ECSS Paris 2023: OP-PN32
INTRODUCTION: Sex differences in coronary artery atherosclerotic plaque composition and resting myocardial blood flow have been observed. Moreover, the relationship between coronary plaque burden and adverse cardiovascular events seems to be sex-dependent. In addition to imaging studies, exercise testing is commonly utilised in the assessment of coronary artery disease (CAD). We studied how coronary plaque burden and myocardial blood flow are associated with maximal workload capacity on exercise testing and how sex impacts these relationships. METHODS: Symptomatic outpatients with suspected obstructive CAD were prospectively enrolled at a tertiary hospital. All participants underwent coronary computed tomography angiography (CTA) to characterise atherosclerotic plaques, and positron emission tomography (PET) with 15O-water to assess myocardial blood flow (MBF) at rest and with intravenous adenosine vasodilation for the global myocardium, left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA) territories. Participants additionally underwent clinical exercise stress testing on a cycle ergometer. Peak workload (last 4 minute average) and haemodynamic variables were reported from exercise testing. Spearman correlations by sex were used with and without partial adjustments to determine correlations. RESULTS: Among the 107 enrolled patients, the peak workload on exercise testing was recorded in 88 patients (55 males, 33 females). Global adenosine-induced MBF and myocardial flow reserve were positively correlated with peak workload in females (r=0.423, p=0.0159 and r=0.511, p=0.0028, respectively), and remained significant when adjusted for age, body mass index and coronary stenosis area percent (r=0.453, p=0.0156 and r=0.663, p=0.0001). The same pattern was seen for myocardial flow reserve for LAD, LCx and RCA territories in females. No associations between peak exercise workload and MBF were seen in the raw or adjusted correlations in males. Males had a significant negative association between peak exercise workload and CTA assessed percent diameter stenosis (r=-0.345, p=0.0106), which remained significant after adjustment for age and BMI (r=-0.381, p=0.0053). There were no associations between coronary artery stenosis severity and peak exercise workload observed in females. CONCLUSION: In patients with suspected CAD, higher peak exercise workload was associated with favourable myocardial blood flow indices in females and milder coronary artery stenosis severity in males. These findings suggest that the relationship between exercise tolerance and CAD phenotype is sex-dependent, and the results from clinical exercise testing in suspected CAD should be interpreted in the context of patient’s sex.
Read CV Anna ScheerECSS Paris 2023: OP-PN32
INTRODUCTION: The primary muscle of inspiration, the diaphragm, has been shown to fatigue following high levels of inspiratory work such as during whole-body endurance exercise or resistive breathing tasks. We have shown that following pressure threshold loading (PTL), females experience less diaphragm fatigue measured via cervical magnetic stimulation (CMS) of the phrenic nerves. A critique of CMS is that it may not supramaximally stimulate the diaphragm. The purpose of this study was twofold: (1) to evaluate sex-based differences in the contractility of the diaphragm by measuring transdiaphragmatic pressure (Pdi) in response to electrical bilateral phrenic nerve stimulation (BPNS), ensuring maximal recruitment, and (2) to determine low frequency fatigue (LFF) of the diaphragm. METHODS: Twenty-three (n=12F, 11M) young and healthy participants participated in the study. The phrenic nerves were located, underwent a recruitment protocol where current was increased by 10 mA until a plateau in Pdi was observed, then increased by 20-30%. Participants performed PTL to task failure at a duty cycle of 0.7 with a breathing frequency of 15 breaths/minute. Diaphragm contractility was assessed via Pdi in response to BPNS as single twitches and 10 Hz paired stimulations. BPNS was performed pre-PTL, post-PTL, and 30 and 60 minutes post PTL. RESULTS: All participants demonstrated a plateau in Pdi, defined as an equal to or less than 20% difference between the final 3 stimulation intensities during the ramp protocol. Immediately post-PTL single twitch Pdi was significantly lower in males than females (-34±18% vs.-23±11% respectively, p<0.05), however there was no difference in 10 Hz Pdi between males and females (-28±31% vs. -20.3±23.4 respectively, p>0.05). Females performed PTL for significantly longer (22.3±15.2 vs. 13.4±7.8 minutes, p<0.05) and accumulated greater diaphragmatic work compared to males (34 843 ± 21 558 vs. 21 867 ± 8 885 H2O·s, p<0.05). There was no difference in single twitch or 10 Hz Pdi between males and females at 30 or 60 minutes post PTL (p>0.05). CONCLUSION: We found that supramaximal stimulation of the phrenic nerves before and after high levels of inspiratory work revealed less diaphragm fatigue in females. These observations are consistent with our previous studies using CMS. These findings suggest that the difference in diaphragm fatigue between males and females is unlikely due to a difference in the calcium release from the sarcoplasmic reticulum during excitation-contraction coupling, as similar levels of LFF were observed between sexes. These results suggest that sex-based differences in diaphragm fatigue likely arise from mechanisms beyond excitation–contraction coupling and warrant further investigation. Funding: Natural Sciences and Engineering Research Council of Canada
Read CV Chloe MathewsECSS Paris 2023: OP-PN32
INTRODUCTION: Physical exercise is a critical stimulus for cerebrovascular health, with acute increases in cerebral blood flow, measured as middle cerebral artery velocity (MCAv) serving as a primary driver for cerebrovascular adaptation. Previous research indicates that MCAv responses may be exercise-modality dependent, peaking at maximal intensity during rowing but at moderate intensity during cycling exercise, but direct comparisons are missing. Evidence suggests potential sex-related differences in MCAv responses during acute exercise. This study compared MCAv responses to rowing and cycling in young males and females during high-intensity all-out exercises. METHODS: Eighteen healthy adults (11 males: 23±5 years; 7 females: 23±3 years; P=.77) completed two 3-minute all-out exercise bouts on a rowing and cycling ergometer in a randomized order, separated by at least 72 hours. Females were tested during the early follicular phase of their menstrual cycle, to minimize hormonal variability. MCAv, end-tidal partial pressure of carbon dioxide (PETCO2), and mean arterial blood pressure (MAP) were recorded continuously. The primary outcome was defined as the change from baseline to the mean value of the final 30 seconds of exercise. Data were analyzed using a repeated measures ANOVA with factors of EXERCISE (Rowing vs. Cycling) and SEX (Males vs. Females). RESULTS: At baseline, MCAv (EXERCISE: P=.15; SEX: P=.14), PETCO2 (EXERCISE: P=.89; SEX: P=.97) and MAP (EXERCISE: P=.84; SEX: P=.22) were similar between groups. During exercise, the change from baseline in MCAv was significantly greater during rowing compared to cycling (P<.01, ηp2=.60), and females showed a higher increase compared to males (P=.02, ηp2=.31). PETCO2 increased to a greater extent during rowing than cycling (P<.01, ηp2=.78), with no significant sex differences (P=.82). MAP responses were similar between exercise modalities (P=.20) and between sexes (P=.34). CONCLUSION: Young adults showed significantly higher MCAv responses during rowing compared to cycling at high-intensity exercise, with females exhibiting a more pronounced increase in MCAv than males. Although the higher PETCO2 observed during rowing (a difference of ~3mmHg on average compared to cycling) contributed to larger increase in MCAv, this difference does not fully account for the magnitude of the MCAv response. The sex-specific difference, where females showed higher increases in MCAv despite similar PETCO2 and MAP responses, suggests that cerebrovascular regulation during high-intensity exercise is sex-dependent. These findings are critical when prescribing exercise modalities to optimize cerebrovascular health.
Read CV Timo KleinECSS Paris 2023: OP-PN32