L. Donato

Circulating levels of cardiac natriuretic peptides (ANP and BNP) measured by highly sensitive and specific immunoradiometric assays in normal subjects and in patients with different degrees of heart failure

Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels increase in patients with heart failure with the progression of clinical symptoms and with the deterioration of hemodynamics; consequently, assay methods for these peptides may be useful in the follow-up of cardiac patients. Non-competitive immunoradiometric assay (IRMA) methods for ANP or BNP do not generally require preliminary extraction and/or purification of the plasma sample, and so may be more suitable than competitive immunoradiometric assay (RIA) methods for the routinary assay of plasma peptide concentrations. We evaluated the analytical characteristics and clinical usefulness of two IRMAs for plasma ANP and BNP, to verify whether these methods may be considered suitable for the follow-up of patients with heart failure. Both methods are based on the solid-phase sandwich IRMA system, which uses two monoclonal antibodies prepared against two sterically remote epitopes of peptide molecule; the first antibody was coated on the beads solid-phase and the second was radiolabeled with 125I. Blood samples were collected from a brachial vein in ice-chilled disposable polypropylene tubes containing aprotinin and EDTA after the patient had rested for at least 20 min in the recumbent position. Plasma samples were immediately separated by centrifugation and stored at −20 C until assay. The IRMA methods showed a better sensitivity and a wider working range sensitivity (about 2 ng/l) than those of RIA methods. Moreover, the normal range found with these methods (ANP= 16.1±8.6 ng/l, 5.2±2.8 pmol/l, BNP= 8.6±8.2 ng/l, 2.5±2.4 pmol/l) was similar to that generally reported using the most accurate methods, such as the other IRMAs or RIAs, using a preliminary extraction and purification of plasma samples with chromatographic procedures. Our results obtained in patients with different degrees of heart failure indicate that plasma ANP and BNP increase with the progression of clinical symptoms (NYHA class) (ANOVA p<0.0001). Indeed, circulating levels of ANP (R=− 0.701, no.=86) and BNP (R=−0.745, no.=55) were significantly (p<0.0001) and negatively correlated with the left ventricular ejection fraction values. Furthermore, a close curvilinear regression (R= 0.960, no.= 215) was found between ANP and BNP values, because plasma BNP progressively increases more than plasma ANP in patients with different stages of heart failure. In conclusion, IRMA methods are preferable for the measurement of plasma ANP and BNP for experimental studies and routine assay because they are more practicable, sensitive and accurate than RIA procedures. Finally, BNP assay appears to be better than ANP for discriminating between normal subjects and patients with different degrees of heart failure.

Chemical and biological effects of iodination on human albumin

The iodination of human albumin by constant-current electrolysis has been studied up to a substitution degree of 25 iodine atoms per molecule. It has been found that iodination occurs at pH 7 with the theoretical yield, the anodic discharge of the iodide ions being the rate-limiting step of the entire process. Moreover, it has been proved that electrolysis per se has no apparent damaging effect on the albumin. The progressive conversion of the tyrosyl groups to mono- and di-iodinated derivatives has been measured, showing that electrolysis at low current values favours a more homogeneous iodination of the protein. When iodination is carried out by electrolysis, up to 10 iodine atoms can be bound per albumin molecule without affecting its biological behaviour. Iodination procedures employing iodine-monochloride or iodide-iodate have a more pronounced damaging effect, the biological behaviour being modified for substitution degrees of about 3 iodine atoms per albumin molecule. Current concepts about the validity of using radioiodine-labelled albumin as a tracer are reviewed. It is concluded that, when iodination occurs as an isolated process in an otherwise undamaged protein, an extensive degree of substitution of the tyrosine residues does not alter the catabolic pattern of the albumin.

Treatment of end-stage congestive heart failure by extracorporeal ultrafiltration

Abstract Although progress in the field of inotropic, diuretic and vasodilator drugs has markedly improved prognosis in patients with acute congestive heart failure (CHF), 1 chronic CHF is a growing problem because of its increased incidence 2 as a result of increased survival from acute episodes and because patients may become nonresponsive to medical treatment. Extracorporeal ultrafiltration (ECUF) makes possible rapid removal, with fewer adverse effects than hemodialysis and peritoneal dialysis, of fluid, electrolytes and other solutes. 3 Therefore, ECUF could be used in patients with refractory CHF as a means of temporarily relieving intolerable or intractable respiratory distress and refractory edema or as an emergency measure to reduce cardiac preload. Furthermore, ECUF could eventually correct the electrolyte alterations frequently found in these patients as a result of long-standing diuretic treatment. This report documents clinical results, both in the acute phase and in the follow-up period, in 8 patients with end-stage CHF who underwent ECUF.

Evaluation of Myocardial Blood Perfusion in Man with Radioactive Potassium or Rubidium and Precordial Counting

The myocardial clearance of potassium may be obtained by precordial counting after a single intravenous injection of K42Cl or Rb86Cl. The theoretical foundations of the method and the technic developed have been presented and discussed.The distribution of the values obtained in normal subjects and in subjects with coronary insufficiency is in agreement with the clinical expectancy, and changes of the observed MCK after nitroglycerin agree with the results obtained by other investigators who measured coronary blood flow by the indirect Fick method.In agreement with the observations of other investigators in rats and dogs, the amount of K42 or Rb86 in the myocardium was found to change very little for an appreciable time interval after the first circulation, despite the significant recirculation and the decreasing arterial concentration. This observation and the fact that MCK values in normal subjects closely agree with the accepted values for coronary blood flow confirm Sapirsteins findings in rats and dogs, and support the view that the organ uptake of Rb86 or K42 immediately after single intravenous injection reflects the fractional organ blood flow.As obtained with the present technic, and similarly with the indirect Fick method, MCK reflects the flow per gram of myocardium and not the total coronary blood flow. MCK, however, has the advantage that every unit volume of myocardium, no matter how well it is perfused or through which vessels it is drained, contributes to the precordial counting rate in variable proportions determined by the efficiency of the counting method.

Perindopril and indapamide reverse coronary microvascular remodelling and improve flow in arterial hypertension

Objectives Patients and animal models of arterial hypertension are characterized by structural and functional abnormalities of the coronary microcirculation. Using a translational approach, we ascertained whether antihypertensive treatment can reverse microvascular remodelling and improve myocardial perfusion. Methods In 20 hypertensive patients with left ventricular hypertrophy, blood pressure, left ventricular mass index and myocardial blood flow were measured at baseline and after 6 months of treatment with perindopril + indapamide. In spontaneously hypertensive rats, blood pressure, coronary flow and histomorphometry of intramural coronary arterioles were measured after 8 weeks of treatment with placebo or perindopril + indapamide. Results In patients, treatment decreased blood pressure (161 ± 10/96 ± 5 to 136 ± 12/81 ± 6 mmHg; P < 0.0001) and left ventricular mass index (93 ± 16 to 85 ± 17 g/m2; P < 0.01) while increasing baseline (0.69 ± 0.13 to 0.88 ± 0.36 ml/min per g; P < 0.05) and hyperaemic myocardial blood flow (1.42 ± 0.32 to 1.94 ± 0.99 ml/min per g; P < 0.05). In rats treated with perindopril + indapamide (n = 11), blood pressure was 93 ± 18/55 ± 18 mmHg compared to 215 ± 18/161 ± 17 mmHg in placebo (n = 6; P < 0.001), baseline flow was unchanged whilst hyperaemic coronary flow was 19.89 ± 3.50 vs. 12.15 ± 0.99 ml/min per g, respectively (P < 0.01). The medial area of intramural arterioles was 1613 ± 409 with perindopril + indapamide and 8118 ± 901 μm2 with placebo (P < 0.001). Conclusion In patients with arterial hypertension and left ventricular hypertrophy, perindopril + indapamide reduced blood pressure and left ventricular mass index and improved resting and hyperaemic myocardial blood flow. Data in rats provide evidence that the improvement in coronary flow observed after treatment is due to reverse remodelling of intramural coronary arterioles and improved microvascular function.

Altered Tissue Degradation and Distribution of Atrial Natriuretic Peptide in Patients With Idiopathic Dilated Cardiomyopathy and Its Relationship With Clinical Severity of the Disease and Sodium Handling

BACKGROUND Atrial natriuretic peptide (ANP) has been suggested to play an important role in heart failure, preserving cardiorenal homeostasis through maintenance of the sodium balance and inhibition of the detrimental effects of the neurohormonal vasoconstrictor system. The current study was designed to investigate whether there is a disturbed renewal and distribution of ANP in patients with idiopathic dilated cardiomyopathy (IDC) with differing clinical severity of disease. METHODS AND RESULTS We used a tracer method to perform a cross-sectional study of 15 IDC patients with differing clinical severity (New York Heart Association functional class I to III), prospectively divided into two groups according to their functional class (group 1, classes I and II; group 2, classes II-III and III). Eleven normotensive, nonobese male volunteers also were studied as a control group. Main ANP kinetic parameters were derived from the disappearance curve of the labeled hormone after the bolus injection of [125I]-labeled ANP. A high-performance liquid chromatography technique was used to separate the radiolabeled hormone in each plasma sample. Patients in group 1 showed higher ANP metabolic clearance rate (MCR) (2731.9 +/- 726.2 mL.min-1.m-2) than patients of group 2 (1718.4 +/- 621.2 mL.min-1.m-2) and control subjects (1873.1 +/- 551.2 mL.min-1.m-2). ANP disposal (MCR) positively correlated with biological hormonal effect (urinary sodium excretion) both in control subjects and in patients. In IDC patients of both groups, however, MCR values were always higher (approximately doubled) than the values found in control subjects at the corresponding sodium excretion. This finding indicates that a reduced ANP biological activity is associated with hormone degradation in patients. Moreover, patients of group 2 showed significantly higher ANP production rates (395.6 +/- 183.8 ng.min-1.m-2) than group 1 (166.0 +/- 139.0 ng.min-1.m-2) and control subjects (130.7 +/- 105.4 ng.min-1.m-2) despite a marked reduction in sodium excretion. Patients with IDC showed a progressive reduction in the total distribution volume (group 1, 19.8 +/- 5.8 L/m2; group 2, 12.7 +/- 6.9 L/m2; control subjects, 27.0 +/- 11.6 L/m2) of the hormone; this probably was due to a reduction in exchanges of ANP with peripheral tissues. CONCLUSIONS Our study demonstrates a markedly altered degradation and distribution of ANP in patients with IDC, even in those at the early stage of clinical disease (classes I and II, group 1) who have ANP plasma levels in the normal range.

Measurement of coronary blood flow by external counting with radioactive rubidium. Critical appraisal and validation of the method.

Method Radioactive Rubidium: Critical Appraisal and Validation of the Measurement of Coronary Blood Flow by External Counting with Online ISSN: 1524-4539 Copyright

Regional Myocardial Blood Flow and Coronary Reserve in Hypertensive Patients The Effect of Therapy

SummaryPatients with essential arterial hypertension demonstrate abnormal vasodilator capacity either during increased cardiac metabolic demand or during pharmacological vasodilation. Structural and functional damage to the coronary microcirculation has been proposed as one of the major causes of impaired coronary reserve in this disease.To assess the role of microvascular impairment in regional myocardial blood flow (MBF), 27 patients with essential hypertension were evaluated by dynamic positron emission tomography (PET) at rest, during atrial pacing and after dipyridamole infusion and compared with 13 healthy subjects. All patients had normal coronary arteries, 17 had moderate to severe hypertension and 10 had mild hypertension. Baseline mean MBF of 0.97 ± 0.25 ml/min/g was significantly increased to 1.60 ± 0.38 during atrial pacing and 2.35 ± 0.95 after dipyridamole infusion (p < 0.01); however, mean flow during atrial pacing and after dipyridamole infusion was significantly lower than in healthy subjects (2.15 ± 0.73 and 3.71 ± 0.86 ml/min/g, p < 0.05 and p < 0.01, respectively). The MBF response to atrial pacing and dipyridamole infusion was similarly depressed in patients with mild and severe hypertension.The study was repeated after 6 months of antihypertensive treatment with the calcium antagonist verapamil or the angiotensin converting enzyme (ACE) inhibitor enalapril in a subgroup of 20 patients as part of a randomised, single-blind clinical trial. This study is still in progress; the initial 16 patients treated with verapamil or enalapril showed an obvious improvement in MBF values during atrial pacing and after dipyridamole infusion after 6 months of therapy (mean MBF: 2.10 ± 0.64 and 2.99 ± 1.63 ml/min/g. respectively, p < 0.05 vs pretreatment values).In conclusion, obvious impairment of MBF during atrial pacing and after dipyridamole infusion was observed in hypertensive patients with normal coronary arteries and this appeared unrelated to the severity of hypertension. Therapy with verapamil or enalapril improved coronary reserve and MBF response to an increase in myocardial oxygen demand.

Ultrafiltration: a rational treatment for heart failure.

Patients with late-stage congestive heart failure with significant fluid overload respond well to ultrafiltration. The response is relatively long-standing and includes enhanced responsiveness to diuretics. Ultrafiltration is simple and highly cost effective. Furthermore, it possesses many advantages over massive or drastic pharmacological therapy. In the following paper, we report our own experience and review the world literature.

Circulating levels of cardiac natriuretic hormones measured in women during menstrual cycle

Alterations in fluid and electrolyte balance represent a common complaint by women during different stages of the menstrual cycle; however, conflicting results concerning the possible role of plasma Atrial Natriuretic Peptide (ANP) modifications during the menstrual cycle have been reported. This may be due to differences in assay methods or in the clinical protocol adopted. Moreover, possible variations in plasma Brain Natriuretic Peptide (BNP) levels during the menstrual cycle have not been studied. We measured the plasma levels of ANP and BNP by means of two highly sensitive and specific immunoradiometric assay (IRMA) methods in 19 normal women without premenstrual symptoms, in order to evaluate whether significant modifications of these hormones are present during the menstrual cycle. Because it is well-known that circulating levels of cardiac hormones show great variations in normal subjects due to their rapid plasma half lifes, blood samples were collected at 2.5-min intervals over a 15-min period on the 5th and 24th days of the cycle. The mean (±SD) values of ANP (follicular phase=15.1±8.7 pg/ml; luteal phase=14.8±9.5 pg/ml) and of BNP (follicular phase=13.0±15.0 pg/ml; luteal phase= 11.2±11.4 pg/ml) did not show significant variations during the menstrual cycle. Moreover, the variability of ANP values (CV=24.8±13.2%) was significantly higher (p=0.0318) than that of BNP values (CV=16.5±8.9%), and a significant correlation was found between the mean ANP and BNP values of the individual women studied (R=0.407, p=0.0437). The values of estradiol, progesterone, LH, FSH and prolactin did not correlate with the ANP or BNP values. In conclusion, our results indicate that circulating levels of cardiac hormones do not show any significant modifications during the menstrual cycle in healthy women.