Raised plasma concentrations of atrial natriuretic peptide are independent of left atrial dimensions in patients with chronic atrial fibrillation

Isolated atrial amyloid: a potential contributor to morbidity and mortality following cardiac surgery

OBJECTIVES

Diffuse cardiac amyloidosis is a significant diagnosis with a poor prognosis. Isolated atrial amyloidosis (IAA) is the most common form of cardiac amyloidosis caused by accumulation of alpha-atrial natriuretic peptide. IAA has been associated with dysrhythmia, but otherwise remains a poorly characterized condition. The impact of incidental IAA on postoperative outcome following cardiac surgery has not previously been reported. The purpose of this study was to examine the impact of isolated atrial amyloid on patient outcomes following cardiac surgery.

METHODS

A retrospective analysis was performed of all patients having excision of the left atrial appendage during cardiac surgery at our centre over a 5-year period. Patients with histological evidence of IAA were compared to patients without this diagnosis. IAA was diagnosed by immunohistochemistry for atrial natriuretic peptide.

RESULTS

A total of 167 patients underwent left atrial appendage excision and of these 26 (15.6%) were found to have IAA. Preoperative characteristics were similar between the 2 groups. A significantly greater proportion of patients with IAA experienced dysrhythmia requiring implantation of a permanent pacemaker (23.1% vs 7.8%, P = 0.03). There was also a significantly elevated incidence of perioperative death in the IAA group (11.5% vs 1.4%, P = 0.03) and inferior 1-year survival (84.6% vs 96.5%, P = 0.02).

CONCLUSIONS

The presence of IAA may be associated with inferior outcomes following cardiac surgery, with increased morbidity in the early postoperative period and inferior long-term survival. Knowledge of the diagnosis preoperatively may facilitate management of patients.

Mineralocorticoid Receptor Antagonism in Patients With Atrial Fibrillation: Findings From the ORBIT-AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) Registry

Background

Mineralocorticoid receptor antagonist (MRA) therapy may be beneficial to patients with atrial fibrillation (AF), but little is known about their use in patients with AF and subsequent outcomes.

Methods and Results

In order to better understand MRA use and subsequent outcomes, we performed a retrospective cohort study of the contemporary ORBIT‐AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) registry. AF progression and cardiovascular outcomes were compared using propensity‐matched Cox proportional hazards modeling according to MRA use at baseline and new MRA use at follow‐up versus patients with no MRA use. Among 7012 patients with nonpermanent AF, 320 patients were taking MRA at enrollment, and 416 patients initiated MRA use during follow‐up. The mean patient age was 72.5 years, 56.3% were men, and 70.4% had paroxysmal AF. Among all patients taking MRAs, 434 (59.0%) had heart failure, 655 (89.0%) had hypertension, and 380 (51.6%) had both. After adjustment, new MRA use was not associated with reduced AF progression (hazard ratio, 1.18; 95% confidence interval, 0.88–1.58; P=0.27) but showed a trend towards lower risk of stroke, transient ischemic attack, or systemic embolism (hazard ratio, 0.17; 95% confidence interval, 0.02–1.23; P=0.08). Results were similar for a comparison of new MRA users and baseline MRA users compared with nonusers.

Conclusions

In community‐based outpatients with AF, the majority of MRA use was for heart failure and hypertension. MRA use also trended towards lower adjusted stroke risk. Future studies should test the hypothesis that MRA use may decrease the risk of stroke in patients with AF.

Cardiac adrenergic control and atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, and it causes substantial mortality. The autonomic nervous system, and particularly the adrenergic/cholinergic balance, has a profound influence on the occurrence of AF. Adrenergic stimulation from catecholamines can cause AF in patients. In human atrium, catecholamines can affect each of the electrophysiological mechanisms of AF initiation and/or maintenance. Catecholamines may produce membrane potential oscillations characteristic of afterdepolarisations, by increasing Ca(2+) current, [Ca(2+)](i) and consequent Na(+)-Ca(2+) exchange, and may also enhance automaticity. Catecholamines might affect reentry, by altering excitability or conduction, rather than action potential terminal repolarisation or refractory period. However, which arrhythmia mechanisms predominate is unclear, and likely depends on cardiac pathology and adrenergic tone. Heart failure (HF), a major cause of AF, causes adrenergic activation and adaptational changes, remodelling, of atrial electrophysiology, Ca(2+) homeostasis, and adrenergic responses. Chronic AF also remodels these, but differently to HF. Myocardial infarction and AF cause neural remodelling that also may promote AF. beta-Adrenoceptor antagonists (beta-blockers) are used in the treatment of AF, mainly to control the ventricular rate, by slowing atrioventricular conduction. beta-Blockers also reduce the incidence of AF, particularly in HF or after cardiac surgery, when adrenergic tone is high. Furthermore, the chronic treatment of patients with beta-blockers remodels the atria, with a potentially antiarrhythmic increase in the refractory period. Therefore, the suppression of AF by beta-blocker treatment may involve an attenuation of arrhythmic activity that is caused by increased [Ca(2+)](i), coupled with effects of adaptation to the treatment. An improved understanding of the involvement of the adrenergic system and its control in basic mechanisms of AF under differing cardiac pathologies might lead to better treatments.

Plasma Natriuretic Peptide Concentrations as a Predictor for Successful Catheter Ablation in Patients With Drug-Refractory Atrial Fibrillation

BACKGROUND

The concentrations of atrial and brain natriuretic peptides (ANP and BNP) are elevated in patients with atrial fibrillation (AF), but the usefulness of their measurement before and after AF ablation has not been reported.

METHODS AND RESULTS

The concentrations of the natriuretic peptides were evaluated in 54 patients undergoing catheter ablation for drug-resistant paroxysmal and persistent AF without heart failure. Based on the outcome, the patients were divided into 2 groups: successful (n=42) or failure (n=12). All patients were asked to keep a log of the duration and frequency of their symptoms and underwent 24-h ECG monitoring at least once after the ablation. The plasma BNP and ANP concentrations, most of which were well below the heart failure range, exceeded the normal range in 69% and 26% of the patients, respectively. The BNP concentration decreased after ablation in the success group (49+/-43 to 27+/-28 pg/ml; p<0.05), however, it was unchanged in the failure group (46+/-35 to 70+/-37 pg/ml; p=0.46). A value of the DeltaBNP (BNP after ablation - BNP before ablation) of </=0 pg/ml identified a successful ablation with a sensitivity of 83% and specificity of 83%. The plasma ANP concentration did not differ statistically between the 2 groups before and after the ablation.

CONCLUSION

A moderate elevation in the BNP concentration is often found in patients with symptomatic paroxysmal and persistent AF, and a reduction in the plasma BNP concentration shortly after the ablation may indicate a successful outcome.

Hemodynamic and Neurohormonal Predictors and Consequences of the Development of Atrial Fibrillation in Dogs With Chronic Heart Failure

BACKGROUND

Heart failure increases the risk of atrial fibrillation (AF), which frequently results in heart failure progression. This prospective study examined the contribution of hemodynamic and neurohormonal activation to the spontaneous occurrence of AF in heart failure, and assessed the effects of AF on left ventricular (LV) function and neurohormonal activation.

METHODS AND RESULTS

Heart failure (LV ejection fraction [LVEF] 25%-30%) was induced in 27 dogs via sequential coronary microembolizations. Hemodynamic and neurohormonal measurements were performed at 1 month (prior to development of AF) and 4 months post-embolization. During the time between measurements, 10 dogs developed spontaneous AF. Plasma norepinephrine concentration (PNE) at 1 month was higher in animals that subsequently developed AF (576 + 101 vs. 425 + 197 pg/mL, P = .03). There were no significant differences between the groups in 1-month LV end-diastolic pressure (LVEDP), pulmonary artery wedge pressure (PAWP), cardiac output, end-diastolic volume (EDV), LVEF, or plasma renin activity (PRA). At 4 months, cardiac output was lower (2.1 + .4 vs. 2.6 + .6 L/h, P = .02) and PNE was higher (1036 + 857 vs. 508 + 288 pg/mL, P = .03) in dogs with AF versus those in sinus rhythm. There were no significant differences between groups in 4-month LVEDP, PAWP, EDV, LVEF, or PRA.

CONCLUSION

Spontaneous AF in heart failure was preceded by a significant increase in PNE. In animals that developed AF, there was a further decline in cardiac output and increase in PNE.

Molecular Determinants of Altered Ca 2+ Handling in Human Chronic Atrial Fibrillation

Background— Abnormal Ca 2+ handling may contribute to impaired atrial contractility and arrhythmogenesis in human chronic atrial fibrillation (cAF). Here, we assessed the phosphorylation levels of key proteins involved in altered Ca 2+ handling and contractility in cAF patients.

Methods and Results— Total and phosphorylation levels of Ca 2+ -handling and myofilament proteins were analyzed by Western blotting in right atrial appendages of 49 patients in sinus rhythm and 52 cAF patients. We found a higher total activity of type 1 (PP1) and type 2A phosphatases in cAF, which was associated with inhomogeneous changes of protein phosphorylation in the cellular compartments, ie, lower protein kinase A (PKA) phosphorylation of myosin binding protein-C (Ser-282 site) at the thick myofilaments but preserved PKA phosphorylation of troponin I at the thin myofilaments and enhanced PKA (Ser-16 site) and Ca 2+ -calmodulin protein kinase (Thr-17 site) phosphorylation of phospholamban. PP1 activity at sarcoplasmic reticulum is controlled by inhibitor-1 (I-1), which blocks PP1 in its PKA-phosphorylated form only. In cAF, the ratio of Thr-35–phosphorylated to total I-1 was 10-fold higher, which suggests that the enhanced phosphorylation of phospholamban may result from a stronger PP1 inhibition by PKA-hyperphosphorylated (activated) I-1.

Conclusions— Altered Ca 2+ handling in cAF is associated with impaired phosphorylation of myosin binding protein-C, which may contribute to the contractile dysfunction after cardioversion. The hyperphosphorylation of phospholamban probably results from enhanced inhibition of sarcoplasmic PP1 by hyperphosphorylated I-1 and may reinforce the leakiness of ryanodine channels in cAF. Restoration of sarcoplasmic reticulum–associated PP1 function may represent a new therapeutic option for treatment of atrial fibrillation.

Time course for recovery of atrial mechanical and endocrine function post DC cardioversion for persistent atrial fibrillation

We prospectively determined the time course of recovery of atrial mechanical and endocrine function in patients following DC cardioversion for persistent atrial fibrillation (AF). Twenty-three consecutive patients underwent successful DC cardioversion (mean age 64 years, 20 male). By 28 days, nine had reverted to atrial fibrillation. Recovery of atrial mechanical (peak A wave velocity) and endocrine function (atrial natriuretic peptide, ANP) were assessed at four time points: immediately pre-cardioversion, and then 4 h, 7 and 28 days post. The 14 patients maintaining sinus rhythm formed the success group. In this group, peak A wave velocity increased significantly over time from 0.28+/-0.03 m/s (mean+/-S.E.M.) at 4 h to 0.50+/-0.03 m/s at day 7 and 0.67+/-0.05 m/s at day 28 (p<0.001). Plasma ANP was 150+/-34 pg/ml immediately prior to DC cardioversion in the success group. This showed an initial dip at 4 h to 44+/-9 pg/ml (p<0.001). By day 7, plasma ANP had increased to 105+/-21 pg/ml (p<0.05 vs. baseline and 4 h) and then appeared to remain constant, being 102+/-19 pg/ml at day 28 (p=0.06 vs. baseline). A similar early reduction in ANP levels was seen in the group who subsequently reverted to atrial fibrillation. Baseline ANP levels did not predict subsequent successful maintenance of sinus rhythm. Initial "stunning" in both atrial mechanical and endocrine function occurs in patients following DC cardioversion for atrial fibrillation. Whilst endocrine function appears to fully recover by day 7, mechanical function continues to improve beyond day 7.

B-Type Natriuretic Peptide in Organic Mitral Regurgitation

Background— B-type natriuretic peptide (BNP) activation observed in cardiac diseases is a predictor of poor outcome; however, in organic mitral regurgitation (MR), BNP determinants and prognostic value are unknown.

Methods and Results— We prospectively enrolled 124 patients with chronic organic MR (aged 63±15 years, 60% males) in whom we measured BNP level and simultaneously quantified MR degree, left ventricular (LV) remodeling, and left atrial (LA) volumes and analyzed long-term outcome. Baseline BNP level (54±67 pg/mL, median 31 pg/mL) was associated univariately with multiple clinical and echocardiographic characteristics, but in multivariate analysis, independent determinants of BNP, beyond age and sex (both P ≤0.01), were LV end-systolic volume index, LA volume, atrial fibrillation, and symptoms (all P <0.02). Conversely, MR degree was not independently associated with BNP. During follow-up, patients with high versus low BNP (≥31 versus <31 pg/mL) displayed lower survival rates (at 5 years, 72±10% versus 95±5%, P =0.03) and higher rates of the combined end point of death and heart failure (at 5 years, 42±10% versus 16±7%, P =0.03). In multivariate analysis, with adjustment for age, sex, functional class, MR severity, and ejection fraction, BNP was independently predictive of mortality (hazard ratio per 10 pg/mL, 1.23 [95% CI 1.07 to 1.48], P =0.004) and of death or heart failure (hazard ratio per 10 pg/mL, 1.09 [95% CI 1.001 to 1.19], P =0.04).

Conclusions— BNP activation in organic MR reflects primarily ventricular and atrial consequences rather than degree of MR. Higher BNP level in patients with organic MR independently predicts adverse events under conservative management. Therefore, BNP activation in organic MR is an emerging biomarker of severity of MR consequences and of poor clinical outcome, and its assessment should be considered in the clinical evaluation and risk stratification of patients with MR.

Nonchannel drug targets in atrial fibrillation

Atrial fibrillation (AF) is the most common clinical arrhythmia and one of the most important factors for ischemic stroke. In general, AF is treated with "channel-blocking drugs" to restore sinus rhythm and warfarin is recommended in the majority of patients to prevent atrial thrombus formation and thromboembolic events. In the recent years, a tremendous amount has been learned about the pathophysiology and molecular biology of AF. Thus, pharmacologic interference with specific signal transduction pathways with "non-channel-blocking drugs" appears promising as a novel antiarrhythmic approach to maintain sinus rhythm and to prevent atrial clot formation. Therefore, this review will highlight some novel "nonchannel drug targets" for AF therapy.

Atrial amyloidosis: an arrhythmogenic substrate for persistent atrial fibrillation

BACKGROUND

Structural changes, like atrial fibrosis, may increase the likelihood of atrial fibrillation (AF) occurring in response to triggering events. The influence of isolated atrial amyloidosis (IAA) is largely unknown.

METHODS AND RESULTS

Right atrial appendages (1 or 2 entire cross sections) were obtained from 245 patients undergoing open-heart surgery. Atrial amyloid was identified by Congo red staining and classified by immunohistochemistry. Amyloid was found in 40 (16.3%) of 245 patients, and all deposits were immunoreactive for atrial natriuretic peptide (ANP). Thirty-eight (15.5%) patients suffered from persistent AF. The presence of amyloid correlated with age and P-wave duration and was related to sex, valve diseases, and the presence of AF (P<0.01). The association between atrial amyloid, AF, and P-wave duration was independent of age and sex. According to multiple logistic regression analysis, amyloid was the only age- and sex-independent predictor for the presence of AF. Atrial fibrosis was not a predictor for AF, and the amount of amyloid correlated inversely with the degree of interstitial fibrosis (P=0.001; r=-0.55).

CONCLUSIONS

Our study provides evidence that IAA affects atrial conduction and increases the risk of AF. The occurrence of IAA depends on age leading to the formation of an amyloid nidus. The progression and consequences of IAA are then influenced by pathological conditions, such as valve diseases, that increase synthesis and secretion of ANP. The inverse correlation between IAA and atrial fibrosis suggests that these patients may not benefit from treatment with ACE inhibitors to reduce the amount of atrial fibrosis.

Short-term effects of sinus rhythm restoration in patients with lone atrial fibrillation: a hormonal study

It is well known that atrial fibrillation can lead to heart failure, and is attributed to rapid ventricular rate (tachycardia-induced cardiomyopathy). Some recent studies suggest the possible existence of an intrinsic left-ventricular factor related to atrial fibrillation, irrespective of other elements. In order to demonstrate the implication of this factor, we measured B-type Natriuretic Peptide, known as a functional marker of left-ventricular dysfunction, in 40 consecutive patients with chronic non-valvular atrial fibrillation, with low ventricular rate and absence of clinical heart failure or echocardiographic left-ventricular dysfunction. In all patients, Brain Natriuretic Peptide (BNP) plasma level was high and dramatically decreased 24 h after external electrical cardioversion (61.4 pg/ml before cardioversion, 23.5 pg/ml 1 day after cardioversion, P<0.002). Our study demonstrates that atrial fibrillation, in absence of high ventricular rate, induces an asymptomatic cardiac alteration that is not detectable by echocardiography.

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.

Increased brain and atrial natriuretic peptides in patients with chronic right ventricular pressure overload: correlation between plasma neurohormones and right ventricular dysfunction

OBJECTIVE

To evaluate the role of plasma neurohormones in the diagnosis of asymptomatic or minimally symptomatic right ventricular dysfunction.

SETTING

Tertiary cardiovascular referral centre.

METHODS

Plasma brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) concentrations were measured in 21 asymptomatic or minimally symptomatic patients with chronic right ventricular pressure overload caused by congenital heart disease, and in seven healthy volunteers. Right ventricular ejection fraction was determined using magnetic resonance imaging.

RESULTS

Right ventricular ejection fraction in the volunteers was higher than in the patients (69.0 (8.2)% v 58.0(12.0)%, respectively; p < 0.006). Left ventricular ejection fraction was 72.3(7.8)% in volunteers and 68.1(11.0)% in patients (NS). There was a significant difference between patients and volunteers in the plasma concentrations of BNP (5.3 (3.5) v 2.3 (1.7) pmol/l, respectively; p < 0.009) and ANP (7.3 (4.5)v 3.6 (1.4) pmol/l; p < 0.05). In both patients and volunteers, mean plasma ANP was higher than mean plasma BNP. Right ventricular ejection fraction was inversely correlated with BNP and ANP (respectively, r = 0.65; p < 0.0002 and r = 0.61; p < 0.002). There was no correlation between left ventricular ejection fraction and BNP (r = 0.2; NS) or ANP (r = 0.52; NS). Similarly, no correlation was shown between the level of right ventricular systolic pressure and either plasma BNP (r = 0.20) or plasma ANP (r = 0.07).

CONCLUSIONS

There was a significant inverse correlation between right ventricular ejection fraction and the plasma neurohormones BNP and ANP in asymptomatic or minimally symptomatic patients with right ventricular pressure overload and congenital heart disease. Monitoring changes in BNP and ANP may provide quantitative follow up of right ventricular dysfunction in these patients.

Increased brain and atrial natriuretic peptides in patients with chronic right ventricular pressure overload: correlation between plasma neurohormones and right ventricular dysfunction

OBJECTIVE

To evaluate the role of plasma neurohormones in the diagnosis of asymptomatic or minimally symptomatic right ventricular dysfunction.

SETTING

Tertiary cardiovascular referral centre.

METHODS

Plasma brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) concentrations were measured in 21 asymptomatic or minimally symptomatic patients with chronic right ventricular pressure overload caused by congenital heart disease, and in seven healthy volunteers. Right ventricular ejection fraction was determined using magnetic resonance imaging.

RESULTS

Right ventricular ejection fraction in the volunteers was higher than in the patients (69.0 (8.2)% v 58.0(12.0)%, respectively; p < 0.006). Left ventricular ejection fraction was 72.3(7.8)% in volunteers and 68.1(11.0)% in patients (NS). There was a significant difference between patients and volunteers in the plasma concentrations of BNP (5.3 (3.5) v 2.3 (1.7) pmol/l, respectively; p < 0.009) and ANP (7.3 (4.5) v 3.6 (1.4) pmol/l; p < 0.05). In both patients and volunteers, mean plasma ANP was higher than mean plasma BNP. Right ventricular ejection fraction was inversely correlated with BNP and ANP (respectively, r = 0.65; p < 0.0002 and r = 0.61; p < 0.002). There was no correlation between left ventricular ejection fraction and BNP (r = 0.2; NS) or ANP (r = 0.52; NS). Similarly, no correlation was shown between the level of right ventricular systolic pressure and either plasma BNP (r = 0.20) or plasma ANP (r = 0.07).

CONCLUSIONS

There was a significant inverse correlation between right ventricular ejection fraction and the plasma neurohormones BNP and ANP in asymptomatic or minimally symptomatic patients with right ventricular pressure overload and congenital heart disease. Monitoring changes in BNP and ANP may provide quantitative follow up of right ventricular dysfunction in these patients.

Hemodynamics, intramucosal pH and regulators of circulation during perioperative epidural analgesia

PURPOSE

To evaluate the effects of perioperative epidural analgesia on hemodynamics, splanchnic perfusion and regulators of circulation.

METHODS

Twenty patients undergoing aortic surgery were randomised into two groups: epidural analgesia group (EAG): epidural analgesia with bupivacaine (15 ml, 0.125%) was started before surgery. Eight and 16 hr postoperatively 10 ml bupivacaine 0.125% and 1 mg morphine were given. Control group (COG): patients received no epidural catheter. Monitoring included pulmonary artery catheter and gastric tonometer. Norepinephrine, epinephrine, renin, ADH, ANP and endothelin were measured: before epidural analgesia (T0), before aortic clamping (T1), 20 min after aortic clamping (T2), after declamping the first leg (T3), at end of surgery (T4), one hour (T5) and 24 hr postoperatively (T6).

RESULTS

At T5 mean arterial blood pressure decreased in EAG compared with baseline (86 +/- 16 to 75 +/- 8 mmHg) and compared with COG (75 +/- 8 vs 84 +/- 11 mmHg). At T2 pulmonary capillary wedge pressure and cardiac index increased and at T6 decreased in both groups. Systemic vascular resistance decreased at T I and at T3-T5 in EAG compared with COG and at T1 and T3-T6 to baseline (1472 +/- 448 to 1027 +/- 184 dyn x sec x cm(-5) x m(-2)). In EAG and in COG, pHi decreased compared with baseline but without group differences. In both groups, epinephrine, norepinephrine, renin, and ADH levels increased from baseline. Endothelin and ANP levels showed no changes.

CONCLUSIONS

Perioperatively administrated epidural bupivacaine has no beneficially effects on hemodynamics, pHi or release of regulators of circulation.

Natriuretic peptide levels in atrial fibrillation: a prospective hormonal and Doppler-echocardiographic study

OBJECTIVES

The objective was to determine the independent association between atrial fibrillation (A-Fib) and activation of natriuretic peptides.

BACKGROUND

The association of A-Fib with activation of N-terminal atrial and brain natriuretic peptides (N-ANPs and BNPs, respectively) is uncertain but of great importance for the diagnostic utilization of natriuretic peptides. This uncertainty is related to the lack of appropriate controls, with left ventricular (LV) and atrial overload similar to A-Fib.

METHODS

We prospectively measured N-terminal atrial and BNPs and endothelin-1 levels in 100 patients and 14 age- and gender-matched control subjects. The 32 patients with A-Fib were compared with 68 patients in sinus rhythm and similar LV and atrial overload (due to mitral regurgitation or LV dysfunction) measured simultaneously with hormonal levels with comprehensive Doppler echocardiography.

RESULTS

Patients with A-Fib compared with those in sinus rhythm had similar symptoms, comorbid conditions, cardioactive medications, pulmonary pressure, left atrial volume, and LV ejection fraction and filling characteristics but demonstrated higher N-ANP levels (2,613 +/- 1,681 vs. 1,654 +/- 1,323 pg/ml, p = 0.007) even after adjustment for the underlying cardiac disease (p < 0.0001). Conversely, BNP levels were similar in both groups (165 +/- 163 vs. 160 +/- 269 pg/ml, p = 0.9). In multivariate analysis, a higher N-ANP level was associated with A-Fib (p = 0.0003), symptom class (p < 0.0001) and endothelin-1 level (p = 0.032) independently of left atrial volume and LV ejection fraction. Conversely, BNP showed no independent association with and was most strongly associated with LV ejection fraction (p < 0.0001).

CONCLUSIONS

Atrial fibrillation is an independent determinant of higher N-ANP levels and blurs its association with LV dysfunction. Conversely, the BNP is not independently associated with A-Fib and is strongly determined by LV dysfunction, for which it is an independent marker.

CGMP levels following ANP challenge are markers of subsequent successful reversion of lone atrial fibrillation to sinus rhythm

The aim of the present study was to assess whether cGMP release to ANP stimulation can be a biochemical marker of subsequent successful electrical cardioversion of lone atrial fibrillation to sinus rhythm. For this purpose, we studied 13 patients with chronic, lone atrial fibrillation of less than one year's duration who presented to our laboratory for electrical therapy of their arrhythmia. Prior to electrical cardioversion, peripheral venous cGMP levels were assessed at baseline and following an intravenous challenge of 50 Ug human ANP. Venous blood samples for cGMP assessment were taken a) at baseline, b) 5 and 10 mins after the end of ANP infusion. ANOVA of repeated measures was used for statistical analysis. Eight of the study patients were successfully cardioverted to sinus rhythm, while the remaining 5 were not. Although no difference was noted between the two groups regarding the mean time of arrhythmia duration as well as left atrial and ventricular dimensions, ANP stimulation provoked significantly greater cGMP release in patients whose arrhythmia reverted to sinus rhythm, when compared with that of patients whose arrhythmia persisted (p < 0.001). Therefore, cGMP levels following ANP challenge might discriminate between patients with chronic AF who are going to be successfully cardioverted and those who are not. These findings imply that the underlying atrial disease might be different in extent/nature between patients with lone AF responsive to cardioversion and those with resistant arrhythmia.

Plasma levels of nitrite/nitrate and platelet cGMP levels are decreased in patients with atrial fibrillation

Patients with atrial fibrillation have been reported to exhibit abnormal hemostasis. Since nitric oxide (NO) exerts antithrombotic effects and attenuates platelet function, we evaluated two indicators of plasma NO levels, the plasma levels of nitrite and nitrate (NOx), and the levels of cGMP in platelets. We also examined whether indicators of plasma NO levels were associated with abnormalities in parameters related to platelet function, blood coagulation, and fibrinolysis. We evaluated 45 patients with chronic sustained atrial fibrillation (33 men and 12 women, age range 63 +/- 2 years) compared with 45 sex- and age- (+/- 2 years) matched nonhospitalized subjects with sinus rhythm. There were no significant differences between the two groups in the incidence of risk factors for stroke except for ischemic heart disease or in echocardiographic parameters. Plasma levels of NOx measured using the Greiss reagent (mean [interquartile range]: 15.6 [9.5 to 25.7] versus 24.1 [14.2 to 40.8] mumol/L, n = 45) and the platelet cGMP levels (0.33 [0.16 to 0.67] versus 0.63 [0.31 to 1.29] pmol/10(9) platelets, n = 9) were significantly (P < .05) lower in the patients with atrial fibrillation than in the control subjects. Plasma levels of D-dimer, beta-thromboglobulin, and fibrinogen were significantly (P < .05) higher in the patients with atrial fibrillation. The two groups did not differ as to the plasma levels of tissue plasminogen activator or plasminogen activator inhibitor-1. Our findings suggest that a decrease in plasma NO levels may account for the hemostatic abnormalities observed in patients with atrial fibrillation.

Pharmacodynamic modeling of furosemide tolerance after multiple intravenous administration

OBJECTIVE

Physiologic indirect-response models have been proposed to account for the pharmacodynamics of drugs with an indirect mechanism of action, such as furosemide. However, they have not been applied to tolerance development. The aim of this study was to investigate the development of tolerance after multiple intravenous dosing of furosemide in healthy volunteers.

METHODS

Three repetitive doses of 30 mg furosemide were given as rapid intravenous infusions at 0, 4, and 8 hours to eight healthy volunteers. Urine samples were collected for a period up to 14 hours after the first dose. Volume and sodium losses were isovolumetrically replaced with an oral rehydration fluid.

RESULTS

Tolerance was demonstrated as a significant decrease in diuretic and natriuretic response over time. Total mean diuresis was 35% lower (p < 0.01) and total mean natriuresis was 52% lower (p < 0.0001) after the third dose of furosemide compared with the first dose. However, there were considerable interindividual variations in the rate and extent of tolerance development for both diuresis and natriuresis. Pharmacokinetic-pharmacodynamic modeling of tolerance development was performed with use of an indirect-response model with an additional "modifier" compartment. This model gave an accurate description of the diuretic and natriuretic data after multiple dosing of furosemide and enabled the estimation of a lag-time for tolerance and a rate constant for tolerance development. Physiologic counteraction was demonstrated as a significant increase in plasma active renin levels (p < 0.00001) and a decrease in atrial natriuretic peptide levels (p < 0.005) during the day, concomitantly with the development of a negative sodium balance. This may be viewed as physiologic reflections of the modifier in our model.

CONCLUSION

Indirect-response models may be successfully applied for tolerance modeling of drugs after multiple dosing.

Atrial natriuretic peptide ANP(1-98) and ANP(99-126) in patients with severe chronic congestive heart failure: relation to echocardiographic measurements. A subgroup analysis from the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS)

Studies in patients with moderate heart failure have shown a positive relation between atrial size and plasma atrial natriuretic peptide (ANP)(99-126) concentrations; however, the relation of the hormone level and left atrial size and left ventricular function in patients with severe chronic heart failure has not been determined. Fifty-three patients from the Cooperative North Scandinavian Enalapril Survival Study with severe chronic heart failure were evaluated with M-mode echocardiography and determination of plasma concentrations of ANP(99-126). In 35 patients, the plasma level of N-terminal ANP(1-98) was also measured. A significant negative relation was found between ANP(1-98), ANP(99-126), and left atrial diameter (r = -.28, P = .05 and r = -.41, P < .005, respectively). Plasma concentrations of both ANP(1-98) and ANP(99-126) were related to left ventricular systolic function as determined by the systolic time interval index (r = .4, P < .05 and r = .29, P < .05, respectively). A significant improvement of left ventricular systolic function was found in the enalapril group but not in the placebo group. After 6 weeks of therapy, no correlation was found between changes in left atrial size or systolic function or changes in either the ANP(1-98) or ANP(99-126) concentration. The results indicate that high ANP(1-98) or ANP(99-126) plasma concentration is determined by the depressed left ventricular function rather than increased left atrial size in patients with chronic severe heart failure. The findings suggest that the ANP release relation to atrial pressure/atrial size is distorted in severe heart failure.

Influence of angiotensin converting enzyme inhibition on relation of atrial natriuretic peptide concentration to atrial pressure in heart failure

OBJECTIVE

To examine the relation between haemodynamics and atrial natriuretic peptide concentration during short term angiotensin converting enzyme inhibition.

DESIGN

Patients were randomly allocated to receive placebo or one of three doses of the angiotensin converting enzyme inhibitor ramipril.

SETTING

Cardiac units of two tertiary referral hospitals.

SUBJECTS

38 Patients with stable congestive heart failure caused by ischaemic heart disease.

METHODS

Data were collected over a 24 hour period and assessed with the aim of distinguishing between the haemodynamic effects on plasma concentrations of atrial natriuretic peptide and the direct effects of the study drug, vasopressin concentrations, and angiotensin converting enzyme activity.

RESULTS

Pulmonary capillary wedge pressure was the main predictor of the plasma concentration of atrial natriuretic peptide. A higher plasma concentration of this peptide with a given pulmonary capillary wedge pressure was found after 24 hours of treatment with 2.5 mg and 5 mg of ramipril. Plasma concentration of the active metabolite, change in arginine vasopressin concentration or degree of angiotensin converting enzyme inhibition did not significantly predict change in plasma concentration of atrial natriuretic peptide or in the ratio of atrial natriuretic peptide concentration to pulmonary capillary wedge pressure.

CONCLUSIONS

A gradual increase in plasma concentration of atrial natriuretic peptide with a given pulmonary capillary wedge pressure, occurs during short term high degree inhibition of angiotensin converting enzyme. The causative mechanisms are yet to be identified. Such a change in the relation between central haemodynamics and atrial natriuretic peptide concentration may contribute to the beneficial effects of angiotensin converting enzyme inhibition in patients with congestive heart failure due to ischaemic heart disease.

Short-term effects of eating on vasoactive hormones and haemodynamics in patients with heart failure

OBJECTIVES

To investigate if eating can influence the measurements of vasoactive hormones or their relationship to important haemodynamic variables.

DESIGN

Haemodynamic variables and plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin and angiotensin enzyme (ACE) activity were measured. During the 24-h study period the patients ate ordinary hospital meals and thus were studied both in the absorptive and post-absorptive phases.

SETTING

Two university hospitals in Sweden participated in the study.

SUBJECTS

Ten patients with heart failure, due to ischaemic heart disease.

INTERVENTION

Eating.

MAIN OUTCOME MEASURES

Change in haemodynamic variables and plasma concentrations of vasoactive hormones related to eating.

RESULTS

After a meal (absorptive phase) pulmonary capillary wedge pressure and plasma concentrations of ANP were significantly lower compared to the postabsorptive phase, 13 +/- 1.7 vs. 16 +/- 1.9 mmHg and 57 +/- 9.5 vs. 72 +/- 12.2 pmol l-1, respectively. The relationship between ANP and its main predictor, pulmonary capillary wedge pressure, was not altered during the study period. Plasma concentration of arginine vasopressin, ACE activity and mean right atrial pressure decreased with time and the cardiac index increased with time over the study period.

CONCLUSIONS

A meal may significantly influence plasma concentrations of ANP. Studies on vasodilator treatment and its interactions with ANP should take account of these basal fluctuations. The present data confirm previous reports on haemodynamic improvement during the first 24 h of supine cardiac catheterization in patients with heart failure, and add new information about decreasing concentrations of arginine vasopressin and ACE.

Plasma concentrations of calcitonin gene-related peptide in fluid overload

To investigate the hypothesis that calcitonin gene-related peptide (CGRP), a potent vasodilator, is an important physiological defence against fluid overload, plasma CGRP concentrations were measured in various degrees of fluid overload in 26 haemodialysis patients, for whom diuresis, mediated by atrial natriuretic peptide (ANP), is not a possible defence mechanism. Plasma CGRP concentrations were positively correlated with the degree of fluid excess (r = 0.815, p = 0.0001) and were significantly higher in 5 patients with severe fluid overload than in those less severely affected (143 [SE 14] vs 52 [11] pmol/l; p less than 0.001). CGRP may be an effective defence against complications of fluid overload since it can increase capitance by vasodilatation.