Biomedical subjects

Denis Chemla

Publications and source records attributed to Denis Chemla.

21 records · Page 2Linked to original sources

PubMed2002

Pulmonary artery pressure-flow relations after prostacyclin in primary pulmonary hypertension.

Exercise tolerance improves within a few weeks after prostacyclin initiation in patients with primary pulmonary hypertension even in the absence of significant changes in resting pulmonary vascular resistance and/or in patients who fail to respond to an acute vasodilator challenge. We tested the hypothesis that this early effect of prostacyclin may be ascribable to an improved pressure-flow response of the pulmonary circulation to exercise. Pulmonary hemodynamic variables at rest and during exercise and the 6-min walking distance were determined before and after 6 wk of continuous intravenous prostacyclin treatment (11 +/- 1.5 ng/kg/min) in seven patients unresponsive to an acute nitric oxide vasodilator test. Mean pulmonary arterial pressure/cardiac index coordinates obtained during exercise were pooled, and the slopes of these plots were compared using covariance analysis. All hemodynamic variables at rest were unchanged after prostacyclin. By contrast, the 6-min walking distance improved in all patients (mean increase, 81 m) and the slope of the mean pulmonary artery pressures/cardiac indexes plot decreased with prostacyclin, from 18.2 to 13.1 mm Hg/L/min/m(2) (p < 0.01). These results suggest that the improvement in exercise tolerance seen after 6 wk of prostacyclin therapy may be ascribable to a decrease in incremental pulmonary vascular resistance during exercise.

Antihypertensive Agents↗

PubMed2002

Empirical estimates of mean aortic pressure: advantages, drawbacks and implications for pressure redundancy.

Mean arterial pressure (MAP) is estimated at the brachial artery level by adding a fraction of pulse pressure (form factor; =0.33) to diastolic pressure. We tested the hypothesis that a fixed form factor can also be used at the aortic root level. We recorded systolic aortic pressure (SAP) and diastolic aortic pressure (DAP), and we calculated aortic pulse pressure (PP) and the time-averaged MAP in the aorta of resting adults (n=73; age 43+/-14 years). Wave reflection was quantified using the augmentation index. The aortic form factor (range 0.35-0.53) decreased with age, MAP, PP and augmentation index (each P<0.001). The mean form factor value (0.45) gave a reasonable estimation of MAP (MAP=DAP+0.45PP; bias=0+/-2 mmHg), and the bias increased with MAP (P<0.001). An alternative formula (MAP=DAP+PP/3+5 mmHg) gave a more precise estimation (bias=0+/-1 mmHg), and the bias was not related to MAP. This latter formula was consistent with the previously reported mean pulse wave amplification of 15 mmHg, and with unchanged MAP and diastolic pressure from aorta to periphery. Multiple linear regression showed that 99% of the variability of MAP was explained by the combined influence of DAP and SAP, thus confirming major pressure redundancy. Results were obtained irrespective of whether the marked differences in heart period and extent of wave reflection between subjects were taken into account. In conclusion, the aortic form factor was strongly influenced by age, aortic pressure and wave reflection. An empirical formula (MAP=DAP+PP/3+5 mmHg) that is consistent with mechanical principles in the arterial system gave a more precise estimate of MAP in the aorta of resting humans. Only two distinct pressure-powered functions were carried out in the (SAP, DAP, MAP, PP) four-pressure set.

Adult↗

PubMed2000

Mechanics of Relaxation of the Human Heart.

Rapid and complete relaxation is a prerequisite for cardiac output adaptation to changes in loading conditions, inotropic stimulation, and heart rate. In the healthy human heart, the rate and extent of relaxation depend mainly on actomyosin cross bridge dissociation and on left ventricular end-systolic volume, rather than on the afterload level.

Journal Article↗