Right Atrial Volume Research Articles

Giant Right Atrium in an Adult

Massive right atrial (RA) enlargement is certainly more common in children than in adults, owing to rare congenital anomalies. Indeed, the largest description of such chamber enlargement was noted in a child, where the RA volume was reported to be 900 ml. We now report one of the largest descriptions of the RA in an adult, in absence of tricuspid stenosis and other common adult associations of RA abnormality, such as chronic pulmonary disease, severe mitral valvular pathology with pulmonary hypertension, and pulmonary embolism or infarct. The RA volume was estimated to be well over 500 ml and was notably disproportionate to that of the left atrium and either ventricle.

Association of Coronary Sinus Diameter with Pulmonary Hypertension

Impaired venous drainage secondary to increased right atrial pressure (RAP) may result in coronary sinus (CS) dilatation. Two hundred fifteen patients referred for transthoracic echocardiography were included in the study. CS diameters were measured from apical four-chamber view with the transducer being slightly tilted posteriorly to the level of the dorsum of the heart. Pulmonary artery systolic pressure (PASP) is estimated by measurement of tricuspid regurgitation velocity (v) and estimate RAP based on size and collapsibility of inferior vena cava (VCI) with the formula PASP: 4v(2)+RAP. Patients with PASP >35 mmHg were considered to have pulmonary hypertension (PH). CS diameter was measured in 80.3% of the patients with normal PASP (8.1 +/- 2.4 mm) and 93.1% of the patients having PH (12.3 +/- 2.5 mm). PASP was significantly correlated with CS diameter (r = 0.647, P < 0.001), RA volume index (r = 0.631, P < 0.001), RV volume index (r = 0.475, P < 0.001), VCI diameter (r = 0.365, P < 0.001), and left ventricular ejection fraction (LVEF) (r =-0.270, P < 0.001). CS diameter was also correlated significantly with estimated RAP (r = 0.557, P < 0.001), RA volume index (r = 0.520, P < 0.001), RV volume index (r = 0.386, P < 0.001), LVEF (r =-0.327, P < 0.001), and VCI diameter (r = 0.313, P < 0.001). Multivariate analyses, testing for independent predictive information of CS size, VCI diameter, RA and RV volume indexes, and estimated RAP for the presence of PH revealed that estimated RAP (beta = 0.465, P < 0.001) and CS size (beta = 0.402, P = 0.003) were the significant predictors. Coronary sinus is dilated in patients with pulmonary hypertension. Coronary sinus diameter significantly correlates with PASP, RAP, right heart chamber volumes, LVEF, and VCI diameter.

Biatrial anatomical reverse remodelling after radiofrequency catheter ablation for atrial fibrillation: evidence from real-time three-dimensional echocardiography

Reports using two-dimensional echocardiography have indicated that radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF) results in a reduction in the left atrial (LA) size. Furthermore, the effect of pulmonary vein isolation (PVI) on right atrial (RA) anatomical remodelling has not been studied. Three-dimensional echocardiography (3DE) allows us to more precisely quantify atrial volume. Our aim was to assess the effect of PVI on biatrial anatomical remodelling using real-time 3DE. We prospectively studied 91 patients (age 59 +/- 8 years, 79 males) referred for RFCA of paroxysmal (n = 79) or chronic (n = 19) AF. Left atrial and RA volumes were measured using real-time 3DE at baseline and after 6 months of follow-up. Data on AF recurrences were also collected. Left atrial volume was significantly reduced at follow-up when compared with baseline (51 +/- 16 vs. 60 +/- 21 mL, P < 0.001). The same occurred with RA volume (43 +/- 17 vs. 50 +/- 20 mL, P = 0.001). The reduction in the LA volume was more marked in patients with chronic than in those with paroxysmal AF (17 +/- 16 vs. 6 +/- 17 mL, P = 0.017). Patients with AF recurrence (23%) showed similar atrial volume reduction compared with those who were seemingly cured. Three-dimensional echocardiography shows evidence of biatrial anatomical reverse remodelling after RFCA for AF. A reduction in the atrial volume occurs despite recurrence of AF.

Evaluation of Right Atrial Size in Patients with Atrial Arrhythmias: Comparison of 2D versus Real Time 3D Echocardiography

This study compares different parameters of right atrial size evaluated by two-dimensional (2D) echocardiography with right atrial volume measured using three-dimensional echocardiography (3DE). One hundred sixty-three consecutive patients with a history of atrial arrhythmias were studied by standard two-dimensional and by real time 3DE. Of these 142 (87%) recordings were of sufficient quality for interpretation of the right atrium by both imaging techniques. The following parameters of right atrial size were measured: apical four-chamber short-axis diameter (4CH short axis), apical four-chamber long axis diameter (4CH long axis), and apical four-chamber planimetry area. The 2D-derived right atrial volume was calculated by using the single plane area-length method (4CH area-length). The 2D parameters were then correlated with right atrial volume measured by real time 3DE. Linear regression analysis showed moderate correlation for four-chamber planimetry area (r = 0.72, P < 0.001) and 2D-derived volume calculation (r of 4CH single plane area-length RA volume = 0.70, P < 0.001). Diameters correlated clearly less well with 3DE volume (r of 4CH short axis = 0.61, 4CH long axis = 0.59, P < 0.001 respectively). Real time 3DE is highly feasible for right atrial volume determination. The results demonstrate that measurements of dimensions using 2D echocardiography may not accurately assess right atrial size. If 3DE is not available, apical 4CH planimetry area is a simple alternative that may be used for evaluating right atrial size in clinical practice. The 2D-derived right atrial volume by single plane area-length method was not better correlated with 3DE volume than four-chamber planimetry area.

Left atrial function and scar after catheter ablation of atrial fibrillation

Catheter ablation of atrial fibrillation (AF) involves extensive radiofrequency ablation (RFA) of the left atrium (LA) around the pulmonary veins. The effect of this therapy on LA function is not fully characterized. The purpose of this study was to determine whether catheter ablation of AF is associated with a change in LA function. LA and right atrial (RA) systolic function was assessed in 33 consecutive patients with paroxysmal or persistent AF referred for ablation using cardiovascular magnetic resonance (CMR) imaging. Steady-state free precession ECG cine CMR imaging was performed before and after (mean 48 days) AF ablation. All patients underwent circumferential pulmonary vein isolation using an 8-mm tip RFA catheter. High spatial resolution late gadolinium enhancement CMR images of LA scar were obtained in 16 patients. Maximum LA volume decreased by 15% (P <.001), and LA ejection fraction decreased by 14% (P <.001) after AF ablation. Maximum RA volume decreased by 13% (P = .018), but RA ejection fraction increased by 5% (P = .008). Mean LA scar volume was 8.1 +/- 3.7 mL. A linear correlation was observed between change in LA ejection fraction and scar volume (r = -0.75, P <.001). Catheter ablation of AF is associated with decreased LA size and reduced atrial systolic function. This change strongly correlates with the volume of LA scar. This finding may have implications for postprocedural thromboembolic risk and for procedures involving more extensive RFA.

Hormonal and environmental control of song control region growth and new neuron addition in adult male house finches, Carpodacus mexicanus

In songbirds, testosterone (T) mediates seasonal changes in the sizes and neuroanatomical characteristics of brain regions that control singing (song control regions; SCRs). One model explaining the mechanisms of the growth of one SCR, the HVC, postulates that in the spring increasing photoperiod and circulating T concentrations enhance new neuron survival, thus increasing total neuron number. However, most research investigating the effects of T on new neuron survival has been done in autumn. The present study investigated the effects of photoperiod and T treatment on SCR growth and new neuron survival in the HVC in photosensitive adult male House Finches, Carpodacus mexicanus, under simulated spring-like conditions. Birds were castrated, given T-filled or empty Silastic capsules and maintained on short days (SD; 8L:16D) or long days (LD; 16L:8D). To mark new cells, birds received bromodeoxyuridine injections 11 days after experimental manipulations began and were sacrificed 28 days later. Testosterone treatment increased the sizes of two SCRs, the HVC and Robust nucleus of the arcopallium (RA). Exposure to LD did not affect HVC volume, but did increase RA volume. Testosterone treatment increased the total number of HVC neurons, but did not affect the number of new HVC neurons. Thus, T initiates SCR growth and increases neuron survival, but effects of T on new neuron incorporation may be limited in photosensitive birds under spring-like conditions. These results provide new insight into the effects of photoperiod and T treatment on vernal SCR growth and new neuron incorporation and support current models explaining this growth.

Early condition, song learning, and the volume of song brain nuclei in the zebra finch (Taeniopygia guttata)

Songbirds are an important model system for the study of the neurological bases of song learning, but variation in song learning accuracy and adult song complexity remains poorly understood. Current models of sexual selection predict that signals such as song must be costly to develop or maintain to constitute honest indicators of male quality. It has been proposed that reductions of nestling condition during song development might limit the expression of song learning. Adult song could thus act as an indicator of early stress as only males that enjoy good condition during development could learn accurately and sing long songs or large repertoires. We tested this hypothesis in the zebra finch by modifying early condition through cross-fostering chicks to small, medium, and large broods. Song learning was very accurate and was found to reflect very closely tutor song characteristics and to depend on the number of males in the tutoring group. Although the brood size manipulation strongly affected several measures of nestling condition and adult biometry, we found no relationship between early condition and song learning scores or song characteristics. Similarly, brain mass and high vocal center (HVC), robust nucleus of the arcopallium (RA), and lateral magnocellular nucleus of the anterior nidopallium (LMAN) volumes did not covary with nestling condition and growth measurements. We found no significant relationship between song repertoire size and HVC and RA volumes, although there was a nonsignificant trend for HVC to increase with increasing proportion of learnt elements in a song. In conclusion, the results provide no evidence for song learning to be limited by nestling condition during the period of nutritional dependence from the parents in this species.

Assessment of factors affecting plasma BNP levels in patients with chronic atrial fibrillation and preserved left ventricular systolic function

Background Several studies have reported that plasma brain natriuretic peptide (BNP) levels are increased in patients with chronic atrial fibrillation (AF). The objective of this study was to assess the factors influencing plasma BNP levels in patients with chronic AF and preserved left ventricular (LV) systolic function. Methods Transthoracic echocardiography was performed in 104 patients (48 men, 56 women; mean age, 63.9 ± 10.7 years) with chronic AF. At the same time, plasma BNP levels were measured with a Triage R kit (Biosite, San Diego, CA). Results Women, long duration of AF, and hypertension were more prevalent in the highest quartile group of BNP levels than in the lowest quartile of BNP. Significant correlations were observed between plasma BNP levels and the following: mitral E velocity ( r = 0.343), mitral annular E′ velocity ( r = − 0.402), ratio of mitral E velocity and mitral annular E′ velocity ( r = 0.487), left atrial(LA) size ( r = 0.653), LA volume index ( r = 0.775), right atrial (RA) volume index ( r = 0.563), maximal velocity ( V max) of mitral regurgitation (MR) ( r = 0.448), tricuspid regurgitation (TR) V max ( r = 0.532) and LV mass index ( r = 0.581). In stepwise multiple linear regression analysis, LA volume index ( β = 0.326, p < 0.001), LV mass index ( β = 0.395, p < 0.001) and duration of AF ( β = 0.492, p < 0.001) independently predicted plasma BNP levels in the study subjects. The patients with increased LA volume index exhibited a longer duration of AF, larger RA volume index and LV mass index, higher MR V max, TR V max and plasma BNP level. Conclusions LA volume index, LV mass index and duration of AF are independent predictors of plasma BNP levels in patients with chronic AF and preserved LV systolic function.

Right atrial size and function in patients with pulmonary hypertension associated with disorders of respiratory system or hypoxemia

Pulmonary hypertension (PH) determines various adaptive changes in right ventricular (RV) geometry which may progressively lead to hypertrophy, mechanical dysfunction and dilatation with pump failure. Right atrium (RA) is theoretically involved in this physiopathological process, but its role has never been investigated. We hypothesized that RA increases volume and function to assist RV during the chronic pressure overload exposition due to PH. We prospectively enrolled 66 consecutive patients referred to our echolab with a diagnosis of PH [defined as pulmonary artery systolic pressure (PASP) >30 mmHg] associated with disorders of the respiratory system and/or hypoxemia and normal RV systolic function. Ejection force was taken up as index of RA systolic function and calculated according to the Manning's formula. Thirty-three healthy subjects for whom PH was definitely excluded by echoDoppler evaluation were used as controls. PASP was 42+/-10 and 20+/-8 mmHg in PH patients and controls, respectively; p=0.00001). In comparison with controls, PH patients exhibited higher RA volume (37+/-13 vs 32+/-13 ml, p=0.04) and RA ejection force (6.7+/-3.0 vs 3.5+/-1.8 Kdynes, p=0.00001). Both variables were positively related to PASP (r=0.23 and 0.48, p=0.02 and 0.00001, respectively). In patients with chronic PH, RA size and systolic function significantly increase and parallel signs of activation of the Frank-Starling mechanism in both right chambers. The magnitude of these phenomena is positively related to PASP levels.

Right Atrial and Ventricular Adaptation to Chronic Right Ventricular Pressure Overload

Increased mortality in patients with chronic pulmonary hypertension has been associated with elevated right atrial (RA) pressure. However, little is known about the effects of chronic right ventricular (RV) pressure overload on RA and RV dynamics or the adaptive response of the right atrium to maintain RV filling. In 7 dogs, RA and RV pressure and volume (conductance catheter) were recorded at baseline and after 3 months of progressive pulmonary artery banding. RA and RV elastance (contractility) and diastolic stiffness were calculated, and RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. With chronic pulmonary artery banding, systolic RV pressure increased from 34+/-7 to 70+/-17 mm Hg (P<0.001), but cardiac output did not change (P>0.78). RV elastance and stiffness both increased (P<0.05), suggesting preserved systolic function but impaired diastolic function. In response, RA contractility improved (elastance increased from 0.28+/-0.12 to 0.44+/-0.13 mm Hg/mL; P<0.04), and the atrium became more distensible, as evidenced by increased reservoir function (49+/-14% versus 72+/-8%) and decreased conduit function (51+/-14% versus 28+/-8%; P<0.002). With chronic RV pressure overload, RV systolic function was preserved, but diastolic function was impaired. To compensate, RA contractility increased, and the atrium became more distensible to maintain filling of the stiffened ventricle. This compensatory response of the right atrium likely plays an important role in preventing clinical failure in chronic pulmonary hypertension.

Assessment of Factors Influencing Plasma BNP Level in Patients with Chronic Atrial Fibrillation and Preserved Left Ventricular Systolic Function

Background and Objectives:Several studies have reported that Brain Natriuretic Peptide (BNP) were increased in patients with chronic atrial fibrillation (AF). The objective of this study was to assess the factors influencing plasma BNP levels in patients with chronic AF and preserved left ventricular (LV) systolic function. Subjects and Methods:Transthoracic echocardiography was performed in 55 patients (25 men, 30 women; mean age 66.6± 11.5 years) with chronic AF. At the same time, plasma BNP was measured with a Triage kit (Biosite, San Diego, California). Results:Women, long duration of AF and hypertension were more prevalent in the highest quartile group of BNP levels than in the lowest quartile group of BNP levels. Significant correlations were observed between plasma BNP levels and the following: mitral E velocity (r=0.339), mitral annular E’-velocity (r=-0.396), ratio of mitral E-velocity and mitral annular E’ velocity (r=0.473), left atrium (LA) size (r=0.648), LA volume index (r=0.744), right atrium (RA) volume index (r=0.554), maximal velocity (Vmax) of mitral regurgitation (MR) (r=0.444), tricuspid regurgitation (TR) Vmax (r=0.544), MR grade (r=0.431), TR grade (r=0.427) and LV mass index (r=0.570). In stepwise multiple linear regression analysis, LA volume index (β=0.299, p=0.014), LV mass index (β=0.404, p<0.001) and duration of AF (β=0.488, p<0.001) independently predicted plasma BNP levels in this study subjects. The patients with increased LA volume index exhibited longer duration of AF, larger RA volume index and LV mass index, higher MR Vmax, TR Vmax, MR and TR grade and plasma BNP level. Conclusion:LA volume index, LV mass index and duration of AF were independent predictors of plama BNP level in patients with chronic AF and preserved LV systolic function. (Korean Circulation J 2005;35:605-612)

Reservoir and conduit function of right atrium: impact on right ventricular filling and cardiac output

The purpose of this study was to investigate the relationship between right atrial (RA) reservoir and conduit function and to determine how hemodynamic changes influence this relationship and its impact on cardiac output. In 11 open-chest sheep, RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. Conduit function was separated into early (before A wave) and late (after A wave) components. The effects of inotropic stimulation, partial pulmonary artery occlusion, and pericardiotomy were tested. At baseline with the pericardium intact, reservoir function accounted for 0.56 (SD 0.13) of RA inflow, early conduit for 0.29 (SD 0.07), and late conduit (during RA contraction) for 0.16 (SD 0.11). Inotropic stimulation decreased conduit function and increased reservoir function, but these effects did not reach statistical significance. With partial pulmonary artery occlusion, early conduit function fell to 0.20 (SD 0.11) (P < 0.04), and the conduit-to-reservoir ratio decreased by 41% (P < 0.03). Similarly, after pericardiotomy, early conduit function fell to 0.14 (SD 0.09) (P < 0.004), reservoir function increased to 0.72 (SD 0.08) (P < 0.04), and, consequently, the early conduit-to-reservoir ratio decreased by 63% (P < 0.006). Cardiac output was inversely related to the conduit-to-reservoir ratio (r = 0.39, P < 0.001). This study demonstrated that the right atrium adjusts its ability to act more as a reservoir than a conduit in a dynamic manner. The RA conduit-to-reservoir ratio was directly related to the right ventricular pressure-RA pressure gradient at the time of maximum RA volume, with increased ventricular pressures favoring conduit function, but it was inversely related to cardiac output, with an increase in the reservoir contribution favoring improved cardiac output.

Effect of Chronic Right Atrial Stretch on Atrial Electrical Remodeling in Patients With an Atrial Septal Defect

Adults with an atrial septal defect (ASD) frequently develop late atrial arrhythmias. We sought to characterize the pattern and persistence of atrial electrical remodeling caused by chronic right atrial (RA) stretch in this group. Thirteen ASD patients without atrial arrhythmia (42+/-10 years old; RA volume, 65+/-16 mL) and 17 normal control subjects (44+/-11 years old; RA volume, 38+/-8 mL) had electrophysiological study to measure (1) atrial effective refractory period (AERP) from the low lateral/high lateral/high septal RA and distal coronary sinus (CS), (2) dispersion of AERP, (3) lateral-RA and CS conduction time during constant pacing, (4) conduction delay across the crista terminalis measuring the number of crista catheter bipoles (0-10) recording discrete double potentials during pacing, (5) corrected sinus node recovery time, and (6) P-wave duration. After ASD closure (8.3+/-5.6 months), follow-up echo studies (n=12) and electrophysiological study (n=4) were performed. The low-lateral AERP, P-wave duration, sinus node recovery time, and extent of conduction delay across the crista terminalis were significantly greater in ASD patients. No differences were found for other measured electrophysiological study parameters. At follow-up, there was incomplete resolution of RA volume (47+/-12 mL; P<0.01 versus before surgery), a trend toward shortening of the AERP at the lateral RA and an increase at the distal CS and high septal RA, but persisting extensive, widely split crista double potentials. Chronic RA stretch because of ASD causes electrical remodeling with modest increases in RA ERP, conduction delay at the crista terminalis, and sinus node dysfunction. Conduction delay at the crista terminalis persists beyond ASD closure and may contribute to the long-term atrial arrhythmia substrate in this condition.

Plasma Levels of Brain Natriuretic Peptide Increase in Patients with Idiopathic Bilateral Atrial Dilatation

Idiopathic bilateral atrial dilatation (IBAD) is an extremely rare anomaly and is usually associated with atrial fibrillation. Plasma levels of atrial natriuretic peptide (ANP) have been shown to increase in patients with atrial fibrillation. However, secretion of ANP and brain natriuretic peptide (BNP) in patients with IBAD remains unclear. We investigated the clinical features of 9 patients with IBAD and 16 age- and sex-matched patients with lone atrial fibrillation (LAF). Plasma levels of ANP and BNP were measured, and echocardiographic parameters were followed. Left (LAV) and right atrial volumes (RAV) were significantly higher in patients with IBAD than in patients with LAF (both p < 0.01). There were no differences between patients with IBAD and LAF in other echocardiographic parameters. The percent increases in LAV and RAV in patients with IBAD exceeded those in patients with LAF (both p < 0.01). Plasma levels of BNP and the BNP/ANP ratios in patients with IBAD were significantly higher than those in patients with LAF (both p < 0.01), but there was no significant difference in plasma levels of ANP. Regarding the clinical course of the patients with IBAD compared with those with LAF, the atrial volume increased gradually, and plasma levels of BNP were significantly higher. These findings suggested that IBAD was not only influenced by long-term atrial fibrillation, but also by subclinical left ventricular dysfunction.

Effects of Testosterone and Photoperiodic Condition on Song Production and Vocal Control Region Volumes in Adult Male Dark-Eyed Juncos (Junco hyemalis)

In seasonally breeding male oscines, song learning and expression are controlled by brain regions (vocal control regions, VCRs) that exhibit seasonal neural plasticity in adulthood. Several VCRs contain androgen receptors, and gonadal androgens play important roles in the control of seasonal structural and functional changes of VCRs. Recent studies also found that adult VCRs are influenced by factors other than gonadal hormones, including photoperiod, but the relative importance of these factors and their mechanisms of action are poorly understood. To address this issue, we investigated the contributions of photoperiod and testicular androgens to the regulation of VCR volumes and to the control of song expression in adult dark-eyed juncos, Junco hyemalis. Exposing castrated (CX) photosensitive males to long days (LD) enhanced their high vocal center (HVc) volumes compared to those of males held on short days (SD). These volumes were not further increased by concurrent testosterone (T) treatment, revealing a marked and gonadal androgen-independent stimulatory influence of photoperiod on the size of this brain region. HVc sizes were smaller in LD-exposed photorefractory than photosensitive males irrespective of whether birds were intact or had been castrated before photoperiodic manipulations, but HVc sizes increased in response to T treatment in intact photorefractory males. Thus, LD exposure can increase HVc volumes in the absence of gonadal T, but large volume induction in photorefractory males requires elevated plasma T levels. Testosterone treatment of SD-exposed photosensitive males increased HVc, but not Area X, MAN, or RA volumes. Only T-treated males sang and this treatment given to castrates was equally effective behaviorally when administered to photosensitive, photostimulated, or photorefractory juncos. This result indicates that the stimulating influence of LD exposure on HVc volumes is insufficient to induce song in the absence of elevated plasma T levels.

Neural correlates of singing behavior in male zebra finches (Taeniopygia guttata)

This study examined the relationship between the volumes of four song control nuclei: the high vocal center (HVC), the lateral part of the magnocellular nucleus of the anterior neostriatum (IMAN), Area X, and the robust nucleus of the archistriatum (RA), as well as syrinx mass, with several measures of song output and song complexity in male zebra finches (Taeniopygia guttata). Male zebra finches' songs were recorded in standardized recording sessions. The syrinx and brain were subsequently collected from each bird. Volumes of the song control nuclei were reconstructed by measuring the cross-sectional area of serial sections. Syrinx mass was positively correlated with RA volume. The volume of IMAN was negatively related to element repertoire size and the number of elements per phrase. We found no other correlations between brain and behavioral measures. This study, combined with others, indicates that the evidence for a general relationship among songbirds between HVC volume and song complexity is equivocal. There are clear species differences in this brain-behavior correlation.

Estimation of Right Atrial Volume and Function by an Online Echocardiographic Edge Detection System.

To define the accuracy of real-time two-dimensional echocardiographic imaging with automatic border detection (ABD) for the assessment of right atrial volume and function, we studied with ABD echocardiography 29 healthy subjects and 43 patients with sinus rhythm and various forms of heart disease. Twenty-three patients had right ventricular (RV) dysfunction (fractional area change < 45%), and 20 had RV hypertrophy from pressure overload. Doppler color flow imaging disclosed moderate-to-severe tricuspid regurgitation (TR) in 20 patients and trivial or no TR in 23. The ABD-derived end-diastolic (EDV) and end-systolic (ESV) volumes by the method of discs were used to compute fractional indexes of right atrial (RA) volume changes. Right atrial emptying fraction (RAEF) percent [(ESV - EDV)/ESV x 100] was calculated. The ABD-derived EDV and ESV correlated well with conventional offline measurements of two-dimensional echocardiographic images in the 43 patients (r = 0.94 for the end-diastolic values; r = 0.93 for the end-systolic values). Intraobserver and interobserver variability showed a high correlation between different measurements (r = 0.97 and 0.90, respectively). RA volumes were significantly higher in the patient population than in the control subjects (148.9 +/- 66.7 ml vs 43.1 +/- 9.2 ml, P < 0.0001). The right atrial emptying fraction (RAEF) was higher in patients with RV pressure overload than in normal subjects (61% +/- 11% vs 46% +/- 9%, P < 0.05) and lower in those with RV dysfunction than in the control subjects (29% +/- 7% vs 46% +/- 9%, P < 0.01). In both groups (RV pressure overload and RV dysfunction), RAEF was higher in patients without or with trivial TR compared with those with significant TR (29% +/- 7% vs 23% +/- 6%; 61% +/- 11% vs 42% +/- 7%; P < 0.05). Thus, changes in right atrial volume and function can be measured noninvasively by the ABD method. This imaging technique may prove to be useful for assessing right atrial size and function under different physiological and pathological conditions and for identifying factors that influence atrial function in right ventricular diseases.

Atrial natriuretic peptide release is more dependent on atrial filling volume than on filling pressure in chronic congestive heart failure

Background The mechanism of atrial natriuretic peptide (ANP) release has been difficult to demonstrate in patient studies because of inaccuracies in measuring atrial volumes using conventional techniques. Methods Magnetic resonance imaging was performed in 28 clinically stable patients (New York Heart Association class 3) with chronic heart failure to determine right atrial (RA), left atrial (LA), and ventricular volumes. In addition, right heart catheterization was serially performed and plasma ANP levels (in picograms per milliliter) were drawn from the right atrium. Results Five patients had to be excluded from data analysis for technical reasons. The remaining 23 patients had the following hemodynamic measurements (mean ± SD): RA mean pressure 7 ± 5 mm Hg, pulmonary artery mean pressure 28 ± 10, pulmonary capillary wedge pressure 21 ± 8 mm Hg, and cardiac index 2.9 ± 1.4 (L/min/m2), respectively. Plasma ANP levels were significantly elevated at 162 ± 117 (normal range 20 to 65 pg/ml, p < 0.05), as were LA and RA volumes compared with healthy controls (RA volume 128 ± 64 ml vs 82 ± 25 ml, p < 0.05; LA volume 157 ± 54 ml vs 71 ± 24 ml, p < 0.01, respectively). ANP showed a stronger relation with atrial volumes (RA volume, r = 0.91, p = 0.0001; LA volume, r = 0.80, p = 0.001) than with atrial pressures (RA mean pressure, r = 0.45, p = 0.03; pulmonary capillary wedge pressure, r = 0.67, p = 0.001). A subgroup analysis of patients with increased RA or LA volumes (>1 SD of mean of controls) revealed a stronger relation between ANP and RA volumes than between ANP and LA volumes. Conclusions These data suggest that increased right heart volume with subsequent increased atrial stretch is the major determinant for ANP release in patients with stable CHF. (Am Heart J 1997;135:592-7.)

Individual variation in neuron number predicts differences in the propensity for avian vocal imitation.

Avian song learning involves memorizing and reproducing song material produced by conspecifics. In several species song repertoire size correlates with the overall volume of two song-related brain regions, the HVc (acronym used as the proper name) and the robust nucleus of the archistriatum (RA). We raised male zebra finches with two adult tutors and found that individual differences in HVc volume and neuron number correlated positively with differences in the number of tutor syllables accurately copied. These results were replicated in a second study. The relationship between RA volume and song learning was similar, but less robust. Importantly, total repertoire size (number of song syllables) did not correlate significantly with anatomical measures of either the HVc or RA. Because previous work suggests that the volume and neuron number of these regions are not regulated by song learning, it is possible that naturally occurring variation in neuron number constrains how much song material can be copied or reproduced.

Two separate areas of the brain differentially guide the development of a song control nucleus in the zebra finch.

A brain nucleus that is important for the generation of song in the adult male zebra finch (Poephila guttata), the robust nucleus of the archistriatum (RA), receives dual inputs from two other telencephalic song nuclei: the hyperstriatum ventrale pars caudale (HVc) and the lateral magnocellular nucleus of the anterior neostriatum (L-MAN). We lesioned each of these afferent inputs to the RA early in development, either by themselves or both at the same time in the same side of the brain, to determine what influences each of these nuclei exerts on the normal development of the RA into adulthood. We found that lesioning the HVc in a 20-day-old male zebra finch prevents the later increase in RA volume and soma size that would normally occur around 35 days post-hatching. MAN lesions at this same early age, on the other hand, had a large effect on reducing the volume and cell number of RA neurons, without affecting soma size. Lesioning both inputs early in development induced considerable RA neuronal cell death and atrophy of the nucleus. This study shows that the development of the RA is affected differently by each of its two input nuclei.