Non-contrast myocardial perfusion in rest and exercise stress using systolic flow-sensitive alternating inversion recovery

Objective To evaluate systolic flow-sensitive alternating inversion recovery (FAIR) during rest and exercise stress using 2RR (two cardiac cycles) or 1RR intervals between inversion pulse and imaging. Materials and methods 1RR and 2RR FAIR was implemented on a 3T scanner. Ten healthy subjects were scanned during rest and stress. Stress was performed using an in-bore ergometer. Heart rate, mean myocardial blood flow (MBF) and temporal signal-to-noise ratio (TSNR) were compared using paired t tests. Results Mean heart rate during stress was higher than rest for 1RR FAIR (85.8 ± 13.7 bpm vs 63.3 ± 11.1 bpm; p < 0.01) and 2RR FAIR (83.8 ± 14.2 bpm vs 63.1 ± 10.6 bpm; p < 0.01). Mean stress MBF was higher than rest for 1RR FAIR (2.97 ± 0.76 ml/g/min vs 1.43 ± 0.6 ml/g/min; p < 0.01) and 2RR FAIR (2.8 ± 0.96 ml/g/min vs 1.22 ± 0.59 ml/g/min; p < 0.01). Resting mean MBF was higher for 1RR FAIR than 2RR FAIR (p < 0.05), but not during stress. TSNR was lower for stress compared to rest for 1RR FAIR (4.52 ± 2.54 vs 10.12 ± 3.69; p < 0.01) and 2RR FAIR (7.36 ± 3.78 vs 12.41 ± 5.12; p < 0.01). 2RR FAIR TSNR was higher than 1RR FAIR for rest (p < 0.05) and stress (p < 0.001). Discussion We have demonstrated feasibility of systolic FAIR in rest and exercise stress. 2RR delay systolic FAIR enables non-contrast perfusion assessment during stress with relatively high TSNR.

Effects of Increased Central Cholinergic Activity on the Metabolic Challenge Induced by Submaximal Exercise in Rats: Adrenomedullary Secretion Influences

<b><i>Aim:</i></b> The aim of this study was to assess the influence of adrenomedullary secretion on the plasma glucose, lactate, and free fatty acids (FFAs) during running exercise in rats submitted to intracerebroventricular (i.c.v.) injection of physostigmine (PHY). PHY i.c.v. was used to activate the central cholinergic system. <b><i>Methods:</i></b> Wistar rats were divided into sham-saline (sham-SAL), sham-PHY, adrenal medullectomy-SAL, and ADM-PHY groups. The plasma concentrations of glucose, lactate, and FFAs were determined immediately before and after i.c.v. injection of 20 μL of SAL or PHY at rest and during running exercise on a treadmill. <b><i>Results:</i></b> The i.c.v. injection of PHY at rest increased plasma glucose in the sham group, but not in the ADM group. An increase in plasma glucose, lactate, and FFAs mobilization from adipose tissue was observed during physical exercise in the sham-SAL group; however, the increase in plasma glucose was greater with i.c.v. PHY. Moreover, the hyperglycemia induced by exercise and PHY in the ADM group were blunted by ADM, whereas FFA mobilization was unaffected. <b><i>Conclusion:</i></b> These results indicate that there is a dual metabolic control by which activation of the central cholinergic pathway increases plasma glucose but not FFA during rest and exercise, and that this hyperglycemic response is dependent on adrenomedullary secretion.

Myocardial adaptation and exercise performance in patients with pulmonary arterial hypertension assessed with patient-specific computer simulations

Computer simulations of the myocardial mechanics and hemodynamics of rest and exercise were performed in nine patients with pulmonary arterial hypertension and 10 control subjects, with the use of data from invasive catheterization and from cardiac magnetic resonance. This approach allowed a detailed analysis of myocardial adaptation to pulmonary arterial hypertension and showed how reduction in right ventricular inotropic reserve is the important limiting factor for an increase in cardiac output during exercise.

Transcutaneous and End-Tidal CO2 Measurements in Hypoxia and Hyperoxia

BACKGROUND: Transcutaneous measurement of carbon dioxide (CO2) has been proposed for physiological monitoring of tactical jet aircrew because in some clinical settings it mirrors arterial CO2 partial pressure (Paco2). End-tidal monitoring in laboratory settings is known to give high-fidelity estimates of Paco2.METHODS: The correspondence between end-tidal (PETco2) and transcutaneous Pco2 (tcPco2) was examined in healthy volunteers under laboratory conditions of hyperoxia and hypoxia. Rest and exercise, skin heating and cooling, hyperventilation, and induced CO2 retention were employed.RESULTS: Neither measure followed all known changes in Paco2 and tcPco2 changed when the skin temperature near the probe changed. Bland-Altman analysis showed significant nonzero slopes under most conditions. Regression analysis indicated that oxygen partial pressure (Po2) in tissue measured as transcutaneous Po2 (tcPo2) is an important explanatory variable for tcPco2 in addition to PETco2, and that local skin temperature also has an effect. Additionally, absorption atelectasis from breathing 100% O2 may cause PETco2 to deviate from Paco2.DISCUSSION: Even as a trend indicator for Paco2, tcPco2 is not useful under conditions that resemble those in the highly dynamic tactical jet aircraft environment. PETco2 is also not a good indicator of CO2 status in pilots who breathe nearly 100% O2.Shykoff BE, Lee LR, Gallo M, Griswold CA. Transcutaneous and end-tidal CO2 measurements in hypoxia and hyperoxia. Aerosp Med Hum Perform. 2021; 92(11):864-872.

Non-Contrast Myocardial Perfusion in Rest and Exercise Stress Using Systolic Flow-Sensitive Alternating Inversion Recovery

Objective: To evaluate systolic flow-sensitive alternating inversion recovery (FAIR) during rest and exercise stress using 2RR (two cardiac cycles) or 1RR intervals between inversion pulse and imaging. Materials and Methods: 1RR and 2RR FAIR was implemented on a 3T scanner. Ten healthy subjects were scanned during rest and stress. Stress was performed using an in-bore ergometer. Heart rate, mean myocardial blood flow (MBF) and temporal signal-to-noise ratio (TSNR) were compared using paired t-tests. Results: Mean heart rate during stress was higher than rest for 1RR FAIR (85.8±13.7bpm vs 63.3±11.1bpm; p<0.01) and 2RR FAIR (83.8±14.2bpm vs 63.1±10.6bpm; p<0.01). Mean stress MBF was higher than rest for 1RR FAIR (2.97±0.76ml/g/min vs 1.43±0.6 ml/g/min; p<0.01) and 2RR FAIR (2.8±0.96 ml/g/min vs 1.22±0.59 ml/g/min; p<0.01). Resting mean MBF was higher for 1RR FAIR than 2RR FAIR (p<0.05), but not during stress. TSNR was lower for stress compared to rest for 1RR FAIR (4.52±2.54 vs 10.12±3.69; p<0.01) and 2RR FAIR (7.36±3.78 vs 12.41±5.12; p<0.01). 2RR FAIR TSNR was higher than 1RR FAIR for rest (p<0.05) and stress (p<0.001). Discussion: We have demonstrated feasibility of systolic FAIR in rest and exercise stress. 2RR delay systolic FAIR enables non-contrast perfusion assessment during stress with relatively high TSNR.

Effects of Acute Heat and Cold Exposures at Rest or during Exercise on Subsequent Energy Intake: A Systematic Review and Meta-Analysis

The objective of this meta-analysis was to assess the effect of acute heat/cold exposure on subsequent energy intake (EI) in adults. We searched the following sources for publications on this topic: PubMed, Ovid Medline, Science Direct and SPORTDiscus. The eligibility criteria for study selection were: randomized controlled trials performed in adults (169 men and 30 women; 20–52 years old) comparing EI at one or more meals taken ad libitum, during and/or after exposure to heat/cold and thermoneutral conditions. One of several exercise sessions could be realized before or during thermal exposures. Two of the thirteen studies included examined the effect of heat (one during exercise and one during exercise and at rest), eight investigated the effect of cold (six during exercise and two at rest), and three the effect of both heat and cold (two during exercise and one at rest). The meta-analysis revealed a small increase in EI in cold conditions (g = 0.44; p = 0.019) and a small decrease in hot conditions (g = −0.39, p = 0.022) for exposure during both rest and exercise. Exposures to heat and cold altered EI in opposite ways, with heat decreasing EI and cold increasing it. The effect of exercise remains unclear.

Realizing the actual magnitudes of aortic diameter and cardiac output: a multisensory learning approach

The conventional physiology courses consist of theoretical lectures, clinical application seminars, numerical exercises, simulations, and laboratory practices. However, in subjects that involve relevant physical quantities, even students who successfully pass exams may be unable to realize the actual quantities involved. For example, students may know what the values of the aortic diameter and cardiac output are, and they may be skilled at calculating changes in variables without being able to realize the actual physical magnitudes of the variables, resulting in limited understanding. To address this problem, here we describe and discuss simple practical exercises specifically designed to allow students to multisensory experience (touch, see, hear) the actual physical magnitudes of aortic diameter and cardiac output in adult humans at rest and exercise. The results obtained and the feedback from a student survey both clearly show that the described approach is a simple and interesting tool for motivating students and providing them with more realistic learning.