A radionuclide method for the simultaneous study of the effects of drugs on central and peripheral haemodynamics.

Abstract

(GTN) have been contrasted using radionuclide techniques. 2 Following intravenous injection of technetium-99m labelled human serum albumin, radionuclide ventriculography was performed by the equilibrium blood pool method using a mobile gamma camera. Simultaneous measurements of 'peripheral venous volume' were made using a collimated scintillation probe positioned above the patient's calf. 3 Ten patients with angina pectoris were studied at rest, after sublingual administration of 0.5 mg GTN and after intravenous administration of 10 mg hydralazine. 4 GTN caused a mean reduction in the end diastolic volume of the left ventricle of 14.6% + 4.5% (P < 0.005) but ejection fraction increased by 0.034 + 0.007 (P < 0.005) so that stroke volume was only reduced by 4.9% ± 5.0% (NS). There was a mean increase in heart rate of 10.8 ± 2.3 beats/min (P < 0.001) but no significant change in cardiac output. The calculated systemic vascular resistance fell by 10.0% ± 5.4% (P < 0.05). Associated with these changes there was a mean increase of 9.6% ± 1.5% (P < 0.05) in the counts from the calf. 5 Hydralazine caused a significant reduction in blood pressure and increase in heart rate. Enddiastolic volume was reduced by 6.0% ± 2.7% but there was a mean increase in ejection fraction of 0.058 ± 0.010 (P < 0.001) so that in this instance stroke volume increased by 9.0% + 3.7% (P < 0.05) and cardiac output increased by 16.4% ± 4.4% (P < 0.005). The calculated systemic vascular resistance fell by 18.9% ± 3.8% (P < 0.001). Despite these haemodynamic changes there was no significant change in counts from the calf. 6 The results confirm that GTN has a predominant venodilator effect while hydralazine acts largely on the arterial bed. These relatively simple radionuclide methods will allow a more detailed assessment of the cardiovascular effects of drugs.

Assessment of venous capacitance. Radionuclide plethysmography: methodology and research applications

“…Our findings are in keeping with previous studies. Wathan et al [57] compared the effects of hydralazine (10 mg i.v.) and GTN (0.6 mg s.l.)…”

'First dose' hypotension and venodilatation [letter]

“…Captopril (and by implication enalapril) reduces venous tone by up to 50% in patients with heart failure (Awan & Mason, 1982;Cowley et al, 1982;Faxon et al, 1981). Recently, using non-invasive radionuclide techniques (Clements et al, 1981;Wathen et al, 1983) captopril was shown to produce a 16% increase in peripheral venous volume, far more than the 11% increase following glyceryl trinitrate. Furthermore the fall in mean arterial blood pressure when commencing captopril correlated Letters to the Editors Br.…”