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Biomedical subjects

J Pepke-Zaba

Publications and source records attributed to J Pepke-Zaba.

26 records · Page 2Linked to original sources
PubMed1990

Validation of impedance cardiography measurements of cardiac output during limited exercise in heart transplant recipients.

Twenty-one patients were studied at rest and during exercise after heart transplantation to compare cardiac output measured by thermodilution and impedance cardiography. Exercise was performed on a bicycle ergometer over a limited range of work load (25 and 50 watt) whilst metabolic gas exchange was recorded. One patient was studied at rest whilst his circulation was maintained by a Jarvik-7 artificial heart. The values of cardiac output measured by impedance cardiography corresponded closely with the flow rate from the artificial heart. There was also close agreement between the impedance and thermodilution measurements of cardiac output at rest and during exercise. Both measurements followed the changes in heart rate and oxygen consumption. Both thermodilution and impedance cardiography methods elicited good reproducibility of cardiac output measurements at rest and during exercise. These observations suggest that the noninvasive and continuous record of cardiac output obtained by impedance cardiography can be used for the postoperative monitoring of heart transplant recipients.

Adult↗
PubMed1990

Impairment of pulmonary endothelium-dependent relaxation in patients with Eisenmenger's syndrome.

A comparison has been made between the endothelium-dependent relaxation of pulmonary arteries (PA) obtained at heart-lung transplantation from 4 patients with Eisenmenger's syndrome and secondary pulmonary hypertension, and PA obtained at lobectomy from 4 patients with lung carcinoma, the controls. All vascular rings were studied immediately after lung excision. PA rings from control patients dose-dependently relaxed to cumulative doses of acetylcholine (ACh, 10(-10) to 10(-5) M), achieving a maximal relaxation of 80 +/- 5% (mean +/- s.e. mean) from precontraction with phenylephrine. By contrast, PA rings from Eisenmenger's syndrome patients achieved a maximal relaxation of only 34 +/- 12% (P less than 0.05, unpaired t test), with even paradoxical contraction at high doses of ACh (10(-6) to 10(-5) M). Sodium nitroprusside (10(-4) M) relaxed all PA rings, with and without endothelium (carefully removed before study), obtained from both control and Eisenmenger's syndrome patients. These results provide the first evidence that endothelium-dependent relaxation of PA mediated by endothelium-derived relaxing factors is impaired in Eisenmenger's syndrome patients with secondary pulmonary hypertension.

Acetylcholine↗
PubMed1990

Atrial natriuretic peptide in primary pulmonary hypertension.

Plasma levels of atrial natriuretic peptide (ANP) were determined during cardiac catheterization in nine patients with primary pulmonary hypertension (PPH) and the effect of prostacyclin infusion via a right heart catheter studied. The role of hypoxia on the release of ANP was investigated in a control group of six normal subjects who underwent an acute hypoxic challenge. Patients showed the typical haemodynamic changes of primary pulmonary hypertension with elevation of mean (SD) pulmonary artery pressure, 71.3 (13.8) mmHg, and low cardiac index, 1.9 (0.5) l.min-1.m-2. Plasma ANP was also elevated; mean pulmonary artery plasma ANP was 96.3 (77.6) pmol.l-1 in PPH patients compared with mean venous plasma ANP of 8.9 (5.6) pmol.l-1 in normal subjects. Prostacyclin infusion in PPH patients and hypoxic challenge in normal subjects did not significantly alter plasma ANP levels. The elevated levels of ANP in PPH are due to the altered haemodynamics secondary to increased pulmonary vascular resistance and may be responsible for the lack of peripheral oedema seen in this condition.

Adult↗
PubMed1990

Acetylcholine and adenosine diphosphate cause endothelium-dependent relaxation of isolated human pulmonary arteries.

Endothelium-dependent vasorelaxation mediated by endothelium-derived relaxing factors (EDRF) has been extensively studied in animals but only limited studies in man are available. Demonstration of EDRF-mediated dilatation of human vessels is fundamental for understanding the mechanisms of vascular diseases in man. We have investigated endothelium-dependent relaxation of isolated human pulmonary arteries. Vascular segments, taken from uninvolved regions of resected lung from eight patients undergoing lobectomy for lung carcinoma, were cut into rings. In rings precontracted with phenylephrine, both acetylcholine (ACh) and adenosine diphosphate (ADP) induced dose-dependent relaxation in the presence of endothelium but not when the endothelium had been carefully removed. The rings without endothelium relaxed completely with sodium nitroprusside, a vasodilator agent acting directly on vascular smooth muscle. Pre-incubation with indomethacin, a cyclo-oxygenase inhibitor which blocks production of prostacyclin, did not alter the vasorelaxant responses to ACh and ADP, suggesting that one (or several) non-prostanoid EDRF(s) are responsible for the endothelium-dependent relaxation of isolated human pulmonary arteries.

Acetylcholine↗
PubMed1988

Low dose infusion of atrial natriuretic peptide causes salt and water excretion in normal man.

1. The effects of low dose infusion of atrial natriuretic peptide (ANP) were observed in double-blind, placebo-controlled study in six fluid-loaded volunteers. After baseline observations, hourly increments of 0.4, 2 and 10 pmol min-1 kg-1 were infused with continuous observation of heart rate, blood pressure and cardiac output. Plasma ANP, aldosterone, and catecholamines, and urinary volume and sodium excretion, were estimated at half-hourly intervals. 2. ANP infusion resulted in an increase of 35, 98 and 207% in urinary sodium excretion and of 10, 20 and 71% in urinary volume when compared with placebo. Plasma ANP was markedly elevated above placebo levels only during infusion of 10 pmol of ANP min-1 kg-1. 3. No change in heart rate of blood pressure was noted during the study, but a significant fall in stroke volume index was observed during active treatment. Plasma levels of aldosterone and catecholamines were not significantly different on the 2 treatment days. 4. The potent natriuretic and diuretic effects of this peptide at plasma concentrations not significantly elevated from physiological suggest a hormonal role for ANP in the homoeostasis of salt and water balance.

Adult↗