Haemodynamic and cardiac metabolic effects of the new {beta}1 agonist prenalterol in patients with cardiac failure

Prenalterol, a ß₁ selective agonist, exerts a positiveinotropic action in animal studies as well as in human volunteersand is effective when administered orally. To assess its immediatehaemodynamic and myocardial metabolic effects, we studied theresponse to prenalterol (50 and 100 µg kg^–1 givenintravenously by cardiac catheterization) in 15 patients withcongestive heart failure secondary to coronary artery diseaseor non-ischaemic cardiomyopathy. At peak effect, cardiac indexincreased from 2.6 ± 0.5 to 3.2 ± 0.81 min^–1m² (mean ± S.D.) (P <0.001); peak rate of left ventricularpressure development rose from 963 ± 242 to 1335 ±411 mmHg s^–1 (P < 0.001); left ventriuclar end-diastolicpressure fell from 25 ± 6 to 17 ± 7 mgHg (P <0.001);coronary sinus blood flow increased from 113 ± 39 to148 ± 55 ml min^–1 (P <0.01); myocardial oxygenconsumption was augmented from 12.7 ± 3.9 to 16.4 ±5.8 ml min^–1 (P < 0.001); and heart rate increasedslightly (from 76 ± 12 to 86 ± 14 beats min^–1;(P <0.05)). No significant changes occurred in left ventricularsystolic pressure, stroke volume index, myocardial lactate extractionrate and myocardial arteriovenous oxygen difference, and nopatients developed angina, ECG changes or ventricular arrhythmias.Infusion of prenalterol effectively improved haemodynamic functionand cardiac metabolism in cardiomyopathy. Therefore this agentdeserves further investigation to evaluate its possible rolefor the long-term therapy of patients with chronic heart failure.     

Monitoring of plasma levels of activated protein C using a clinically applicable oligonucleotide‐based enzyme capture assay

Summary. Background: Human‐activated protein C (APC) is a serine protease with anticoagulant, anti‐inflammatory and cytoprotective functions. This feature renders APC to be a promising vascular‐inflammatory biomarker.Objective: The aim of the present study was the development and validation of a technique that allows the measurement of APC plasma levels under practical laboratory conditions.Methods/patients: Based on the APC‐binding ssDNA aptamer HS02‐52G we developed an oligonucleotide‐based enzyme capture assay (OECA) that quantifies aptamer‐captured APC through hydrolysis rates of a fluorogenic peptide substrate. After optimization of pre‐analytical conditions, plasma APC levels were measured in healthy individuals and patients undergoing hip replacement surgery.Results and conclusion: A combination of APC–OECA with an aprotinin‐based quenching strategy allowed APC analysis with a limit of detection as low as 0.022 ± 0.005 ng mL^?1 (0.39 ± 0.10 pmol L^?1) and a limit of quantification of 0.116 ± 0.055 ng mL^?1 (2.06 ± 0.98 pmol L^?1). While APC plasma levels in healthy individuals fell below the quantifiable range of the APC–OECA platform, levels substantially increased in patients undergoing hip replacement surgery reaching peak values of up to 12 ng mL^?1 (214 pmol L^?1). When normalized to the amount of thrombin generated, interindividual variabilities in the APC generating capacity were observed. In general, with a turn‐around time from blood sampling to generation of test results of < 7 h, the APC–OECA platform allows sensitive and rapid determination of circulating APC levels under pathological conditions.     

Myocardial Thallium201imaging in hypertrophic obstructive cardiomyopathy

Thallium ²⁰¹ Myocardial perfusion imaging was performed at restand during exercise in 14 patients with hypertrophic obstructivecardiomyopathy without coronary artery disease. The regionalmyocardial Thallium²⁰¹-uptake and distribution ratio of thesepatients were analysed by a semiquantitalive computerized methodand compared with those of six normal subjects. Four of the14 patients had no Thallium²⁰¹ imaging defect. Out of a totalof260 analysed regions of interest in the remaining patients,five regions with reversible and 25 with irreversible Thallium²⁰¹defects could be demonstrated. Most of these defects were localizedin the interventricular septum. The Thallium²⁰¹ defects werenot related to the age of the patients and there was no relationshipbetween the occurrence of reversible Thallium²⁰¹ defects anda pathological myocardial lactate extraction rate during maximalatrial pacing. In patients with left ventricular outflow obstructionat rest (n= 10) the percentage of irreversible defect regionsin the Thallium²⁰¹-scintigram (8.5%) was more than twice ashigh as in those patients with a provocable pressure gradient(3.9%). These data suggest that hypertrophic obstructive cardiomyopathyis often associated with regional ischemia or fibrosis despitenormal coronary arteries. Therefore, in these patients, Thallium201scintigraphy can not be used as a non-invasive screening methodto exclude or prove coronary artery disease     

Hemodynamic and cardiac metabolic effects of inotropic stimulation with dobutamine in patients with coronary artery disease

The hemodynamic and myocardial metabolic effects of two intravenousdoses (5 and 10 ug/kg/min) of dobutamine were measured in 15patients with congestive heart failure secondary to coronaryartery disease. Dobutamine at 5 µg/kg/min induced an increasein peak rate of left ventricular pressure rise (dp/dt_max) from1004 ± 261 to 1386 ± 469 mm Hg x s^–1, coronarysinus blood flow (CSF) from 98 ± 34 to 128 ± 60ml/min and myocardial oxygen consumption (MVO₂) from 10.5 ±3.8 to 14.3 ± 6.9 ml/min. It decreased mean left ventricularend-diastolic pressure (LVEDP) from 24 ± 6 to 20 ±8 mm Hg. All changes were significant (P < 0.01). No significantchanges occurred in mean heart rate, left ventricular systolicpressure, arterio-coronary venous oxygen content differenceand mean myocardial lactate extraction rate. Dobutamine at 10 µg/kg/min further increased dp/dt_maxto 1545 ± 408 mm Hg x s^–1, CSF to 146 ±75 ml/min and MVO₂ to 17 ± 9.1 ml/min. Because mean heartrate also increased significantly from 73 ± 15 to 90± 23 beats/min it is possible that the concomitant increasein myocardial oxygen demand was no longer offset by the reductionin preload (further decrease of LVEDP to 18 ± 7 mm Hg).Thus, myocardial oxygen demand was inadequately met, myocardiallactate extraction rate decreased significantly (34 ±16 to 14 ± 20%, P < 0.01) and signs of myocardialischemia developed in three of the 15 patients. For this reason, heart rate should be monitored closely if dobutamineis given to patients with limited capacity to increase myocardialblood flow and oxygen delivery to the myocardium.     

An Increase in Endothelial Intracellular Calcium and F-Actin Precedes the Extravasation of Interleukin-2-Activated Lymphocytes

Objective : Interleukin-2 (IL-2) induces protein leakage from the microcirculation and activates lymphocytes; yet it is unclear how it alters endothelial barrier function. Here, we report of a new continuous monitoring system that allows for the continuous measurement and correlation of endothelial calcium, permeability to albumin, and extravasation of lymphocytes. Methods : IL-2 activated lymphocytes (IL-2 LYMPH) or unstimulated lymphocytes (LYMPH) were co-incubated with human microvascular endothelial cells (HMVEC). Endothelial albumin permeability, lymphocyte extravasation, intracellular calcium mobilization, and f-actin distribution were examined using a new continuous monitoring system. Results : The clearance rate of fluorescein isothiocyanate-labeled-human serum albumin (FITC-HSA) in the presence of IL-2 LYMPH peaked at 20 minutes, whereas the clearance rate of LYMPH peaked at 40 minutes. Approximately 40 minutes after the peak in the clearance rate to albumin, extravasation of carboxyfluorescein-labeled lymphocytes was detected. Peak clearance rates for the extravasation of IL-2 LYMPH occurred at approximately 40 minutes after the addition of the lymphocytes to the HMVEC, whereas the peak clearance rate for the LYMPH occurred at 60 minutes after their addition. Both FITC-HSA and lymphocyte extravasation were measured concurrent to endothelial intracellular calcium mobilization by FURA-2. There was an increase in calcium activation after the addition of IL-2 stimulated lymphocytes (71 ± 5.1 nmol/L to 185 ± 18.9 nmol/L) compared with unstimulated lymphocytes (71 ± 5.1 nmol/L to 110 ± 12.2 nmol/L). The addition of IL-2 had little or no effect on endothelial actin, whereas the unstimulated lymphocytes and, to a greater extent, IL-2 LYMPH increased the presence of transversing stress fibers and decreased peripheral actin. Conclusions : The findings reported here suggest that the permeability and extravasation events that occur upon addition of lymphocytes proceeds by a calcium- and actin-dependent mechanism and that incubation of lymphocytes with IL-2 enhances normal lymphocyte mechanisms of extravasation.