<0.001). Conclusion: Our findings suggest that CR beliefs varied by SES while utilization did not. For CR-eligible patients experiencing socioeconomic disadvantage, at-home CR may be a preferred alternative to center-based CR to increase CR participation and adherence.

Background: Despite expert opinion recommending patient-tailored cardiac rehabilitation (CR) after acute aortic dissection, both patient participation in CR and the associated risk factor modification after CR following aortic dissection repair are poorly understood. Objectives: To describe the characteristics of patients referred to CR, as well as the enrollment rate and outcomes of those referred to CR following thoracic aortic dissection. Methods: We reviewed electronic health records of adults (≥18) discharged alive following thoracic aortic dissection surgery across the Mayo Clinic Enterprise (01/01/2020-11/15/2022) with follow-up to 05/15/2024 (IRB #24-001141). Data are presented using summary statistics. Results: During the study period, 85 patients were included (median [IQR] age: 65 [50-75] years; 40% female; Table 1 ). Across 84% (N=71) who were referred to CR at discharge, 55% (N=39) enrolled. In those patients referred versus not referred to CR, the prevalence of type A dissection (75% vs. 43%), end-organ involvement (27% vs. 0%), and underlying CAD (54% vs. 21%) were greater while current tobacco use (9% vs. 29%) was lower. Of those enrolled at Mayo Clinic (N=16), CR was started 35 (28-65) days following surgery. These patients completed 21 (13-30) CR sessions at an exercise intensity of 59% (50-65%) maximum predicted heart rate. CR was discontinued in 44% (N=7) due to non-cardiac reasons ( Table 2 ). Of the 9 patients who completed CR, general health status (Dartmouth index: 19 [17-21] vs. 26 [22-34]), depressive symptoms (PHQ-9: 1 [0-1] vs. 4 [1-4]), and exercise capacity (6MWT: 214 [196-244] vs. 384 [305-597] meters) improved ( Table 2 ). There were no reported complications or deaths, with stable aortic sizes reported at 18 months. Conclusions: CR improves functional capacity and well-being without complications in patients after thoracic aortic dissection surgery. Further investigation is needed to better assess CR efficacy and usage in this population.

Exercise-induced respiratory muscle fatigue contributes to limiting exercise tolerance. Accordingly, better understanding the exercise conditions under which respiratory muscle fatigue occurs is warranted. Although heavy-intensity as well as short- and long-duration severe-intensity exercise performed to intolerance elicit diaphragm and expiratory muscle fatigue, we find, for the first time, that the relationship between exercise intensity, exercise duration, and the magnitude of exercise-induced fatigue is different for the diaphragm compared with the expiratory muscles.

Cardiogenic pulmonary edema is a life-threatening complication in patients with heart failure (HF) resulting from increased alveolar Cl- secretion and inhibition of alveolar epithelial Na+ channels (ENaC). Not all HF patients develop pulmonary edema, despite similar clinical characteristics, suggesting a genetic component to edema formation in response to cardiac failure. The ENaC are crucial for alveolar fluid clearance, with the alpha subunit demonstrating particular importance. We have previously found that genetic variation of the alpha subunit (SCNN1A) of ENaC, an alanine (A) to threonine (T) substitution, influences ion regulation during exercise and in response to albuterol. In the present study, we sought to determine the influence of the threonine variant (T663; AT/TT group) on lung fluid regulation in response to normobaric hypoxia, an environmental condition known to increase pulmonary capillary hydrostatic stress in healthy humans. Lung ion and fluid changes were assessed using exhaled Na+ (ENa+) and the lung diffusing capacity for carbon monoxide and nitric oxide (DLCO and DLNO, respectively) to determine alveolar-capillary membrane conductance (DM). 19 healthy subjects (n=8 vs. 11, %female=50 vs. 62%, age=27±1 vs. 28±2yrs., ht=171±3 vs. 173±2cm, wt=69±6 vs.72±3kg , BMI=23±1 vs.24±1kg/m2 , for AA and AT/TT, respectively) completed two overnight visits in a hypoxic tent simulating just over 5,400m. The visits were randomized to inhaled placebo (P) or inhaled amiloride (Aml, 1.5mg in 5ml normal saline, used to inhibit ENaC activity) with ENa+, DLCO, and DM assessed at baseline and following 12 hours of hypoxic exposure. There was an effect of genotype on the ENa+ response to hypoxia with placebo that was abolished with amiloride, but no effect of genotype on the diffusing capacity of the lung (Table). These results suggest that genetic variation of SCNN1A may influence ion regulation in the lung under conditions of elevated hydrostatic stress.