Normal sublingual microcirculation during painful crisis in sickle cell disease.

Obstruction of the microcirculation is the most important cause of painful crisis in sickle cell disease (SCD). Extensive microvascular obstruction has been observed in mouse models of SCD. A technique to determine the extent of the microcirculatory obstructions in humans may be helpful in the clinical setting and for research purposes. Therefore, we measured sublingual microcirculation longitudinally in patients with SCD admitted with painful crisis. Sublingual microcirculation was recorded with side-stream darkfield (SDF) imaging and semi-quantified with a microvascular flow index (MFI) on a range from 0 to 4 (arbitrary units; from 0 (no flow) to 4 (hyperdynamic flow)). Thirteen consecutive adult sickle cell patients admitted with painful crises were included and provided 47 measurements of MFI in 14 episodes of painful crisis. Seven patients provided baseline measurements and seven healthy controls were studied. The mean (+/-standard error of the mean) MFI during painful crisis was 2.6+/-0.1 and did not change during the painful crisis. The mean MFI of patients with SCD during steady state (2.7+/-0.1) and the mean MFI of the controls (2.7+/-0.1) were not different from the mean MFI during painful crisis. During painful crisis irregular microvascular perfusion, expressed by the distribution width of the microvascular blood flow velocity, correlated negatively (r=-0.484; P=0.002) with hemoglobin concentration. We conclude that sublingual microcirculatory blood flow velocity is not disturbed in sickle cell patients during painful crisis.

Stroke volume measurements with first-pass dynamic positron emission tomography: comparison with cardiovascular magnetic resonance.

BACKGROUND: The assessment of forward stroke volume (SV) using dynamic, first-pass cardiac positron emission tomography (PET) was shown to be feasible in a limited number of studies with small numbers of subjects. The aim of this study was to compare first-pass derived SV with cardiovascular magnetic resonance imaging (CMR)-obtained values in a larger population of subjects. METHODS AND RESULTS: Fifty-nine subjects with varying degrees of cardiac function were studied. Stroke volume was assessed using oxygen-15-labeled water (H(2)(15)O) dynamic first-pass PET for both the right ventricle (RV) and left ventricle (LV), and compared with the findings of aorta velocity-encoded phase-contrast CMR. The PET-estimated SV was higher for the RV than for the LV (133 +/- 34 vs 116 +/- 31 mL, P < .01, +/- SD), and both were higher compared with values obtained by CMR (81 +/- 20 mL, both P < .01, +/- SD). Although significant, the correlations between PET and CMR were moderate for both the RV (r = 0.37, P < .01) and the LV (r = 0.40, P < .01, +/- SD). Bland-Altman analysis revealed a progressive overestimation with increasing SV measured in either ventricle. CONCLUSIONS: First-pass dynamic H(2)(15)O PET for the assessment of forward SV is feasible, although values are progressively overestimated with increasing SV, particularly when the RV is used, and correlations with aorta velocity-encoded phase-contrast CMR are moderate. These findings are probably protocol-dependent and warrant further study before the use of first-pass dynamic H(2)(15)O PET in clinical or research settings can be advocated.