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- Lubberink, Mark, et al.
(författare)
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Myocardial Oxygen Extraction Fraction Measured Using Bolus Inhalation of O-15-Oxygen Gas and Dynamic PET
- 2011
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 52:1, s. 60-66
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the accuracy of oxygen extraction fraction (OEF) measurements using a dynamic scan protocol after bolus inhalation of O-15(2). The method of analysis was optimized by investigating potential reuse of myocardial blood flow (MBF), perfusable tissue fraction, and blood and lung spillover factors derived from separate O-15-water and (CO)-O-15 scans. Methods: Simulations were performed to assess the accuracy and precision of OEF for a variety of models in which different parameters from O-15-water and (CO)-O-15 scans were reused. Reproducibility was assessed in 8 patients who underwent one 10-min dynamic scan after bolus injection of 1.1 GBq of O-15-water, two 10-min dynamic scans after bolus inhalation of 1.4 GBq of O-15(2), and a 6-min static scan after bolus inhalation of 0.8 GBq of (CO)-O-15 for region-of-interest definition. Results: Simulations showed that accuracy and precision were lowest when all parameters were determined from the O-15(2) scan. The optimal accuracy and precision of OEF were obtained when fixing MBF, perfusable tissue fraction, and blood spillover to values derived from a O-15-water scan and estimating spillover from the pulmonary gas volume using an attenuation map. Optimal accuracy and precision were confirmed in the patient study, showing an OEF test-retest variability of 13% for the whole myocardium. Correction of spillover from pulmonary gas volume requires correction of the lung time-activity curve for pulmonary blood volume, which could equally well be obtained from a O-15-water rather than (CO)-O-15 scan. Conclusion: Measurement of OEF is possible using bolus inhalation of O-15(2) and a dynamic scan protocol, with optimal accuracy and precision when other relevant parameters, such as MBF, are derived from an additional O-15-water scan.
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| 2. |
- Vermeltfoort, Ilse A., et al.
(författare)
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Feasibility of subendocardial and subepicardial myocardial perfusion measurements in healthy normals with (15)O-labeled water and positron emission tomography
- 2011
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 18:4, s. 650-656
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Tidskriftsartikel (refereegranskat)abstract
- Positron emission tomography (PET) enables robust and reproducible measurements of myocardial blood flow (MBF). However, the relatively limited resolution of PET till recently prohibited distinction between the subendocardial and the subepicardial layers in non-hypertrophied myocardium. Recent developments in hard- and software, however, have enabled to identify a transmural gradient difference in animal experiments. The aim of this study is to determine the feasibility of subendocardial and subepicardial MBF in normal human hearts assessed with (15)O-labeled water PET. Twenty-seven healthy subjects (mean age 41 +/- A 13 years; 11 men) were studied with (15)O-labeled water PET to quantify resting and hyperaemic (adenosine) MBF at a subendocardial and subepicardial level. In addition, cardiac magnetic resonance imaging was performed to determine left ventricular (LV) volumes and function. Mean rest MBF was 1.46 +/- A 0.49 in the subendocardium, and 1.14 +/- A 0.342 mL center dot A min(-1) center dot A g(-1) in the subepicardium (P < .001). MBF during vasodilation was augmented to a greater extent at the subepicardial level (subendocardium vs subepicardium: 3.88 +/- A 0.86 vs 4.14 +/- A 0.88 mL center dot A min(-1) center dot A g(-1), P = .013). The endocardial-to-epicardial MBF ratio decreased significantly during hyperaemia (1.35 +/- A 0.23 to 1.12 +/- A 0.20, P < .001). Hyperaemic transmural MBF was inversely correlated with left ventricular end-diastolic volume index (LVEDVI) (r (2) = 0.41, P = .0003), with greater impact however at the subendocardial level. (15)O-labeled water PET enables MBF measurements with distinction of the subendocardial and subepicardial layers in the normal human heart and correlates with LVEDVI. This PET technique may prove useful in evaluating patients with signs of ischaemia due to coronary artery disease or microvascular dysfunction.
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| 3. |
- Wong, Yeun Ying, et al.
(författare)
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Right ventricular failure in idiopathic pulmonary arterial hypertension is associated with inefficient myocardial oxygen utilization
- 2011
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Ingår i: Circulation Heart Failure. - 1941-3289 .- 1941-3297. ; 4:6, s. 700-706
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundIn idiopathic pulmonary arterial hypertension (IPAH), increased right ventricular (RV) power is required to maintain cardiac output. For this, RV O2 consumption (MVO2) must increase by augmentation of O2 supply and/or improvement of mechanical efficiency–ratio of power output to MVO2. In IPAH with overt RV failure, however, there is evidence that O2 supply (perfusion) reserve is reduced, leaving only increase in either O2 extraction or mechanical efficiency as compensatory mechanisms. We related RV mechanical efficiency to clinical and hemodynamic parameters of RV function in patients with IPAH and associated it with glucose metabolism.Methods and ResultsThe patients included were in New York Heart Association (NYHA) class II (n=8) and class III (n=8). They underwent right heart catheterization, MRI, and H215O-, 15O2-, C15O-, and 18FDG-PET. RV power and O2 supply were similar in both groups (NYHA class II versus class III: 0.54±0.14 versus 0.47±0.12 J/s and 0.109±0.022 versus 0.128±0.026 mL O2/min per gram, respectively). RV O2 extraction was near-significantly lower in NYHA class II compared with NYHA class III (63±17% versus 75±16%, respectively, P=0.10). As a result, MVO2 was significantly lower (0.066±0.012 versus 0.092±0.010 mL O2/min per gram, respectively, P=0.006). RV efficiency was reduced in NYHA class III (13.9±3.8%) compared with NYHA class II (27.8±7.6%, P=0.001). Septal bowing, measured by MRI, correlated with RV efficiency (r=−0.59, P=0.020). No relation was found between RV efficiency and glucose uptake rate. RV mechanical efficiency and ejection fraction were closely related (r=0.81, P<0.001).ConclusionsRV failure in IPAH was associated with reduced mechanical efficiency that was partially explained by RV mechanical dysfunction but not by a metabolic shift.
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| 4. |
- Wong, Yeun Ying, et al.
(författare)
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Supine-exercise-induced oxygen supply to the right myocardium is attenuated in patients with severe idiopathic pulmonary arterial hypertension
- 2011
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Ingår i: Heart. - : BMJ. - 1355-6037 .- 1468-201X. ; 97:24, s. 2069-2074
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundImpaired right ventricular (RV) myocardial blood flow (MBF) has been associated with RV dysfunction and fatal RV failure in idiopathic pulmonary hypertension during stress. MBF and O2 extraction from myocardial capillaries (O2 extraction fraction (OEF)) influence myocardial O2 supply.ObjectiveTo determine how the baseline RV OEF affects the amount of MBF increase induced by supine exercise, the authors hypothesise that higher baseline OEF (H-OEF) results in limited O2 extraction during exercise and that MBF must therefore be increased to obtain sufficient O2.MethodsIn 18 patients with idiopathic pulmonary hypertension, baseline OEF, resting MBF and exercise-induced MBF at 40% of maximal cardiopulmonary exercise testing load were measured using positron emission tomography and [15O]O2, [15O]H2O and [15O]CO.ResultsFor the whole population, exercise increased RV MBF from 0.68±0.16 to 1.13±0.38 ml/min/g (p<0.0001). The MBF exercise-to-rest ratio (reserve) was 1.7±0.7. The median baseline OEF was 0.73 at which the patient population was split into H-OEF and lower baseline OEF (L-OEF). Baseline MBF values (0.61±0.11 and 0.74±0.17 ml/min/g, respectively) were similar, and exercise induced a significant MBF increase in both groups (p=0.0001). However, exercise-induced increase in MBF was significantly less in the H-OEF group than in the L-OEF group (0.97±0.30 and 1.30±0.39 ml/min/g, respectively, p<0.05). Moreover, H-OEF patients had lower baseline stroke volume and cardiac output than the L-OEF group (52±19 ml and 4.0±1.1 l/min vs 78±18 ml and 5.5±0.9 l/min, respectively, both p<0.05).ConclusionsH-OEF patients were hemodynamically poorer and showed a lower exercise-induced MBF increase compared to L-OEF patients, suggesting exercise-induced O2 supply limitation.
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