Taylor, Jenna L

Background Cardiac rehabilitation (CR) improves peak oxygen uptake (VO 2 peak) and body composition in patients with cardiovascular disease. However, improvement in VO 2 peak is not observed in all patients following a CR program, and whether VO 2 peak non-responders also demonstrate limited changes in body composition remains unclear. This study aimed to examine the association between changes in VO 2 peak and body composition in patients undergoing a CR program. Methods Retrospective analysis of patients who completed CR between 2015 and 2022 at Mayo Clinic. The study included 143 patients who completed cardiopulmonary exercise testing and dual-energy X-ray absorptiometry pre- and post-CR. Patients were grouped by the change in relative VO 2 peak response to CR (responders= Δ>0 vs non-responders=Δ ≤0 mL/kg/min). Two-way repeated ANOVA was used to compare groups, and regression models were used to examine the associations between baseline body composition and changes in body composition with VO 2 peak change. Results Among the cohort, 26% were classified as non-responders based on relative VO 2 peak measurements. Both groups exhibited a significant improvement in most body composition variables including body fat mass, body fat percentage, body lean percentage, and fat mass index (all p<0.001), with no differences in the percentage of change in body composition variables between groups (p>0.05). Regression models demonstrated that neither baseline body composition nor changes in body composition were significantly associated with changes in VO 2 peak. Conclusion Our data suggest that baseline and change in body composition were not significantly associated with changes in VO 2 peak in patients undergoing the CR program.

Background Cardiac rehabilitation (CR) leads to increased exercise capacity (VO 2 peak) and risk reduction of major adverse cardiovascular events (MACEs). Women exhibit blunted VO 2 peak improvements following CR. The purpose was to examine sex differences in the clinical predictors of VO 2 peak improvement and odds of MACEs following CR. Methods From 1999 to 2017, all consecutive patients undergoing cardiopulmonary exercise testing before and after CR were included. Sex differences in peak exercise metrics in response to CR were compared. Multiple logistic regression models were fit to assess clinical predictors of VO 2 peak improvement (defined as >0% from pre‐CR) and MACEs following CR for men and women. Results A total of 513 men and 158 women were included. Men had greater increases in VO 2 peak than women following CR ( P =0.001). For men, independent predictors of VO 2 peak improvement following CR included higher CR session attendance (odds ratio [OR], 1.04 [95% CI, 1.02–1.06]), peripheral artery disease (OR, 0.47 [95% CI, 0.25–0.86]), and pre‐CR VO 2 peak (OR, 0.98 [95% CI, 0.97–0.99]) (all, P <0.02). Independent predictors of lower odds of MACEs following CR in men included higher number of CR sessions (OR, 0.97 [95% CI, 0.95–0.99]), pre‐CR VO 2 peak (OR, 0.98 [95% CI, 0.97–0.99]), surgical CR indication (OR, 0.34 [95% CI, 0.18–0.68]), and no history of peripheral artery disease (OR, 2.94 [95% CI, 1.60–5.38]) (all, P <0.02). For women, the selected clinical characteristics were not statistically significant independent predictors of VO 2 peak improvement or odds of MACEs (except for diabetes) following CR. Conclusions These findings suggest that clinical predictors of VO 2 peak improvement and odds of MACEs following CR are sex specific.

Dynamic cerebral autoregulation (CA) refers to the brain's ability to maintain stable cerebral blood flow despite fluctuations in blood pressure (BP). Impaired CA has been associated with cardiovascular disease severity and cognitive decline. On the other hand, enhanced cardiorespiratory fitness appears to be protective against both cerebrovascular dysregulation and cognitive decline, with an unclear link between the two. However, among individuals with cardiovascular disease, the impact of exercise-based cardiac rehabilitation (CR) on CA remains unclear. Therefore, the aim of this study was to test the hypothesis that a 12-week CR program would improve dynamic CA in adults with CVD. To address this question, data were collected from 14 patients enrolled in the Mayo Clinic CR program following a cardiac-related hospital admission (age: 43-70 yrs; n=3 females), which included moderate-high intensity aerobic exercise 3 times/week for 12-weeks. Continuous measures of middle cerebral artery velocity (MCAv; transcranial doppler) and finger BP (photoplethysmography) were obtained during 3-minutes of rest and a 3-minute sit-to-stand protocol (0.025Hz frequency) pre- and post the CR program. Transfer function analyses were used to provide an index of dynamic CA. BP-MCAv coherence in the low frequency (LF) and very low frequency (vLF) domains at rest were not different pre- and post- CR (LF: 0.48±0.19 vs 0.43±0.16; P=0.54; vLF: 0.51±0.12 vs 0.47±0.16; P=0.14). Similarly, gain and phase values at rest were not different pre- and post- CR (gain LF: 0.66±0.37 vs 0.58±0.33; P=0.16; vLF: 0.87±0.53 vs 0.74±0.43; P=0.21; phase LF: 0.41±0.30 vs 0.43±0.26; P=0.64; vLF: 0.72±0.53 vs 0.66±0.16; P=0.18). In contrast, during the sit-to-stand protocol, coherence was lower following CR (pre vs post LF: 0.81±0.13 vs 0.79±0.16; p<0.01; vLF: 0.80±0.09 vs 0.79±0.14; p<0.01). In addition, gain was reduced post CR (pre vs post LF: 0.59±0.35 vs 0.55±0.31; P=0.02; vLF: 0.76±0.33 vs 0.61±0.37; p<0.01), suggesting CR-induced improvements in CA efficiency. However, phase remained unchanged pre- and post- CR during the sit-to-stand protocol (LF: 1.01±0.71 vs 0.84±0.58; P=0.17; vLF: 1.16±0.69 vs 1.08±0.60; P=0.19). Taken together, these findings demonstrate that a 12-week exercise-based CR program improves dynamic CA efficiency after a cardiac event. These novel results highlight the potential role of exercise training in improving cerebrovascular regulation. Funding: NIH AG073726 and Mayo Clinic This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

AbstractAimWe investigated whether a commercial bi‐level positive airway pressure (BPAP) device, would improve peripheral oxygen saturation (SpO2) during recreational aviation up to 12,500 feet without supplemental oxygen. Ten adults with recreational flight experience (age:47 ± 14; female = 5) completed a standardized flight profile in an unpressurised aircraft, involving randomized crossover design at 8,000 feet and 12,500 feet with BPAP or control. SpO2, middle cerebral artery velocity (MCAv), heart rate (HR), respiratory rate (RR), and relative tidal volume (TV) index were measured continuously. Psychomotor vigilance test (3‐min) assessed reaction time halfway through taxi and altitude stages. Altitude significantly (p < 0.05) decreased mean SpO2, MCAv, and RR, and increased TV index and HR. There was no effect of altitude (p > 0.05) on reaction time. BPAP increased mean SpO2 at 8,000 feet [Control: 92 ± 1%; BPAP: 94 ± 2%; mean difference (MD) = 2 ± 2%; p = 0.002] and 12,500 feet [Control: 86 ± 4%; BPAP: 89 ± 4%; MD = 2 ± 3%; p = 0.013]. BPAP lowered MCAv at 8,000 feet [Control: 53 ± 10 cm/s; BPAP: 50 ± 9 cm/s; MD = ‐3 ± 2 cm/s; p = 0.001] and 12,500 feet [Control: 52 ± 10 cm/s; BPAP: 50 ± 8 cm/s; MD = ‐2 ± 3 cm/s; p = 0.041]. BPAP increased TV index at 8,000 feet (Control: 6.6 ± 1.3; BPAP:8.1 ± 1.8; MD = 1.9 ± 0.8; p < 0.001) but not 12,500 feet, without effect on RR or reaction time. This study provides preliminary results that BPAP may improve mean SpO2 for recreational aviators up to 12,500 feet without supplemental oxygen.

Introduction: Cardiac rehabilitation (CR) is known to improve peak oxygen uptake (VO 2 peak) and body composition (BC). However, not all CR patients improve VO 2 peak and it remains unclear if non-responders also exhibit limited improvement in BC. This study aimed to examine if non-responders to VO 2 peak also demonstrate limited improvement in BC and whether BC is related to VO 2 peak changes in CR patients. Methods: Retrospective analysis of patients who completed CR between 2015 and 2022 at Mayo Clinic. The study included 143 patients who completed both dual-energy X-ray absorptiometry and cardiopulmonary exercise testing before and after CR. Patients were grouped by VO 2 peak response to CR (36 non-responders=Δ≤0 vs 107 responders=Δ>0 mL/kg/min). Within and between-group differences were assessed by paired and independent t-tests respectively. Regression models were used to evaluate whether baseline BC or ΔBC predict VO 2 peak changes. Results: As an entire cohort there were significant mean improvements in VO 2 peak and BC (Table 1, p<0.05). VO 2 peak increased in 75% of patients (responders: Δ 2.9±2 vs non-responders: Δ -2.1 ±2, mL/kg/min, p<0.05). There were no significant differences in baseline characteristics between groups including BC (Table 2, p>0.05); however, non-responders had significantly shorter duration and exercise sessions compared to responders (Table 2, p<0.001). Non-responders for VO 2 peak exhibited a significant improvement in body fat mass, body lean percentage, body fat percentage, and fat mass index (all p<0.001), with no differences in ΔBC between groups (Table 3). Regression models revealed no significant BC predictors for VO 2 peak. Conclusion: Despite significant improvements in BC, 25% of patients did not improve VO 2 peak with CR. These data suggest VO 2 peak improvement is not related to baseline BC or change in BC. These findings suggest the need for additional strategies to maximize improvements in VO 2 peak for patients undergoing CR.

Introduction: Patients with coronary artery disease (CAD) are at increased risk of cognitive decline. A proposed mechanism is cerebral hypoperfusion related to vascular dysfunction and impaired cerebral blood flow regulation Hypothesis: Patients with CAD will have lower cerebrovascular function than age- and sex-matched controls, assessed as reactivity to a vasodilatory carbon dioxide (CO 2 ) stimulus. Methods: Adults 40-70years old with CAD were recruited on enrollment to a cardiac rehabilitation program following a cardiac event or hospitalization. Age and sex-matched adults without known disease or cardiovascular risk factors were recruited as healthy controls. Cognitive function was assessed by the Fluid Composite of the NIH Cognition Toolbox. Following a familiarization visit, participants underwent a stepped CO 2 protocol (room air, 2% CO 2 , 4% CO 2 , 6% CO 2 ) while continuously measuring middle cerebral artery velocity (MCAv) using transcranial doppler ultrasound, mean arterial pressure (MAP), ventilation (VE), and end-tidal CO 2 . Cerebrovascular conductance (CVCi) was calculated as MCAv/MAP. Cerebrovascular reactivity was calculated as the linear regression slope of CVCi against the change in end-tidal CO 2 . The reactivity of MAP and VE (or chemosensitivity) were also calculated. Results: 19 patients with CAD and 10 healthy controls were recruited ( Table 1 ). Compared with controls, patients with CAD had a 2-fold lower cerebrovascular reactivity (p=0.003), higher MAP reactivity (p<0.05), and a trend towards higher chemosensitivity (p<0.1) ( Table 2 ). There were no group differences in resting CVCi or cognition ( Table 2 ). After adjustment for age and sex, lower cerebrovascular reactivity was associated with lower peak oxygen uptake, diabetes, and smoking history ( Table 3 ). Conclusions: Compared with healthy controls, we report that patients with CAD have significantly lower cerebrovascular function, with no differences in cognitive function.

Abstract Background: Doppler ultrasound of the common carotid artery is used to infer central hemodynamics. For example, change in the common carotid artery corrected flow time (ccFT) and velocity time integral (VTI) are proposed surrogates of changing stroke volume. However, conflicting data exist which may be due to inadequate beat sample size and measurement variability – both intrinsic to handheld systems. In this brief communication, we determined the correlation between changing ccFT and carotid VTI during progressively severe central blood volume loss and resuscitation. Methods: Measurements were obtained through a novel, wireless, wearable Doppler ultrasound system. Sixteen participants (ages of 18–40 years with no previous medical history) were studied across 25 lower body-negative pressure protocols. Relationships were assessed using repeated-measures correlation regression models. Results: In total, 33,110 cardiac cycles comprise this analysis; repeated-measures correlation showed a strong, linear relationship between ccFT and VTI. The strength of the ccFT-VTI relationship was dependent on the number of consecutively averaged cardiac cycles (R 1 cycle = 0.70, R 2 cycles = 0.74, and R 10 cycles = 0.81). Conclusions: These results positively support future clinical investigations employing common carotid artery Doppler as a surrogate for central hemodynamics.

Introduction: Arrhythmias commonly occur during clinical exercise stress testing (EST), however there are limited data on prognostic significance, particularly differences between individuals with minor versus significant arrhythmia burden. Hypothesis: We hypothesized that significant but not minor arrhythmia burden during EST would be predictive of future all-cause mortality. Methods: Adults who underwent clinically indicated EST at Mayo Clinic Rochester between September 1993 and April 2017 were included and followed-up until March 2021 using the National Death Index to ascertain survival status. Expert clinician coding pertaining to arrhythmia burden during EST were used to group individuals (see Table 1 ). Cox proportional hazard models adjusted for known predictors of exercise-induced arrhythmias, were used to test the association of arrhythmia burden with all-cause mortality. Results: A total of 30796 individuals were included (age: 55±14yrs; female: 36%; Table 1 ). Mean follow-up was 8.8±3.6yrs, with a total of 2516 deaths. Arrhythmia during EST was associated with all-cause mortality compared with no arrhythmia (HR: 1.72; 95% CI: 1.58-1.88; p<0.001), however significant arrhythmia showed greater association compared with minor arrhythmia (HR: 2.07; 95% CI: 1.81-2.38; p<0.001). Both minor and significant arrhythmia during EST were significant predictors of all-cause mortality compared with no arrhythmia ( Figure, Table 2 ), however, after model adjustments, only significant arrhythmia was associated with all-cause mortality (HR: 1.40; 95% CI: 1.21-1.63; p<0.001) ( Table 2 ). Conclusions: After multivariate adjustment, significant arrhythmia burden during EST showed a 40% increased future risk of all-cause mortality, Conversely, adjusting for age and sex attenuated the effect of minor arrhythmia burden during EST on incidence of death. These results highlight the clinical significance of arrhythmia burden during exercise testing.

A wireless, wearable Doppler ultrasound offers a new paradigm for linking physiology to resuscitation medicine. To this end, the image analysis of simultaneously-acquired venous and arterial Doppler spectrograms attained by wearable ultrasound represents a new source of hemodynamic data. Previous investigators have reported a direct relationship between the central venous pressure (CVP) and the ratio of the internal jugular-to-common carotid artery diameters. Because Doppler power is directly related to the number of red cell scatterers within a vessel, we hypothesized that (1) the ratio of internal jugular-to-carotid artery Doppler power (V/APOWER) would be a surrogate for the ratio of the vascular areas of these two vessels and (2) the V/APOWER would track the anticipated CVP change during simulated hemorrhage and resuscitation. To illustrate this proof-of-principle, we compared the change in V/APOWER obtained via a wireless, wearable Doppler ultrasound to B-mode ultrasound images during a head-down tilt. Additionally, we elucidated the change in the V/APOWER during simulated hemorrhage and transfusion via lower body negative pressure (LBNP) and release. With these Interesting Images, we show that the Doppler V/APOWER ratio qualitatively tracks anticipated changes in CVP (e.g., cardiac preload) which is promising for both diagnosis and management of hemodynamic unrest.