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At least 1,297 records · Page 72Linked to original sources
PubMed1986

Physical and functional association of the atrial natriuretic peptide receptor with particulate guanylate cyclase as demonstrated using detergent extracts of bovine lung membranes.

Coupling of the atrial natriuretic peptide (ANP) receptor to particulate guanylate cyclase has been demonstrated kinetically and chromatographically using bovine lung plasma membranes and their detergent extracts. Addition of ANP to the membrane suspension stimulated guanylate cyclase activity 2-5-fold indicating the presence of ANP-sensitive particulate guanylate cyclase. The enzyme retained the ability to respond to ANP even after solubilization with digitonin. Characterization of the solubilized enzyme by gel filtration and affinity chromatography revealed that the ANP receptor and particulate guanylate cyclase exist as a functionally but not covalently linked stable complex.

Animals↗
PubMed2005

A Kir2.1 gain-of-function mutation underlies familial atrial fibrillation.

The inward rectifier K(+) channel Kir2.1 mediates the potassium I(K1) current in the heart. It is encoded by KCNJ2 gene that has been linked to Andersen's syndrome. Recently, strong evidences showed that Kir2.1 channels were associated with mouse atrial fibrillation (AF), therefore we hypothesized that KCNJ2 was associated with familial AF. Thirty Chinese AF kindreds were evaluated for mutations in KCNJ2 gene. A valine-to-isoleucine mutation at position 93 (V93I) of Kir2.1 was found in all affected members in one kindred. This valine and its flanking sequence is highly conserved in Kir2.1 proteins among different species. Functional analysis of the V93I mutant demonstrated a gain-of-function consequence on the Kir2.1 current. This effect is opposed to the loss-of-function effect of previously reported mutations in Andersen's syndrome. Kir2.1 V93I mutation may play a role in initiating and/or maintaining AF by increasing the activity of the inward rectifier K(+) channel.

Adult↗
PubMed2001

The normal sequence of right and left atrial contraction.

OBJECTIVE: To study the sequence of atrial activation and the interatrial electromechanical delay (IEmD) noninvasively in healthy subjects during sinus rhythm (SR). METHODS AND RESULTS: In 66 SR healthy subjects P-wave activation was analyzed by means of vectorcardiography. The timing of atrial contractions was measured as the intervals between the P-wave and the A-wave of the Doppler right and left ventricular inflows (P-A(t) and P-A(m)), and IEmD was calculated as the algebraic difference P-A(m)- P-A(t). In the horizontal plane the vectorcardiographic P-loop was anteroposterior ("typical", 41 subjects), anterior (18), or posterior (7). IEmD (mean +/- SE 17 +/- 8 ms) was directly related to R-R and P-R intervals. IEmD was significantly shorter in anterior and posterior P loops than in the typical (6.5 +/- 5.3 and 8.1 +/- 10.1, respectively, vs 24.2 +/- 3.1 ms). In the posterior P-loop group, who exhibited longer P-A(t), mitral E-wave velocity and E/A ratio were reduced, and left atrial booster function was increased. CONCLUSION: IEmD was widely variable in SR, reflecting the origin site of sinus impulse, which independently influenced ventricular filling dynamics.

Adolescent↗
PubMed2005

Atrial natriuretic peptide inhibits ovarian functions in female mice.

OBJECTIVE: To investigate the effects of atrial natriuretic peptide (ANP) on ovarian regulation in mice through intraperitoneal administration. STUDY DESIGN: Forty-two ICR strain female mice were divided into seven groups, including one control. Each mouse received ovarian hyperstimulation. ANP was prepared with saline at concentrations of 0 (as control), 2, 4, 8, 10, 20, and 30 ng/g of body weight. The solution was intraperitoneally applied to each referred group (n = 6) 1 h before the hMG and hCG injections. The mice were sacrificed next morning and blood samples were collected for analysis. RESULTS: A significant reduction in both ovarian weight and the number of oocytes was found as the ANP dosage increased. ANP treatment decreased both serum estradiol and progesterone levels. The pituitary FSH and LH contents elevated significantly by ANP at a dosage larger than 4 ng/g of body weight; however, both serum FSH and LH levels remained unchanged. Histologically, there were remarkable ovarian inhibitory features, i.e. reduction in size and number of follicles, arrest of follicular growth and diminution of ovulation. CONCLUSION: Intraperitoneal administration of ANP inhibits the follicular growth, ovulation and steroidogenesis in female mice. These effects are attributed to the direct action of ANP on ovaries.

Animals↗
PubMed1987

Effects of centrally administered atrial natriuretic peptide on renal functions.

In order to assess the effects of centrally administered atrial natriuretic peptide (ANP) on renal water and electrolytes handling, arterial blood pressure, plasma vasopressin, renin activity, aldosterone, and ANP concentrations, synthetic alpha-human ANP (alpha-hANP) was administered intracerebroventricularly at a dose of 2.6 pmol.kg-1.min-1 for 30 min in pentobarbital-anaesthetized dogs (N = 6). In the control study (N = 6), artificial cerebrospinal fluid was infused. Intracerebroventricular administration of alpha-hANP increased significantly urine flow from 178 +/- 37 to 303 +/- 43 microliter/min (mean +/- SEM), sodium excretion from 27.3 +/- 8.9 to 54.4 +/- 10.5, mumol/min, potassium excretion from 16.1 +/- 3.7 to 24.0 +/- 5.1 mumol/min, and osmolar and negative free water clearances, accompanied by a significant rise in renal blood flow from 77.0 +/- 14.6 to 94.9 +/- 16.9 ml/min. Whereas glomerular filtration rate fell significantly, blood pressure and heart rate did not change. Plasma ANP, aldosterone, and PRA did not change significantly during the experiment, but plasma AVP were slightly but significantly decreased from 52 +/- 11 to 34 +/- 6 nmol/l. On the other hand, these parameters showed no changes in the control study, except a significant fall in glomerular filtration rate and a significant rise in PRA. Thus, it has been confirmed that ANP centrally brings about diuresis, natriuresis, and kaliuresis via some unknown mechanisms independent of the release of these hormones.

Aldosterone↗
PubMed1994

[Surgery for atrial fibrillation by the Cox technique. Apropos of 2 cases].

The authors report the cases of two patients who underwent surgery of atrial fibrillation by Cox's technique. In one case, it was associated with mitral valvuloplasty for atrial fibrillation of 4 years' duration; sinus rhythm was restored on the 19th postoperative day; it persisted at 11 months without antiarrhythmic drugs. On the other case, it was associated with mitral valve replacement for atrial fibrillation of 7 years' duration in a patient with dilated cardiomyopathy and a poor left ventricle; sinus rhythm was restored by electrical cardioversion during the 4th postoperative month; it persisted at 9 months with antiarrhythmic therapy. Cox's technique allows: 1) definitive suppression of atrial fibrillation, 2) restoration of atrioventricular synchronisation, 3) preservation of atrial transport function. The indications are paroxysmal or permanent atrial fibrillation, invalidating and resistant to medical therapy; atrial fibrillation of over 3 years' duration associated with mitral regurgitation requiring valvular repair and atrial fibrillation of invalidating primary cardiomyopathy.

Aged↗
PubMed2001

Compensatory responses of left atrial conduit flow to atrial fibrillation with acute myocardial infarction in a canine model.

The aim of this study was to examine the interaction of acute atrial fibrillation (Af) and acute myocardial infarction (AMI) on left atrial (LA) and left ventricular (LV) filling in atrioventricular (A-V) sequential paced, open chest, anesthetized dogs. Left atrial conduit function was determined from pulmonary venous flow (PVF) and detailed analysis of early diastolic flow with the use of micromanometers and transmitral Doppler echocardiography. We studied 8 dogs with regular ventricular rates to avoid the confounding effect of ventricular arrhythmia in Af. In the control stage, Af increased the diastolic PVF volume to the left atrium compared with that during regular A-V pacing (from 0.58 +/- 0.11 mL/beat to 0.70 +/- 0.13 mL/beat, P <.05), as a compensatory response to the impaired systolic PVF volume (from 0.56 +/- 0.12 mL/beat to 0.41 +/- 0.11 mL/beat, P <.05). As a result, cardiac output was maintained. However, in the AMI stage, Af decreased cardiac output (from 0.95 +/- 0.32 L/min to 0.80 +/- 0.23 L/min, P <.05 versus AMI with A-V pacing), and decreased diastolic PVF volume (from 0.46 +/- 0.13 mL/beat to 0.33 +/- 0.14 mL/beat, P <.05 versus AMI with A-V pacing). These changes were associated with a prolonged LV isovolumic pressure decay rate. Our study demonstrates that Af does not affect cardiac output in the setting of normal LV function at a controlled ventricular rate because enhanced LA conduit flow compensates for impaired LA reservoir function. In contrast, in the setting of AMI, the compensatory response to Af is attenuated because of abnormal LV relaxation, resulting in a decrease in cardiac output.

Animals↗
PubMed1992

Clinical and electrophysiologic effects of intravenous dofetilide (UK-68,798), a new class III antiarrhythmic drug, in patients with angina pectoris.

Dofetilide (UK-68,798) is a new class III antiarrhythmic agent. In animal experiments it selectively prolongs the refractory periods parallel to the action potential duration without any influence on upstroke velocity or conduction parameters. The present double-blind, placebo-controlled study was designed to show the effect of dofetilide on basic electrophysiologic parameters in patients with coronary artery disease. Eighteen patients (aged 31 to 64 years) with symptoms of stable angina pectoris admitted for routine coronary angiography were recruited. They were randomly allocated to receive either placebo or 1 of 2 dose levels of dofetilide intravenously with 6 patients in each group. Paired electrophysiologic variables were compared before and after administration of dofetilide. Both active dose levels produced significant prolongations (p less than 0.05) of 10 to 23% in atrial effective refractory period, 6 to 16% in ventricular effective refractory period and 11 to 15% in ventricular functional refractory period. Atrial functional refractory period was prolonged by 14 to 22% at the high-dose level (p less than 0.05). No effect was observed on conduction parameters (PA, AH, HV, PR or QRS intervals), sinus cycle length or sinus node recovery. The selective prolongation of the refractory periods in both atrium and ventricle, combined with a lack of effect on cardiac conduction parameters, indicates that this drug could be useful in the treatment of both atrial and ventricular reentrant tachyarrhythmias and fibrillation.

Adult↗
PubMed1982

[Physiologic stimulation: the future or a passing phase?].

Pacing techniques achieving normal AV synchrony are termed "physiologic". All rely on an atrial pacing or/and pacing system usually coupled with ventricular pacing. The major advantage is haemodynamic, usually related to the varying ventricular pacing rate obtained with atrial sensing systems only. Problems related to the more complex implantation technique, the cost of this system, its limited lifetime, more frequent iatrogenic complications and in particular the risk of reentry electronic "tachycardias" with the presently available models including an atrial sensing function, should limit the use of these devices to patients who really need AV synchrony if the implantation is technically possible, i.e., in our opinion, 10 to 15% of patients.

Arrhythmias, Cardiac↗
PubMed1988

Interventricular septal motion and left ventricular function in patients with atrial septal defect.

In order to assess whether the paradoxical motion of the interventricular septum seen in patients with atrial septal defect (ASD) is due to a true abnormality in septal contraction, eight patients with ASD (age, 1.6-17 years) and eight age-matched control patients were studied using qualitative and quantitative two-dimensional (2D) and M-mode echocardiography. 2-D-echocardiographic images recorded from the parasternal short-axis projection at the level of the papillary muscles and 2D-directed M-mode tracings at this level were obtained. Comprehensive wall motion analysis of the left ventricular (LV) endocardial and epicardial borders was performed using both fixed reference and center of mass (floating reference) models. Our results indicate that interventricular septal wall motion and function are normal in patients with ASD. The apparent "paradoxical" motion is due to excessive anterior motion of the entire left ventricle, and is present only when a fixed reference system is used to assess myocardial motion, but is not present when a center of mass (floating reference system) is employed. Left ventricular function assessed by % area and perimeter change, mean radial shortening fraction, and mean radial wall thickening (2D) as well as LV shortening fraction and septal and posterior wall thickening (M-mode) was not significantly different between the two groups. Standard M-mode tracings can therefore be used to assess LV function despite this apparent abnormal septal motion.

Adolescent↗
PubMed2006

The effect of patient sex on recurrence of atrial fibrillation following successful direct current cardioversion.

BACKGROUND: The effect of patient sex on recurrence of atrial fibrillation after a successful direct current cardioversion is unknown. METHODS: This prospective study included 773 patients (486 [63%] men and 287 [37%] women) undergoing successful direct current cardioversion of atrial fibrillation between May 2000 and July 2003. Patient characteristics at presentation were recorded. The primary end point was the time between cardioversion and the first documented recurrence of arrhythmia. RESULTS: At presentation, women were older and had a higher prevalence of hypertension and valvular disease compared with men. In addition, women had worse mechanical left atrial appendage function. Arrhythmia recurrence was more prevalent in women (50.0% at 1 year compared with 43.4% in men, and 75.8% at 2 years compared with 67.0% in men; P = .03). On the basis of multivariate analysis, patient sex was a significant predictor of arrhythmia recurrence. There was no significant difference in overall mortality between men and women. CONCLUSIONS: Women were more likely than men to have recurrence of atrial fibrillation after successful direct current cardioversion. Patient sex should be taken into account with other clinical factors when making the decision about cardioversion for atrial fibrillation.

Aged↗
PubMed2004

Determinants of atrial fibrillation development in patients with hypertrophic cardiomyopathy.

Predictors of the development of atrial fibrillation (AF) in patients who have hypertrophic cardiomyopathy (HC) have not been extensively studied, although, in these patients, AF contributes to the exacerbation of symptoms and the development of heart failure. The present study determined the role of left atrial (LA) function in the development of AF in patients who have HC. One hundred fifty consecutive patients who had HC, had no history of AF, and who were followed for 5.2 +/- 2.9 years constituted the study population. Using M-mode echocardiography, we measured LA function as global LA fractional shortening and LA diameter. LA volume was measured from 2-dimensional 4-chamber views by the method of disks. During follow-up, 20 patients developed AF. LA function was an independent predictor of AF (odds ratio 0.716, p = <0.001), whereas LA diameter and volume were predictors in addition to age. Kaplan-Meier analysis showed that LA dysfunction carried a high risk of AF. Thus, in patients who have HC, LA function is a strong predictor of AF development and is independent of age.

Adolescent↗
PubMed1995

Atrioventricular sequential pacing using transesophageal atrial pacing in combination with a temporary DDD pacemaker for atrial tracking and ventricular pacing.

OBJECTIVE: To determine whether atrioventricular (A-V) sequential pacing can be accomplished using transesophageal atrial pacing (TAP) in combination with a temporary DDD pacemaker for tracking the TAP stimuli and pacing the ventricle via temporary epicardial electrodes. DESIGN: Prospective; patients enrolled consecutively. SETTING: Nonuniversity teaching hospital. PARTICIPANTS: Ten adults undergoing cardiac surgery requiring cardiopulmonary bypass. INTERVENTIONS: Two to six hours after the termination of cardiopulmonary bypass, atrial pacing was initiated via TAP. The atrial system of a temporary DDD pacemaker was connected to surface electrocardiogram (ECG) electrodes. If the temporary pacemaker could track the TAP stimuli and emit pacing stimuli resulting in ventricular capture, A-V sequential pacing was considered to have occurred. The patients were immediately restudied in the same manner with the change that the temporary DDD pacemaker sensed the TAP stimuli via temporary atrial bipolar epicardial electrodes rather than surface ECG electrodes. MEASUREMENTS AND MAIN RESULTS: Dual pacemaker A-V sequential pacing was accomplished in 17 out of 20 attempts. The atrial system of the temporary DDD pacemaker was able to sense the TAP stimulus via temporary atrial bipolar epicardial leads in 10 out of 10 patients and directly from surface ECG electrodes (right arm/left arm) in 7 out of 10 patients. CONCLUSIONS: This report demonstrates that it is possible to A-V sequentially pace using TAP in combination with a temporary DDD pacemaker for tracking the TAP stimulus and pacing the ventricle via temporary epicardial leads. This technique may be useful when A-V sequential pacing is needed and functional temporary atrial leads are not available.

Adult↗
PubMed2005

Effects of human atrial natriuretic peptide on cardiac function and hemodynamics in patients with high plasma BNP levels.

Both atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) bind preferentially to the natriuretic peptide A receptor. Therefore, we hypothesized that the positive inotropic and lusitropic effects of ANP might be blunted in patients with moderate congestive heart failure and high BNP levels. Micromanometers and conductance catheters were used to obtain relatively load-insensitive left ventricular pressure-volume analysis in order to compare the myocardial and load-altering actions of ANP in 20 patients with low and high plasma BNP levels. In the low-BNP group (plasma BNP levels <230 pg/ml), ANP infusion significantly decreased end-systolic pressure and end-diastolic pressure and volume, increased end-systolic elastance, and shortened left ventricular relaxation. By contrast, in the high-BNP group (plasma BNP levels >230 pg/ml), the effect of ANP infusion on LV contractility was blunted but its beneficial effects on LV diastolic function and LV-arterial coupling remained. Thus, ANP infusion may improve LV diastolic function even in patients with moderate heart failure and high plasma BNP levels.

Aged↗
PubMed1985

Pre-operative sinus node function in adult patients with atrial septal defect (ostium secundum type).

The authors studied, pre-operatively, the sinus node function in adult patients with secundum atrial septal defect and large left-right shunts, using Holter ECG and electrophysiological tests. Sinus node electrophysiological tests were found abnormal in 17 out of 26 patients; on the contrary, Holter monitoring was always within normal limits. The authors believe that concealed sinus node dysfunction existing before surgical correction may be a cause of early, acute, and reversible, post-operative sick sinus syndrome.

Adolescent↗
PubMed1991

Atrial natriuretic factor responses to volume expansion in pregnant and nonpregnant sheep.

Isotonic volume expansion results in atrial natriuretic factor release by cardiac myocytes. Because pregnancy produces well-established alterations in fluid homeostasis and cardiovascular function, changes in atrial natriuretic factor responses may also occur. This study compares plasma atrial natriuretic factor responses to short-term volume expansion in pregnant and nonpregnant sheep. Seven pregnant and six nonpregnant ewes were chronically instrumented and subjected to a series of four experiments consisting of a control group (no infusion) and groups that received 10 ml/kg, 25 ml/kg, and 40 ml/kg isotonic saline infusion over a 30-minute period. The order of the experiments was random and separated by greater than or equal to 48 hours. Plasma atrial natriuretic factor, osmolality, right atrial pressure, blood pressure, and urine flow were measured over a 150-minute observation period. After volume expansion, plasma atrial natriuretic factor levels rose significantly from 39 +/- 4 pg/ml (mean +/- SEM) to 49 +/- 7 pg/ml, 36 +/- 4 pg/ml to 62 +/- 19 pg/ml, and 39 +/- 6 pg/ml to 67 +/- 14 pg/ml in the nonpregnant group 10 ml/kg, 25 ml/kg, and 40 ml/kg experiments, respectively. In the pregnant groups, plasma atrial natriuretic factor levels rose from 50 +/- 2 pg/ml to 75 +/- 20 pg/ml, 43 +/- 5 pg/ml to 57 +/- 5 pg/ml, and 46 +/- 4 pg/ml to 67 +/- 7 pg/ml, respectively. Differences in atrial natriuretic factor responses were not seen between pregnant and nonpregnant groups at any volume expansion level. As expected, atrial pressure and urine flow significantly increased after all volume expansion experiments. Pregnant and nonpregnant groups were similar with respect to atrial pressure and urine flow responses. Over various volume expansion levels significant associations were seen between atrial pressure, atrial natriuretic factor, and urine flow. These relationships were unaltered by pregnancy. In summary, atrial natriuretic factor responses to volume expansion do not appear to differ between pregnant and nonpregnant sheep.

Animals↗
PubMed1989

Plasma atrial natriuretic factor and graft function in renal transplant recipients.

In order to determine the relationships between allograft function and the recipient's plasma concentrations of atrial natriuretic factor (ANF), plasma ANF was measured by radioimmunoassay for 14 days after cadaveric renal transplantation in 9 patients aged 19-64 years. All received immunosuppression with prednisolone, azathioprine, and cyclosporine. No patient was in heart failure. During the study period, six grafts functioned, and three were nonfunctioning--two due to rejection and one to acute tubular necrosis. Plasma ANF concentration at the time of transplantation was 48 +/- 16 pmol/L (mean +/- SEM) range 15-145 pmol/L. In the six patients with functioning grafts, ANF declined in parallel with the fall in serum creatinine (658 +/- 35 to 210 +/- 34 mumol/L). In the three with nonfunctioning grafts, serum creatinine and plasma ANF concentration both increased. There was overall a significant linear relation between serum creatinine and plasma ANF (r = 0.527, P less than 0.001). The changes in plasma ANF after renal transplantation bore no relationship to changes in body weight or blood pressure. However, plasma ANF concentration was related to allograft fractional sodium excretion (r = 0.687, p less than 0.001). We conclude that elevated plasma ANF concentrations in end-stage renal disease are restored to normal by successful renal transplantation, implying that renal function is a determinant of plasma ANF concentration. Circulating plasma ANF may also have a direct effect on allograft sodium excretion.

Adult↗