Increased circulating atrial natriuretic factor (ANF) release during induced ventricular tachycardia

Interaction of prolactin, ANPergic, oxytocinergic and adrenal systems in response to extracellular volume expansion in rats

The present study evaluated the effect of acute extracellular volume expansion (EVE) induced by intravenous injection of isotonic (0.15 m NaCl) or hypertonic saline (0.3 m NaCl) on prolactin, corticosterone, vasopressin, oxytocin and atrial natriuretic peptide (ANP) secretion. Male Wistar rats were treated with bromocriptine, sulpiride or dexamethasone. After isotonic and hypertonic EVE, the control group showed a significant increase in the plasma concentrations of prolactin, corticosterone, ANP and oxytocin. The increase in ANP and oxytocin levels in response to hypertonic EVE was more pronounced than to isotonic EVE. Bromocriptine and sulpiride treatments did not modify corticosterone, ANP and oxytocin responses to either isotonic or hypertonic EVE. The increases in prolactin and oxytocin, but not ANP, were blocked in dexamethasone pretreated rats. In conclusion, isotonic or hypertonic EVE induced an increase in the plasma concentrations of prolactin, corticosterone, ANP and oxytocin. The increases in ANP and oxytocin were independent of plasma concentrations of prolactin. The increases in prolactin and oxytocin were blocked by the inhibition of the hypothalamo-pituitary-adrenal (HPA) axis by dexamethasone. However, dexamethasone did not alter the increase in ANP secretion induced by isotonic or hypertonic EVE. Therefore, prolactin might participate in regulation of the hydroelectrolytic balance in mammals; however, in the present study, there was no evidence for direct interaction with ANPergic and oxytocinergic systems. In addition, the responses of prolactin and oxytocin induced by isotonic or hypertonic EVE are modulated by the HPA axis.

Atrial natriuretic peptide level after cardioversion of chronic atrial fibrillation

Heart endocrine studies concerning patients with chronic atrial fibrillation (AF) have become increasingly important. Atrial natriuretic peptide (ANP) is released from atrial myocytes. The increased level of ANP in patients with AF is probably caused by the hemodynamic effect of the arrhythmia. The aim of this study was to explore plasma ANP levels in patients with chronic AF and to describe plasma ANP concentration changes following sinus rhythm (SR) restoration. The study group was comprised of 42 patients, aged between 43 and 76 years with chronic AF (more than 1 month) and a relatively controlled ventricular response (85.8+/-11.3 beats/min). Plasma ANP levels were measured before and 24 h after AF cardioversion. The control group comprised of 11 subjects. All had normal SR without history of AF and were compatible in age, sex and concomitant diseases with the examined group. ANP level values were expressed as mean+/-standard deviation. The mean plasma ANP level in the AF group was significantly higher than in the control group (59.5+/-15.6 vs. 34.3+/-10.2 pg/ml, P<0,001). Electrical or pharmacological cardioversion was performed in 42 patients. SR was successfully restored in 35 patients. Plasma ANP concentrations decreased significantly from baseline values (from 59.4+/-16.6 to 31.4+/-15.0 pg/ml, P<0.001) 24 h after cardioversion in the successful group, while they remained unchanged (60.2+/-10.7 to 59.4+/-10.4 pg/ml, NS) in patients with an unsuccessful cardioversion.

CONCLUSION

The mean concentration of ANP in patients with chronic AF was nearly two-times higher than in the control group with sinus rhythm. Conversion to SR was associated with a significant decrease and normalization in plasma ANP concentrations.

Vasoactive peptide release in relation to hemodynamic and metabolic changes during rapid ventricular pacing

Plasma atrial natriuretic peptide (ANP) concentration increases during ventricular arrhythmias and rapid ventricular pacing but less is known about plasma brain natriuretic peptide (BNP) and endothelin (ET-1). In the present study concentrations of ANP, the amino terminal part of the proANP (NT-proANP), BNP, and ET-1 were measured in the coronary sinus and femoral artery before and at the end of rapid ventricular pacing in 15 patients with coronary arterial disease. The changes were compared with the changes in mean arterial blood pressure, pulmonary capillary wedge pressure (PCWP), transcardiac differences in pH, pCO2, lactate, and norepinephrine. There was an increase in PCWP and a transient decrease in blood pressure after initiation of pacing. Pacing caused a decrease in ST-segment, transcardiac difference of norepinephrine, lactate extraction, pCO2 difference, and an increase in pH difference. Concentration of ANP in the coronary sinus and femoral artery and its transcardiac difference increased during pacing (P < 0.001), whereas changes in NT-proANP were small and BNP and ET-1 levels remained unchanged. The change in transcardiac ANP difference correlated with the change in lactate (r = 0.53, P < 0.05) but not that of norepinephrine, PCWP, or blood pressure. The results show that the plasma concentration of ANP increases more than that of NT-proANP during rapid ventricular pacing. Ischemia-induced release of ANP and its diminished elimination may contribute to the increased plasma ANP level.

Hemodynamic recovery, atrial natriuretic peptide, and catecholamines during simulated ventricular tachycardia: effects of ventriculoatrial conduction

Ventriculoatrial (VA) sequence and neurohumoral responses may be important modulators of hemodynamic recovery during VT. We studied the effects of VA conduction on blood pressure recovery, and levels of atrial natriuretic peptide (ANP), epinephrine, and norepinephrine during simulated VT. After diagnostic coronary angiography, VT was simulated by rapid right ventricular pacing (150 beats/min, 3 mins) in a consecutive series of patients. Whenever the patients demonstrated VA dissociation during ventricular pacing, they were included in the study. After 10 minutes of recovery, a group of nine patients then underwent an additional VA pacing (150 beats/min, 3 mins, VA delay of 150 msec). Intra-arterial blood pressure was continuously monitored, and plasma ANP and catecholamine levels were measured before, during, and after both pacing protocols. The mean arterial pressures declined rapidly by 26% and 30% after initiation of ventricular and VA pacing, respectively. The blood pressure then gradually recovered, the hemodynamic recovery being better during VA pacing. Plasma ANP and catecholamine levels increased toward the end of both pacing periods. The observed increase in ANP concentration was more prominent during VA pacing than ventricular pacing (P < 0.001), whereas catecholamine levels increased similarly. The results show that during simulated VT hemodynamic recovery is partially dependent on VA sequence. The increases in circulating ANP and catecholamines occur too slowly to account for the rapid changes in blood pressures observed after initiation of simulated VT. Therefore, other mechanisms, such as reflex stimulation of the sympathoadrenergic nervous system, must be involved, too. ANP release increases when atrial contraction frequency increases, but the exact determinants for this release remain unknown.

The acute effects of induced tachycardia on coronary sinus and arterial plasma levels of atrial natriuretic peptide and on arterial catecholamines

Atrial natriuretic peptide (ANP) was measured in coronary sinus (CS) plasma in seven patients with induced tachycardia. Right atrial pressure (RAP) and femoral artery (FA) levels of ANP, noradrenaline (NA) and adrenaline (A) were measured before and after 5 min with tachycardia. During tachycardia, ANP in CS plasma increased from 381 +/- 273 (mean +/- SD) to 1376 +/- 1191 pmol l-1 (p < 0.0001), and ANP levels in FA plasma from 89 +/- 48 to 231 +/- 151 pmol l-1 (p < 0.005). A significant increase was observed for peak RAP, whereas mean RAP remained unaltered. While no correlation existed between the increase in CS plasma ANP level and RAP, significant correlations were found between the changes in FA plasma ANP and RAP, and between FA plasma levels of ANP and NA. Following tachycardia, significant correlations were found both between ANP in CS and FA plasma and between the changes in these plasma levels. Whereas the changes in FA plasma levels of ANP during tachycardia seems dependent of RAP and arterial plasma levels of NA, the CS plasma ANP level appears to be independent of the two factors, probably because CS plasma ANP are drained mainly from the left side of the heart.

Plasma atrial natriuretic peptide response to direct current cardioversion of atrial fibrillation in patients with mitral stenosis

OBJECTIVES

The purpose of this study was to evaluate the effect of direct current cardioversion therapy on the plasma concentration of atrial natriuretic peptide and to determine the main factors that influence the change in plasma atrial natriuretic peptide levels in patients with atrial fibrillation.

BACKGROUND

In atrial arrythmias, whether the fast atrial rate itself or the associated elevation of atrial pressure, or both, contributes to the increase in atrial natriuretic peptide is a subject of debate.

METHODS

In 15 patients with mild mitral stenosis, plasma atrial natriuretic peptide levels were measured and transmitral flow pattern was obtained by continuous wave Doppler echocardiography immediately before cardioversion and at 5 min, 4 h, 24 h and 5 days after direct current cardioversion. Mean mitral pressure gradient and atrial filling fraction were calculated on the basis of transmitral flow.

RESULTS

In three patients who did not have a successful return to sinus rhythm, plasma atrial natriuretic peptide levels remained elevated after cardioversion. In 12 patients who maintained sinus rhythm, plasma atrial natriuretic peptide levels were significantly reduced from 79 +/- 29 to 36 +/- 11 pg/ml 4 h after cardioversion to sinus rhythm. However, the mitral pressure gradient did not change significantly during the observation period. There were progressive increases in atrial filling fraction throughout the observation period. From 4 h to 5 days after direct current cardioversion, plasma atrial natriuretic peptide levels gradually increased concomitantly with the recovery of atrial mechanical function.

CONCLUSION

The reduction of plasma atrial natriuretic peptide levels after direct current cardioversion might be due to recovery from the high rate of atrial firing and not to an alteration in the mitral pressure gradient. Direct current cardioversion itself does not seem to influence atrial natriuretic peptide secretion. The increase in atrial natriuretic peptide levels from 4 h to 5 days after cardioversion concomitantly with an increase in atrial filling fraction may be due to recovery of atrial mechanical function.

Atrial natriuretic factor release during rapid ventricular pacing: interplay between autonomic and hemodynamic stimulants

Plasma levels of atrial natriuretic factor (ANF) and norepinephrine are markedly elevated during episodes of ventricular tachycardia. Although atrial distention appears to be the major stimulus for ANF release, reflex changes in autonomic tone might also contribute. Plasma ANF and norepinephrine levels, sinus node cycle length, systolic blood pressure, and mean right atrial pressure were therefore assessed during rapid right ventricular pacing at 150 beats/min for 10 minutes. In five patients (group 1) observations were made without autonomic blockade, and another five patients (group 2) had ventricular pacing after cardiac autonomic blockade. In group 1 systolic blood pressure fell during ventricular pacing from 122 +/- 4 to 105 +/- 5 mm Hg (p < 0.02), norepinephrine levels increased from 195 +/- 26 to 411 +/- 71 pg/ml (p < 0.02), and sinus node cycle length decreased from 936 +/- 99 to 688 +/- 58 msec (p < 0.02). Right atrial pressure was elevated from 2.6 +/- 0.6 to 7.4 +/- 0.6 mm Hg (p < 0.02), and ANF levels increased from 161 +/- 23 to 240 +/- 26 pg/ml (p < 0.05). Whereas systolic blood pressure, norepinephrine, sinus cycle length, and right atrial pressure returned promptly to baseline levels when ventricular pacing was stopped, ANF levels continued to rise (296 +/- 37 pg/ml; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Supraventricular tachycardia, right atrial pressure, atrial natriuretic peptide and polyuria--a necessary sequence?

The release of atrial natriuretic peptide (ANP) may be stimulated by tachycardia and the evidence from human studies suggests that this is mediated by a rise in atrial pressure. However, animal experiments suggest that tachycardia can by itself increase ANP levels without increasing right atrial pressure (RAP). We report here the case of a healthy volunteer who had supraventricular tachycardia (SVT) whilst participating in a study evaluating the relationship between changes in RAP and changes in ANP. The ANP levels rose following the SVT but there was no rise in RAP, suggesting that heart rate can modulate ANP levels without changes in RAP as has been shown in animal experiments.

Blood pressure, plasma atrial natriuretic peptide and catecholamines during rapid ventricular pacing and effects of beta-adrenergic blockade in coronary artery disease

To study neurohumoral control mechanisms of the hemodynamic response to ventricular tachycardia, arterial blood pressure, plasma atrial natriuretic peptide (ANP) and catecholamine levels were monitored during simulated ventricular tachycardia before and after administration of beta blockade. Tachycardia was simulated by ventricular pacing at 150 beats/min for 150 seconds in 9 patients without and 14 with angiographically demonstrable coronary artery disease (CAD). The effects of intravenous propranolol (0.15 mg/kg) were evaluated in 7 control subjects and in 13 patients with CAD. Arterial blood pressure decreased to its minimum within 5 seconds after onset of pacing in all patients, the decrease being 27 and 30% (p = not significant) in the groups without and with CAD, respectively. Propranolol did not affect the initial decline, but blunted subsequent recovery. The ANP baseline levels were similar in both groups, increasing by 60% (p less than 0.05) and 71% (p less than 0.02) in the groups without and with CAD, respectively, during ventricular pacing. After administration of propranolol the increase in ANP was 180% in both groups. Rapid ventricular pacing did not affect catecholamine levels before propranolol, but after propranolol norepinephrine increased by 71 (p less than 0.02) and 97% (p less than 0.01) in patients without and with CAD, respectively. There was a significant correlation (r = 0.53, p = 0.001) between pacing-induced ANP and norepinephrine changes, but changes in arterial blood pressure did not correlate with those in either of these hormones. Thus, beta-adrenergic blockade blunts blood pressure recovery during simulated ventricular tachycardia. However, this is partly counterbalanced by increased circulating norepinephrine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid changes of atrial natriuretic peptide concentration during percutaneous transluminal coronary angioplasty

In 34 patients undergoing routine coronary angioplasty, concentrations of atrial natriuretic peptide (ANP), plasma renin (PR), and plasma aldosterone (PA) were estimated before, during, and after vessel occlusion and were correlated with hemodynamic changes. For the group as a whole, averaged right atrial pressure rose significantly (p less than 0.001) from 4.4 +/- 1.8 mm Hg at baseline to 6.7 +/- 3.0 mm Hg during vessel occlusion, and average right atrial ANP concentrations increased significantly (p less than 0.005) from 50.1 +/- 18.8 pg/ml to 59.7 +/- 21.4 pg/ml during balloon inflation. Data analysis of subgroups did not show any differences in right atrial pressure elevations between patients with left anterior descending artery (LAD) or right coronary artery (RCA) disease; ANP elevation was significant only in patients with LAD occlusion (p less than 0.001). In individual patients no statistically significant correlations were found to be present between changes in right atrial pressures and changes in atrial ANP concentrations. During vessel occlusion, PR dropped from 0.86 +/- 1.11 ng/ml/hr to 0.65 +/- 0.85 ng/ml/hr (p less than 0.001) in all patients, and PA decreased from 63.0 +/- 50.9 ng/ml to 52.2 +/- 43.4 ng/ml (p less than 0.01). Our data support the concept that, although an increase in right atrial pressure leads to ANP release in the majority of patients, atrial pressure and stretch are not the only regulatory factors of ANP release in humans.

Atrial natriuretic peptide response to cardioversion of atrial flutter and fibrillation and role of associated heart failure

Plasma atrial natriuretic peptide (ANP) concentrations were measured before and 1 hour after cardioversion in 40 patients (27 with atrial flutter and 13 with atrial fibrillation) admitted for elective cardioversion. Fourteen (11 with atrial flutter and 3 with atrial fibrillation) had clinical evidence of congestive heart failure (CHF). Conversion to sinus rhythm was successful in 39 patients. The mean ANP concentration in the entire group decreased after cardioversion from 38 +/- 4 to 17 +/- 2 pmol/liter (p less than 0.001). In the subgroup with CHF, the ANP level, which was not significantly higher than that in the group without CHF, decreased from 47 +/- 8 to 19 +/- 3 pmol/liter (p less than 0.01). Neither mode of cardioversion (spontaneous 1, pharmacologic 2 and direct-current countershock 36) nor associated CHF influenced ANP response to cardioversion. One patient with atrial flutter and "failed cardioversion" had unchanged ANP level. The decrease after cardioversion in ANP concentration correlated with its control level (r = 0.88, p less than 0.001) but not with the decrease in heart rate. The ANP level in patients with atrial fibrillation was 45 +/- 9 vs 38 +/- 5 pmol/liter in those with atrial flutter (difference not significant). Arrhythmia duration, left atrial size, and ventricular rate or arterial blood pressure did not correlate with ANP concentration in any subgroup. It is concluded that (1) the ANP level is elevated comparably in patients with both atrial flutter and fibrillation regardless of the presence or absence of CHF; and (2) the level decreases, independent of the mode of cardioversion or presence of CHF, promptly after successful cardioversion.

Atrial natriuretic peptide levels reflect hemodynamic changes under pacemaker stimulation

Pacemaker stimulation influences plasma levels of atrial natriuretic peptide (ANP). This study evaluated in individuals without impaired myocardial function whether a consecutive increase of pacing rates results in reduced alteration of plasma ANP levels mirroring a putative decrease of atrial contribution to cardiac output. In nine resting patients with DDD pacemakers, absolute and relative ANP plasma levels were determined under DDD (175 msec AV delay) and VVI pacing at a pacing rate of 72, 82, 92, and 113 beats/min. When pacing rates were consecutively increased, higher plasma ANP concentrations were measured. However, the differences in relative ANP levels were nearly identical. Therefore, it seems likely that the atrial contribution to cardiac output at high pacing rates is less important than at lower frequencies, at least when the overall myocardial function is not impaired.

Plasma prohormone atrial natriuretic peptides 1-98 and 31-67 increase with supraventricular and ventricular arrhythmias

Recently two peptides consisting of amino acids (AA) 1-30 and 31-67 of the N-terminus of the 126 AA prohormone of atrial natriuretic factor (pro ANF) as well as atrial natriuretic factor (ANF, AA 99-126; C-terminus) were found to have vasodilatory and natriuretic properties. These peptides as well as ANF circulate in man as part of the N-terminus of the prohormone. To determine if the polyuria, associated with both ventricular and supraventricular arrhythmias, is associated with increased circulating concentrations of the N-terminus and C-terminus of the ANF prohormone, 20 individuals with spontaneous arrhythmias, including ten persons with atrial fibrillation, six with paroxysmal supraventricular tachycardia, and four with ventricular tachycardia, were evaluated before and after conversion to sinus rhythm. In all 20 patients, the circulating concentrations of the whole N-terminus (ie, AA 1-98), the midportion of the N-terminus (pro ANF 31-67) that circulates as a distinct 3900 molecular weight peptide after being proteolytically cleaved from the N-terminus, and the C-terminus were significantly higher (p less than 0.001) than their concentration in 54 persons with sinus rhythm. With conversion to sinus rhythm, the plasma C-terminus concentration of these 20 arrhythmia patients decreased to the level of persons with sinus rhythm within 30 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of intravenous procainamide during ventricular tachycardia

Radionuclide angiography was used to study the hemodynamic effects of intravenous procainamide during stable monomorphic ventricular tachycardia. In four patients studied without procainamide, the ejection fraction was 25% +/- 2.4% during normal sinus rhythm, dropped to 11.3% +/- 2.2% (p less than 0.05) at the onset of ventricular tachycardia, increased to 16.7% +/- 1.7% after remaining in ventricular tachycardia for 10 minutes, and returned to 25.3% +/- 3.7% in sinus rhythm. In the 10 study patients, ejection fraction dropped from 36% +/- 5.8% in sinus rhythm to 25% +/- 5.1% in ventricular tachycardia (p less than 0.2). Ejection fraction decreased further (23% +/- 5.0%) following low doses of procainamide (140 +/- 52 mg) despite cycle length prolongation (354 +/- 18 msec versus 373 +/- 21 msec, p less than 0.5). In 8 of 10 patients, there was a progressive increase in the ejection fraction (28.8% +/- 4.1%). Ventricular tachycardia onset also resulted in a decrease in cardiac output and end-diastolic and end-systolic volumes. Two patients who tolerated procainamide in sinus rhythm showed hemodynamic collapse secondary to procainamide during ventricular tachycardia. We conclude that in some patients hemodynamic intolerance to an antiarrhythmic drug may only become evident during ventricular tachycardia.

Concentrations of plasma atrial natriuretic factor during and after reversion of ventricular tachycardia

Plasma concentrations of immunoreactive atrial natriuretic factor were considerably increased (mean 745 (376) pg/ml) in 15 patients during spontaneous ventricular tachycardia. There was no significant relation, however, between concentrations of plasma atrial natriuretic factor and systolic arterial blood pressure during tachycardia. Samples taken 30 minutes and 24 hours after reversion of ventricular tachycardia to sinus rhythm showed that, although plasma concentrations of atrial natriuretic factor had fallen significantly, they were still raised after 24 hours. Raised concentrations of atrial natriuretic factor during ventricular tachycardia did not seem to contribute significantly to the hypotension that is often associated with the arrhythmia.

[Atrial natriuretic factor]

Although ANF research started 30 years ago, the atrial natriuretic factor (ANF) was only discovered recently (1981). The presence of such a factor has been suspected for many years because of histological and physiological arguments. In 1956, Kish found "dense granules" in the atrial walls of guinea pigs. Gauer and Henry could explain some of their experimental results on diuresis and natriuresis only by suggesting the presence of a third hormonal factor, but neither by the renin-angiotensin system, nor the anti-diuretic hormone. Hall et al. were the first to recognize a link between the granules and water and sodium metabolism. But it was De Bold who published the crucial experiment in 1981: injecting right atrial extracts to anaesthetized rats rapidly induced intense and transitory diuresis and natriuresis. ANF was born, and, at the same time, the concept of the heart as an endocrine gland. Indeed, ANF corresponds to the strict definition of a hormone. It has the following properties: natriuresis and diuresis via an increase in glomerular filtration fraction without any major changes in renal plasma flow; direct vasodilation of the large arteries with only few effects on small arterioles and veins. The stimuli for ANF secretion are mechanical and pharmacological, especially drugs currently used by anaesthetists. Atrial distension is the main mechanical stimulus. An increase in atrial transmural pressure is always followed by a release in ANF, but this effect is not constant for increases in intra-luminal pressure. It is the former pressure gradient alone that reflects the volume of the right atrium, the mechanical stimulus for ANF secretion. Tachycardia, or, more precisely, an increase in the atrial contraction rate, also leads to an important release of ANF. Cardiac nerves are not necessary for this, as demonstrated by studies in heart transplant patients. Only few pharmacological agents have been shown to really stimulate ANF secretion. In rats, morphine has a direct secretory effect, whereas ketamine hydrochloride, diethylether and chloral hydrate do so by increasing the release of catecholamines. The effects of alpha, beta adrenergic agonists and calcium agonists remain controversial. ANF, which has diuretic and vasodilator effects, plays a part, together with the renin-angiotensin system and the anti-diuretic hormone, in blood volume control in mammals. However, it has a special role to play, because it is a rapid release hormone: rapid vascular filling leads to an increase in ANF in less than 1 minute, with a parallel increase in diuresis.