Aerobic Interval Training Reduces the Burden of Atrial Fibrillation in the Short Term: A Randomized Trial.

BACKGROUND: Exercise training is an effective treatment for important atrial fibrillation (AF) comorbidities. However, a high level of endurance exercise is associated with an increased AF prevalence. We assessed the effects of aerobic interval training (AIT) on time in AF, AF symptoms, cardiovascular health, and quality of life in AF patients. METHODS AND RESULTS: Fifty-one patients with nonpermanent AF were randomized to AIT (n=26) consisting of four 4-minute intervals at 85% to 95% of peak heart rate 3 times a week for 12 weeks or to a control group (n=25) continuing their regular exercise habits. An implanted loop recorder measured time in AF continuously from 4 weeks before to 4 weeks after the intervention period. Cardiac function, peak oxygen uptake (o2peak), lipid status, quality of life, and AF symptoms were evaluated before and after the 12-week intervention period. Mean time in AF increased from 10.4% to 14.6% in the control group and was reduced from 8.1% to 4.8% in the exercise group (P=0.001 between groups). AF symptom frequency (P=0.006) and AF symptom severity (P=0.009) were reduced after AIT. AIT improved o2peak, left atrial and ventricular ejection fraction, quality-of-life measures of general health and vitality, and lipid values compared with the control group. There was a trend toward fewer cardioversions and hospital admissions after AIT. CONCLUSIONS: AIT for 12 weeks reduces the time in AF in patients with nonpermanent AF. This is followed by a significant improvement in AF symptoms, o2peak, left atrial and ventricular function, lipid levels, and QoL. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01325675.

Comparison of a new methodology for the assessment of 3D myocardial strain from volumetric ultrasound with 2D speckle tracking.

An alternative approach to extract 3D myocardial strain based on elastic registration of the ultrasound images (3DSE) was developed by our lab. The aim of the present study was to test its clinical performance by comparing strain values obtained by 3DSE with the ones obtained with 2D speckle tracking (2DST). Standard 2D B-mode and volumetric datasets were acquired in 12 patients with coronary heart disease (CHD) and in 12 control subjects. Longitudinal (ε(LL)), circumferential (ε(CC)) and radial (ε(RR)) strain values were obtained from 2D datasets using commercially available 2DST software and from volumetric datasets using the 3DSE approach. 3DSE provided lower strain values than 2DST. With both approaches global ε(LL) and ε(CC) were significantly lower in patients with CHD than in controls. Global ε(LL) and ε(CC) correlated well between both methods (R = 0.83, R = 0.86, respectively), while segmental correlations were moderate [R = 0.63 (ε(LL)), R = 0.41 (ε(CC))]. The highest differences in ε(LL) values obtained by the two methods and the highest number of erroneous ε(LL) with 3DSE were observed in the basal LV segments. This study shows that in real-life datasets our 3DSE method provides global and regional ε(LL) and ε(CC) values that are comparable with the ones obtained from 2DST, even though they are not interchangeable with each other. As only a single acquisition is required, 3D methods may offer advantages over the current 2D techniques. However, the accuracy of the 3DSE can still be improved by solving the problems that appear with deformation estimation in the basal segments.

One-arm maximal strength training improves work economy and endurance capacity but not skeletal muscle blood flow.

Maximal strength training with a focus on maximal mobilization of force in the concentric phase improves endurance performance that employs a large muscle mass. However, this has not been studied during work with a small muscle mass, which does not challenge convective oxygen supply. We therefore randomized 23 adult females with no arm-training history to either one-arm maximal strength training or a control group. The training group performed five sets of five repetitions of dynamic arm curls against a near-maximal load, 3 days a week for 8 weeks. This training increased maximal strength by 75% and improved rate of force development during both strength and endurance exercise, suggesting that each arm curl became more efficient. This coincided with a 17-18% reduction in oxygen cost at standardized submaximal workloads (work economy), and a 21% higher peak oxygen uptake and 30% higher peak load during maximal arm endurance exercise. Blood flow assessed by Doppler ultrasound in the axillary artery supplying the working biceps brachii and brachialis muscles could not explain the training-induced adaptations. These data suggest that maximal strength training improved work economy and endurance performance in the skeletal muscle, and that these effects are independent of convective oxygen supply.

Reproducibility in echocardiographic assessment of the left ventricular global and regional function, the HUNT study.

AIMS: The study aimed to compare the inter-observer reproducibility of new and traditional measurements of the left ventricular (LV) global and regional function. METHODS AND RESULTS: Two experienced echocardiographers performed 20 complete echo/Doppler examinations and 50 analyses on ten healthy subjects. All recordings were analysed for systolic and diastolic conventional and deformation measurements by both echocardiographers. Inter-observer mean error (absolute difference divided by the mean) was 4% and lowest (P = 0.001) for systolic M-mode annulus excursion. Mean error for the regional deformation indices was significantly higher than for all the global measurements (all P < 0.001). Mean error for analyses of the same recording was 34% (P = 0.002) lower for global systolic indices and 44% (P < 0.001) lower for global diastolic indices than inter-observer mean error for analyses made in separate recordings. CONCLUSION: Systolic M-mode annulus excursion showed better inter-observer reproducibility than other traditional and newer measurements of LV systolic and diastolic function. Repeated analyses of the same recordings underestimate the more clinically relevant inter-observer reproducibility by approximately 40% for most measurements of LV function.

3-D speckle tracking for assessment of regional left ventricular function.

Speckle tracking in 2-D ultrasound images has become an established tool for assessment of left ventricular function. The recent development of ultrasound systems with capability to acquire real-time full volume data of the left ventricle makes it possible to perform speckle tracking in three dimensions, and thereby track the real motion of the myocardium. This paper presents a method for assessing local strain and rotation from 3-D speckle tracking in apical full-volume datasets. The method has been tested on simulated ultrasound data based on a computer model of the left ventricle, and on patients with myocardial infarction. When applied on simulated ultrasound data, the method showed good agreement with strain and rotation traces calculated from the reference motion, and the method was able to capture segmental differences in the deformation pattern, although the magnitudes of strains were systematically lower than the reference strains. When applied on patients, the method demonstrated reduced strain in the infarcted areas. Bulls-eye plots of regional strains showed good correspondence with wall motion scoring based on 2-D apical images, although the dyskinetic and hypokinetic regions were not apparent in all strain components.

New noninvasive method for assessment of left ventricular rotation: speckle tracking echocardiography.

BACKGROUND: Left ventricular (LV) torsion is due to oppositely directed apical and basal rotation and has been proposed as a sensitive marker of LV function. In the present study, we introduce and validate speckle tracking echocardiography (STE) as a method for assessment of LV rotation and torsion. METHODS AND RESULTS: Apical and basal rotation by STE was measured from short-axis images by automatic frame-to-frame tracking of gray-scale speckle patterns. Rotation was calculated as the average angular displacement of 9 regions relative to the center of a best-fit circle through the same regions. As reference methods we used sonomicrometry in anesthetized dogs during baseline, dobutamine infusion, and apical ischemia, and magnetic resonance imaging (MRI) tagging in healthy humans. In dogs, the mean peak apical rotation was -3.7+/-1.2 degrees (+/-SD) and -4.1+/-1.2 degrees, and basal rotation was 1.9+/-1.5 degrees and 2.0+/-1.2 degrees by sonomicrometry and STE, respectively. Rotations by both methods increased (P<0.001) during dobutamine infusion. Apical rotation by both methods decreased during left anterior descending coronary artery occlusion (P<0.007), whereas basal rotation was unchanged. In healthy humans, apical rotation was -11.6+/-3.8 degrees and -10.9+/-3.3 degrees, and basal rotation was 4.8+/-1.7 degrees and 4.6+/-1.3 degrees by MRI tagging and STE, respectively. Torsion measurement by STE showed good correlation and agreement with sonomicrometry (r=0.94, P<0.001) and MRI (r=0.85, P<0.001). CONCLUSIONS: The present study demonstrates that regional LV rotation and torsion can be measured accurately by STE, suggesting a new echocardiographic approach for quantification of LV systolic function.