Background Moderate intensity exercise training (MIT) is safe and effective for patients with hypertrophic cardiomyopathy, yet the efficacy of high intensity training (HIT) remains unknown. This ...study aimed to compare the efficacy of HIT compared with MIT in patients with hypertrophic cardiomyopathy. Methods and Results Patients with hypertrophic cardiomyopathy were randomized to either 5 months of MIT, or 1 month of MIT followed by 4 months of progressive HIT. Peak oxygen uptake (V˙O
; Douglas bags), cardiac output (acetylene rebreathing), and arteriovenous oxygen difference (Fick equation) were measured before and after training. Left ventricular outflow gradient and volumes were measured by echocardiography. Fifteen patients completed training (MIT, n=8, age 52±7 years; HIT, n=7, age 42±8 years). Both HIT and MIT improved peak V˙O
by 1.3 mL/kg per min (
=0.009). HIT (+1.5 mL/kg per min) had a slightly greater effect than MIT (+1.1 mL/kg per min) but with no statistical difference (group×exercise
=0.628). A greater augmentation of arteriovenous oxygen difference occurred with exercise (Δ1.6 mL/100 mL
=0.005). HIT increased left ventricular end-diastolic volume (+17 mL, group×exercise
=0.015) compared with MIT. No serious arrhythmias or adverse cardiac events occurred. Conclusions This randomized trial of exercise training in patients with hypertrophic cardiomyopathy demonstrated that both HIT and MIT improved fitness without clear superiority of either. Although the study was underpowered for safety outcomes, no serious adverse events occurred. Exercise training resulted in salutary peripheral and cardiac adaptations. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03335332.
Abstract only
Background:
Exercise intolerance occurs in patients with hypertrophic cardiomyopathy (HCM) in part due to impaired augmentation of stroke volume (SV reserve) and diastolic dysfunction. ...Systolic-diastolic (S-D) coupling characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during diastole. S-D coupling declines with age and is further reduced in patients with heart failure. Impaired S-D coupling may contribute to impaired cardiac response to exercise in patients with HCM.
Hypothesis:
We hypothesized that S-D coupling is associated with peak oxygen uptake (peak VO
2
) and peak cardiac output (Qc) patients with HCM.
Methods:
Patients with HCM (HCM: n=25, age=46 ± 8.9 years) and healthy, sedentary adults (CON: n=115, age=50 ± 9.7 years) underwent cardiopulmonary exercise testing and resting echocardiography. S-D coupling is the relationship between LV longitudinal excursion of the mitral annulus during systole (S
exc
) and early diastole (ED
exc
) measured with tissue Doppler imaging. Peak VO
2
(Douglas bag), peak Qc (C
2
H
2
rebreathe), and SV reserve were assessed during maximal treadmill exercise. Linear regression was performed between S-D coupling and peak VO
2
, peak Qc, and SV reserve and multivariate regression with age as a covariate.
Results:
S-D coupling was reduced in HCM (HCM: 0.56±0.10, CON: 0.63±0.08, p <0.001). In CON, S-D coupling was independently associated with age (r = 0.52, p <0.001), but not peak VO
2
(r = 0.26, p = 0.473) or peak Qc (r = 0.04, p = 0.538). In HCM, S-D coupling was associated with peak VO
2
(r = 0.46 p = 0.019) and peak Qc (r = 0.56, p = 0.003) with a trend in SV reserve (r = 0.36, p = 0.071) (Figure), independent of age (VO
2
p = 0.020, Qc p = 0.004).
Conclusion:
Impaired systolic-diastolic coupling is associated with fitness and the cardiac response to exercise in patients with HCM. Inefficient S-D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM.
Despite advances in medical and cardiac resynchronization therapy (CRT), individuals with chronic congestive heart failure (CHF) have persistent symptoms, including exercise intolerance. Optimizing ...cardio-locomotor coupling may increase stroke volume and skeletal muscle perfusion as previously shown in healthy runners. Therefore, we tested the hypothesis that exercise stroke volume and cardiac output would be higher during fixed-paced walking when steps were synchronized with the diastolic compared with systolic portion of the cardiac cycle in patients with CHF and CRT.
Ten participants (58±17 years of age; 40% female) with CHF and previously implanted CRT pacemakers completed 5-minute bouts of walking on a treadmill (range, 1.5-3 mph). Participants were randomly assigned to first walking to an auditory tone to synchronize their foot strike to either the systolic (0% or 100±15% of the R-R interval) or diastolic phase (45±15% of the R-R interval) of their cardiac cycle and underwent assessments of oxygen uptake (V̇o
; indirect calorimetry) and cardiac output (acetylene rebreathing). Data were compared through paired-samples
tests.
V̇o
was similar between conditions (diastolic 1.02±0.44 versus systolic 1.05±0.42 L/min;
=0.299). Compared with systolic walking, stroke volume (diastolic 80±28 versus systolic 74±26 mL;
=0.003) and cardiac output (8.3±3.5 versus 7.9±3.4 L/min;
=0.004) were higher during diastolic walking; heart rate (paced) was not different between conditions. Mean arterial pressure was significantly lower during diastolic walking (85±12 versus 98±20 mm Hg;
=0.007).
In patients with CHF who have received CRT, diastolic stepping increases stroke volume and oxygen delivery and decreases afterload. We speculate that, if added to pacemakers, this cardio-locomotor coupling technology may maximize CRT efficiency and increase exercise participation and quality of life in patients with CHF.
Background
In patients with hypertrophic cardiomyopathy (HCM), impaired augmentation of stroke volume and diastolic dysfunction contribute to exercise intolerance. Systolic–diastolic (S‐D) coupling ...characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during early diastole. Impaired S‐D coupling may contribute to the impaired cardiac response to exercise in patients with HCM.
Methods
Patients with HCM (n = 25, age = 47 ± 9 years) and healthy adults (n = 115, age = 49 ± 10 years) underwent a cardiopulmonary exercise testing (CPET) and echocardiogram. S‐D coupling was defined as the ratio of LV longitudinal excursion of the mitral annulus during early diastole (EDexc) and systole (Sexc) and compared between groups. Peak oxygen uptake (peak V̇O2) (Douglas bags), cardiac index (C2H2 rebreathe), and stroke volume index (SVi) were assessed during CPET. Linear regression was performed between S‐D coupling and peak V̇O2, peak cardiac index, and peak SVi.
Results
S‐D coupling was lower in HCM (Controls: 0.63 ± 0.08, HCM: 0.56 ± 0.10, p < 0.001). Peak V̇O2 and stroke volume reserve were lower in patients with HCM (Peak VO2 Controls: 28.5 ± 5.5, HCM: 23.7 ± 7.2 mL/kg/min, p < 0.001, SV reserve: Controls 39 ± 16, HCM 30 ± 18 mL, p = 0.008). In patients with HCM, S‐D coupling was associated with peak V̇O2 (r = 0.47, p = 0.018), peak cardiac index (r = 0.60, p = 0.002), and peak SVi (r = 0.63, p < 0.001).
Conclusion
Systolic–diastolic coupling was impaired in patients with HCM and was associated with fitness and the cardiac response to exercise. Inefficient S‐D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM.
Systolic Diastolic Coupling represents the portion of systolic excursion (Sexc) recovered during early diastole (EDexc)(Left) and can be measured using Tissue Doppler Imaging of the mitral annulus (Top, Right). S‐D Coupling is significantly lower in patients with Hypertrophic Cardiomyopathy compared to healthy controls (Bottom, Right).
Abstract
New measurements from the Arctic ± 40 days around the summer solstice show reflected sunlight from north of 80°N decreases 20–35%. Arctic sea ice coverage decreases 7–9% over this same time ...period (as reported by the NSIDC) implying Arctic sea ice albedo decreases in addition to the sea ice receding. Similar Antarctic measurements provide a baseline to which Arctic measurements are compared. The Antarctic reflected sunlight south of 80°S is up to 30% larger than the Arctic reflectance and is symmetric around the solstice implying constant Antarctic reflectivity. Arctic reflected sunlight 20 days after solstice is > 100W/m
2
less than Antarctic reflected sunlight. For perspective, this is enough heat to melt > 1 mm/hour of ice. This finding should be compared with climate models and in reanalysis data sets to further quantify sea ice albedo’s role in Arctic Amplification. The measurements were made with previously unpublished pixelated radiometers on Global Positioning System satellites from 2014 to 2019. The GPS orbits give each radiometer instantaneous and continuous views of 37% of the Earth, two daily full views of the Arctic and Antarctic. Furthermore, the GPS constellation gives full-time full-Earth coverage that may provide data that complements existing limited field of view instruments that provide a less synoptic Earth view.
There is no consensus on how quickly the earth's ice sheets are melting due to global warming, nor on the ramifications to sea level rise. Due to its potential effects on coastal populations and ...global economies, sea level rise is a grave concern, making ice melt rates an important area of study. The ice‐sheet science community consists of two groups that perform related but distinct kinds of research: a data community, and a model building community. The data community characterizes past and current states of the ice sheets by assembling data from field and satellite observations. The modeling community forecasts the rate of ice‐sheet decline with computational models validated against observations. Although observational data and models depend on one another, these two groups are not well integrated. Better coordination between data collection efforts and modeling efforts is imperative if we are to improve our understanding of ice sheet loss rates. We present a new science gateway, GHub, a collaboration space for ice sheet scientists. This web‐accessible gateway will host datasets and modeling workflows, and provide access to codes that enable tool building by the ice sheet science community. Using GHub, we will collect and centralize existing datasets, creating data products that more completely catalog the ice sheets of Greenland and Antarctica. We will build workflows for model validation and uncertainty quantification, extending existing ice sheet models. Finally, we will host existing community codes, enabling scientists to build new tools utilizing them. With this new cyberinfrastructure, ice sheet scientists will gain integrated tools to quantify the rate and extent of sea level rise, benefitting human societies around the globe.
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