Biomedical subjects

A Buck

Publications and source records attributed to A Buck.

93 records · Page 6Linked to original sources

PubMedDate not supplied

An approach to ventricular efficiency by use of carbon 11-labeled acetate and positron emission tomography.

BACKGROUND: Positron emission tomography-derived 11C-labeled acetate kinetics have been shown to reflect myocardial oxidative metabolism. The objective of the study was to use this metabolic imaging technique in combination with an evaluation of left ventricular work as an index of ventricular mechanical efficiency. METHODS AND RESULTS: The effects of ventricular ejection fraction and loading on this index were studied quantitatively in a canine experimental model. There was a curvilinear relationship between efficiency and the end-diastolic volume per unit mass (r = 0.84), which appeared to integrate the main determinants of left ventricular mechanical performance successfully and allowed the detection of a decreased ventricular efficiency in acute experimental heart failure. CONCLUSIONS: This approach appears to have the potential to assess the energetic working point of the ventricle in clinical heart disease and follow the effects of therapy. The data demonstrate the feasibility of an estimate of ventricular efficiency that relies on noninvasive data-acquisition techniques.

Acetic Acid↗

PubMedDate not supplied

Increased myocardial blood flow during acute exposure to simulated altitudes.

BACKGROUND: Although only poor data exist on changes in myocardial blood flow (MBF) under acute hypoxia, patients with known coronary artery disease are advised not to exceed a moderate altitude exposure of about 2000 m above sea level. METHODS AND RESULTS: We measured MBF with positron emission tomography using O-15--labeled water in 8 healthy human volunteers (aged 26 +/- 3 years [mean +/- SD]) at baseline (450 m above sea level, Zurich, Switzerland) and during acute hypoxic hypoxemia induced by inhalation of 2 hypoxic gas mixtures corresponding to altitudes of 2000 and 4500 m. MBF remained unchanged at 2000 m (increase of 10%, not significant) but increased significantly at 4500 m (62%, P <.001), exceeding the relative increase in rate pressure product. CONCLUSIONS: Our results may explain why exposure to an altitude of 2000 m (corresponding to the cabin pressure in most airplanes during flight) is clinically well tolerated, even by patients with reduced coronary flow reserve, such as those with coronary artery disease. However, at an altitude of 4500 m, MBF increases significantly, supporting the recommendation that patients with impaired flow reserve avoid exposure to higher altitudes.

Acute Disease↗

PubMedDate not supplied

Misdiagnosed HIV infection in pregnant women: implications for clinical care.

Out of nearly 900 women in a research study of human immunodeficiency virus infection in pregnancy, 8 were subsequently found not to be infected. Misdiagnoses could have resulted from (a) laboratory errors or specimen mixups; (b) failure to follow the testing algorithm recommended by the Centers for Disease Control and Prevention to confirm results; (c) women perceiving they were infected by high-risk behavior in the absence of testing, despite the receipt of negative test results, or based on screening results only; or (d) factitious disorder, HIV Munchausen syndrome, or malingering. Because of the potentially devastating impact of an HIV diagnosis and the toxicity of HIV therapies, health care providers should obtain independent confirmation of the diagnosis before initiating treatment or followup for HIV based on patient report or provider referral. Quality test interpretation and counseling must be ensured. Therapeutic interventions may be indicated for persons intentionally and falsely presenting themselves as HIV-infected.

Adult↗