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Objective: To compare measurement of left ventricular mass (LVM) by M-mode echocardiography and magnetic resonance imaging (MRI) in hypertensive subjects., Design: A prospective study., Subjects: Twenty-four untreated hypertensive patients [19 men and five women, aged 51 +/- 2 (mean +/- SEM) years, supine blood pressure 159/101 +/- 3/1 mmHg]., Setting: The Blood Pressure Unit, St Georges Hospital Medical School and Magnetic Resonance Unit, Royal Brompton National Heart and Lung Hospital, London., Main Outcome Measures: LVM estimated both by M-mode echocardiography and by MRI., Results: Using three standard M-mode formulae, widely different values of LVM were obtained with echocardiography [American Society of Echocardiography (ASE) 319 +/- 21 g, Penn 273 +/- 19 g. Teichholz 191 +/- 11 g]. By MRI, the LVM was 232 +/- 11 g. The differences between MRI and echocardiography could not be explained in terms of the timing of measurements in the cardiac cycle. When single-slice MRI measurements at the appropriate level were applied to the ASE and Penn formulae, the LVM was again overestimated., Conclusion: Our study has shown major differences in LVM estimated using methods based on one-dimensional (echocardiography) compared with three-dimensional (MRI) data. These differences seem to be largely the result of the geometrical assumptions on which M-mode measurements are based. Our findings have important clinical implications for the assessment of the severity and response to treatment of left ventricular hypertrophy in hypertensive patients.

Objective: Our aim was to evaluate duplex ultrasound imaging in the identification of renal artery stenosis using a new technique to enhance the recorded Doppler signal., Design: Colour Doppler studies of interlobar renal arteries were performed before and after enhancement using an intravenous contrast of galactose microparticle suspension containing microbubbles (Levovist, Schering) in patients with angiographically confirmed renal artery stenosis., Setting: Blood Pressure Unit, St. George's Hospital Medical School, and Department of Radiology. The Middlesex Hospital, London, UK., Participants: Twenty-one consecutive hypertensive patients in whom the diagnosis of renal artery stenosis was made on digital subtraction angiography., Main Outcome Measures: The diagnosis of haemodynamically significant renal artery stenosis (> or = 60% on angiography)., Results: With Levovist, there was a 20 db increase in the Doppler intensity and, as a result, intrarenal signals were much more clearly delineated and distinct spectral waveforms were obtained from all but one kidney, which was occluded. Significant associations were found between the degree of stenosis (as assessed by angiography) and the following Doppler parameters: diastolic velocity (F = 7.6; P < 0.01), acceleration time (F = 33.5, < 0.0001), peak systolic velocity (F = 37.7, P < 0.0001) and acceleration (F = 60.0; P < 0.0001). Without enhancement, there were five false-positive and two false-negative examinations (sensitivity 85%; specificity 79%) using the acceleration cut-off value of 3.5 m/s2 to identify haemodynamically significant renal artery stenosis (> or = 60% on angiography). After contrast enhancement, there were only three false-positive and one false-negative examinations (sensitivity 94% and specificity of 88%) using the acceleration cut-off value of 3.75 m/s2 and the examination time was reduced by approximately half (sensitivity and specificity of 90% using the acceleration cut-off value of 3.5 m/s2)., Conclusions: Our results suggest that renal duplex scanning using contrast enhancement is a promising new non-invasive technique in screening patients with suspected renal artery stenosis. Contrast enhancement produces more reproducible spectral waveforms, improves accuracy and halves the examination time.

Objective: To determine whether there is a reduction in human forearm skin capillary density in essential hypertension., Subjects and Methods: We compared the number of capillary loops in the forearm skin of 12 patients with established, uncomplicated essential hypertension (mean blood pressure 180/109 mmHg) with that in carefully matched control subjects, using intravital capillaroscopy and fluorescein angiography., Results: There was a significant reduction in forearm skin capillary density in the hypertensive patients compared with the normotensive subjects. This represents a reduction by approximately 20% in capillary density. Capillary density was inversely correlated with blood pressure in the hypertensive patients alone (r = -0.4, P < 0.05) and in the whole group., Conclusion: The present study demonstrates a reduction in capillary density in the forearm of patients with essential hypertension. If this rarefaction in the forearm is also present in other vascular beds, it could result in an approximately 20% increase in peripheral resistance, which might play an important additional role in determining blood pressure.

Objectives: To measure calcium,magnesium-ATPase (Ca-ATPase) activity and membrane fluidity in patients with essential hypertension compared with normotensive subjects; to investigate the interrelationship between membrane fluidity and the activity of the Ca-ATPase; and to assess the importance of circulating lipids on the Ca-ATPase and membrane fluidity., Methods: Ca-ATPase and membrane fluidity were measured in erythrocyte membranes. Kinetic parameters [maximal activity (Vmax), apparent dissociation constant and allosteric number] of the Ca-ATPase activity were measured, in the presence of saturating calmodulin, in 38 normotensives and 57 essential hypertensives. Fluorescent polarization anisotropy, as an index of membrane fluidity, was measured, using the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium DPH (TMA-DPH) in 37 normotensives and 44 hypertensives. Of these 22 were paired for age, sex and race., Results: There was no significant difference in the Vmax and allosteric number of the Ca-ATPase between the normotensives and hypertensives, but there was a trend for the hypertensives to have a reduced calcium affinity. In contrast, hypertensive subjects had significantly lower membrane fluidity. Sex and serum triglycerides level were important determinants of membrane fluidity in both groups. Comparisons between normotensives and hypertensives demonstrated decreased fluidity in the hypertensives independent of sex and serum triglycerides level, although the differences, especially with TMA-DPH, were more pronounced in the females. In both groups there were negative correlations between Vmax and both DPH and TMA-DPH anisotropy., Conclusion: The present study demonstrates that essential hypertension is associated with a generalized alteration in the erythrocyte membrane physical and chemical properties. However, despite the positive correlation between Vmax and membrane fluidity, the present study also demonstrates that essential hypertension is not associated with a major abnormality in the activity of the erythrocyte Ca-ATPase in isolated membranes.

Objective: To examine the changes in plasma brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP) and blood pressure in patients with essential hypertension on a low, normal and high sodium intake., Design and Methods: Twelve patients with mild-to-moderate essential hypertension were studied. Plasma, urinary and blood pressure measurements were made with the patients on their usual sodium intake, then on the fifth day of a low (10 mmol/day) and on the fifth day of a high (350 mmol/day) sodium intake, the sequence being allocated randomly., Results: Plasma levels of BNP and ANP increased significantly on the high sodium intake compared with when the patients were on their normal diet. The mean blood pressure on the high sodium intake was not significantly different from that with the patients on their normal diet. In contrast, plasma BNP and ANP decreased on the low sodium intake, but were not significantly different compared with when the patients were on their normal diet. However, there was a significant reduction in the mean blood pressure on the low sodium intake compared with when the patients were on their normal diet. Compared with the normal diet, BNP and ANP plasma levels showed similar percentage decreases on the low sodium intake and similar percentage increases on the high sodium intake., Conclusions: These findings suggest that BNP and ANP are released in response to a common stimulus during changes in dietary sodium intake. The changes in plasma BNP and ANP observed with sodium restriction and sodium loading indicate the potential importance of BNP and ANP as a dual peptide system contributing to the maintenance of sodium balance and blood pressure regulation in patients with essential hypertension, during changes in dietary sodium intake.

The effects on serum ionized calcium (ICa) and pH of different storage conditions of blood or serum, and of physiological influences such as over-ventilation, food intake and dietary sodium intake have been investigated. Temperature and time-related changes in ICa occurred with storage and were minimized by immediate separation of serum and storage at 4 degrees C, (6 h or less). Elevation of serum ICa and a fall in pH accompanied increased salt intake; over-ventilation induced an elevation of serum pH and a reduction in ICa. Day-to-day intra-individual variation of ICa was 0.93%. We proceeded to examine a group of age-, sex- and race-matched hypertensive and normotensive subjects under standardized conditions designed to minimize such technical and physiological artefacts. ICa was not significantly different in the two groups; however, serum pH was significantly elevated in the hypertensive group. In the combined group of normotensive and hypertensive subjects, serum pH was significantly correlated with blood pressure. Exclusion of the black subjects from the analysis did not alter the findings.