[Use of diuretics in acute decompensated heart failure]

Patients with acute heart failure usually present with dyspnoe and edema secondary to elevated intracardiac filling pressure resulting from volume overload. Despite significant progress in understanding heart failure, the treatment strategy for acute heart failure did not change in the same way. Diuretics, especially loop diuretics, are the most common therapy used in this setting. Intravenous diuretics act acutely by exerting a modest vasodilatory response and chronically by reducing circulating blood volume. Despite near universal use of diuretics in patients hospitalized with acute heart failure, nearly half of these patients are discharged from hospital without weight loss. This could be due to inadequate diuresis, overdiuresis with subsequent volume replacement and diuretic resistance. Aggressive diuresis carries a significant risk of electrolyte and volume depletion with subsequent arrythmias, hypotension, and worsening renal function. Actually there were scant data available from randomized clinical trials to guide therapeutic choice with diuretics. Thus, the choice and dosing of diuretic therapy must be individualized based on general knowledge of potency and pharmacokinetic and pharmacodynamic considerations.

The influence of continuous venovenous haemodialysis on the pharmacokinetics of multiple oral moxifloxacin administration to patients with severe renal dysfunction

AIM

We investigated single dose and steady-state pharmacokinetics of moxifloxacin in eight venovenous haemodialysis patients.

METHODS

Plasma, dialysate and urine pharmacokinetic parameters for moxifloxacin and its main metabolites were calculated after single and multiple (7 days) dosing with 400 mg day(-1).

RESULTS

Moxifloxacin pharmacokinetics after a single dose and at steady state (multidose day 7) were comparable in patients with impaired renal function and healthy subjects (geometric mean/%CV AUC mg l(-1) h single dose 37.0/24.3 in haemodialysis patients vs. 29.8/22.6 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 99.34%, 154.60%; steady state 40.4/29.1 haemodialysis patients vs. 33.9/20.1 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 90/39%, 156.93%). In haemodialysis patients plasma concentrations of moxifloxacin at steady-state were elevated compared with those after a single 400 mg dose (AUC mg l(-1) h, geometric mean/%CV, 40.4/29.1) compared with 37.0/24.3; 95% CI for ratio of steady-state to single dose 87.29%, 136.52%, as were concentrations of metabolite M1 3.21/34.6 compared with 2.02/45.3, 95% CI for ratio of steady state to single dose 14.21%, 175.07%. Haemodialysis cleared about 9% of the dose as unchanged moxifloxacin.

CONCLUSIONS

No dose adjustments are required for venovenous haemodialysis patients on oral moxifloxacin therapy.

Distinct tumour necrosis factor alpha, interferon gamma, interleukin 10, and cytotoxic T cell antigen 4 gene polymorphisms in disease occurrence and end stage renal disease in Wegener's granulomatosis

BACKGROUND

Cytokines and T cell regulatory proteins play an important role in the pathogenesis of Wegener's granulomatosis (WG).

OBJECTIVE

To investigate cytokine and cytotoxic T cell antigen-4 (CTLA4) gene polymorphisms and HLA class II alleles in generalised WG.

METHODS

The distribution of cytokine and cytotoxic T cell antigen 4 (CTLA4) gene polymorphisms and HLA class II alleles was analysed in 32 patients with generalised WG and 91 healthy controls. Genotyping was carried out for HLA-DRB1 and HLA-DQB1 and for polymorphism of the genes encoding TNF alpha (-238, -308, -376), TGF beta (codon 10 and 25), IFN gamma (+874), IL6 (-174), IL10 (-592, -819, -1082), CTLA4 (-318, +49), and the (AT)(n) repeats of the CTLA4 gene. In addition, stratification analysis was carried out according to the presence (n = 15) or absence (n = 17) of end stage renal disease.

RESULTS

An increase in the IFN gamma +874 T/T (odds ratio (OR) = 3.14) and TNF alpha -238 G/A (OR = 5.01) genotypes was found in WG patients. When ESRD positive and negative patients were compared, the IFN gamma +874 A/A and the CTLA4 -318 C/C genotypes were found more often in the ESRD subgroup (OR = 10.6 and OR = 2.25). WG patients without ESRD had a higher frequency of the IL10 GCC/ACC promotor genotype (OR = 0.13) and long CTLA4 (AT)(n) repeats (OR = 0.4). No effect was seen for HLA-DR and -DQ markers.

CONCLUSIONS

Disease susceptibility and clinical course in WG may be associated with distinct polymorphisms of cytokine and CTLA4 genes.

Resistant hypertension in patients with chronic aortic dissection

Strict blood pressure control is pivotal in the management of patients with aortic dissection (AD), but is frequently difficult to achieve. We determined antihypertensive medical therapy and levels of blood pressure (BP) control in 40 patients with chronic AD. Patient charts were reviewed for clinical variables, serial BP measurements, and antihypertensive drug therapy. Patients were divided into two groups: patients in group 1 had effective BP control (<135/80 mmHg), patients in group 2 had resistant hypertension (BP>/=135/80 mmHg despite prescription of at least three antihypertensive drugs). Overall, systolic BP (SBP) was 130+/-20 mmHg, and diastolic BP (DBP) was 72+/-13 mmHg. Patients received a median of 4 (1-6) antihypertensive drugs. beta-blockers were used in 38/40 (95%) patients. Effective BP control was achieved in 24/40 (60%) patients (group 1), while 16/40 (40%) patients had resistant hypertension (group 2) despite receiving significantly more antihypertensive drugs (5 [4-6] vs 4 [1-5], P=0.001). Mean SBP was 116+/-9 (101-132) mmHg in group 1 and 151+/-13 (137-181) mmHg in group 2 (P<0.001); there was no difference in DBP. Group 2 patients had a significantly higher body mass index and were younger than patients in group 1. In conclusion, in the majority of patients with chronic AD, effective BP control can be achieved, but usually requires the combination of multiple antihypertensive drugs. However, in a significant proportion of patients (40%), who appear to be younger and more obese, medical therapy fails to achieve effective BP control despite use of a multiple drug regimen.

Erdheim-Chester disease: case report with multisystemic manifestations including testes, thyroid, and lymph nodes, and a review of literature

Erdheim-Chester disease is a rare non-Langerhans' cell histiocytosis with characteristic radiological and histological features. This entity is defined by a mononuclear infiltrate consisting of lipid laden, foamy histiocytes that stain positively for CD68. About half of those affected have extraskeletal manifestations, including involvement of the hypothalamus-pituitary axis, lung, heart, retroperitoneum, skin, liver, kidneys, spleen, and orbit. This report describes the case of a 50 year old white man who presented with hypogonadism and diabetes insipidus. At necropsy, extensive organ involvement was found, including the testes, thyroid, and lymph nodes. This is the first report of thyroid and lymph node infiltration in this disease. Because of the endocrinological symptoms, neurosarcoidosis and hypophysitis are important diseases in the differential diagnosis. This report also includes a review of the literature concerning rare organ manifestations and patients presenting primarily with similar symptoms.

The T-allele of the C825T polymorphism is associated with higher arterial stiffness in young healthy males

Arterial stiffening is the major cause of increasing systolic blood pressure in arterial hypertension. Increased arterial stiffness is one major mechanism responsible for morbidity and mortality in hypertension. A C825T polymorphism was identified in the gene encoding the G-protein beta3 subunit (GNB3), and an association of the T-allele with hypertension was demonstrated in several studies. In order to identify a pathogenetic link between hypertension and arterial stiffness, we compared two indices of arterial stiffness, pulse wave velocity (PWV) and augmentation index, in young, healthy men with and without the 825T-allele under resting conditions. PWV was determined from pressure tracing over carotid and femoral arteries in 99 subjects (CC: n=43; CT&TT: n=56). Augmentation index was derived in 72 subjects (CC: n=30; CT&TT: n=42) by pulse wave analysis using radial applanation tonometry. Carriers of the 825T-allele exhibited a significantly higher PWV compared to subjects with the CC genotype (6.0+/-0.1 m/s (TC&TT) vs 5.7+/-0.1 m/s (CC); P=0.0251). There was also a significant difference (P = 0.0448) in augmentation index between carriers of the T-allele (CT&TT: 3.4+/-2.9%) and controls with the CC -genotype (-5.0+/-4.1 %). There was no difference in any other anthropometric (age, height, weight, body mass index) or haemodynamic (heart rate, peripheral and central blood pressure). In summary, the C825T polymorphism is associated with higher arterial stiffness in young, healthy males. Arterial stiffening may pathogenetically contribute to the development of hypertension in carriers of the T-allele.

A new system for regional citrate anticoagulation in continuous venovenous hemodialysis (CVVHD)

BACKGROUND

CVVHD is an established renal replacement therapy in hemodynamically unstable ICU patients. Various methods for regional citrate anticoagulation have been developed to minimize bleeding complications. Metabolic alkalosis, the risk of severe hypocalcemia and need for continuous calcium substitution as well as treatment-associated hypernatremia have limited the success of systems employed so far. We have developed a new technique for regional citrate anticoagulation in CVVHD to overcome these deficiencies and have performed a validation study.

METHODS

One hundred and thirty-three filters with an overall treatment duration of 3,324 hours were used in 19 critically ill patients with bleeding complications. We used a calcium-containing dialysate (1.81 mmol/l Ca) to avoid mandatory systemic calcium supplementation. Sodium bicarbonate was added to the dialysate in variable concentrations (13 - 34 mmol/l) to control acid-base status and prevent hypernatremia. The resulting dialysate sodium concentrations were between 121 and 140 mmol/l. Blood flow was set at 75 ml /min. Infusion of a solution containing trisodium citrate and citric acid with an overall citrate concentration of 113 mmol/l was started at 250 ml/h. Primary endpoints were pre- and post-filter ionized calcium (Ca(i)) concentrations, base excess and serum sodium. Filter life was assessed as a secondary end-point.

RESULTS

Control of electrolyte balance and azotemia was excellent (prefilter serum Ca(i) 1.06 +/- 0.012 mmol/l (+/- SEM), post-filter Ca(i) 0.23 +/- 0.01 mmol/l, base excess -0.39 +/- 0.4 mmol/l, serum sodium 137 +/- 4 mmol/l, mean serum creatinine 1.8 +/- 0.07 mg/dl). Normal base excess was achieved with a mean dialysate bicarbonate concentration of 26 mmol/l at a mean citrate infusion rate of 266 +/- 4 ml/h. After 48 hours, 25% of filters were still patent, mean filter life was 26 +/- 1.6 hours. No patient developed serious CVVHD-related adverse events.

CONCLUSION

The new regional citrate anticoagulation system for CVVHD is safe, feasible and can avoid major complications of previously described methods, especially hypocalcemia, alkalosis and hypernatremia.

[Quality of life and psychosocial factors during treatment with antihypertensive drugs. A comparison of captopril and quinapril in geriatric patients]

BACKGROUND

There is an increasing prevalence of older adults (> 65 years) with hypertension and the need for antihypertensive medication. It is well established that elderly hypertensive patients benefit from drug treatment with regards to cardiovascular morbidity and mortality. Due to the comorbidity and reduced quality of life (QOL) in the elderly, drug-induced changes of well-being and QOL are especially important to maintain compliance and social abilities. Whereas in most studies different antihypertensive agents exerted similar influences on QOL, Captopril was found to be superior to other antihypertensives in some trials.

PATIENTS AND METHOD

In this controlled non-randomized study 100 elderly hypertensive patients (mean age 75.4 +/- 7.2 years; 56% female) were treated with Captopril (25-50 mg twice daily) or the newer ACE-inhibitor Quinapril (5-20 mg per day). Blood pressure and QOL were recorded initially and after 6 months, assessment of QOL was based on a validated questionnaire (PLC).

RESULTS

Blood pressure fell from 153/82 mm Hg to 142/80 mm Hg with Captopril and 154/82 to 142/80 mm Hg [corrected] with Quinapril. An improvement of QOL was only seen with Quinapril, mainly due to better mood and lower depression scores. Analysis of underlying psychosocial factors on QOL found lack of social support, female sex and a current life event as additional significant negative influences on QOL.

CONCLUSION

A favorable antidepressive effect of Quinapril in elderly hypertensive patients is concluded and should be studied in further investigations.

Haemodynamic characterization of young normotensive men carrying the 825T-allele of the G-protein beta3 subunit

A C825T polymorphism was recently identified in the gene for the G-protein beta3 subunit, the T-allele being associated with hypertension. To better understand the underlying pathophysiological mechanisms, we compared the haemodynamics of young healthy males with and without the T-allele. In three studies, subjects were investigated with regard to cardiac and vascular function at rest and following intravenous administration of the beta-adrenoceptor antagonist, propranolol, and the alpha2-adrenoceptor agonist, alpha-methylnoradrenaline, and with regard to local venous vasoconstriction in the dorsal hand vein in situ following infusion of the alpha2-adrenoceptor agonist, azepexol. alpha2-Adrenoceptor agonists were chosen as vasoconstrictor drugs since alpha2-adrenoceptors couple to pertussis toxin (PTX)-sensitive G-proteins and since in-vitro studies have demonstrated enhanced signal transduction of PTX-dependent pathways in the presence of the T-allele. Total peripheral resistance was determined as a parameter of vasoconstrictor tone and heart rate, stroke volume and systolic time intervals for cardiac function. T-allele carriers had a significantly elevated stroke volume and lower total peripheral resistance at baseline. After propranolol, their fall in stroke volume was significantly greater. During alpha-methylnoradrenaline infusion, elevation of total peripheral resistance was not increased relative to controls. Similarly, the constriction response of the dorsal hand vein to azepexol was not different. Our study does not support the idea of increased vasoconstrictor tone in T-allele carriers either at rest or during stimulation of alpha2-adrenoceptors. However, this allele may be associated with elevated cardiac stroke volume.

Endothelin-A receptor antagonist inhibits angiotensin II and noradrenaline in man

AIMS

Endothelin-1 (ET-1) is a potent vasoconstrictor produced by the vascular endothelium. The interactions of ET with the mediators of the sympathetic nervous system and the renin-angiotensin-system in humans are unclear.

METHODS

We studied the effects of the ETA-selective antagonist BQ-123 and the ETB-selective antagonist BQ-788 (both 10(-10)-10(-8) M) on ET-1 (10(-16)-10(-10) M), angiotensin II (AT, 10(-16)-10(-10) M) and noradrenaline (NA, 10(-16)-10(-10) M) induced vasoconstriction in the human skin microcirculation in vivo in 25 healthy male volunteers using laser Doppler flowmetry and double injection technique.

RESULTS

BQ-123 caused a dose-dependent vasodilatation (maximum effect: + 949 +/- 84 AUC-PU, P < 0.001), whereas BQ-788 induced mild vasoconstriction (maximum effect: -388 +/- 96 AUC-PU, P < 0.01). In the presence of BQ-123, but not BQ-788, ET-1, AT and NA caused markedly less vasoconstriction at any tested agonist dose; the effect was most pronounced on ET-1 (maximum effect at 10(-14) M: + 814 +/- 93 AUC-PU vs ET alone, P < 0.001), followed by noradrenaline (maximum effect at 10(-16) M: +580 +/- 107 AUC-PU vs NA alone, P < 0.01) and angiotensin II (maximum effect at 10(-14) M: + 493 +/- 111 AUC-PU vs AT alone, P < 0.001).

CONCLUSIONS

ETA-selective antagonism inhibits vasoconstriction to AT and NA in vivo in healthy subjects. This beneficial effect may be useful for the treatment of patients with cardiovascular disease including hypertension especially in combination therapy with sympatholytic agents and inhibitors of the renin-angiotensin system.

Antihypertensive drugs and the sympathetic nervous system

The sympathetic nervous system (SNS) plays an important role in the regulation of blood pressure homeostasis and cardiac function. Furthermore, the increased SNS activity is a predictor of mortality in patients with hypertension, coronary artery disease and congestive heart failure. Experimental data and a few clinical trials suggest that there are important interactions between the main pressor systems, i.e. the SNS, the renin-angiotensin system and the vascular endothelium with the strongest vasoconstrictor, endothelin. The main methods for the assessment of SNS activity are described. Cardiovascular drugs of different classes interfere differently with the SNS and the other pressor systems. Pure vasodilators including nitrates, alpha-blockers and dihydropyridine (DHP)-calcium channel blockers increase SNS activity. Finally, central sympatholytics and possibly phenylalkylamine-type calcium channel blockers reduce SNS activity. The effects of angiotensin-II receptor antagonists on SNS activity in humans is not clear; experimental data are discussed in this review. There are important interactions between the pressor systems under experimental conditions. Recent studies in humans suggest that an activation of the SNS with pure vasodilators in parallel increases plasma endothelin. It can be assumed that, in cardiovascular diseases with already enhanced SNS activity, drugs which do not increase SNS activity or even lower it are preferable. Whether this reflects in lower mortality needs to be investigated in intervention trials.

The nitric oxide synthase inhibitor L-NMMA potentiates noradrenaline-induced vasoconstriction: effects of the alpha2-receptor antagonist yohimbine

OBJECTIVE

Alpha2-adrenoceptors can be found both on vascular smooth muscle cells and on the endothelium, where they exert opposing effects on vascular tone. In vitro, the stimulation of alpha2-adrenoceptors on endothelial cells leads to the release of vasodilating substances like nitric oxide (NO) and prostanoids. Little is known of this mechanism in vivo.

DESIGN AND METHODS

We investigated the effects of the NO-synthase inhibitor L-NMMA (10(-6) mol) and the alpha2-adrenoceptor antagonist yohimbine (YO, 10(-10)-10(-6) mol) on noradrenaline (NA, 10(-12)-10(-8) mol)-induced vasoconstriction in the forearm skin microcirculation of 16 healthy volunteers using double injection technique and laser Doppler flowmetry. Results are expressed in perfusion units (PU) as differences from baseline and control in mean +/- SEM; the area under the time-response-curve was calculated (AUC).

RESULTS

NA (10(-8)- 10(-12) mol) caused a marked, dose-dependent reduction in blood flow (mean effect -745 +/- 84 AUC PU; P< 0.001 versus saline). NA-induced vasoconstriction was enhanced by L-NMMA (mean effect -916 +/- 72 AUC PU; P< 0.001 versus NA). YO (10(-6)-10(-10) mol) induced a significant, dose-dependent vasodilation (mean effect +/- 446 +/- 110 AUC PU; P < 0.05 versus control); high doses of YO (10(-6) mol) inhibited NA constriction (P < 0.001 versus NA), whereas lower doses of YO (10(-8)/10(-10) mol) had no effect or even increased NA-induced constriction. In the presence of L-NMMA, YO (10(-8) and 10(-10) mol) further potentiated NA-induced vasoconstriction (mean effect -1165 +/- 108 AUC PU; NS versus NA).

CONCLUSION

These data demonstrate, that in humans in vivo, endogenous NO attenuates noradrenergic constriction. The effects of YO suggest that endothelial alpha2-adrenoceptors are involved in the release of NO and other vasodilating substances. Furthermore, there is an additive NO-independent vasodilation, which can be unmasked by L-NMMA.

Systemic, pulmonary, and renal hemodynamic effects of endothelin ET(A/B)-receptor blockade in patients with maintained left ventricular function

Endothelin-1 (ET-1) regulates vascular tone in congestive heart failure and modulates renal function. Its role in patients with normal left ventricular (LV) function and its renal effects are unclear. Cardiac and renal hemodynamics were studied in 24 patients with normal LV function and coronary arteries after single-dose, double-blind, randomized administration of TAK-044 (25, 50, or 100 mg, i.v.), an ET(A/B)-receptor antagonist, or placebo. Hemodynamics were monitored using Swan-Ganz and arterial catheters, and ET levels were measured. Renal function was assessed by clearance techniques. In the absence of a dose-response relation, TAK-044 patients were analyzed as a single group. Most hemodynamic effects occurred during the first 4 h. TAK-044 reduced mean arterial (-9.3 mm Hg, p < 0.001), pulmonary (-1.8 mm Hg, p = 0.01), and pulmonary capillary wedge pressure (-1.6 mm Hg, p < 0.001) between 30 min and 4 h. Mean reduction in systemic vascular resistance was 279 dyne/s/cm2 (p < 0.001), whereas heart rate increased 6.1 beats/min (p < 0.001) and cardiac index by 0.37 L/m2 (p = 0.01). Stroke volume index, right atrial pressure, and pulmonary vascular resistance did not change. TAK-044 increased renal plasma flow in proportion to the increase in cardiac output (+119 ml/min, 4 h after TAK-044; p < 0.05) and ET-1 levels (2.5-fold; p < 0.05). No serious side effects were noted. In patients with normal cardiac function, ET-receptor blockade causes vasodilation and reduces systemic but not pulmonary vascular resistance and increases cardiac index and renal plasma flow.

Skin microcirculation in healthy subjects and patients with arteriosclerosis

The concept to use the human skin microcirculation as a pharmacological in-vivo test system is old; however, methods developed in the 50s have been abandoned because of side effects and/or use of radioactive substances. We describe a newly developed minimally invasive method that allows in-vivo pharmacology in the human skin microcirculation injecting very low doses of a substance of drug without any systemic effects. The double injection technique (DIT) bears the potential to predict the effects of a drug and/or the vascular reactivity or dysfunction of other less accessible areas of the circulation (e.g. the myocardium). The DIT has been applied for studies in healthy volunteers and patients with atherosclerosis; the focus of interest was endothelial (dys-)function and the effect of exogenous vasoactive drugs. Using endothelin antagonists, we investigated the role of endogenous endothelin under physiological conditions and in atherosclerosis. The NO-synthase inhibitor L-NMMA has been applied to study the L-arginine-NO-pathway and the role of endothelial adrenoceptors. Ongoing studies with the DIT comparing coronary and skin microcirculation may help to develop minimally invasive methods to predict the effects of drugs and vascular function in the heart.

Adrenoceptors mediating the cardiovascular and metabolic effects of alpha-methylnoradrenaline in humans

alpha-Methylnoradrenaline is a widely used tool to study alpha2-adrenoceptor function, but its selectivity for this receptor has not been validated in humans in vivo. To characterize the adrenoceptors mediating cardiovascular and metabolic effects of alpha-methylnoradrenaline in humans, we have performed graded i.v. infusions of alpha-methylnoradrenaline in a randomized, placebo-controlled crossover study in six young, healthy males in the absence and presence of the beta-adrenoceptor antagonist propranolol, the alpha1-adrenoceptor antagonist doxazosin, and the alpha2-adrenoceptor antagonist yohimbine. alpha-Methylnoradrenaline dose-dependently increased heart rate, systolic blood pressure, cardiac output, blood glucose, serum insulin, free fatty acids, and gastrin, shortened the duration of heart rate-corrected electromechanical systole, and decreased diastolic blood pressure, total peripheral resistance, and plasma noradrenaline. Propranolol completely reversed the rise in heart rate and cardiac output, the fall in peripheral resistance, the shortening of electromechanical systole, and the rise in insulin; it blunted the increase in free fatty acids and gastrin. Yohimbine did not significantly influence most parameters but significantly potentiated the rise in insulin, blunted the increase in glucose, and prevented the fall in noradrenaline. Doxazosin was largely without effect on any of these parameters. We conclude that i.v. administered alpha-methylnoradrenaline primarily acts on beta-adrenoceptors in the human cardiovascular and metabolic system, but an alpha2-adrenergic component of the response is detectable for changes of plasma noradrenaline, blood glucose, and serum insulin. Whereas alpha-methylnoradrenaline is selective for alpha2- over alpha1-adrenoceptors, beta-adrenoceptor blockade is required to unmask alpha-adrenoceptor-mediated vasoconstriction.

Endothelin in cardiovascular control: the role of endothelin antagonists

Endothelin (ET) is a potent vasoconstrictor associated with various cardiovascular diseases. ET mediates its effects through ET receptors on vascular smooth muscle cells as well as on the vascular endothelium. Furthermore, a neurotransmitter role for ET has been suggested on the basis of experimental and human in vivo studies. ET antagonists are potent tools for studying the effects of ET and its receptors. They have been widely used in vitro and in experimental models of cardiovascular disease, where ET levels are elevated and reactivity to ET is altered. Promising clinical trials in hypertension, coronary artery disease, and congestive heart failure are discussed in this review. Different forms of renal failure are associated with markedly increased ET levels, and ET antagonists experimentally improve renal function in these models. Extrapolating from experimental and first clinical experience, ET antagonists could be useful in the treatment of hypertension, coronary artery disease, congestive heart failure, and renal failure, especially in combination with other drugs, ie, angiotensin converting enzyme inhibitors. The inhibition of ET-induced stimulation of nociception allows for speculation that ET antagonists might even have analgesic properties.

Accuracy of a new wrist cuff oscillometric blood pressure device: comparisons with intraarterial and mercury manometer measurements

Accurate measurement of arterial blood pressure is of great importance for the diagnosis and treatment of hypertension. Because of the chronic nature of antihypertensive drug therapy, the involvement of the patient in blood pressure control is desirable. Such an involvement, however, is only feasible if simple, user-friendly, and precise blood pressure measurement devices are available. In this study we tested a new wrist cuff oscillometric blood pressure measurement device in 100 consecutive patients undergoing cardiac catheterization. Blood pressures were simultaneously taken intraarterially (axillary artery) and with a mercury manometer and stethoscope or noninvasive measurement device (OMRON R3). Intraarterial measurements were directly compared with two measurements taken in random order with either an arm cuff mercury manometer or the wrist cuff device. Systolic and diastolic blood pressure as assessed with the mercury manometer was higher, especially when compared with the intraarterial and the wrist cuff values, which were comparable. Correlations of blood pressure values with intraarterial measurement were 0.86 systolic and 0.75 diastolic (P < .01) for the wrist cuff and 0.84 systolic (P < .01) and 0.59 diastolic (P < .05) for the mercury manometer measurements. Reproducibility of both measurements was good for the wrist cuff device ([systolic/diastolic]: r = 0.94/0.92; P < .01) and the mercury manometer (r = 0.97/0.88; P < .01). Both methods overestimated high diastolic values, whereas only the wrist cuff underestimated high systolic values. Thus, the new oscillometric wrist cuff blood pressure measurement device measures arterial blood pressure with great accuracy and reproducibility. As compared with intraarterial values, the wrist cuff device overestimated high diastolic and underestimated high systolic blood pressure values. Blood pressure values as measured by the mercury manometer were higher than intraarterial values and those of the wrist cuff. Both noninvasive devices overestimated high diastolic values.

I1-imidazoline agonist moxonidine decreases sympathetic nerve activity and blood pressure in hypertensives

Moxonidine is an I1-imidazoline receptor agonist that reduces blood pressure in hypertensives. Experimental data suggest that moxonidine inhibits central sympathetic activity. However, whether such a mechanism is involved in vivo in humans is still unclear. We investigated the effects of 0.4 mg moxonidine orally on muscle sympathetic nerve activity and heart rate in an open study in 8 healthy volunteers. Furthermore, we studied the effects of 0.4 mg moxonidine on muscle sympathetic nerve activity, heart rate, blood pressure, 24-hour blood pressure profile, and hormone plasma levels in 25 untreated hypertensives in a double-blind, placebo-controlled study. Moxonidine decreased muscle sympathetic nerve activity in both healthy volunteers (P<0.05 versus baseline) and hypertensives (P<0.02 versus placebo). Plasma norepinephrine also decreased (P<0. 01), whereas plasma epinephrine and renin levels did not change (P=NS). Furthermore, moxonidine decreased systolic (P<0.0001) and diastolic (P<0.001) blood pressure. Heart rate decreased after moxonidine in healthy subjects (P<0.05); in hypertensives, heart rate decreased during the night hours (P<0.05) but not during daytime (P=NS). Plasma levels of LDL, HDL, and total cholesterol were not influenced by the drug (P=NS). Moxonidine decreases systolic and diastolic blood pressure by inhibiting central nervous sympathetic activity. This makes this new drug suitable for the treatment of human hypertension and possibly for other cardiovascular diseases with increased sympathetic nerve activity, ie, ischemic heart disease and heart failure.

Hemodynamic and coronary effects of the endothelin antagonist bosentan in patients with coronary artery disease

BACKGROUND

Endothelin is a potent endothelium-derived vasoconstrictor peptide with proliferative properties. Elevated levels of the peptide occur in coronary artery disease; however, its pathophysiological role as a regulator of coronary tone and structure is uncertain. Endothelin-receptor antagonists are specific tools to clarify this issue and might be useful in the treatment of coronary artery disease.

METHODS AND RESULTS

In a double-blind, placebo-controlled randomized study, we investigated the effects of the ETA/ETB endothelin-receptor antagonist bosentan or placebo on systemic and coronary hemodynamics in 28 patients with angiographically documented stable coronary artery disease by quantitative coronary angiography and an intracoronary Doppler guidewire. Bosentan 200 mg IV decreased systolic blood pressure (P<0. 05), whereas heart rate increased slightly (P<0.05). Coronary diameter increased, particularly in vessels with no or mild angiographic changes (P<0.01). Glycerol trinitrate did not further dilate these segments, whereas coronary diameter increased significantly after nitrate in the placebo group. The increase in coronary diameter after bosentan correlated inversely with plasma LDL-cholesterol levels (P<0.01) in both stenotic and angiographically normal coronary segments. Coronary flow velocity did not change. Bosentan was well tolerated.

CONCLUSIONS

Endogenous endothelin exerts a vasoconstrictor tone in epicardial coronary arteries of patients with coronary artery disease, as evidenced by the vasodilation exerted by the combined ETA/ETB endothelin-receptor antagonist bosentan under acute conditions. Bosentan can safely be given to these patients. Hence, further long-term studies are necessary to determine the therapeutic potential of endothelin-receptor antagonists in patients with coronary artery disease.

Role of sympathetic nervous system in hypertension and effects of cardiovascular drugs

The sympathetic nervous system (SNS) plays an important role in the regulation of cardiac performance and peripheral circulation. Changes in SNS activity measured as catecholamines in plasma or organ spillover have been implicated in the pathogenesis of hypertension. Recent studies using microneurography to directly assess peripheral sympathetic nerve activity have demonstrated an increase in sympathetic activity in patients with borderline hypertension at rest and during hypoxia. We have recently shown that resting muscle sympathetic nerve activity is comparable in offspring of hypertensive and normotensive parents. However, during mental arithmetic the increase in muscle sympathetic nerve activity and blood pressure was significantly more pronounced in offspring of hypertensive than in offspring of normotensive parents, but resting blood pressure was in the normotensive range and comparable in both groups. These data indicate that the response to mental stress results in a more pronounced activation of SNS in normotensive subjects with a genetic background of hypertension. In other cardiovascular disease states such as acute myocardial infarction and heart failure activity of the SNS may determine prognosis significantly. Some calcium antagonists which are successfully used to treat patients with hypertension and stable angina pectoris may have unfavourable effects in patients with impaired left ventricular function. This could be due in part to baroreceptor-mediated activation of the SNS, an effect which seems to be related to pharmacokinetics and pharmacodynamics of the drugs. In contrast, angiotensin converting enzyme inhibitors seem to directly decrease sympathetic nerve activity. This may explain at least in part their beneficial effects in patients with impaired left ventricular function. Thus, the SNS as a regulator of the cardiovascular system also plays an important role in the pathophysiology of cardiovascular diseases such as hypertension, myocardial infarction and heart failure. Furthermore, drug therapy could have a significant impact on the activity of the SNS.

Endothelin-1 induces vasodilation in human skin by nociceptor fibres and release of nitric oxide

AIMS

Endothelin is a peptide produced by endothelial cells with many biological properties. In the human skin microcirculation endothelin induces neurogenic vasodilation associated with burning pruritus. We investigated the mechanisms involved in this response.

METHODS

The effects of prolonged pretreatment with capsaicin, a specific inhibitor of polimodal nociceptor fibres, and of the nitric oxide synthase inhibitor L-NMMA on endothelin-1-induced vasodilation were studied in 15 human subjects. Furthermore, we investigated the effects of the ET(A)-selective antagonist PD147953 on bradykinin-induced vasodilation.

RESULTS

After local injection, endothelin-1 caused vasoconstriction at the injection site and a profound vasodilation in the surrounding area (flare reaction, P<0.01). This response was specific and not induced by saline, albumin, acetylcholine or an ET-antagonist. Prolonged capsaicin pretreatment inhibited endothelin-1 induced vasodilation in the area surrounding the injection site, but not the central vasoconstriction at the injection site. Bradykinin also induced a marked vasodilation in the area surrounding the injection site; this was not inhibited by an ETA-selective antagonist, while the flare reaction was. L-NMMA applied at the site of the flare reaction prevented endothelin-1-induced vasodilation.

CONCLUSIONS

Endothelin-1 in the human skin microcirculation stimulates polimodal nociceptor fibres leading to the release of nitric oxide. This response may play a pathophysiological role in inflammatory processes in the human skin.

Calcium antagonists and sympathetic nerve activation: are there differences between classes?

ACTIONS OF THE SYMPATHETIC NERVOUS SYSTEM: The sympathetic nervous system is an important cardiovascular regulator, particularly during stress and exercise; its sympathetic nervous activity is regulated in centers in the brain stem and transmitted to organs and blood vessels that are innervated by sympathetic nerve endings. In the heart, the sympathetic nervous system increases heart rate and contractility. The effect of the sympathetic nervous system in different vascular beds depends on the degree of innervation, the distribution of postjunctional receptors and the effect of local mediators. Overactivation of the sympathetic nervous system may lead to hypertension and is involved in heart failure. The degree of sympathetic activation determines prognosis in heart failure. Hence, vasodilators ideally should also blunt sympathetic activity, or at least avoid activating it. DIFFERENCES AMONG CALCIUM ANTAGONISTS: Calcium antagonists are widely used for the treatment of hypertension and coronary artery disease. Their main mechanism of action is inhibition of L-type Ca2+ channels. Short-acting nifedipine leads to a marked increase in heart rate, sympathetic nerve activity and plasma catecholamines, similar to those induced by a cold pressor test. With long-acting nifedipine heart rate does not increase, but sympathetic nerve activity does increase. Other calcium antagonists have been less thoroughly investigated, but indirect evidence suggests differences between the different classes. Verapamil and diltiazem lower heart rate. Plasma noradrenalin measurements suggest that verapamil does not stimulate the sympathetic nervous system, but tends to suppress it. Second-generation dihydropyridines with longer duration of action do not increase heart rate; their effects on peripheral sympathetic nerve activity are not clear. Thus, in summary, the different classes of calcium antagonists differ with regard to their effects on sympathetic nerve activation. A decrease in heart rate and nerve activity might be beneficial for long-term prognosis, particularly in hypertension and heart failure.

Differential activation of cardiac and peripheral sympathetic nervous system by nifedipine: role of pharmacokinetics

OBJECTIVES

We sought to study the effects of short-acting and long-acting nifedipine on the sympathetic nervous system (SNS), heart rate (HR) and blood pressure (BP) of normotensive subjects under baseline conditions and during SNS stimulation.

BACKGROUND

Calcium channel antagonists in different pharmacokinetic formulations are widely used in patients with coronary artery disease or hypertension. Short-acting formulations activate the SNS, an action that may be disadvantageous in patients with coronary disease, especially if left ventricular function is impaired. The effects of slow-release formulations on the SNS are unknown.

METHODS

We used microneurography to investigate the influence of nifedipine (5 mg; 10 mg; and slow-release [GITS], 60 mg) on muscle sympathetic nerve activity (MSA) and skin sympathetic nerve activity (SSA) in healthy volunteers.

RESULTS

Peak plasma levels after short-acting and slow-release nifedipine were achieved within 60 min and 330 min, respectively. Short-acting (10 mg, n = 10) and slow-release (n = 10) nifedipine, but not placebo, markedly activated MSA and increased plasma norepinephrine; plasma endothelin increased only with slow-release nifedipine. HR increased after short-acting nifedipine, but not after nifedipine GITS. Nifedipine had no effect on SSA (n = 6). Blockade of cardiac sympathetic activity (with esmolol) led to similar decreases in HR with or without nifedipine, whereas parasympatholysis (with atropine) led to similar increases in HR with or without nifedipine. The cold pressor test markedly increased MSA in all treatment groups and further increased MSA beyond the increase induced by nifedipine.

CONCLUSIONS

Nifedipine markedly increased MSA, but not SSA, independently of drug release formulation. In contrast, HR increased with short-acting, but not with slow-release, nifedipine. Therefore, nifedipine activates cardiac and peripheral sympathetic nerves differently depending on pharmacokinetics. These effects of nifedipine may be disadvantageous in cardiac patients with increased sympathetic activity or congestive heart failure, or both.

Differential effects of captopril and nitrates on muscle sympathetic nerve activity in volunteers

BACKGROUND

The sympathetic nervous system (SNS) is an important regulator of cardiovascular function. Activation of SNS plays an important role in the pathophysiology and the prognosis of cardiovascular diseases such as heart failure, acute coronary syndromes, arrhythmia, and possibly hypertension. Vasodilators such as adenosine and sodium nitroprusside are known to activate SNS via baroreflex mechanisms. Because vasodilators are widely used in the treatment of patients with cardiovascular diseases, the aim of the present study was to assess the influence of clinically used dosages of isosorbide dinitrate and captopril on sympathetic nerve activity at rest and during stimulatory maneuvers.

METHODS AND RESULTS

Twenty-eight healthy volunteers were included in this double-blind placebo-controlled study, and muscle sympathetic nerve activity (MSA; with microelectrodes in the peroneal nerve), blood pressure, heart rate, and neurohumoral parameters were measured before and 90 minutes after the oral administration of 40 mg isosorbide dinitrate or 6.25 mg captopril. Furthermore, a 3-minute mental stress test and a cold pressor test were performed before and 90 minutes after drug administration. Resting MSA did not change after captopril and decreased compared with placebo (P < .05 versus placebo), whereas isosorbide dinitrate led to a marked increase in MSA (P < .05). Systolic blood pressure was reduced by isosorbide dinitrate (P < .05), whereas captopril decreased diastolic blood pressure (P < .05). The increases in MSA, blood pressure, and heart rate during mental stress were comparable before and after drug administration regardless of the medication. During cold pressor test, MSA and systolic and diastolic blood pressures increased to the same degree independent of treatment, but after isosorbide dinitrate, the increase in MSA seemed to be less pronounced. Heart rate did not change during cold stimulation. Plasma renin activity increased after captopril and isosorbide dinitrate (P < .05), whereas placebo had no effect. Endothelin-1 increased after placebo and isosorbide dinitrate (P < .05) but not after captopril.

CONCLUSIONS

Thus, captopril suppressed MSA despite lowering of diastolic blood pressure but allowed normal adaptation of the SNS during mental or physical stress. In contrast, the nitrate strongly activated the SNS under baseline conditions. These findings demonstrate that vasodilators differentially interact with the SNS, which could be of importance in therapeutic strategies for the treatment of patients with cardiovascular diseases.

Endothelin and calcium antagonists in the skin microcirculation of patients with coronary artery disease

BACKGROUND

Endothelin, a potent endothelium-derived vasoconstrictor peptide, is elevated in coronary artery disease (CAD); however, its pathophysiological role is uncertain. Calcium antagonists are widely used in patients with CAD. Using laser Doppler flowmetry, we investigated the influence of two endothelin antagonists and the calcium antagonist diltiazem on endogenous and exogenous endothelin in the skin microcirculation of CAD patients and healthy control subjects.

METHODS AND RESULTS

Both endothelin antagonists and diltiazem applied intradermally induced vasodilation in CAD patients, which was more pronounced with the ETA/ETB antagonist than with the ETA antagonist or diltiazem. Exogenous endothelin led to profound vasoconstriction in CAD patients and healthy volunteers. Both endothelin antagonists and diltiazem blunted the vasoconstriction to exogenous endothelin in CAD patients and young healthy volunteers and less so in old healthy volunteers. However, compared with both endothelin antagonists, a 10-times-higher dose of diltiazem was required. Systemic diltiazem (240 mg, slow release) attenuated endothelin-induced vasoconstriction in CAD patients. Neurogenic vasodilation to exogenous endothelin was inhibited by both endothelin antagonists.

CONCLUSIONS

This study demonstrates that endogenous endothelin of CAD patients contributes to the regulation of vascular tone in the skin microcirculation not only through ETA receptors but also possibly through ETB receptors. Diltiazem inhibited endothelin-induced vasoconstriction, but endothelin antagonists were slightly more effective. Thus, endothelin antagonists represent potent new tools to interfere with the vascular effects of endothelin in CAD patients. Future studies must confirm these findings in other areas of the circulation.

Endothelin and endothelin antagonists: potential role in cardiovascular and renal disease

Endothelin-1 is a recently discovered peptide mainly released from endothelial cells. Hypoxia and ischemia as well as numerous factors such as angiotensin 11, thrombin and transforming growth factor beta 1 stimulate the formation of the peptide. On the other hand the synthesis of endothelin is inhibited by nitric oxide and atrial natriuretic peptide via the formation of cyclic guanosine monophosphate. Released from endothelial cells endothelin-1 mediates transient vasodilation followed by a profound and longlasting vasoconstriction. Endothelin is also a mitogen for smooth muscle proliferation. Endothelins exert their biological effects via activation of specific receptors. Two different receptors have been cloned from mammalian tissues (ET(A) and ET(B) receptors). On vascular smooth muscle cells both receptors mediate contractions. Endothelial cells only express ET(B) receptors linked to the formation of nitric oxide and/or prostacyclin formation. Increased plasma concentrations of endothelin-1 have been described in a variety of diseases such as pulmonary hypertension, arteriosclerosis, renal failure, acute coronary syndromes, heart failure, migraine and vascular diseases. Recently an increasing number of endothelin receptor antagonists have been synthetized, which have been shown to inhibit endothelin-mediated vasoconstriction. Clinical studies are now ongoing to elucidate the pathophysiologic role of endothelin and the potential benefit of the blockade of the system in different disease states.

Increased activation of sympathetic nervous system and endothelin by mental stress in normotensive offspring of hypertensive parents

BACKGROUND

The pathogenesis of essential hypertension is still uncertain, but genetic factors and the sympathetic nervous system are likely to be involved. Sympathetic nerve activity and hormonal circulatory control mechanisms, however, are affected by blood pressure itself. Hence, early functional changes are best investigated in normotensive subjects at risk to develop hypertension, such as normotensive offspring of hypertensive parents.

METHODS AND RESULTS

Muscle sympathetic nerve activity (MSA) was measured in the peroneal nerve of 10 normotensive offspring of parents with essential hypertension and 8 offspring of normotensive parents. Measurements were performed under resting conditions, during a 10-minute period of hypoxia (12.5% O2/87.5% N2) and during a 3-minute mental stress test. The tests were separated by a 30-minute resting period. Plasma samples for determination of norepinephrine and endothelin were collected before and after the tests. Baseline values of MSA were comparable in offspring of hypertensive and normotensive parents. During hypoxia, MSA, heart rate, and norepinephrine and endothelin plasma levels increased in offspring of hypertensive and normotensive parents to a comparable degree, whereas no significant changes in blood pressure and plasma norepinephrine levels were observed in either group. During mental stress, MSA and plasma norepinephrine and endothelin increased only in offspring of hypertensive parents (P < .001 to .01). In parallel, blood pressure increased significantly only in offspring of hypertensive parents (P < .001 to .05) but heart rate increased in both groups (P < .001 to .05).

CONCLUSIONS

The activity of the sympathetic nervous system and plasma norepinephrine and endothelin levels are increased during mental stress only in offspring of hypertensive parents, whereas the response to hypoxia was similar in offspring of hypertensive and normotensive parents, suggesting a genetically determined abnormal regulation of the sympathetic nervous system to certain stressful stimuli in offspring of hypertensive parents. This may play a role in the pathogenesis of essential hypertension.

[Sympathetic nervous system and endothelial function in heart failure]

Congestive heart failure is a frequent cardiovascular disease with a poor prognosis in advanced stages. Activation of neurohumoral systems such as the renin-angiotensin system and the sympathetic nervous system as well as impairment of local regulatory mechanisms (i.e. adrenoceptors, endothelial factors) play an important role in the pathogenesis and prognosis of the disease. The increase in peripheral resistance is due to imbalance of vasoconstrictors and vasodilators in favour of the vasoconstrictors and to changes in endothelial function, i.e. impaired production of nitric oxide, increased production of endothelin. Sodium and volume retention as well as the activation of the renin-angiotensin system increase preload. The sympathetic nervous system, which is known to be an independent negative prognostic factor, is activated and interacts with the renin-angiotensin system; however, up to now it is uncertain, whether these pathophysiological findings contribute to the development of congestive heart failure or if they are only secondary phenomena.

[Therapeutic measures following acute myocardial infarct: differential use of PTCA, surgery and drugs]

Myocardial infarction represents a crossroads in the natural history of coronary artery disease. The prognosis is determined by the severity of coronary artery disease, infarct size (and hence ejection fraction), and age of the patient. After infarction, patients may remain symptomless, or suffer angina, silent ischemia, reinfarction, heart failure or sudden death. Hence patient management after infarction includes (1) estimation of risk, (2) the use of stress tests to detect ischemia and rhythm disorders, (3) PTCA or bypass if required and (4) medical therapy. Cardiac catheterization is indicated in patients with angina or silent ischemia, non-Q wave infarction or large infarctus; its use is less well established in patients without ischemia and left ventricular dysfunction, but this indication is nevertheless increasingly accepted. PTCA is primarily utilized in patients with single or two vessel disease, while coronary bypass surgery is indicated in patients with left main or three vessel disease. All these measures are designed to improve symptoms and prognosis. For secondary prevention medical therapy should be used to treat cardiovascular risk factors (antihypertensive drugs, lipid-lowering drugs etc.), to inhibit platelets (aspirin, ticlopidine) or coagulation (coumarins), to block neurohumoral activation (betablocker, ACE-inhibitors), for vasoconstriction (calcium channel blockers, nitrates) and to suppress arrhythmias. The large number of drugs requires reasoned use depending on the risk profile of the individual patient. Cardiovascular risk factors should be treated appropriately. Platelet inhibitors should be given to all patients except those with atrial fibrillation or large ventricles (coumarins). Betablockers reduce mortality, reinfarction and sudden death after infarction and hence should be used if no contraindications exist. ACE-inhibitors are particularly effective in improving symptoms and prognosis in patients with impaired left ventricular function. Calcium antagonists should be used with caution and only in patients with normal left ventricular function. Nitrates are primarily effective in improving symptoms in patients with angina or heart failure. Antiarrhythmic drugs (amiodarone) are only useful in patients with complex arrhythmias. Digitalis has been shown to improve symptoms in patients with heart failure, while other inotropic drugs are virtually no longer used. These guidelines allow reasoned differential therapy after myocardial infarction to the maximum benefit of the patient and at minimum cost.

Vascular protective effects of ACE inhibitors and calcium antagonists: theoretical basis for a combination therapy in hypertension and other cardiovascular diseases

Hypertension is an important cardiovascular risk factor. High blood pressure per se is not a disease but a hemodynamic alteration associated with vascular disease. Two classes of drugs are especially effective in lowering blood pressure and preventing cardiovascular complications, angiotensin converting enzyme (ACE) inhibitors and calcium antagonists. The hemodynamic effects of ACE inhibitors and calcium antagonists are complementary. While ACE inhibitors inhibit the renin-angiotensin system and reduce sympathetic outflow, calcium antagonists dilate large conduit and resistance arteries. Certain calcium antagonists, such as verapamil, lower heart rate. In the blood vessel wall, the local vascular effects of ACE inhibitors and calcium antagonists are also complementary. While ACE inhibitors inhibit activation of angiotensin I into angiotensin II and prevent the breakdown of bradykinin (which stimulates nitric oxide and prostacyclin formation), calcium antagonists inhibit the effects of vasoconstrictor hormones such as angiotensin II at the level of vascular smooth muscle by reducing calcium inflow and facilitating the vasodilator effects of nitric oxide. Calcium antagonists reduce smooth muscle cell proliferation and atherosclerosis. In hypertensive animals, verapamil and trandolapril normalize endothelial dysfunction. In large angiographic trials, nifedipine and nicardipine reduced the development of new atherosclerotic plaques. After myocardial infarction, verapamil reduces mortality and cardiac events in patients without heart failure. In contrast, ACE inhibitors are effective after myocardial infarction in patients with impaired left ventricular function. Urinary albumin excretion rate decreases during ACE inhibitor therapy or with a calcium antagonist such as verapamil; combination of the two drugs has an additive effect. In resistance arteries, hypertension is associated with an increased media/lumen ratio. ACE inhibitors, but not beta-blockers, markedly improve these structural changes. In summary, ACE inhibitors and calcium antagonists have a complementary profile, both in their hemodynamic and local vascular action. Hence, combination therapy with these two classes of drugs appears particularly useful in patients with hypertension, not only to lower blood pressure, but hopefully to achieve improved cardiovascular protection.

Local regulation of the coronary circulation in health and disease: role of nitric oxide and endothelin

Coronary artery disease is the leading cause of morbidity and mortality in western countries. Its pathogenesis is unknown, but involves enhanced vasoconstriction, increased interaction of platelets and monocytes with the vessel wall, as well as proliferation, migration and extracellular matrix formation of vascular smooth muscle. The endothelium lies in a strategic anatomical position between circulating blood and vascular smooth muscle cells. This supports the concept that dysfunction of these cells significantly contributes to coronary artery disease. Besides other mediators, endothelial cells are a source of nitric oxide and endothelin. Nitric oxide is a vasodilator, an inhibitor of both platelet function and proliferation and migration of vascular smooth muscle. Endothelin is a potent vasoconstrictor that facilitates proliferation. Under pathological conditions, in particular the presence of cardiovascular risk factors, endothelial dysfunction occurs and is a major contributor to the increase in platelet vessel wall interaction, vasoconstriction and proliferation in the coronary system. Endothelium-dependent vasodilation is usually reduced and endothelium-dependent constrictor responses, as well as endothelin production, are augmented. Hence, endothelial cells are important targets and mediators of coronary artery disease.

[Mechanisms of acute coronary syndrome]

The pathogenesis of coronary artery disease is characterized by an increased vasoconstriction, activation of platelet vessel wall interactions as well as the invasion of monocytes into the subintima with deposition of lipids as well as proliferation and migration of vascular smooth muscle cells. In the acute coronary syndromes plaque rupture as well as activation of platelets and coagulation as well as coronary vasoconstriction play an important role. Clinically these mechanisms lead to unstable angina and myocardial infarction. For the understanding of acute coronary syndromes, the mechanisms operative in the healthy blood vessel wall are important. Healthy coronary arteries are in a constant state of vasodilatation, platelets as well as the coagulation cascade are inactivated and vascular smooth muscle cells of the media are quiescent. Endothelial mediators such as nitric oxide, prostacyclin and tissue plasminogen activators and other mediators play an important role in this regard. The continuous release of nitric oxide and prostacyclin keeps the coronary circulation in a state of vasodilatation and inhibits platelet vessel wall interaction. Other mediators of the endothelium also inhibit coagulation and migration and proliferation of vascular smooth muscle cells. On the other hand in patients with cardiovascular risk factors and possibly also in those with genetic disposition as well as with aging, these mechanisms are impaired and in turn increased vasoconstrictor responses of coronary arteries, activation of platelet vessel wall interaction, invasion of monocytes into the subintima with lipid storage and proliferation/-migration of vascular smooth muscle cells occur. A cause oriented therapy of coronary artery disease and of acute coronary syndromes in particular must be based on these pathophysiological mechanisms.

Endothelin and endothelin antagonists: pharmacology and clinical implications

Endothelins (ET) are a family of peptides with potent biological properties. Endothelial cells produce exclusively ET-1 while other tissues produce ET-2 and ET-3. The production of ET requires an increase in intracellular Ca2+. This increase can be induced by physical chemicals (i.e. hypoxia) or receptor-operated stimuli (i.e. thrombin, angiotensin II, arginine vasopressin, transforming growth factor beta 1, interleukin-1). Most of ET is released abluminally towards vascular smooth muscle and less luminally. The main vascular effect of ET are vasodilation (transient), profound and sustained vasoconstriction as well as proliferation of vascular smooth muscle. These biological effects are mediated by distinct receptors. Three ET receptors have been cloned, i.e. ETA-, ETB- and ETC-receptors. In vascular tissue ETA-receptors are expressed on vascular smooth muscle and responsible for vasoconstriction. ETB-receptors are expressed on endothelium and linked to nitric oxide and/or prostacyclin release. Activation of these receptors explains the transient vasodilation with intraluminal application of ET. Vascular smooth muscle cells can express ETB-receptors which contribute to ET-induced vasoconstriction particularly at lower concentrations. The role of the recently cloned ETC-receptor in the vasculature is still uncertain. ET production is increased (as judged from circulating plasma levels) in vascular disease and atherosclerosis in particular, in myocardial infarction and heart failure, pulmonary hypertension and renal disease. ET production is increased in arterial hypertension remains controversial. Non-peptidic ET antagonists have been developed which either block ETA- receptors or ETA- and ETB-receptors simultaneously. The advantage of ETA-receptors is that they leave the endothelium-dependent vasodilation to ET (via ETB-receptor) intact. However, ETB-mediated contraction remains unaffected by these antagonists. In contrast ETA-/ETB-antagonists fully prevent ET-induced vasoconstriction, however, they also inhibit the endothelial effects of the peptide. ET antagonists interfere with the effects of ET in isolated vascular tissue (including that obtained from humans) as well as in vivo. In humans, ETA as well as ETA-/ETB-antagonists inhibit endothelin-induced vasoconstriction. Hence in summary ET are a family of potent peptides with profound effects in the vasculature. Several studies suggest a role of ET in cardiovascular disease. The newly developed ET-antagonists are potent and selective tools to delineate the (patho-)physiological roles of ET and may become a new class of cardiovascular drugs.

[Acute hemolysis with subsequent life-threatening pancreatitis in hemodialysis. A complication which is not preventable with current dialysis equipment]

A retrospective study was undertaken of 14 patients (eleven men, three women; mean age 52 [33-68] years in whom haemolysis had occurred during chronic haemodialysis (n = 12) or haemofiltration (n = 2). The haemolysis was of mechanical cause in eight patients, by an osmotic mechanism in one, and of unknown cause in five. Cardinal symptoms were nausea in 14 patients, abdominal pain in nine, vomiting in eight and raised blood pressure in ten. The plasma was discoloured in all patients and there was also an increase in free haemoglobin (110-2400 mg/dl) and (or) lactate dehydrogenase (311-7403 U/l). In all of eleven patients in whom it was measured the activity of serum amylase and (or) lipase was more than doubled (to 73-2400 U/l and 473-16,740 U/l, respectively). All patients were treated symptomatically, three had a blood exchange, two others plasma separation. Eight patients recovered within a few days, but necrotizing pancreatitis developed in six, three of whom died while two had permanent sequelae. This series shows that dialysis-induced acute haemolysis can cause life-threatening pancreatitis. Narrowings within the extracorporeal circuit, not always recognized in current dialysis equipment, are the most frequent cause of the mechanical haemolysis.

Endothelin receptor antagonists inhibit endothelin in human skin microcirculation

Endothelin is a potent vasoconstrictor peptide produced by endothelial cells, but its role in physiology and disease is uncertain. We investigated the influence of the endothelin-A-selective receptor antagonist PD 147953 and the nonselective endothelin receptor antagonist PD 145065 on the effects of endothelin-1 and endothelin-3 in the skin microcirculation of healthy volunteers, using laser Doppler flowmetry. A double injection model was developed, allowing simultaneous injection of two substances, ie, agonist and antagonist or saline. The injection of saline led to a well-defined vasodilation at the injection site (maximum increase, from 19 +/- 2 to 97 +/- 15 perfusion units at 6 minutes; P < .001; n = 10). Endothelin-1 (10(-12) mol) decreased blood flow (difference from saline control, -79 +/- 14 perfusion units; P < .001; n = 11) within the injection wheal (diameter, 4 to 5 mm), while endothelin-3 had no effect. In the surrounding area (at 8 mm from the injection site), both endothelin-1 (+116 +/- 32 perfusion units; P < .001; n = 11) and endothelin-3 (+59 +/- 16 perfusion units; P < .001; n = 11) markedly increased blood flow. Both endothelin receptor antagonists slightly increased blood flow (maximum difference from control, +56 +/- 18 [PD 147953] and +31 +/- 10 [PD 145065] perfusion units; P < .05; n = 8) and inhibited endothelin-1-induced (P < .01) vasoconstriction. The vasoconstriction to norepinephrine was not affected by the endothelin antagonist PD 147953. Endothelin-1- and endothelin-3-induced vasodilation in the surrounding area were also inhibited by both endothelin antagonists or by lidocaine.(ABSTRACT TRUNCATED AT 250 WORDS)