Baroreflex sensitivity following acute upper-body exercise in the cold among stable coronary artery disease patients.

Background: A cold environment and exercise separately affect the autonomic nervous system (ANS), baroreflex sensitivity (BRS), and blood pressure variability (BPV) but their combined effects on post-exercise recovery are not known. Our cross-over trial examined these responses following upper-body static and dynamic exercise performed in a cold and neutral environment in patients with coronary artery disease (CAD). Methods: 20 patients with stable coronary artery disease performed both graded static (10%-30% of maximal voluntary contraction) and dynamic (light, moderate and high perceived intensity) upper-body exercise at -15°C and +22°C for 30 min. Electrocardiogram and continuous blood pressure were measured to compute post-exercise (10 and 30 min after exercise) spectral powers of heart rate (HR), blood pressure variability and BRS at low (0.04-0.15 Hz) and high (0.15-0.4 Hz) frequencies. Results: Static upper-body exercise performed in a cold environment increased post-exercise high frequency (HF) spectral power of heart rate (HF RR) (p < 0.001) and reduced heart rate (p = 0.001) and low-to-high frequency (LF/HF) ratio (p = 0.006) more than in a neutral environment. In addition, post-exercise mean BRS (p = 0.015) and high frequency BRS (p = 0.041) increased more following static exercise in the cold than in a neutral environment. Dynamic upper-body exercise performed in a cold environment reduced post-exercise HF BRS (p = 0.019) and systolic blood pressure (p = 0.003). Conclusion: Static upper-body exercise in the cold increased post-exercise BRS and overall vagal activity but without reduced systolic blood pressure. Dynamic upper-body exercise in the cold reduced post-exercise vagal BRS but did not affect the other parameters. The influence of cold exposure on post-exercise autonomic and cardiovascular responses following static upper-body exercise require further studies. This information helps understanding why persons with cardiovascular diseases are vulnerable to low environmental temperature. ClinicalTrials.gov: NCT02855905 (04/08/2016).

The effects of submaximal exercise and cold exposure on blood coagulation parameters in coronary artery disease patients.

BACKGROUND: Both exercise and cold exposure increase blood coagulation potential but their combined effects are not known. The purpose of the present study was to assess blood coagulation factors in response to submaximal exercise in the cold environment among patients with stable coronary artery disease (CAD). METHODS: Sixteen men (61.1 ± 7.1 years) with stable CAD participated in three 30-min experimental conditions (seated rest in - 15 °C and exercise in both + 22 °C and - 15 °C) in random order. The employed exercise consisted of brisk walking (66-69% of maximal heart rate). Factor VII (FVII), fibrinogen, D-dimer and von Willebrand factor (vWF) were analyzed from blood samples obtained before, immediately and one hour after each experiment. RESULTS: On average, FVII activity (95% confidence interval, CI) was 123 (108-143) %, 123 (106-140) %, 121 (103-139) % (baseline, recovery 1, recovery 2), fibrinogen concentration (95% CI) 3.81 (3.49-4.12) g/l, 3.71 (3.34-4.08) g/l, 3.65 (3.26-4.05) g/l, D-dimer concentration (95% CI) 0.42 (0.28-0.56) µg/ml, 0.42 (0.29-.55) µg/ml and 0.39 (0.29-0.49) µg/ml, and vWF activity (95% CI) 184 (135-232) %, 170 (128-212) % and 173 (129-217) % after exercise in the cold. Average FVII activity varied from 122 to 123%, fibrinogen concentration from 3.71 to 3.75 g/l, D-dimer concentration from 0.35 to 0.51 µg/ml and von Willebrand factor activity from 168 to 175% immediately after each three experimental condition. CONCLUSIONS: Our findings suggest that submaximal lower body exercise carried out in a cold environment does not significantly affect blood coagulation parameters among patients with stable CAD.

Central aortic hemodynamics following acute lower and upper-body exercise in a cold environment among patients with coronary artery disease.

Exercise is beneficial to cardiovascular health, evidenced by reduced post-exercise central aortic blood pressure (BP) and wave reflection. We assessed if post-exercise central hemodynamics are modified due to an altered thermal state related to exercise in the cold in patients with coronary artery disease (CAD). CAD patients (n = 11) performed moderate-intensity lower-body exercise (walking at 65-70% of HRmax) and rested in neutral (+ 22 °C) and cold (- 15 °C) conditions. In another protocol, CAD patients (n = 15) performed static (five 1.5 min work cycles, 10-30% of maximal voluntary contraction) and dynamic (three 5 min workloads, 56-80% of HRmax) upper-body exercise at the same temperatures. Both datasets consisted of four 30-min exposures administered in random order. Central aortic BP and augmentation index (AI) were noninvasively assessed via pulse wave analyses prior to and 25 min after these interventions. Lower-body dynamic exercise decreased post-exercise central systolic BP (6-10 mmHg, p < 0.001) and AI (1-6%, p < 0.001) both after cold and neutral and conditions. Dynamic upper-body exercise lowered central systolic BP (2-4 mmHg, p < 0.001) after exposure to both temperatures. In contrast, static upper-body exercise increased central systolic BP after exposure to cold (7 ± 6 mmHg, p < 0.001). Acute dynamic lower and upper-body exercise mainly lowers post-exercise central BP in CAD patients irrespective of the environmental temperature. In contrast, central systolic BP was elevated after static exercise in cold. CAD patients likely benefit from year-round dynamic exercise, but hemodynamic responses following static exercise in a cold environment should be examined further.Clinical trials.gov: NCT02855905 04/08/2016.

Endothelial function in response to exercise in the cold in patients with coronary artery disease.

BACKGROUND: Regular long-term physical exercise has favourable effects on endothelial function in patients with coronary artery disease (CAD). However, the effects of an acute exercise bout in the cold on endothelial function are not known. METHODS: At first, the effects of moderate-intensity aerobic lower-body exercise were assessed in CAD patients (n = 16) in a neutral [+22°C] and cold [-15°C] environment. Secondly, responses to static and dynamic upper-body exercise in a neutral [+22°C] and cold [-15°C] environment were investigated in CAD patients (n = 15). All experiments were performed in a random order. Endothelial function was measured by flow-mediated dilation (FMD) of the brachial artery in response to reactive hyperaemia, before and after the exposures in a neutral environment. RESULTS: No significant temperature*exercise*condition (pre-post) interaction was observed in FMD% when comparing rest versus aerobic exercise or static versus dynamic upper-body exercise. Relative reactive hyperaemia during FMD protocol, measured by changes in shear rate, was elevated after rest compared to aerobic exercise (p = .001) and after static compared to dynamic upper-body exercise (p < .001). However, no significant temperature*exercise*condition interaction was observed when FMD% was normalized for shear rate. CONCLUSIONS: Endothelial function to an acute bout of exercise among CAD patients was not modified by the environmental temperature where the exercise was performed. The present findings argue against the hypothesis that exercise in cold environmental conditions impairs endothelial function in patients with CAD.

High Home Blood Pressure Variability Associates With Exaggerated Blood Pressure Response to Cold Stress.

BACKGROUND: Exaggerated sympathetic cardiovascular (CV) reactivity to stress associates with elevated risk for clinical and preclinical end points of CV disease. It would be useful to identify these individuals, preferably from feasible measurements commonly used in health care. Our study examined the association between home blood pressure (BP) variability and cardiac workload response to whole-body cold exposure. METHODS: Seventy-five men (55-65 years, 46 hypertensive) measured BP at home twice in the morning and evening for a week. We computed systolic home BP variability as SD of daily means and divided the subjects into groups demonstrating either high or low BP variability. They were exposed to whole-body cold exposure (-10 °C, wind 3 m/second, 15 minutes, winter clothes, standing). BP and heart rate were measured at 3-minute intervals during, and 15 minutes before and after the exposure. Rate-pressure product (RPP) was calculated to represent cardiac workload. RESULTS: Subjects with high systolic home BP variability demonstrated a greater RPP increase in cold conditions compared to those with low BP variability [mean change from baseline (95% CI): 1,850 (1,450 to 2,250) bpm × mm Hg vs. 930 (610, 1,250) bpm × mm Hg, P < 0.01]. This was related to the augmented systolic BP change [31(28, 35) mm Hg vs. 23(20, 26) mm Hg, P < 0.01]. Home BP variability correlated with cold-related RPP (rS = 0.34, P = 0.003) and systolic BP (rS = 0.38, P < 0.001) responses. CONCLUSIONS: Moderate whole-body cold exposure increased BP and cardiac workload more among those with higher systolic home BP variability, independently of home BP level. Elevated home BP variability may indicate augmented sympathetically mediated vascular reactivity for environmental stressors. PUBLIC TRIALS REGISTRY NUMBER: Trial Number NCT02007031.

Good safety practice in a randomized controlled trial (CadColdEx) involving increased cardiac workload in patients with coronary artery disease.

BACKGROUND: Methodological information acknowledging safety of cardiac patients in controlled medical experiments are lacking. The descriptive report presents one good practice for considering safety in a randomized controlled study involving augmented cardiovascular strain among persons with coronary artery disease (CAD). METHODS: The patients were pre-selected by a cardiologist according to strictly defined selection criteria. Further confirmation of eligibility included screening of health. In addition, assessments of physical capacity by a graded bicycle ergometer test were implemented and safety monitored by an exercise physiologist and medical doctor. In this context, an emergency simulation was also carried out. A total of 18 CAD patients each underwent four different experimental interventions where either temperature (+ 22 °C and - 15 °C) and the level of exercise (rest and brisk walking) were employed for 30 min in random order (72 experiments). Baseline (20 min) and follow-up (60 min) measurements were conducted resting at + 22 °C. ECG, and brachial blood pressure were measured and perceived exertion and symptoms of chest pain inquired throughout the experiments. An emergency nurse was responsible for the health monitoring and at least two persons followed the patient throughout the experiment. A medical doctor was available on call for consultation. The termination criteria followed the generally accepted international guidelines for exercise testing and were planned prior to the experiments. RESULTS: The exercise test simulation revealed risks requiring changes in the study design and emergency response. The cardiovascular responses of the controlled trials were related to irregular HR, ST-depression or post-exercise hypotension. These were expected and the majority could be dealt on site by the research personnel and on call consultation. Only one patient was encouraged to seek for external health care consultation. CONCLUSIONS: Appropriate prospective design is a key to safe implementation of controlled studies involving cardiac patients and stimulation of cardiovascular function. This includes careful selection of participants, sufficient and knowledgeable staff, as well as identifying possible emergency situations and the required responses. TRIAL REGISTRATION: ClinicalTrials ID: NCT02855905 .

Cardiovascular responses to cold and submaximal exercise in patients with coronary artery disease.

Regular year-round exercise is recommended for patients with coronary artery disease (CAD). However, the combined effects of cold and moderate sustained exercise, both known to increase cardiac workload, on cardiovascular responses are not known. We tested the hypothesis that cardiac workload is increased, and evidence of ischemia would be observed during exercise in the cold in patients with CAD. Sixteen men (59.3 ± 7.0 yr, means ± SD) with stable CAD each underwent 4, 30 min exposures in a randomized order: seated rest and moderate-intensity exercise [walking, 60%-70% of max heart rate (HR)] performed at +22°C and -15°C. Systolic brachial blood pressure (SBP), HR, electrocardiogram (ECG), and skin temperatures were recorded throughout the intervention. Rate pressure product (RPP) and ECG parameters were obtained. The combined effects of cold and submaximal exercise were additive for SBP and RPP and synergistic for HR when compared with rest in a neutral environment. RPP (mmHg·beats/min) was 17% higher during exercise in the cold (18,080 ± 3540) compared with neutral (15,490 ± 2,940) conditions ( P = 0.001). Only a few ST depressions were detected during exercise but without an effect of ambient temperature. The corrected QT interval increased while exercising in the cold compared with neutral temperature ( P = 0.023). Recovery of postexercise blood pressure was similar regardless of temperature. Whole body exposure to cold during submaximal exercise results in higher cardiac workload compared with a neutral environment. Despite the higher RPP, no signs of myocardial ischemia or abnormal ECG responses were observed. The results of this study are useful for planning year-round exercise-based rehabilitation programs for stable CAD patients.

Hypertension Does Not Alter the Increase in Cardiac Baroreflex Sensitivity Caused by Moderate Cold Exposure.

Exposure to cold increases blood pressure and may contribute to higher wintertime cardiovascular morbidity and mortality in hypertensive people, but the mechanisms are not well-established. While hypertension does not alter responses of vagally-mediated heart rate variability to cold, it is not known how hypertension modifies baroreflex sensitivity (BRS) and blood pressure variability during cold exposure. Our study assessed this among untreated hypertensive men during short-term exposure comparable to habitual winter time circumstances in subarctic areas. We conducted a population-based recruitment of 24 untreated hypertensive and 17 men without hypertension (age 55-65 years) who underwent a whole-body cold exposure (-10°C, wind 3 m/s, winter clothes, 15 min, standing). Electrocardiogram and continuous blood pressure were measured to compute spectral powers of systolic blood pressure and heart rate variability at low (0.04-0.15 Hz) and high frequency (0.15-0.4 Hz) and spontaneous BRS at low frequency (LF). Comparable increases in BRS were detected in hypertensive men, from 2.6 (2.0, 4.2) to 3.8 (2.5, 5.1) ms/mmHg [median (interquartile range)], and in control group, from 4.3 (2.7, 5.0) to 4.4 (3.1, 7.1) ms/mmHg. Instead, larger increase (p < 0.05) in LF blood pressure variability was observed in control group; response as median (interquartile range): 8 (2, 14) mmHg(2), compared with hypertensive group [0 (-13, 20) mmHg(2)]. Untreated hypertension does not disturb cardiovascular protective mechanisms during moderate cold exposure commonly occurring in everyday life. Blunted response of the estimate of peripheral sympathetic modulation may indicate higher tonic sympathetic activity and decreased sympathetic responsiveness to cold in hypertension.