Do metaboreceptors alter heat loss responses following dynamic exercise?

Metaboreceptor activation during passive heating is known to influence cutaneous vascular conductance (CVC) and sweat rate (SR). However, whether metaboreceptors modulate the suppression of heat loss following dynamic exercise remains unclear. On separate days, before and after 15 min of high-intensity treadmill running in the heat (35°C), eight males underwent either 1) no isometric handgrip exercise (IHG) or ischemia (CON), 2) 1 min IHG (60% of maximum, IHG), 3) 1 min IHG followed by 2 min of ischemia (IHG+OCC), 4) 2 min of ischemia (OCC), or 5) 1 min IHG followed by 2 min of ischemia with application of lower body negative pressure (IHG+LBNP). SR (ventilated capsule), cutaneous blood flow (Laser-Doppler), and mean arterial pressure (Finometer) were measured continuously before and after dynamic exercise. Following dynamic exercise, CVC was reduced with IHG exercise (P < 0.05) and remained attenuated with post-IHG ischemia during IHG+OCC relative to CON (39 ± 2 vs. 47 ± 6%, P < 0.05). Furthermore, the reduction in CVC was exacerbated by application of LBNP during post-IHG ischemia (35 ± 3%, P < 0.05) relative to IHG+OCC. SR increased during IHG exercise (P < 0.05) and remained elevated during post-IHG ischemia relative to CON following dynamic exercise (0.94 ± 0.15 vs. 0.53 ± 0.09 mg·min(-1)·cm(-2), P < 0.05). In contrast, application of LBNP during post-IHG ischemia had no effect on SR (0.93 ± 0.09 mg·min(-1)·cm(-2), P > 0.05) relative to post-IHG ischemia during IHG+OCC. We show that CVC is reduced and that SR is increased by metaboreceptor activation following dynamic exercise. In addition, we show that the metaboreflex-induced loading of the baroreceptors can influence the CVC response, but not the sweating response.

Sex-related differences among patients undergoing surgical aortic valve replacement-a propensity score matched study.

OBJECTIVES: We investigated the sex-related difference in characteristics and 2-year outcomes after surgical aortic valve replacement (SAVR) by propensity-score matching (PSM). METHODS: Data from 2 prospective registries, the INSPIRIS RESILIA Durability Registry (INDURE) and IMPACT, were merged, resulting in a total of 933 patients: 735 males and 253 females undergoing first-time SAVR. The PSM was performed to assess the impact of sex on the SAVR outcomes, yielding 433 males and 243 females with comparable baseline characteristics. RESULTS: Females had a lower body mass index (median 27.1 vs 28.0 kg/m2; P = 0.008), fewer bicuspid valves (52% vs 59%; P = 0.036), higher EuroSCORE II (mean 2.3 vs 1.8%; P < 0.001) and Society of Thoracic Surgeons score (mean 1.6 vs 0.9%; P < 0.001), were more often in New York Heart Association functional class III/IV (47% vs 30%; P < 0.001) and angina Canadian Cardiovascular Society III/IV (8.2% vs 4.4%; P < 0.001), but had a lower rate of myocardial infarction (1.9% vs 5.2%; P = 0.028) compared to males. These differences vanished after PSM, except for the EuroSCORE II and Society of Thoracic Surgeons scores, which were still significantly higher in females. Furthermore, females required smaller valves (median diameter 23.0 vs 25.0 mm, P < 0.001). There were no differences in the length of hospital stay (median 8 days) or intensive care unit stay (median 24 vs 25 hours) between the 2 sexes. At 2 years, post-SAVR outcomes were comparable between males and females, even after PSM. CONCLUSIONS: Despite females presenting with a significantly higher surgical risk profile, 2-year outcomes following SAVR were comparable between males and females.

Heat stress attenuates the increase in arterial blood pressure during isometric handgrip exercise.

The purpose of this study was to examine arterial blood pressure responses during isometric handgrip (IHG) exercise performed at increasing levels of heat stress. Ten male subjects performed 1 min of IHG exercise at 60 % of maximal voluntary contraction under no heat stress (NHS), moderate heat stress [MHS, 0.6 °C increase in esophageal temperature (T (es))] and high heat stress (HHS, 1.4 °C increase in T (es)). For all conditions, IHG exercise significantly elevated mean arterial pressure (MAP) (NHS: 124 ± 6 vs. 90 ± 4 mmHg, MHS: 112 ± 6 vs. 89 ± 6 mmHg, HHS: 107 ± 7 vs. 91 ± 5 mmHg, P ≤ 0.05) and cardiac output (CO) (NHS: 9.0 ± 1.5 vs. 6.1 ± 0.6 L/min, MHS: 9.8 ± 1.8 vs. 7.6 ± 1.3 L/min, HHS: 10.0 ± 2.0 vs. 8.5 ± 1.9 L/min, P ≤ 0.05) relative to baseline, whereas no differences in total peripheral resistance (TPR) were observed (P > 0.05). However, the relative increases in MAP and CO were significantly reduced during MHS (MAP: 23 ± 6 mmHg, CO: 2.1 ± 0.9 L/min) and HHS (MAP: 16 ± 7 mmHg, CO: 1.5 ± 0.8 L/min) compared to NHS (34 ± 5 mmHg, CO: 2.9 ± 1.1 L/min, P ≤ 0.05). Furthermore, these elevations were significantly attenuated during HHS compared to MHS (P ≤ 0.05). Our findings show that heat stress attenuates the increase in arterial blood pressure during isometric handgrip exercise and this attenuation is cardiac output dependent, since TPR did not change during exercise for all heat stress conditions.

Durability of bioprosthetic aortic valve replacement in patients under the age of 60 years - 1-year follow-up from the prospective INDURE registry.

OBJECTIVES: We report 1-year safety and clinical outcomes in patients <60 years undergoing bioprosthetic surgical aortic valve intervention. METHODS: The INSPIRIS RESILIA Durability Registry is a prospective, multicentre registry to assess clinical outcomes of patients <60 years. Patients with planned SAVR with or without concomitant replacement of the ascending aorta and/or coronary bypass surgery were included. Time-related valve safety, haemodynamic performance and quality of life (QoL) at 1 year were assessed. RESULTS: A total of 421 patients were documented with a mean age of 53.5 years, 76.5% being male and 27.2% in NYHA class III/IV. Outcomes within 30 days included cardiovascular-related mortality (0.7%), time-related valve safety (VARC-2; 5.8%), thromboembolic events (1.7%), valve-related life-threatening bleeding (VARC-2; 4.3%) and permanent pacemaker implantation (3.8%). QoL was significantly increased at 6 months and sustained at 1 year. Freedom from all-cause mortality at 1 year was 98.3% (95% confidence interval 97.1; 99.6) and 81.8% were NYHA I versus 21.9% at baseline. No patient developed structural valve deterioration stage 3 (VARC-3). The mean aortic pressure gradient was 12.6 mmHg at 1 year and the effective orifice area was 1.9 cm2. CONCLUSIONS: The 1-year data from the INSPIRIS RESILIA valve demonstrate good safety and excellent haemodynamic performance as well as an early QoL improvement. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov: NCT03666741.

Divergent roles of plasma osmolality and the baroreflex on sweating and skin blood flow.

Plasma hyperosmolality and baroreceptor unloading have been shown to independently influence the heat loss responses of sweating and cutaneous vasodilation. However, their combined effects remain unresolved. On four separate occasions, eight males were passively heated with a liquid-conditioned suit to 1.0°C above baseline core temperature during a resting isosmotic state (infusion of 0.9% NaCl saline) with (LBNP) and without (CON) application of lower-body negative pressure (-40 cmH2O) and during a hyperosmotic state (infusion of 3.0% NaCl saline) with (LBNP + HYP) and without (HYP) application of lower-body negative pressure. Forearm sweat rate (ventilated capsule) and skin blood flow (laser-Doppler), as well as core (esophageal) and mean skin temperatures, were measured continuously. Plasma osmolality increased by ∼10 mosmol/kgH2O during HYP and HYP + LBNP conditions, whereas it remained unchanged during CON and LBNP (P ≤ 0.05). The change in mean body temperature (0.8 × core temperature + 0.2 × mean skin temperature) at the onset threshold for increases in cutaneous vascular conductance (CVC) was significantly greater during LBNP (0.56 ± 0.24°C) and HYP (0.69 ± 0.36°C) conditions compared with CON (0.28 ± 0.23°C, P ≤ 0.05). Additionally, the onset threshold for CVC during LBNP + HYP (0.88 ± 0.33°C) was significantly greater than CON and LBNP conditions (P ≤ 0.05). In contrast, onset thresholds for sweating were not different during LBNP (0.50 ± 0.18°C) compared with CON (0.46 ± 0.26°C, P = 0.950) but were elevated (P ≤ 0.05) similarly during HYP (0.91 ± 0.37°C) and LBNP + HYP (0.94 ± 0.40°C). Our findings show an additive effect of hyperosmolality and baroreceptor unloading on the onset threshold for increases in CVC during whole body heat stress. In contrast, the onset threshold for sweating during heat stress was only elevated by hyperosmolality with no effect of the baroreflex.

Hyperthermia modifies muscle metaboreceptor and baroreceptor modulation of heat loss in humans.

The relative influence of muscle metabo- and baroreflex activity on heat loss responses during post-isometric handgrip (IHG) exercise ischemia remains unknown, particularly under heat stress. Therefore, we examined the separate and integrated influences of metabo- and baroreceptor-mediated reflex activity on sweat rate and cutaneous vascular conductance (CVC) under increasing levels of hyperthermia. Twelve men performed 1 min of IHG exercise at 60% of maximal voluntary contraction followed by 2 min of ischemia with simultaneous application of lower body positive pressure (LBPP, +40 mmHg), lower body negative pressure (LBNP, -20 mmHg), or no pressure (control) under no heat stress. On separate days, trials were repeated under heat stress conditions of 0.6°C (moderate heat stress) and 1.4°C (high heat stress) increase in esophageal temperature. For all conditions, mean arterial pressure was greater with LBPP and lower with LBNP than control during ischemia (all P ≤ 0.05). No differences in sweat rate were observed between pressure conditions, regardless of the level of hyperthermia (P > 0.05). Under moderate heat stress, no differences in CVC were observed between pressure conditions. However, under high heat stress, LBNP significantly reduced CVC by 21 ± 4% (P ≤ 0.05) and LBPP significantly elevated CVC by 14 ± 5% (P ≤ 0.05) relative to control. These results show that sweating during post-IHG exercise ischemia is activated by metaboreflex stimulation, and not by baroreflexes. In contrast, our results suggest that baroreflexes can influence the metaboreflex modulation of CVC, but only at greater levels of hyperthermia.

Ice cooling vest on tolerance for exercise under uncompensable heat stress.

This study was conducted to evaluate the effectiveness of a commercial, personal ice cooling vest on tolerance for exercise in hot (35°C), wet (65% relative humidity) conditions with a nuclear biological chemical suit (NBC). On three separate occasions, 10 male volunteers walked on a treadmill at 3 miles per hour and 2% incline while (a) seminude (denoted CON), (b) dressed with a nuclear, biological, chemical (NBC) suit with an ice vest (V) worn under the suit (denoted NBCwV); or (c) dressed with an NBC suit but without an ice vest (V) (denoted NBCwoV). Participants exercised for 120 min or until volitional fatigue, or esophageal temperature reached 39.5°C. Esophageal temperature (T(es)), heart rate (HR), thermal sensation, and ratings of perceived exertion were measured. Exercise time was significantly greater in CON compared with both NBCwoV and NBCwV (p < 0.05), whereas T(es), thermal sensation, heart rate, and rate of perceived exertion were lower (p < 0.05). Wearing the ice vest increased exercise time (NBCwoV, 103.6 ± 7.0 min; NBCwV, 115.9 ± 4.1 min) and reduced the level of thermal strain, as evidenced by a lower T(es) at end-exercise (NBCwoV, 39.03 ± 0.13°C; NBCwV, 38.74 ± 0.13°C) and reduced thermal sensation (NBCwoV, 6.4 ± 0.4; NBCwV, 4.8 ± 0.6). This was paralleled by a decrease in rate of perceived exertion (NBCwoV, 14.7 ± 1.6; NBCwV, 12.4 ± 1.6) (p < 0.05) and heat rate (NBCwoV, 169 ± 6; NBCwV, 159 ± 7) (p < 0.05). We show that a commercially available cooling vest can significantly reduce the level of thermal strain during work performed in hot environments.

Durability of bioprosthetic aortic valves in patients under the age of 60 years - rationale and design of the international INDURE registry.

BACKGROUND: There is an ever-growing number of patients requiring aortic valve replacement (AVR). Limited data is available on the long-term outcomes and structural integrity of bioprosthetic valves in younger patients undergoing surgical AVR. METHODS: The INSPIRIS RESILIA Durability Registry (INDURE) is a prospective, open-label, multicentre, international registry with a follow-up of 5 years to assess clinical outcomes of patients younger than 60 years who undergo surgical AVR using the INSPIRIS RESILIA aortic valve. INDURE will be conducted across 20-22 sites in Europe and Canada and intends to enrol minimum of 400 patients. Patients will be included if they are scheduled to undergo AVR with or without concomitant root replacement and/or coronary bypass surgery. The primary objectives are to 1) determine VARC-2 defined time-related valve safety at one-year (depicted as freedom from events) and 2) determine freedom from stage 3 structural valve degeneration (SVD) presenting as morphological abnormalities and severe haemodynamic valve degeneration at 5 years. Secondary objectives include the assessment of the haemodynamic performance of the valve, all stages of SVD, potential valve-in-valve procedures, clinical outcomes (in terms of New York Heart Association [NYHA] function class and freedom from valve-related rehospitalisation) and change in patient quality-of-life. DISCUSSION: INDURE is a prospective, multicentre registry in Europe and Canada, which will provide much needed data on the long-term performance of bioprosthetic valves in general and the INSPIRIS RESILIA valve in particular. The data may help to gather a deeper understanding of the longevity of bioprosthetic valves and may expand the use of bioprosthetic valves in patients under the age of 60 years. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03666741 (registration received September, 12th, 2018).

Dabigatran: patient management in specific clinical settings.

Dabigatran, a direct thrombin inhibitor, is licensed for the prevention of venous thromboembolism after knee and hip replacement, the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation and for the treatment of acute venous thromboembolism. As dabigatran has a favourable benefit-risk profile, it is being increasingly used. Dabigatran differs from vitamin K antagonists as regards its pharmacological characteristics and its impact on certain laboratory tests, and also in the lack of a direct antagonist that can reverse dabigatran-induced anticoagulation. In emergency settings such as acute bleeding, emergency surgery, acute coronary syndrome, thrombolysis for ischaemic stroke or overdosing, specific strategies are required. A working group of experts from various disciplines has developed strategies for the management of dabigatran-treated patients in emergency settings.

Intra-aortic Filtration in Cardiac Surgery: An Effective Method to Reduce Neurologic Injury in High-Risk Patients.

Cardiac surgery is associated with a significant risk of adverse outcomes, particularly neurologic and renal. Embolic events are the primary source of these deleterious consequences. Intraaortic filtration is the only current technology shown to effectively capture particulates released during cardiac procedures and decrease morbidity and mortality. Although most surgical candidates may potentially benefit from intraaortic filtration, some patients are more likely to experience improved outcomes. Based on the evidence reported in the literature and the extensive experience of the authors, the following opinion details the authors' rationale and recommendations for patient selection for intraaortic filtration during cardiac surgery.

The p38 SAPK pathway is required for Ha-ras induced in vitro invasion of NIH3T3 cells.

Constitutive activation of the ras oncoprotein plays a critical role in cancer invasion and metastasis. Particularly, ras-related protease expression such as the serine protease urokinase plasminogen activator (u-PA) has been implicated in mediating cancer cell invasion. Previous studies have shown that ras-mediated u-PA expression is regulated through the mitogen- (MAPK) and stress-activated protein kinase (SAPK) signal transduction pathways extracellular signal-regulated kinase (ERK) and c-Jun-activating kinase (JNK). We therefore asked the question, if ras-related cell invasion might additionally require the third MAPK/SAPK signal transduction cascade, p38. Indeed, we found that ras induces invasion based on the activation of certain p38 protein kinase isoforms, in particular, p38alpha. Moreover, ras activation through transient or stable expression of a Ha-rasEJ mutant induced the expression of u-PA. This was found to be a consequence of an increase of u-PA m-RNA, which was paralleled by only a modest activation of the u-PA promoter. In conclusion, we provide evidence for the requirement of a novel ras-p38alpha-u-PA pathway for ras-dependent cellular invasion.