Effect of diltiazem and verapamil on endothelin release by cultured human coronary smooth-muscle cells and endothelial cells

Recent data suggest that endothelin (ET) production is enhanced in coronary atherosclerotic lesions. In several studies, an anti-atherosclerotic effect has been attributed to calcium-channel antagonists. This study aimed to investigate whether ET release from cultured human coronary artery smooth muscle and endothelial cells is influenced by the calcium-channel antagonists diltiazem and verapamil. Coronary plaque smooth-muscle cells (SMCs) were isolated from primary stenosis plaque material. Normal coronary smooth muscle and endothelial cells were obtained from organ donors. Addition of diltiazem (5, 15, 25, 50, or 100 micrograms/ml) and verapamil (0.25, 2.5, 25, 50, or 75 micrograms/ml) to the culture medium induced in all three cell types a dose-dependent reduction in ET secretion (coronary plaque SMCs: diltiazem 98.1 +/- 1.5, 94.9 +/- 5.0, 82.0 +/- 6.4**, 63.3 +/- 3.7***, 38.9 +/- 2.4***; control 108.4 +/- 2.8; verapamil 97.0 +/- 7.7, 91.9 +/- 5.5, 67.3 +/- 4.5**, 30.6 +/- 3.0***, 27.6 +/- 2.2***; control 103.4 +/- 6.1 pg/10(4) cells, n = 6; normal coronary SMCs: diltiazem 9.6 +/- 0.7, 8.7 +/- 0.6, 5.4 +/- 0.5***; 3.7 +/- 0.5***, 3.2 +/- 0.4***; control 10.7 +/- 0.5; verapamil 10.3 +/- 0.9, 10.0 +/- 0.7, 6.6 +/- 0.5***, 4.0 +/- 0.3***, 3.0 +/- 0.3***; control 11.1 +/- 0.6 pg/10(4) cells, n = 6; means +/- SEM, **p < 0.01, ***p < 0.001 vs. control). These data suggest that ET release from cultured coronary smooth muscle and endothelial cells is decreased by diltiazem and verapamil. In further studies, it remains to be elucidated whether the local application of diltiazem or verapamil might have a beneficial effect on the progression of coronary atherosclerosis.

Time-dependent changes of heart rate variability after percutaneous transluminal angioplasty

OBJECTIVES

It is not known whether the improvement of myocardial perfusion by percutaneous transluminal coronary angioplasty (PTCA) is followed by a response of the autonomic nervous system depending on the recovery of the myocardium. In this study we investigated changes of heart rate variability parameters in patients before and after PTCA at different time intervals.

METHODS

In 42 patients with coronary artery disease documented on angiography, before and after PTCA 24-hour measurements of heart rate variability (HRV) were performed from Holter tapes. The time elapsed between the two measurements was 3 to 4 days in 26 patients and 6 to 8 months in 16 patients. Time domain parameters of HRV were calculated.

RESULTS

Comparison of the two recordings showed that the parameters rMSSD, pNN50, and SDNN index decreased, whereas SDNN and SDANN increased. These changes were not statistically significant. A subgroup analysis revealed different results for patients with and without previous myocardial infarction: the parasympathetically and more sympathetically influenced parameters revealed different changes in these groups. Other variables such as ejection fraction or severity of coronary artery disease did not influence the HRV results. Although no statistically significant difference was seen on comparison of the patients with different recording intervals, patients with a longer interval between the two measurement periods showed higher values of all HRV parameters closer to normalized values. This observation may be explained by a delayed recovery of myocardial function after successful revascularization by PTCA.

Modulation of Ca2+-activated K+ channels in human vascular cells by insulin and basic fibroblast growth factor

Insulin and basic fibroblast growth factor (bFGF) play an important role in the pathogenesis of atherosclerosis and have been shown to have vasodilatory effects. Since modulation of vascular ion channels determines membrane potential and thereby influences essential Ca2+-dependent intracellular pathways, we have investigated the effect of insulin and bFGF on Ca2+-activated K+ channels (BKCa) in human umbilical vein endothelial cells (HUVEC) and smooth muscle cells. The latter were obtained from either atherosclerotic plaques (SMCP) or from media segments (SMCM) of human coronary arteries. Using the patch-clamp technique, insulin (100 microU/ml) caused a significant increase in BKCa open-state probability in SMCP and HUVEC, whereas no significant changes were observed in SMCM. Basic FGF (30 ng/ml) revealed a significant increase in BKCa activity in HUVEC and a significant decrease in the BKCa open-state probability in SMCP, but caused no changes in SMCM. Thus, growth factors modulate vascular BKCa in a cell-type specific manner, which may be of importance concerning vasoactive and atherogenic effects of growth factors.

Comparison of the proximal flow convergence method and the jet area method for the assessment of the severity of tricuspid regurgitation

AIMS

To compare the value of the proximal flow convergence method and the jet area method for the determination of the severity of tricuspid regurgitation.

METHODS AND RESULTS

The proximal isovelocity surface area radius and the jet area/length were measured in 71 consecutive patients with angiographically graded (grade 0/I-III) tricuspid regurgitation. Rank correlation coefficients with the angiographic grade were 0.71 (P < 0.001) for the proximal isovelocity surface area radius (aliasing border of 28 cm.s-1), 0.66 (P < 0.001) for the jet area, and 0.63 (P < 0.001) for the jet length. The proximal isovelocity surface area radius was significantly correlated with the jet area/length (correlation coefficients 0.82/0.77, P < 0.001). Correct differentiation between mild to moderate (grade I-II) and severe (grade III) tricuspid regurgitation was achieved in 62 of 71 patients (87%) by means of the proximal isovelocity surface area radius, in 61 of 71 (86%) by the jet area, and in 62 of 71 (87%) by the jet length. Grade III tricuspid regurgitation was not identified in five of 21 patients (24%) by means of the proximal isovelocity surface area radius, in six of 21 (29%) by the jet area, and in seven of 21 (33%) by the jet length.

CONCLUSION

The flow convergence method and the jet area method are of similar value for the determination of the severity of tricuspid regurgitation. Both methods differentiated mild to moderate from severe tricuspid regurgitation in most patients. However, underestimation of severe tricuspid regurgitation in 20-30% of the cases represents a serious limitation of both methods.

Direct enzyme immunometric measurement of plasma big endothelin-I concentrations and correlation with indicators of left ventricular function

Recent studies have suggested that the plasma concentrations of endothelin-1, a potent vasoconstrictive peptide, are increased in patients with congestive heart failure. This study aimed to evaluate a new direct ELISA for big endothelin-1 (the precursor of endothelin-1), in comparison with a big endothelin-1 ELISA using plasma sample extraction, and to investigate whether plasma big endothelin-1 concentrations correlate with indicators of left ventricular function. The direct ELISA yielded significantly (P < 0.001) lower results than the assay with extracted samples (0.9 +/- 0.5 pmol/L vs 2.7 +/- 1.9 pmol/L; n = 90); however, the results of the two assays were closely correlated (r = 0.86, P < 0.001). Plasma big endothelin-1 concentrations exhibited a significant (P < 0.001) negative correlation (r = -0.46, r = -0.40) with the left ventricular ejection fraction and a significant positive correlation (r = 0.40, P < 0.001; r = 0.36, P < 0.01) with the left ventricular end-diastolic pressure and the left ventricular end-diastolic (r = 0.42, r = 0.38, P < 0.001) and end-systolic (r = 0.52, r = 0.47, P < 0.001) volume indices. Plasma big endothelin-1 concentrations were notably greater in patients with New York Heart Association (NYHA) class II-IV symptoms than in patients without cardiac disease or in patients categorized to NYHA class I. These data suggest that plasma big endothelin-1 concentrations, measured by a direct ELISA, correlate with hemodynamic indicators and symptoms of left ventricular dysfunction.

Heart-rate variability for discrimination of different types of neuropathy in patients with insulin-dependent diabetes mellitus

It has been shown that patients with insulin-dependent diabetes mellitus (IDDM) may reveal abnormal alterations in heart-rate variability (HRV) due to autonomic neuropathy. This study was performed to prove whether heart-rate variability can be used to stratify diabetic patients with different types of neuropathy. 48 patients with IDDM (age 17-64 yr) underwent standard function tests to assess autonomic and peripheral neuropathy. According to the results of these tests they were divided into 4 groups: Group 1: 18 patients without autonomic or peripheral neuropathy. Group 2: 13 patients with peripheral neuropathy. Group 3: 7 patients with autonomic neuropathy. Group 4: 9 patients with autonomic and peripheral neuropathy. HRV was measured by continuous 24-hours monitoring and time domain parameters were calculated. The results were compared with sex and age-matched healthy controls according to the individual characteristics of the groups and among each subgroup. Our results showed that in Group 1 there was a significant difference of time domain parameters indicative of parasympathetic influence, i.e. rMSSD and pNN50 in comparison to the control subjects (p = 0.002, p = 0.008). These results depended on the duration of diabetes; a subgroup of patients with a duration of IDDM of less than 2 years had no significant differences of HRV values. Group 2 showed the same significant differences. Group 3 and 4 showed significant differences in all measured time domain variables (SDNN, SDANN, SDNN index, rMSSD and pNN50) in comparison to the control subjects (p < 0.04). A comparison of group 1 with group 2 offered significant differences in rMSSD and pNN50 (p = 0.004, p = 0.003). Comparing group 1 with group 3 and 4, all HRV parameters showed significant differences (p < 0.03). In conclusion, HRV is able to distinguish between patients with different types of neuropathy depending on the involvement of parasympathetic or more sympathetic influenced parameters. Furthermore, this method is able to unmask early manifestations of neurological disorders prior to their detection by neurological function tests.

Influence of physical activity on 24-hour measurements of heart rate variability in patients with coronary artery disease

This study assessed the influence of physical activity on time domain variables of heart rate variability (HRV) during 24-hour electrocardiographic registrations. Changes in time domain variables of HRV (in particular SDNN) obtained from Holter recordings were proven as strong predictors of cardiac events in patients with coronary artery disease. Although 24-hour measurements of HRV recordings are a standard technique, little is known about the effects of the environment during the registration period. This applies especially to the type and nature of physical activity. In a prospective study, 106 patients with angiographically proven coronary artery disease were randomized into 2 groups. Group 1 consisted of 54 patients with recordings under normal daily physical activities. Group 2 consisted of 52 patients who were immobilized during the recording. Both groups were comparable concerning clinical parameters. The results of 24-hour measurements of HRV with analysis of time domain variables (SDNN, SDANN, SDNN index, rMSSD, and pNN50) were compared among the 2 patients groups, and with a healthy control group. Comparison of immobilized patients with healthy controls showed statistically significant differences of all HRV parameters (p <0.01). However, when comparing the activity group with healthy controls, none of the parameters showed any significant differences. Comparison of the subgroups revealed statistically significant differences of the parameters SDNN, SDANN (p <0.01), and borderline results for rMSSD and pNN50 (p = 0.05). Our results indicate that time domain variables of HRV calculated from 24-hour recordings are significantly influenced by the level of physical activity and the upright posture during registration. This methodologic aspect has to be considered, especially if HRV measurements are used as prognostic markers in patients with coronary heart disease.

Seasonal variations of rheological and hemostatic parameters and acute-phase reactants in young, healthy subjects

The incidence of cardiovascular diseases is increased in winter months. Recent studies have shown seasonal changes in plasma viscosity, fibrinogen, and factor VII activity with elevated levels during winter. An increase in these factors generates a "hypercoagulable state," which may lead to a rise in cardiovascular morbidity and mortality. It has been suggested that an increase in upper respiratory infections might be the underlying cause for the raised acute-phase reactants, in particular fibrinogen, during the winter season. We investigated seasonal variations of 26 parameters, determining blood rheology and hemostasis in 16 healthy volunteers (8 men and 8 women) aged 20 to 41 years. They were seen at monthly intervals over a period of 1 year. Seasonal variation with peak fitted values in the winter months was found for plasma viscosity (P < .001 for the seasonal difference), red blood cell deformability (P < .001), whole blood viscosity (P < .001), hemoglobin (P < .001), hematocrit (P < .001), mean corpuscular volume (P = .001), platelet count (P = .01), alpha 1-glycoprotein (P < .001), fibrinogen (measured by immunonephelometry; P < .001), plasminogen activator inhibitor-1 (P = .002), LDL cholesterol (P = .003), and triglyceride levels (P < .001). HDL cholesterol (P < .001) and cortisol (P = .001) showed inverse seasonal patterns, with a maximum during summertime. No statistically significant seasonal variations were seen for red blood cell aggregation, complement factor C4, total cholesterol, ceruloplasmin, haptoglobin, white blood cell count, and plasminogen. These data do not support the hypothesis that increased morbidity and mortality from cardiovascular diseases during winter may be mainly attributable to increased synthesis of acute-phase proteins due to infections. The cause for the seasonal variations in rheological and hemostatic parameters remains unclear and should be studied in more detail.

Immunohistochemical colocalization of the terminal complex of human complement and smooth muscle cell alpha-actin in early atherosclerotic lesions

There is substantial evidence that activated components of the complement cascade are present in atherosclerotic lesions, and it was suggested some years ago that smooth muscle cells may be an important target of complement attack by the terminal components of the cascade, C5b-9, also called the membrane attack complex. Recent in vitro studies have shown that assembly of membrane attack complex on smooth muscle cells leads to the release of monocyte chemotactic protein-1, and, if this were to occur in vivo, then it could be responsible for the recruitment of monocytes into the lesion. In this study we have investigated the localization of C5b-9 in early atherosclerotic lesions of human coronary arteries, collected from autopsies, by immunohistochemical staining, C5b-9 was found to colocalize widely with smooth muscle cell alpha-actin, but not with intact macrophages, thus supporting the hypothesis that interaction of complement with smooth muscle cells may indeed be important in atherogenesis.

Estradiol concentrations in premenopausal women with coronary heart disease

BACKGROUND

Because of the beneficial effects of estrogen, premenopausal women are normally protected against coronary heart disease (CHD) and are at lower risk for myocardial infarction; consequently, CHD occurs very rarely in menstrually active women. Given this background, the aim of the present study was to test the hypothesis that decreased concentrations of estrogen are associated with CHD in premenopausal women.

METHODS

Fourteen premenopausal women with CHD were investigated and compared with a healthy control group comparable for age and cardiovascular risk factors. Relevant characteristics of patients and controls were assessed: age, blood pressure, body mass index, total cholesterol and high-density lipoprotein cholesterol, triglycerides, former pregnancies, ovariectomy and related surgical interventions, smoking history and former use of oral contraceptives. To ensure the premenopausal status of the participants, the regularity of the menstrual cycle and the follicle-stimulating hormone concentrations were also assessed. Plasma estradiol and progesterone and urine estrone concentrations (24 h urine collection) were measured at day 6 after estimated ovulation to assess the relative increase in plasma estradiol and progesterone during the second half of the menstrual cycle.

RESULTS

Compared with the control group, premenopausal women with CHD had significantly lower concentrations of plasma estradiol (408.9 +/- 141 pmol/l and 287.8 +/- 109 pmol/l respectively; P = 0.0228) and total estrogen (2061 +/- 693 pg/mumol creatinine and 1607 +/- 448 pg/mumol creatinine respectively; P = 0.025) in the urine. However, the progesterone concentrations were not significantly different between the groups. These findings might be explained by a partial ovarian dysfunction, as the patient group had a significantly higher number of tubal sterilizations (eight compared with one).

CONCLUSION

Our data provide support for the hypothesis that decreased concentrations of estradiol might be an additional pathogenetic factor for the development of CHD in menstrually active premenopausal women.

Ca(2+)-activated K+ channels in human smooth muscle cells of coronary atherosclerotic plaques and coronary media segments

The behavior of Ca(2+)-activated K+ channels of large conductance (BKCa) in smooth muscle cells, which were obtained from atherosclerotic plaque material (SMCP) and from media segments (SMCM) of human coronary arteries, were compared using the patch-clamp technique. Voltage-clamp protocols in cell-attached patches revealed the characteristic voltage-dependent activation of BKCa in both cell groups. Single-channel conduction as 216.4 +/- 16.7 pS (n = 6) in SMCP and 199.9 +/- 6.7 pS (n = 6) in SMCM in symmetrical 140 mM K+ solutions. Using outside-out patches, external perfusion with 500 microM tetraethylammonium ions caused a typical "flickery block" of the unitary current. The selective BKCa channel inhibitor iberiotoxin (50 nM) effectively blocked BKCa, channel activity. Comparing BKCa open-state probabilities (P0) at +80 mV in cell-attached patches, a highly significant difference between SMCP (P0 = 0.1438 +/- 0.1301; n = 15) and SMCM (P0 = 0.0093 +/- 0.0044; n = 15; Kruskal-Wallis test, p < 0.001) was found. In contrast to this finding, there was no significant difference in the open-state probability of BKCa, between SMCP (P0 = 0.542 +/- 0.0237; n = 9) and SMCM (P0 = 0.0472 +/- 0.0218; n = 10; p = n.s.) using inside-out patches. The results show an interesting difference in the behavior of large conductance Ca(2+)-activated K+ channel in SMCP compared to SMCM with a significantly higher channel activity in human smooth muscle cells obtained from coronary atherosclerotic plaque material. This finding may indicate an important functional role of BKCa channels in the development of atherosclerosis.

Signal-averaged electrocardiogram in patients with insulin-dependent (type 1) diabetes mellitus with and without diabetic neuropathy

The purpose of this study was to investigate the presence of ventricular late potentials derived from signal-averaged ECG in patients with IDDM with and without diabetic neuropathy. Eighty patients with IDDM but without evidence of cardiac disease and 80 age-matched healthy control subjects were investigated. The corrected QT interval was measured from the standard surface electrocardiogram. Ventricular late potentials were derived from signal-averaged electrocardiogram. Out of the 80 diabetic patients, 20 had an autonomic neuropathy, 20 had an isolated peripheral neuropathy, and 40 had no symptoms of neuropathy. The corrected QT interval was significantly prolonged in patients with an autonomic neuropathy as compared with the control group (436 +/- 23 ms(x 5) vs 384 +/- 23 ms(x 5), p < 0.001). In the other patient groups there was no significant prolongation of the corrected QT interval. Ventricular late potentials were present in 3 diabetic patients with an isolated peripheral neuropathy and in 1 control subject (NS). No diabetic patient with an autonomic neuropathy had ventricular late potentials. Our data did not indicate an increased incidence of ventricular late potentials derived from signal-averaged electrocardiogram in diabetic patients independent of a coexisting diabetic neuropathy or a prolonged corrected QT interval.

High-dose diltiazem prevents migration and proliferation of vascular smooth muscle cells in various in-vitro models of human coronary restenosis

BACKGROUND

Restenosis after coronary angioplasty is considered to be caused mainly by increased migration and proliferation of smooth muscle cells (SMC). The concept of local, site-specific delivery of pharmacologic therapies has opened the door for new, high-dose drug regimes.

METHODS AND RESULTS

SMC were isolated by enzymatic disaggregation with collagenase/elastase from human coronary plaque tissue of 29 patients (pSMC) and post mortem from the coronary media of 33 corpses (mSMC). Endothelial cells were isolated from human umbilical veins by enzymatic disaggregation with collagenase/dispase. By positive reaction with antibodies against smooth muscle alpha-actin and von Willebrand factor cells were identified as SMC or endothelial cells. In proliferation studies 5-150 micrograms/ml diltiazem was added to the culture media of pSMC, mSMC and endothelial cells. After 5 days there was a significant dose-dependent inhibition of cell proliferation (for pSMC with > 50 micrograms/ml, for mSMC with > 25 micrograms/ml, and for endothelial cells with > 5 micrograms/ml). In migration studies the effect of 5-150 micrograms/ml diltiazem on the velocity of migration of pSMC was investigated over a period of 48 h. Administration of diltiazem at concentrations of 100 and 150 micrograms/ml caused a significant inhibition of the migration of pSMC. The cytoskeletal components smooth muscle alpha-actin, vimentin, and alpha-tubulin of pSMC and the expression of von Willebrand factor of endothelial cells were investigated after an incubation period of 5 days with 50 and 150 micrograms/ml diltiazem. In the transfilter coculture model the effect of 50 micrograms/ml diltiazem on mSMC was investigated after mechanical injury of cocultured endothelial cells. Administration of diltiazem at a concentration of 50 micrograms/ml inhibited the development of a neointimal proliferate in the transfilter coculture model significantly (P < 0.001).

CONCLUSIONS

A high dose of diltiazem inhibited the migratory and proliferative activities of coronary SMC significantly. In further experimental studies the effect of locally applied high doses of diltiazem on postangioplasty restenosis should be elucidated.

Influence of pulse repetition frequency and high pass filter on color Doppler maps of converging flow in vitro

Assessment of regurgitant flow by the flow convergence method is based on reading absolute velocities from color Doppler maps. Velocity overestimation by high pass filtering above 100 Hz has been reported. An extremely low filter, however, is impracticable in patients. A ratio of pulse repetition frequency (PRF)/filter of 10/1 usually results in good quality color maps as judged visually. We studied in vitro the influence of RPF and filter on the absolute velocities within color maps of the flow convergence, keeping PRF/filter at 10/1. The color maps were also compared with computerized flow simulations. Flow across different orifice plates was scanned using two different setups for each flow condition: low velocity setup (PRF 600-2500 Hz, filter 50-300 Hz) and high (PRF 1500-6000 Hz, filter 200-600 Hz). From the color maps, velocity profile curves were read along the flow center line across the flow convergence. The high velocity setup provided artefact-free color maps at a distance d = 2-4 through 8-11 mm to the orifice, the low setup at d = 6-8 through 18 mm. Within the overlapping range (d = 6-8 through 8-11 mm), the resulting curves showed no significant differences in local velocity, with a slight trend towards higher velocities with the high velocity setup (2.2-2.9%). The simulations agreed well with color Doppler except for slightly lower values at d > 10-12 mm. Changes in PRF and filter have no significant influence on the absolute velocities displayed within color maps as long as PRF/filter is kept close to 10/1.

[Unmasking an exclusively retrograde accessory pathway by catecholamines]

A 52-year-old man with frequent episodes of narrow QRS complex tachycardias with rates of 150/min was admitted for electrophysiological evaluation and treatment. P waves could be seen in the ST-segment of the surface ECG during tachycardia. Atrial stimulation during electrophysiological testing was not able to induce tachycardia. During atrial stimulation, there was no evidence of conduction via an accessory pathway or of dual AV node conduction properties. Ventricular stimulation showed complete ventriculoatrial block. After intravenous administration of the catecholamine orciprenaline, single atrial extrastimuli induced an AV macro-reentrant tachycardia with a rate of 165/min. VA conduction showed the earliest retrograde atrial activation in the left anterolateral area. Thus, there was an accessory pathway which only conducted in ventriculoatrial direction and only during adrenergic stimulation. After successful radiofrequency catheter ablation, complete ventriculoatrial block was recorded even after repeat administration of orciprenaline during ventricular stimulation. This case confirms the need to administer catecholamines in every undiagnosed tachycardia during electrophysiological testing to reveal the mechanism of the tachycardia.

Functional upregulation of the vascular endothelial growth factor receptor KDR by hypoxia

BACKGROUND

Vascular endothelial growth factor (VEGF) is a specific endothelial mitogen and chemoattractant that has been shown to be useful for inducing therapeutic angiogenesis in ischemic myocardium and found to stimulate mitogenicity and chemotaxis of endothelial cells through the receptor tyrosine kinase KDR. Although VEGF expression is upregulated by hypoxic stimuli, regulation of KDR remained unknown under these conditions.

METHODS AND RESULTS

With the use of human umbilical vein endothelial cells and transfected porcine aortic endothelial cells, KDR protein was found to be upregulated under hypoxic conditions (2% O2) in both cell types. This process of KDR upregulation was found to be reversible, was maximal after 24 hours of hypoxia, and was regulated on a posttranscriptional level. Furthermore, the susceptibility for VEGF-induced mitogenicity was enhanced under hypoxic conditions as shown by [3H]-thymidine incorporation assay. The activated state of increased VEGF function in hypoxic endothelial cells was associated with elevated tyrosine phosphorylation of KDR as demonstrated by anti-phosphotyrosine blot.

CONCLUSIONS

These data indicate that hypoxia stimulates VEGF-dependent signaling not only by upregulation of VEGF ligand but also by functional upregulation of a specific signaling receptor. Therefore, these data provide evidence that the endothelium plays an active role in hypoxia-induced angiogenesis.

Influence of the mechanism of regurgitation on the quantification of mitral regurgitation by the proximal flow convergence method and the jet area method

In 84 patients mitral regurgitation was quantified by angiography. The mechanism of regurgitation was determined by echocardiography (organic, n = 54, functional, n = 30). The radii of the proximal isovelocity surface areas in the flow convergence region for 28 and 41 cm.s-1 blood flow velocity and the area and length of the regurgitant jet were measured using colour flow Doppler imaging. The radii of the proximal isovelocity surface areas correlated more closely with the angiographic grade than the jet parameters irrespective of the mechanism of regurgitation. In more than 90% of the patients, grades I-II mitral regurgitation were correctly differentiated from grades III-IV by means of the radii of the proximal isovelocity surface areas. Using the jet parameters, the differentiation was correct in 50-90% of the patients depending on the mechanism of regurgitation. The jet area method particularly failed to identify grades III-IV organic mitral regurgitation due to a high prevalence of eccentric jets in these patients. It is concluded that the proximal flow convergence method was suitable for the quantification of mitral regurgitation irrespective of the mechanism of mitral regurgitation. On the other hand, the value of the jet area method depended largely on the regurgitation mechanism.

Different effects of estrogen and progesterone on experimental atherosclerosis in female versus male rabbits. Quantification of cellular proliferation by bromodeoxyuridine

BACKGROUND

The aim of the present study was to compare the effect of estrogen and progesterone on the development of experimental atherosclerosis in female versus male rabbits to assess possible sex-specific differences.

METHODS AND RESULTS

A total of 32 female and 32 male New Zealand White rabbits were ovariectomized or castrated. In addition to a 0.5% cholesterol diet, the rabbits received estradiol alone (1 mg/kg body wt [BW] per week), progesterone alone (25 mg/kg BW per week), or combined estradiol-progesterone in these dosages during 12 weeks. Ovariectomized female and castrated male rabbits served as control groups without hormone treatment. Before excision of the vessels, bromodeoxyuridine labeling was performed to determine the extent of cellular proliferation in the atherosclerotic lesions. The aortic arch was analyzed immunohistologically and morphometrically. An inhibitory effect of estrogen on intimal plaque size was found in female rabbits compared with the ovariectomized control group (0.7 +/- 0.5 versus 3.7 +/- 2.5 mm2, P < .002; proliferating cells, 3.1 +/- 1.8% versus 8.5 +/- 2.6%, P < .002). In combination with progesterone, however, estrogen was not able to reduce intimal plaque size or cellular proliferation. In contrast, estradiol in castrated male rabbits was not associated with an inhibitory effect on cellular proliferation or intimal thickening compared with controls (estrogen treatment, 7.6 +/- 2.1% proliferating cells and 2.8 +/- 1.0 mm2 neointima; control group, 7.2 +/- 2.1% cellular proliferation and 2.9 +/- 1.2 mm2 intimal thickening).

CONCLUSIONS

Our data suggest that the atheroprotective effect of estrogen is probably due to a mechanism that is present in female rabbits only.

Reproducibility of left ventricular volume measurements at rest and during bicycle exercise in patients with congestive heart failure: a combined radionuclide and haemodynamic study

A series of 14 patients with heart failure due to coronary artery disease and impaired left ventricular function underwent radionuclide ventriculography with simultaneous thermodilution measurement of cardiac output by pulmonary artery catheter on two occasions (m1, m2) separated by 6 weeks in order to determine the reproducibility of haemodynamic and left ventricular volume measurements at rest and during supine bicycle exercise. The patients were in NYHA grade II or III and had baseline left ventricular ejection fractions below 40%. Derived haemodynamic variables were calculated from the thermodilution cardiac output and from the radionuclide ejection fraction as follows: stroke volume = thermodilution cardiac output/heart rate; left ventricular end-diastolic volume = stroke volume/ejection fraction; left ventricular end-systolic volume = end-diastolic volume - stroke volume. The percentage difference (PD) between each pair of data (m1, m2) was calculated using the following formula: PD = 100% x (m2-m1)/m1. The data showed that reproducible measurements of left ventricular volume can be obtained at rest and during exercise. The mean (+/- S.D.) PD values for end-systolic volume and end-diastolic volume at rest were - 0.1 +/- 17% and - 0.2 +/- 13%, respectively. The mean PD values for end-systolic volume and end-diastolic volume during exercise were - 0.3 +/- 19% and - 0.7 +/- 15%, respectively. By contrast, the reproducibility of the pulmonary capillary wedge pressure measurements was poor, as reflected by a PD value of 14 +/- 51% for exercise pulmonary capillary pressure. Combining radionuclide ventriculography and the thermodilution measurement of cardiac output is useful for measuring left ventricular volume at rest and during exercise in patients with heart failure. This minimally invasive technique allows for a comprehensive assessment of left ventricular performance and appears to be particularly suited for assessing the effects of therapeutic interventions aimed at minimizing the progressive left ventricular enlargement in heart failure.

Suramin is a potent inhibitor of vascular endothelial growth factor. A contribution to the molecular basis of its antiangiogenic action

Vascular Endothelial Growth Factor (VEGF) is a specific endothelial mitogen and an important angiogenic factor in vivo, capable of inducing therapeutic angiogenesis when administered to ischemic myocardium. Suramin, originally developed as an anti-trypanosomal agent, was recently shown to exert an antiangiogenic action. We have tested the hypothesis, whether the antiangiogenic effect of suramin may be mediated via inhibition of VEGF function. Using cultured endothelial cells and a [3H]thymidine incorporation assay we were able to show, that the action of VEGF upon mitogenicity is inhibited by suramin in a dose-dependent manner. The same was true for inhibition of VEGF-induced chemotaxis of endothelial cells. Suramin inhibited VEGF-inducible tyrosine phosphorylation of KDR as determined by in vitro kinase assay. Moreover, suramin was shown to inhibit VEGF-induced tyrosine phosphorylation of KDR in intact cells, indicating an interaction of suramin with the VEGF-receptor KDR as the cause of its inhibitory activity. The antiangiogenic effect of suramin may be mediated-at least in part-by inhibition of VEGF function. Given the feasibility of in vivo use, suramin may be a valuable tool for investigating the functional role of angiogenesis in the cardiovascular system.

Increased endothelin release by cultured human smooth muscle cells from atherosclerotic coronary arteries

OBJECTIVES

Endothelin, a 21-amino acid peptide initially purified from the medium of cultured endothelial cells, is a potent vasoconstrictor exerting its effects predominantly in a paracrine or autocrine manner. Recent data indicate that endothelin is also synthesized by cultured vascular smooth muscle cells and that endothelin is an effective stimulator of smooth muscle cell proliferation. This study aimed to investigate the endothelin release of cultured human smooth muscle cells, isolated from coronary plaques and from normal coronary tunica media, and to determine circulating endothelin concentrations in patients with coronary artery disease compared to control subjects.

METHODS

Coronary plaque material was extracted by thrombendarterectomy during aorto-coronary bypass grafting (n = 19). Segments of normal coronary arteries were obtained at autopsy (n = 33). Cells were isolated by enzymatic disaggregation and identified as smooth muscle cells with antibodies against smooth muscle alpha-actin. Venous blood samples were drawn from patients with coronary artery disease undergoing cardiac catheterization (n = 32) and from control subjects (n = 38). Endothelin concentrations in culture medium and in plasma samples were measured by radioimmunoassay after Sep Pak C18 extraction.

RESULTS

Cultured smooth muscle cells, isolated from coronary plaques, released a significantly (P < 0.001) higher amount of immunoreactive endothelin into the culture medium (39.2 +/- 3.9 pg/10(4) cells, mean +/- s.e.m., 31 supernatant samples) than smooth muscle cells from normal coronary tunica media (3.9 +/- 0.8 pg/10(4) cells, 28 samples). Circulating endothelin concentrations were slightly elevated (P < 0.01) in patients with coronary artery disease (3.8 +/- 0.2 pg/ml) compared to control subjects (3.0 +/- 0.2 pg/ml).

CONCLUSIONS

These data suggest that the endothelin production is markedly increased in smooth muscle cells of coronary atherosclerotic plaques. The enhanced endothelin release may stimulate smooth muscle cell proliferation in a paracrine or autocrine manner and thus may contribute to the development or progression of coronary artery disease.