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- Diller, Gerhard-Paul, et al.
(författare)
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Exercise intolerance in adult congenital heart disease : comparative severity, correlates, and prognostic implication.
- 2005
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Ingår i: Circulation. - 0009-7322 .- 1524-4539. ; 112:6, s. 828-35
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Although some patients with adult congenital heart disease (ACHD) report limitations in exercise capacity, we hypothesized that depressed exercise capacity may be more widespread than superficially evident during clinical consultation and could be a means of assessing risk.METHODS AND RESULTS: Cardiopulmonary exercise testing was performed in 335 consecutive ACHD patients (age, 33+/-13 years), 40 non-congenital heart failure patients (age, 58+/-15 years), and 11 young (age, 29+/-5 years) and 12 older (age, 59+/-9 years) healthy subjects. Peak oxygen consumption (peak VO2) was reduced in ACHD patients compared with healthy subjects of similar age (21.7+/-8.5 versus 45.1+/-8.6; P<0.001). No significant difference in peak VO2 was found between ACHD and heart failure patients of corresponding NYHA class (P=NS for each NYHA class). Within ACHD subgroups, peak VO2 gradually declined from aortic coarctation (28.7+/-10.4) to Eisenmenger (11.5+/-3.6) patients (P<0.001). Multivariable correlates of peak VO2 were peak heart rate (r=0.33), forced expiratory volume (r=0.33), pulmonary hypertension (r=-0.26), gender (r=-0.23), and body mass index (r=-0.19). After a median follow-up of 10 months, 62 patients (18.5%) were hospitalized or had died. On multivariable Cox analysis, peak VO2 predicted hospitalization or death (hazard ratio, 0.937; P=0.01) and was related to the frequency and duration of hospitalization (P=0.01 for each).CONCLUSIONS: Exercise capacity is depressed in ACHD patients (even in allegedly asymptomatic patients) on a par with chronic heart failure subjects. Lack of heart rate response to exercise, pulmonary arterial hypertension, and impaired pulmonary function are important correlates of exercise capacity, as is underlying cardiac anatomy. Poor exercise capacity identifies ACHD patients at risk for hospitalization or death.
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| 2. |
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| 3. |
- Johansson, Bengt, et al.
(författare)
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The effects of breath-holding on pulmonary regurgitation measured by cardiovascular magnetic resonance velocity mapping.
- 2009
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - 1097-6647 .- 1532-429X. ; 11:1, s. 1-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Pulmonary regurgitation is a common and clinically important residual lesion after repair of tetralogy of Fallot. Cardiovascular magnetic resonance (CMR) phase contrast velocity mapping is widely used for measurement of pulmonary regurgitant fraction. Breath-hold acquisitions, usually acquired during held expiration, are more convenient than the non-breath-hold approach, but we hypothesized that breath-holding might affect the amount of pulmonary regurgitation. METHODS: Forty-three adult patients with a previous repair of tetralogy of Fallot and residual pulmonary regurgitation were investigated with CMR. In each, pulmonary regurgitant fraction was measured from velocity maps transecting the pulmonary trunk, acquired during held expiration, held inspiration, by non-breath-hold acquisition, and also from the difference of right and left ventricular stroke volume measurements. RESULTS: Pulmonary regurgitant fraction was lower when measured by velocity mapping in held expiration compared with held inspiration, non-breath-hold or stroke volume difference (30.8 vs. 37.0, 35.6, 35.4%, p = 0.00017, 0.0035, 0.026). The regurgitant volume was lower in held expiration than in held inspiration (41.9 vs. 48.3, p = 0.0018). Pulmonary forward flow volume was larger during held expiration than during non-breath-hold (132 vs. 124 ml, p = 0.0024). CONCLUSION: Pulmonary regurgitant fraction was significantly lower in held expiration compared with held inspiration, free breathing and stroke volume difference. Altered airway pressure could be a contributory factor. This information is relevant if breath-hold acquisition is to be substituted for non-breath-hold in the investigation of patients with a view to re-intervention.
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| 4. |
- Miknaitis, G., et al.
(författare)
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The ESSENCE supernova survey : Survey optimization, observations, and supernova photometry
- 2007
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 666:2, s. 674-693
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Forskningsöversikt (refereegranskat)abstract
- We describe the implementation and optimization of the ESSENCE supernova survey, which we have undertaken to measure the dark energy equation-of-state parameter, w = P/(rho c(2)). We present a method for optimizing the survey exposure times and cadence to maximize our sensitivity to w for a given fixed amount of telescope time. For our survey on the CTIO 4 m telescope, measuring the luminosity distances and redshifts for supernovae at modest redshifts (z approximate to 0: 5 +/- 0: 2) is optimal for determining w. We describe the data analysis pipeline based on using reliable and robust image subtraction to find supernovae automatically and in nearly real time. Since making cosmological inferences with supernovae relies crucially on accurate measurement of their apparent brightnesses, we describe our efforts to establish a thorough calibration of the CTIO 4 m telescope's natural photometric system. In its first four years, ESSENCE has discovered and spectroscopically confirmed 102 Type Ia supernovae, at redshifts from 0.10 to 0.78, identified through an impartial, effective methodology for spectroscopic classification and redshift determination. We present the resulting light curves for all of the Type Ia supernovae found by ESSENCE and used in our measurement of w, presented in a companion paper by Wood-Vasey and coworkers.
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| 5. |
- Narayan, P., et al.
(författare)
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Association of hemoglobin delivery with left ventricular structure and function in hypertensive patients: Losartan Intervention for End Point Reduction in Hypertension Study
- 2006
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Ingår i: Hypertension. - 1524-4563. ; 47:5, s. 868-73
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have shown associations of high levels of hemoglobin (Hgb) or blood viscosity with cardiac events and with left ventricular (LV) hypertrophy (LVH). To assess the relations of LV mass and function with Hgb delivery (ie, the physiological carrier of oxygen), we calculated the product of Hgb concentration and Doppler-derived cardiac output in 864 hypertensive participants with electrocardiographic LVH (359 women) in the Losartan Intervention for End Point Reduction in Hypertension echocardiography substudy. Among women, Hgb delivery was positively related to internal dimension, septal and posterior wall thicknesses, LV mass, endocardial and midwall fractional shortening, and peak A wave velocity and negatively to total peripheral resistance index, E/A ratio, deceleration time, and the isovolumic relaxation time. Among men, Hgb delivery was positively related to LV internal dimension, LV mass, and A velocity, and negatively to LV midwall shortening, relative wall thickness, peripheral resistance index, and E/A ratio. In multivariable analyses that adjusted for age, diastolic blood pressure, body mass index, and total cholesterol, hemoglobin delivery in women was related positively to LV fractional shortening, midwall shortening, LV mass mitral valve A velocity, and LV internal dimension and negatively to mitral valve deceleration time and isovolumic relaxation time. Among men, Hgb delivery had positive independent relations to mitral valve A velocity, LV internal dimension, midwall shortening, and LV mass and negative relations to the E/A ratio and relative wall thickness. Thus, in hypertensive LVH, higher oxygen delivery capacity is associated with higher LV mass and impaired early diastolic LV filling.
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| 6. |
- Narayan, V.
(författare)
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Proposed strategy to sort semiconducting nanotubes by band-gap
- 2007
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 36:1, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- We propose a strategy that uses a tunable infra-red source and an alternating non-linear potential defined by an electrode to sort a suspension of assorted semiconducting nanotubes. The band-gap scales with the inverse of the nanotube diameter, hence the infra-red frequency can be tuned to create excitons in some of the nanotubes, these excitons will be polarized by the potential. Since, a polarized exciton is a dipole, the excited nanotubes will experience a net force and may then diffuse towards the electrode, unlike the other nanotubes. We discuss experimental parameters such as IR intensity, electrode design, and potential frequency for a pilot experiment to sort nanotubes with lengths ˜ 0.5 µ m. The basic physics of the system has been illustrated using a Hartree model applied to nanotubes with nanoscale lengths. The calculated exciton binding energy suddenly drops to zero and the force on the nanotube increases dramatically when the exciton disassociates as the nanotube moves towards the electrode. The quantum adiabatic theorem shows that excitons will be adiabatically polarized for potential frequencies typical for experiments ˜ 1 - 10 MHz. The analysis indicates that the manipulation of nanotubes with nanometer lengths requires nanoscale electrodes. © 2006 Elsevier B.V. All rights reserved.
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| 7. |
- Wood-Vasey, W. M., et al.
(författare)
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Observational constraints on the nature of dark energy : First cosmological results from the ESSENCE supernova survey
- 2007
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 666:2, s. 694-715
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Forskningsöversikt (refereegranskat)abstract
- We present constraints on the dark energy equation-of-state parameter, w = P/(rho c(2)), using 60 SNe Ia fromthe ESSENCE supernova survey. We derive a set of constraints on the nature of the dark energy assuming a flat universe. By including constraints on (Omega(M), w) from baryon acoustic oscillations, we obtain a value for a static equation-of-state parameter w = -1:05(-0.12)(+0: 13) (stat 1 sigma) +/- 0: 13 (sys) and Omega(M) = 0:274(-0.020)(+0:033) (stat 1 sigma) with a bestfit chi(2)/dof of 0.96. These results are consistent with those reported by the Supernova Legacy Survey from the first year of a similar program measuring supernova distances and redshifts. We evaluate sources of systematic error that afflict supernova observations and present Monte Carlo simulations that explore these effects. Currently, the largest systematic with the potential to affect our measurements is the treatment of extinction due to dust in the supernova host galaxies. Combining our set of ESSENCE SNe Ia with the first-results Supernova Legacy Survey SNe Ia, we obtain a joint constraint of w = -1:07(-0: 09)(+0:09) (stat 1 sigma) +/- 0: 13 ( sys), Omega(M) 0:267(-0:028)(+0:028) (stat 1 sigma) with a best-fit chi(2)/dof of 0.91. The current global SN Ia data alone rule out empty (Omega(M) = 0), matter-only Omega(M) = 0: 3, and Omega(M) = 1 universes at > 4.5 sigma. The current SN Ia data are fully consistent with a cosmological constant.
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