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Sökning: WFRF:(Knuuti Juhani)

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  • Föregående 1[2]3Nästa
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  • Laaksonen, Marko, 1975-, et al. (författare)
  • Left-ventricular hypertrophy associates to impaired maximal myocardial perfusion in endurance-trained men
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • Long-term endurance training induces morphological adaptations in heart, such as left-ventricular (LV) hypertrophy caused by wall thickening and cavity enlargement. Interestingly, these anatomical changes in the heart are strikingly similar to certain pathophysiological changes (Pellicia 2000). Previous studies have shown that the perfusion response in myocardium during dipyridamole- or adenosine infusion is decreased in several pathophysiological states with LV hypertrophy (e.g. Stolen et al. 2004). However, studies in endurance athletes with LV hypertrophy have shown contradictory results on myocardial perfusion response ranging from reduced to increased myocardial perfusion during dipyridamole- or adenosine-induced vasodilation compared to untrained men (Kjaer et al. 2005; Kalliokoski et al. 2002). The degree of hypertrophy could explain the discrepant findings in studies in athletes, but it has not been thoroughly investigated. Thus, we examined totally 31 endurance athletes (ET) and 25 untrained (UT) men in order to study the association between myocardial functional and anatomical parameters measured with echocardiography, and myocardial perfusion (at rest and during maximal vasodilation induced by iv adenosine) measured with Positron Emission Tomography. Both VO2max (60+-5 vs 42+-8 ml/kg/min, p<0.001) and LVmass index (169+-27 vs 102+-15 g/m2, p<0.001) were markedly higher in ET. Resting myocardial perfusion was similar between the groups (ET 0.7+-0.2 vs UT 0.8+-0.2 ml/g/min, p=0.22) whereas adenosine-stimulated perfusion was lower in ET (2.9+-1.0 vs 3.7+-1.0 ml/g/min, p<0.01). VO2max correlated inversely with adenosine-stimulated perfusion in ET (r=-0.39, p=0.03) and with resting perfusion in UT (-0.49, p=0.01). Forward LV work correlated linearly with resting perfusion in both groups (ET r=0.54, p<0.01; UT r=0.50, p=0.01). ET group was further divided into three subgroups according to LVmass index (ET1: LVmass index <150g/m2, n=9; ET2 LVmass index 150-180 g/m2, n=12; ET3 LVmass index >180 gm2, n=10). Adenosine-induced myocardial perfusion decreased gradually when LVmass increased (UT 3.7+-1.+0 vs ET1 3.3+-0.9 vs ET2 2.7+-1.4 vs ET3 2.6+-0.5 mL g-1 min-1, p=0.008). LVmass index was also inversely related to adenosine-induced perfusion in entire study population (r=-0.46, p<0.01). Therefore, these results suggest that endurance training-induced severe cardiac hypertrophy impairs myocardial perfusion capacity. Kalliokoski K et al. (2002) Med Sci Sports Exerc 34:948-53 Kjaer A et al. (2005) Am J Cardiol 96:1692-98 Pellicia A (2000) Curr Cardiol Rep 2(2):166-71 Stolen KQ et al (2004) 10(2):132-40
  • Laaksonen, Marko, 1975-, et al. (författare)
  • Muscle free fatty-acid uptake associates to mechanical efficiency during exercise in humans
  • 2018
  • Ingår i: Frontiers in Physiology. - 1664-042X .- 1664-042X. ; 9:AUG
  • Tidskriftsartikel (refereegranskat)abstract
    • Intrinsic factors related to muscle metabolism may explain the differences in mechanical efficiency (ME) during exercise. Therefore, this study aimed to investigate the relationship between muscle metabolism and ME. Totally 17 healthy recreationally active male subjects were recruited and divided into efficient (EF; n=8) and inefficient (IE; n=9) groups, which were matched for age (mean±SD 24±2 vs. 23±2 yrs), BMI (23±1 vs. 23±2 kg m-2), physical acitivity levels (3.4±1.0 vs. 4.1±1.0 sessions/week), and V ̇O2peak (53±3 vs. 52±3 mL kg-1 min-1), respectively, but differed for ME at 45% of VO2peak intensity during submaximal bicycle ergometer test (EF 20.5±3.5 vs. IE 15.4±0.8 %, P < 0.001). Using Positron Emission Tomography, muscle blood flow (BF) and uptakes of oxygen (mVO2), fatty acids (FAU) and glucose (GU) were measured during dynamic submaximal knee-extension exercise. Workload-normalized BF (EF 35±14 vs. IE 34±11 mL 100g-1 min-1, P = 0.896), mVO2 (EF 4.1±1.2 vs. IE 3.9±1.2 mL 100g-1 min-1, P = 0.808), and GU (EF 3.1±1.8 vs. IE 2.6±2.3 μmol 100g-1 min-1, P = 0.641) as well as the delivery of oxygen, glucose, and fatty acids, as well as respiratory quotient were not different between the groups. However, FAU was significantly higher in EF than IE (3.1±1.7 vs. 1.7±0.6 μmol 100g-1 min-1, P < 0.047) and it also correlated with ME (r=0.56, P < 0.024) in the entire study group. EF group also demonstrated higher use of plasma fatty acids than IE, but no differences in use of plasma glucose and intramuscular energy sources were observed between the groups. These findings suggest that the effective use of plasma fatty acids is an important determinant of mechanical efficiency during exercise.
  • Laaksonen, Marko, 1975-, et al. (författare)
  • Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise
  • 2010
  • Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 30:4, s. 241-249
  • Tidskriftsartikel (refereegranskat)abstract
    • The association between muscle oxygen uptake (VO2) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one-legged knee-extension exercise at variable intensities using positron emission tomography and a-v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI-1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI-2). Muscle perfusion and O2 delivery during HI-1 (26 ± 5 and 5·4 ± 1·0 ml 100 g−1 min−1) and HI-2 (28 ± 4 and 5·8 ± 0·7 ml 100 g−1 min−1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g−1 min−1). Muscle VO2 was also higher during both HI workloads (HI-1 3·3 ± 0·4 and HI-2 4·1 ± 0·6 ml 100 g−1 min−1) than LOW (1·4 ± 0·4 ml 100 g−1 min−1; P<0·01) and 25% higher during HI-2 than HI-1 (P<0·05). O2 extraction was higher during HI workloads (HI-1 62 ± 7 and HI-2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O2 extraction tended to be higher (P = 0·08) during HI-2 when compared to HI-1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one-legged knee-extension exercise at variable intensities, skeletal muscle perfusion and O2 delivery are unchanged between high-intensity workloads, whereas muscle VO2 is increased during the second high-intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O2 delivery and uptake. We propose that the excess muscle VO2 during the second high-intensity workload is derived from working muscle cells.
  • Laaksonen, Marko S, 1975-, et al. (författare)
  • VO2peak, myocardial hypertrophy, and myocardial blood flow in endurance-trained men
  • 2014
  • Ingår i: Medicine and science in sports and exercise. - 1530-0315. ; 46:8, s. 1498-1505
  • Tidskriftsartikel (refereegranskat)abstract
    • INTRODUCTION: Endurance training induces cardiovascular and metabolic adaptations, leading to enhanced endurance capacity and exercise performance. Previous human studies have shown contradictory results in functional myocardial vascular adaptations to exercise training, and we hypothesized that this may be related to different degrees of hypertrophy in the trained heart. METHODS: We studied the interrelationships between peak aerobic power (V̇O2peak), myocardial blood flow (MBF) at rest and during adenosine-induced vasodilation, and parameters of myocardial hypertrophy in endurance-trained (ET, n = 31) and untrained (n = 17) subjects. MBF and myocardial hypertrophy were studied using positron emission tomography and echocardiography, respectively. RESULTS: Both V̇O2peak (P < 0.001) and left ventricular (LV) mass index (P < 0.001) were higher in the ET group. Basal MBF was similar between the groups. MBF during adenosine was significantly lower in the ET group (2.88 ± 1.01 vs 3.64 ± 1.11 mLg-1min-1, P < 0.05) but not when the difference in LV mass was taken into account. V̇O2peak correlated negatively with adenosine-stimulated MBF, but when LV mass was taken into account as a partial correlate, this correlation disappeared. CONCLUSIONS: The present results show that increased LV mass in ET subjects explains the reduced hyperemic myocardial perfusion in this subject population and suggests that excessive LV hypertrophy has negative effect on cardiac blood flow capacity.
  • Morton, Geraint, et al. (författare)
  • Quantification of absolute myocardial perfusion in patients with coronary artery disease: comparison between cardiovascular magnetic resonance and positron emission tomography
  • Ingår i: Journal of the American College of Cardiology. - : Elsevier USA. - 0735-1097. ; 60:16, s. 55-1546
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: The aim of this study was to compare fully quantitative cardiovascular magnetic resonance (CMR) and positron emission tomography (PET) myocardial perfusion and myocardial perfusion reserve (MPR) measurements in patients with coronary artery disease (CAD).BACKGROUND: Absolute quantification of myocardial perfusion and MPR with PET have proven diagnostic and prognostic roles in patients with CAD. Quantitative CMR perfusion imaging has been established more recently and has been validated against PET in normal hearts. However, there are no studies comparing fully quantitative CMR against PET perfusion imaging in patients with CAD.METHODS: Forty-one patients with known or suspected CAD prospectively underwent quantitative (13)N-ammonia PET and CMR perfusion imaging before coronary angiography.RESULTS: The CMR-derived MPR (MPR(CMR)) correlated well with PET-derived measurements (MPR(PET)) (r = 0.75, p < 0.0001). MPR(CMR) and MPR(PET) for the 2 lowest scoring segments in each coronary territory also correlated strongly (r = 0.79, p < 0.0001). Absolute CMR perfusion values correlated significantly, but weakly, with PET values both at rest (r = 0.32; p = 0.002) and during stress (r = 0.37; p < 0.0001). Area under the receiver-operating characteristic curve for MPR(PET) to detect significant CAD was 0.83 (95% confidence interval: 0.73 to 0.94) and for MPR(CMR) was 0.83 (95% confidence interval: 0.74 to 0.92). An MPR(PET) ≤1.44 predicted significant CAD with 82% sensitivity and 87% specificity, and MPR(CMR) ≤1.45 predicted significant CAD with 82% sensitivity and 81% specificity.CONCLUSIONS: There is good correlation between MPR(CMR) and MPR(PET.) For the detection of significant CAD, MPR(PET) and MPR(CMR) seem comparable and very accurate. However, absolute perfusion values from PET and CMR are only weakly correlated; therefore, although quantitative CMR is clinically useful, further refinements are still required.
  • Naum, Alexandru, et al. (författare)
  • Motion detection and correction for dynamic: 15O-water myocardial perfusion PET studies
  • 2005
  • Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - 1619-7070. ; 32:12, s. 1378-1383
  • Tidskriftsartikel (refereegranskat)abstract
    • Patient motion during dynamic PET studies is a well-documented source of errors. The purpose of this study was to investigate the incidence of frame-to-frame motion in dynamic ( 15)O-water myocardial perfusion PET studies, to test the efficacy of motion correction methods and to study whether implementation of motion correction would have an impact on the perfusion results. We tested manual, in-house-developed motion correction software and an automatic motion correction using a rigid body point model implemented in MIPAV (Medical Image Processing, Analysis and Visualisation) software. At rest, patient motion was found in 18% of the frames, but during pharmacological stress the fraction increased to 45% and during physical exercise it rose to 80%. Both motion correction algorithms significantly decreased (p<0.006) the number of moved frames and the amplitude of motion (p<0.04). Motion correction significantly increased MBF results during bicycle exercise (p<0.02). Applying motion correction for the data acquired during exercise clearly changed the MBF results, indicating that motion correction is required for these studies.
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