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Biomedical subjects

F W Amann

Publications and source records attributed to F W Amann.

At least 109 records · Page 6Linked to original sources
PubMed1982

Elevated adrenaline and increased alpha-adrenoceptor-mediated vasoconstriction in essential hypertension.

In patients with essential hypertension, plasma adrenaline, regardless of age, was consistently higher than in normotensive controls; adrenaline correlated with heart rate and the vasodilator response in the forearm circulation produced by postjunctional alpha 1-adrenoceptor blockade with prazosin. This dilator response to prazosin was greater in hypertensive patients. Together, this suggests elevated sympathetic activity and enforced vasoconstriction via postjunctional alpha 1-adrenoceptors in essential hypertension. beta-Adrenoceptor-mediated cardiovascular responses decrease with age and even more with high blood pressure, which contributes to unopposed alpha-adrenoceptor-mediated vasoconstriction. This could explain the transition from an early high cardiac output into a later high peripheral resistance form of hypertension.

Adaptation, Physiological↗
PubMed1982

Verapamil-induced vasodilation is enhanced in essential hypertension.

The dependency of arteriolar tone on calcium influx was studied in 11 patients with essential hypertension (EHT) and compared to 11 age-matched normotensive (NT) subjects by measuring the forearm blood flow (FAF) response to intraarterial infusion of the calcium channel blocker verapamil (Verap) and the nonspecific vasodilator sodium nitroprusside (Nip) with venous occlusion plethysmography. Verap in incremental dosages induced a greater increase in forearm blood flow (delta FAF) in EHTs than in NTs, whereas there was no significant difference in delta FAF following Nip. When delta FAF to Verap was adjusted for delta FAF to Nip, it was still greater in EHTs. In EHTs delta FAF to all dosages of Verap correlated positively with basal plasma epinephrine concentration, and at the two highest dosages of Verap, associated with a decrease in systemic blood pressure, it correlated negatively with plasma renin activity and plasma angiotensin II concentration. Thus, increased dependency of arteriolar tone on calcium influx is related to the activity of the sympathetic nervous system in EHT. This association may be due to a common derangement in transmembranous ionic fluxes in the vascular smooth muscle cells and sympathetic neurons in EHT.

Adult↗
PubMed1981

Echocardiographic features of the correctly functioning St. Jude Medical valve prosthesis.

The St. Jude Medical valve (SJM) is a new low-profile bileaflet prosthesis with central flow. We investigated 10 patients with aortic valve replacement and 11 with mitral valve replacement by means of combined echocardiography and phonocardiography. In patients with aortic valve replacement, echocardiography revealed during systole the anterior and posterior part of the ring together with both leaflets. During diastole, patients with mitral valve replacement showed part of the anterior leaflet and the entire posterior leaflet together with the posterior ring. Distinctive opening sounds were missing. In aortic prostheses, maximal opening followed S1 0.06 +/- 0.02 second. An amplitude of the posterior leaflet of 9.8 +/- 1.3 mm and a leaflet separation of 4.8 +/- 0.9 mm were measured. In mitral prostheses the maximal opening followed A2 0.10 +/- 0.02 second, the Q-closure interval was 0.07 +/- 0.03 second and leaflet separation was 4.4 +/- 0.8 mm. In both aortic and mitral positions, high values for opening and closing velocities were measured, and closing velocities exceeded opening rates. These findings establish the normal pattern and values in echocardiography and phonocardiography for patients with aortic valve replacement as well as mitral valve replacement with SJM prostheses.

Adult↗
PubMed1981

Plasma noradrenaline concentration and alpha-adrenoceptor-mediated vasoconstriction in normotensive and hypertensive man.

1. Plasma noradrenaline concentrations and blood pressure were measured in 45 patients with essential hypertension and 34 matched normotensive subjects. Plasma noradrenaline was similar in both groups, but in the hypertensive patients plasma noradrenaline correlated with blood pressure. 2. The increase in forearm flow in response to an intra-arterial infusion of phentolamine was determined in 12 of the hypertensive and 14 of the normotensive subjects to assess the alpha-adrenoceptor-mediated component of vascular resistance. Although the dilator response to phentolamine was similar in both groups, in the hypertensive patients it was correlated with the control plasma noradrenaline (r = 0.83, P less than 0.01) as well as the height of mean blood pressure (r = 0.73, P less than 0.01). 3. These results suggest that in hypertensive patients plasma noradrenaline can be a marker for both sympathetic activity and the alpha-adrenoceptor-mediated component of vascular resistance.

Adolescent↗
PubMed1981

Age-related decrease in cardiac and peripheral vascular responsiveness to isoprenaline: studies in normal subjects.

1. Changes in forearm blood flow to intra-arterial infusion of isoprenaline and the chronotropic response to intravenous boluses of isoprenaline were measured in 15 healthy volunteer subjects, eight younger than 25 years and seven older than 50 years. Intra-arterial blood pressure and basal plasma renin activity, adrenaline and noradrenaline were also measured. 2. Young subjects exhibited a greater increase in forearm blood flow than old subjects, to all four doses of isoprenaline used, a greater cardiac isoprenaline responsiveness (measured by the increase in heart rate; P less than 0.001) and a higher renin (P less than 0.02). 3. Resting values of blood pressure, forearm blood flow, adrenaline and noradrenaline were not significantly different in young and old subjects. In the latter, noradrenaline correlated with forearm blood flow (r = -0.77, P less than 0.05), forearm vascular resistance (r = 0.86, P less than 0.02) and mean arterial pressure (r = 0.83, P less than 0.02), whereas in the younger subjects forearm blood flow was related to adrenaline (r = 0.78, P less than 0.05). 4. These data provide evidence for an age-related parallel reduction in cardiac, peripheral vascular and renal beta-adrenoceptor-mediated responses.

Adolescent↗
PubMed1981

Lack of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy with oxprenolol.

The possibility of beta-adrenoreceptor hypersensitivity after abrupt withdrawal of long-term therapy (8-18 months) with the slow-release (SR) formulation of oxprenolol (160-320 mg/day) was assessed in six patients with uncomplicated essential hypertension. The chronotropic dose 25 of isoproterenol (the dose that increases the resting heart rate by 25 beats/min), plasma concentration of catecholamines, triiodothyronin and thyroxin, plasma renin activity and aldosterone, hemoglobin, hematocrit and oxyhemoglobin dissociation were measured on the last day of oxprenolol SR intake and 1, 2, 3, 6 and 13 days after abrupt replacement by identical placebo tablets. The chronotropic dose 25 of isoproterenol (microgram/m2), which was greater than 25.6 in all patients on the last day of oxprenolol SR, fell to 4.83 +/- 2.03 on the second day and to 3.50 on the third day after its abrupt withdrawal and reached a minimal value on the thirteenth day (2.78 +/- 0.30). Throughout the study, plasma concentrations of catecholamines, triiodothyronin and thyroxin and oxyhemoglobin dissociation remained unchanged. Plasma renin activity and plasma aldosterone, which were suppressed during oxprenolol administration, rose significantly during placebo, coinciding with a significant fall in hematocrit and hemoglobin. No major subjective symptoms were reported by the patients. Thus, hypersensitivity of beta-adrenoreceptor-mediated responses was not demonstrated after sudden withdrawal of oxprenolol SR.

Adrenergic beta-Antagonists↗
PubMed1980

[Enhanced alpha adrenoreceptor-mediated vasoconstrictor component in essential hypertension].

Changes in forearm blood flow in response to infusions of the postsynaptic alpha blocking agent prozosin (0.5 microgram/min/100 ml forearm tissue) and of the nonspecific vasodilating drug sodium nitroprusside (0.6 microgram/min/100 ml forearm tissue) into the brachial artery were assessed in 24 patients with essential hypertension (EHT) and in 16 age-matched normotensive subjects (NT). Under basal conditions forearm blood flow was higher in EHT (4.0 +/- 0,2 vs. 2.6 +/- 0.3 ml/min/100 ml forearm tissue, p less than 0.001). Forearm blood flow response to prazosin was greater in EHT than in NT (7.7 +/- 0.8 vs. 2.6 +/- 0.3, p less than 0.001) while sodium nitroprusside responses were similar in EHT and NT (13.8 +/- 0.8 vs 13.0 +/- 0.8 vs. 13.0 +/- 0.1, n.s.). These results indicate an enhanced alpha adrenoceptor-mediated vasoconstrictor component in EHT and help to explain the effectiveness of antihypertensive drugs which interfere with sympathetic control of vascular resistance.

Adult↗
PubMed1980

Plasma catecholamines and cardiac, renal and peripheral vascular adrenoceptor-mediated responses in different age groups of normal and hypertensive subjects.

The role of the sympathetic nervous system in cardiac, renal and peripheral vascular adrenoceptor-mediated responses was investigated in patients with essential hypertension and age-matched normotensive subjects. Regardless of age plasma adrenaline was significantly higher in hypertensive when compared with normotensive subjects. This suggests a sympatho-adrenal factor in essential hypertension. Plasma noradrenaline tended to increase with age but its similarity between normotensive and hypertensive subjects points to similar postganglionic neural activity and/or similar overflow of noradrenaline into the circulation. On the other hand, beta-adrenoceptor-mediated tachycardia in response to exercise and intravenous isoproterenol as well as the forearm vasodilator response to intraarterial isoproterenol decreased in normal subjects with older age. In hypertensives this age-dependent beta-receptor-related effect tends to be enhanced as judged from the greater reduction of cardiac isoproterenol sensitivity and the blunted renin response to exercise stimulation. The dilator response to alpha-adrenoceptor blockade with phentolamine was not different in both groups. Therefore a qualitative rather than quantitative derangement of sympathetic control of vascular resistance - in which beta-dilator effects are reduced and alpha-constrictor mechanisms prevail - may contribute to the maintenance of established hypertension.

Adult↗
PubMed1979

[The echocardiogram in mitral anulus calcification].

In agreement with the known high incidence of mitral anulus calcification in elderly patients, the authors have found corresponding calcifications in echocardiographic examinations in 61 patients as the single or additional cause of an abnormal systolic or diastolic murmur. The intracardiac calcifications were known of from the chest X-ray only in 6 patients. The echocardiograms served to locate and estimate the amount of the calcification. Calcifications of the aortic cusps, found in 75% of patients, may be of degenerative origin. The echocardiographic presentation of the degenerative calcifications can be misinterpreted either as postrheumatic valvular disease, posterior pericardial effusion or hypertrophic cardiomyopathy. Registration by continuous sector scan was necessary to differentiate these entities.

Aged↗