Source mass and positioning system for an accurate measurement of G.

We report on a system of well-characterized source masses and their precision positioning system for a measurement of the Newtonian gravitational constant G using atoms as probes. The masses are 24 cylinders of 50 mm nominal radius, 150.2 mm nominal height, and mass of about 21.5 kg, sintered starting from a mixture of 95.3% W, 3.2% Ni, and 1.5% Cu. Density homogeneity and cylindrical geometry have been carefully investigated. The positioning system independently moves two groups of 12 cylinders along the vertical direction by tens of centimeters with a reproducibility of a few microns. The whole system is compatible with a resolution DeltaG/G<10(-4).

The duration of Holter monitoring in patients with syncope. Is 24 hours enough?

To determine the incremental yield of ambulatory monitoring in the evaluation of syncope, three serial 24-hour Holter recordings were obtained in a consecutive series of 95 patients with syncope, the cause of which was not explained by history, physical examination, or 12-lead electrocardiogram. The mean age of patients was 61 years and 41% were men. Major electrocardiographic abnormalities were found in 26 patients (27%), including unsustained ventricular tachycardia (19 patients), pauses of at least 2 seconds (8 patients), profound bradycardia (1 patient), and complete heart block (1 patient). The first 24-hour Holter recording had at least one major abnormality in 14 patients (15%) (95% confidence interval, 8.3% to 23.4%). Of the 81 patients without a major abnormality on the first Holter recording, the second Holter recording had major abnormalities in 9 (11%) (95% confidence interval, 5.1% to 20.0%). Of the 72 patients without a major abnormality on the first two Holter recordings, only 3 patients (4.2%) had a major abnormality on the third Holter recording (95% confidence interval, 0.8% to 11.7%). Four factors were significantly associated with an increased likelihood of a major abnormality on 72 hours of monitoring: age above 65 years (relative risk, 2.2), male gender (relative risk, 2.0), history of heart disease (relative risk, 2.2), and an initial nonsinus rhythm (relative risk, 3.5). These results suggest that 24 hours of Holter monitoring is not enough to identify all potentially important arrhythmias in patients with syncope. Monitoring may need to be extended to 48 hours if the first 24-hour Holter recording is normal.

Changes in HDL-cholesterol and lipoprotein Lp(a) after 6-month treatment with finasteride in males affected by benign prostatic hyperplasia (BPH).

Androgen effects on lipoproteins, mainly high density lipoprotein (HDL), could be exerted by a direct interaction of testosterone (T) or dihydrotestosterone (DHT) with liver androgen receptors. To assess if T needs to be converted into DHT to affect lipid metabolism, 13 patients were studied, affected with benign prostatic hyperplasia (BPH) and treated with an inhibitor of 5 alpha-reductase (finasteride). They were compared with 15 untreated controls. At baseline and after 3 and 6 months of therapy, each patient was evaluated as for lipoprotein and hormone concentrations, as well as for nutritional status. Body composition was assessed by anthropometry and bio-impedance analysis (BIA). Treatment was associated with a significant increase of HDL-cholesterol (HDL-C), mainly HDL3 subclass, and lipoprotein(a) (Lp(a)), as well as a decline of DHT, whereas no significant changes were apparent for T, estradiol (E2), sex hormone binding hormone (SHBG) and body composition indexes. However, no significant associations between DHT and lipid relative changes were apparent at bivariate correlation analysis. This finding was confirmed by comparing patient subsets identified by cluster analysis, according to HDL subclass individual responses. Rather, a slight association with E2 for HDL2 (positive) and HDL3 (negative) was found. In conclusion, finasteride can modify HDL and Lp(a) concentrations. However, by the data, these effects cannot be definitively attributed to the changes in DHT synthesis induced by finasteride, since a direct and non-specific interference of the drug on liver metabolism cannot be excluded.

Exercise-related ventilatory abnormalities and survival in congestive heart failure.

This retrospective study of 104 New York Heart Association class 1 to 4 heart failure patients undergoing exercise stress testing with gas exchange analysis demonstrated that the ventilatory equivalent for carbon dioxide at anaerobic threshold is useful in determining prognosis in patients with severe congestive heart failure, particularly when used in combination with peak exercise oxygen consumption. A ventilatory equivalent for carbon dioxide >50 and peak oxygen consumption < or =15.0 ml/kg/min defines a very high-risk patient group who should be prioritized for transplantation.

Aging-related decline of gonadal function in healthy men: correlation with body composition and lipoproteins.

OBJECTIVE: To assess if androgen decline in physiological aging contributes to the concomitant changes in body composition and lipoprotein levels. DESIGN: Cross-sectional, observational study. SETTING: A university-based outpatient center. SUBJECTS: The study comprised 206 healthy volunteers (aged 18-95 years). MEASUREMENTS: Blood samples were drawn after an overnight fast for the assay of hormones (free testosterone (FT), estradiol (E2), and sex hormone-binding globulin (SHBG)) and lipids (total cholesterol, triglycerides, high-density lipoprotein cholesterol, and lipoprotein Lp(a)). At the same time, body composition was assessed by both anthropometry (fat mass percentage (FM%) estimated from four measures of skinfold thickness using the Durnin and Womersley equation and the Siri equation) and by bioimpedance analysis (FM% estimated using the Segal or Deurenberg equations, respectively, for subjects younger or older than 62 years). RESULTS: A significant age-related decline was found for FT and E2 concentrations, whereas SHBG levels were related positively with age. No significant association was apparent between hormonal changes and the concomitant modifications of body composition and lipoproteins. Only SHBG showed a significant inverse association between FM% and the waist-to-hip ratio, independent of age. The comparison between older hypogonadal (with FT levels below the lower limit of the normality range assessed in younger subjects) and eugonadal men did not show any significant differences in body composition or lipid profile. CONCLUSIONS: This study suggests that, in men, androgen decline caused by normal aging does not significantly affect some targets of testosterone action, such as body composition and lipid metabolism. Therefore, androgen supplementation in hypogonadal older men cannot be expected to influence nutritional status and body composition to the same extent that it does other main targets of testosterone action, such as sexual activity and muscle strength. However, we cannot exclude that selected subsets of older patients with low testosterone levels, especially if affected by catabolic disease, could benefit from the effects of androgen administration on nutritional status.

QRS loop areas in selective right ventricular overload: relation to hemodynamic status.

The utility of vectorcardiographic relative QRS loop area criteria in identifying significant hemodynamic abnormality (a mean pulmonary artery pressure greater than 25 mmHg and/or a pulmonary to systemic flow ratio greater than 1.5) in patients with cardiac lesions associated with selective right ventricular overload was investigated in a consecutive series of patients, 291 with Heart Disease and 135 Controls. The specificity and predictive value of individual abnormally increased right quadrant areas were greater than 90% and greater than 80%, respectively. The predictive value of an isolated increase in left anterior area greater than 70% in identifying the absence of significant hemodynamic abnormality (= 91%) was similar to a negative VCG (= 80%). False positive increases in right quadrant areas were found only in association with counterclockwise transverse plane QRS loop rotation. The predictive value of a counterclockwise loop rose from 77% to 86% by increasing the diagnostic requirement for an abnormal increase in right inferior and posterior area from 20%, respectively, to 26%, respectively.

Ventilatory drive during exercise in congestive heart failure.

BACKGROUND: Continuous increases in the ventilatory equivalent for carbon dioxide (the ratio of minute ventilation to carbon dioxide production, an index of ventilatory drive) during exercise in patients with congestive heart failure would suggest that factors other than carbon dioxide excessively stimulate ventilation during exercise, and may be an important factor in exercise-related dyspnea and fatigue in these patients. METHODS AND RESULTS: Eighty-five patients with congestive heart failure and 17 normal control subjects underwent symptom-limited exercise testing with gas-exchange analysis. Patients were divided into four functional classes (A-D, Weber's classification) based on peak exercise oxygen consumption. In all heart failure patient groups and in control subjects the ventilatory equivalent for carbon dioxide decreased (P < .005, class D; P < .0001, all other groups) from rest to anaerobic threshold. Three isolated patients showed a continuous increase in ventilatory drive during exercise (mean peak oxygen consumption 13.7 mL/kg/min). In the lowest functional class (D) the ventilatory equivalent for carbon dioxide was greater than in all other groups at rest, at anaerobic threshold, and at peak exercise (P < .01). CONCLUSIONS: In all heart failure groups and in normal control subjects ventilatory drive, as determined by the ventilatory equivalent for carbon dioxide, decreases during exercise, Continuous increases in ventilatory drive during exercise are infrequently seen, suggesting that factors other than carbon dioxide production do not excessively stimulate ventilation in heart failure patients during exercise.

Pulsus paradoxus: definition and relation to the severity of cardiac tamponade.

Based on 101 control patients, the 95% confidence limit for the inspiratory decrease in arterial systolic pressure (delta SYST, mm Hg) and the percentage decrease in arterial systolic pressure (% delta SYST = delta SYST/expiratory systolic pressure) were determined to be 12 mm Hg and 9%, respectively. In 65 patients with pericardial effusion, the severity of cardiac tamponade was estimated on the basis of the percentage increase in cardiac output resulting from pericardiocentesis: absent = less than 20% (n = 24), mild = 20% to 49% (n = 9), and moderate or severe = greater than or equal to 50% (n = 32). The accuracy of a delta SYST greater than 12 mm Hg and % delta SYST greater than 9% in the identification of tamponade was 92% and 97%, respectively. A % delta SYST greater than 15% with relative hypotension (expiratory systolic pressure less than or equal to 120 mm Hg) or a delta SYST greater than 25 mm Hg or inspiratory pulse obliteration was found in 31 of 32 patients with moderate or severe tamponade compared to 2 of the 33 remaining patients. We conclude that the inspiratory decline in arterial systolic pressure can be used to accurately estimate the level of hemodynamic embarrassment resulting from pericardial effusion.

Left ventricular diastolic function during positive end-expiratory pressure. Impact of right ventricular ischemia and ventricular interaction.

The individual and additive effects of positive end-expiratory pressure (PEEP) and right coronary artery (RCA) occlusion on left ventricular end-diastolic pressure-volume relations (LVEDPVR) were examined in six anesthetized dogs. Right ventricular (RV) and left ventricular (LV) ejection fractions (EF), end-diastolic volume (EDV) and end-systolic volumes (ESV) were measured by thermodilution as PEEP was added before and after RCA occlusion. PEEP alone caused a decline in cardiac output, transmural left atrial pressure (LAP) (6.0 +/- 0.6 to 3.2 +/- 1.4 mm Hg, p less than 0.05), and LVEDV (49 +/- 3 to 36 +/- 4 ml, p less than 0.05). RVEDV, the mean slope (+/- SD) of the LVEDPVR (0.37 +/- 0.16 to 0.30 +/- 0.19) and LAP at a common LV volume (35 ml, V35) did not change with PEEP. RCA occlusion caused cardiac output and RVEF (38 +/- 5 to 27 +/- 5%, p less than 0.05) to decline and RVESV (25 +/- 4 to 33 +/- 6 ml, p less than 0.05) to increase. RVEDV, the slope of the LVEDPVR, and LAP at V35 were unchanged from baseline. The addition of PEEP after RCA occlusion caused cardiac output to decline further. However, unlike before occlusion, there was no change in LAP (6.5 +/- 1.3 to 5.0 +/- 1.4 mm Hg) despite a decline in LVEDV (47 +/- 3 to 29 +/- 6 ml, p less than 0.05). RVESV and RVEDV increased with PEEP after RCA occlusion as did LAP at V35. The slope of the mean LVEDPVR tended to increase (0.98 +/- 1.03).(ABSTRACT TRUNCATED AT 250 WORDS)